基于能量法的隧道围岩定量的稳定性评价

The pressure arch effect limits the influence range of excavation on the surrounding rock, reduces the geological pressure on underground structures, and serves as an important indicator for evaluating the stability of underground engineering. By accounting for the energy transfer process in surrounding rock during the tunnel-induced pressure arch formation, this paper proposes a novel approach for determining the range of the pressure arch around tunnels—the energy density difference (EDD) method. Numerical analysis is conducted to evaluate the effects of tunnel span, internal friction angle, and lateral pressure coefficient on post-excavation energy density fields and pressure arch zones in tunnels. Comparative studies with three existing approaches confirm the EDD method’s efficacy in identifying the arch zones of tunnel-surrounding rock. Critically, the proposed approach addresses the controversy regarding the determination of the deviation degree of principal stress vectors and provides a physically meaningful interpretation of the formation and evolution mechanisms of pressure arches.

Under the action of dissolution, rock masses form solution fissure leading to changes in their internal structure, which in turn affect their engineering mechanical properties and failure characteristics. Karst rock masses usually have a significant impact on the stability of tunnel surrounding rocks in karst stratum. This article utilizes digital image processing technology and particle flow discrete element method to numerically reconstruct calculation models of limestone with different degree of dissolution. A series of uniaxial compression discrete element numerical experiments were conducted on karst limestone with different degree of dissolution, analyzing the stress-strain relationship, mechanical parameters, failure modes, and energy changes of limestone with different degree of dissolution. Research results indicated the following: (1) The karst limestone model constructed based on digital image processing technology can effectively characterize the dissolution features of karst limestone, and numerical simulation experiments can effectively characterize the mechanical behavior of karst limestone. (2) As the degree of dissolution increases, the stress-strain curve of karst limestone gradually exhibits bimodal or multimodal characteristics, and the uniaxial compressive strength of karst limestone shows an exponential decrease trend, while the elastic modulus shows a linear decrease trend. (3) Under high degree of dissolution, the existence of pore structure causes the stress skeleton inside the karst limestone to be damaged, and the number of shear and tensile cracks is continuously decreasing. The distribution of internal force chains is dispersed, making the karst limestone more prone to failure. (4) During the process of karst limestone failure, most of the input total strain energy is first converted into elastic strain energy, and only a small portion is converted into dissipative strain energy. The increase in the degree of dissolution significantly reduces the total energy input and the storage limit of elastic strain energy during the uniaxial compression failure process of karst limestone, and increases the degree of strain energy dissipation.

According to non-equilibrium evolution stability and control theory, over force is the internal effective driving force of unrecoverable time-dependent deformation. The distribution of over force reflects the failure position and mode of tunnel. The opposite force of over force is the optimal reinforcement force to prevent unrecoverable time-dependent deformation and provides a quantitative and accurate reinforcement design method for tunnel. The plastic complementary energy (PCE) is the norm of over force. The curve of PCE versus time provides a unified quantitative criterion of real time dynamic stability evaluation of tunnel in time-dependent deformation process under various external disturbing factors. Based on the curve of PCE versus time, the stresses of lining structure in different supporting time after excavation are studied comparatively. The results show that the stress of lining structure will be very high if supporting time is too early. The surrounding rock of tunnel will be unstable due to damage evolution if supporting time is too late. There is an optimal supporting time when the stress of lining structure will not be too high and the surrounding rock will not lose stability. The curve of PCE versus time can be used to guide reinforcement design and evaluate reinforcement effect.

Abstract Efficiently utilizing and excavating existing construction technologies to obtain potential data information represents a significant challenge in the realm of intelligent tunnel construction. Considering the judgment bias inherent to the manual experience of the traditional surrounding rock grading method, this article proposes an intelligent real-time method for surrounding rock grading based on information collection technology and artificial intelligence. This approach relies on studying the connection between multifunctional drilling rig parameters and the properties of the adjacent rock in tunnel building. The method classified the rock surrounding the “Fengjian Expressway in the Three Gorges Reservoir Area” from the Ministry of Communications Science and Technology demonstration project, and the results showed that: (1) it is a multi-method verification protocol synergizing on-site measurements, laboratory tests, and AI algorithms to eliminate subjective judgment errors and it is an optimized parameter selection mechanism identifying critical drilling indices for rock-property correlations and (2) back-propagation neural network model demonstrating 98.6% accuracy – the highest among tested intelligent algorithms. This methodology bridges empirical engineering practices with data-driven intelligence, offering a replicable solution for infrastructure projects in complex geological environments.

Energy dissipation is a fundamental characteristic of rock failure, and energy-based analysis methods have been increasingly applied in various rock engineering contexts. However, comprehensive studies on the complete energy evolution process of surrounding rock failure induced by deep tunnel excavation remain limited. Considering the effects of intermediate principal stress and the dilatancy behavior of plastic surrounding rock, this study derives, validates, and optimizes an elastoplastic analytical method that incorporates the triaxial stress path and nonlinear behavior of surrounding rock. Based on the principle of energy dissipation, a semi-analytical energy solution accounting for longitudinal excavation effects is further established. The energy evolution and damage development within surrounding rock under tunnel excavation are analyzed for rock masses with different properties. Results indicate that under high in-situ stress conditions, tunnel excavation in elastic-brittle hard rock triggers a rapid surge in the damage variable beyond 100% once the energy storage limit is surpassed, causing brittle failure and sudden energy release toward the cavity, with a fully damaged zone swiftly forming along the longitudinal direction as the excavation face progresses. In contrast, soft rock tunnels display a more gradual damage progression, where the maximum damage variable often remains below 100%, and energy is primarily dissipated through crack propagation and extrusion deformation, leading to a broader range of energy dissipation and significant macro-level deformation, despite a lower longitudinal energy evolution rate. In practical engineering, energy-based analysis proves valuable for developing early warning systems and designing tailored measures to address diverse geotechnical hazards.

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The deterioration of the mechanical properties of rock mass in underground engineering due to energy dissipation and microfracture accumulation under cyclic loading and unloading (CLU) has become a hot research topic in recent years. In order to elucidate the relationship between energy dissipation and the dilation processes, an incremental CLU mode is proposed and employed in triaxial tests in this paper. First, the methods and the procedures of the test were proposed to enhance the success rate, and the triaxial tests under incremental CLU were performed at confining pressures ranging from 0 MPa to 50 MPa. Second, the damage variables were defined and calculated from the perspective of energy dissipation, and the relationships between the damage variables and the energy parameters, as well as principal strains (plastic strain and plastic shear strain) were analyzed in detail. Third, a two-parameter shear dilation angle model was established under different confining pressures. The results show that the failure mode is tensile failure in conventional uniaxial compression, and is X-type shear failure in the uniaxial test with incremental CLU, and is shear dilatation failure mode in the triaxial test with incremental CLU, due to volume dilatation and damage accumulation after significant energy dissipation. The energy dissipation rates for single loading and unloading showed a “U” shaped trend as the number of the CLU increased. The reason for this observation is that the energy dissipation rate is greater due to the particle compaction in the initial compaction stage and structural damage of rock material in failure stage. The dilation angle first experiences a nonlinear rapid increase to a certain peak value and then gradually decays, as the rock shear dilation and failure occur gradually with the accumulation and development of cracks.

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The structural stability of coal seam roof rock mass under dynamic load in engineering practice is directly influenced by the dynamic characteristics of weakly consolidated coal measures rock. A study was conducted on two types of rocks, mudstone and siltstone, around the roof of coal seam No. 31 in Renlou Coal Mine, northern Anhui Province. Rock-like specimens were created using similar materials for analysis. The mechanical properties, energy dissipation characteristics, and fractal characteristics of these rocks were investigated using a 75 mm Split Hopkinson Pressure Bar (SHPB) test system at five different impact velocities. The findings are as follows: 1) As the impact velocity increases, the strain rate of the rock linearly increases while the dynamic uniaxial compressive strength exponentially increases. 2) With an increase in strain rate, there is a negative correlation between rock fragmentation and a positive correlation with the number of fragments produced; additionally, the fractal dimension shows an increasing quadratic term function relationship. 3) There exists a linear positive correlation between incident energy and impact velocity; moreover, as incident energy increases, so does the amount of energy lost due to rock breakage. These research results provide both theoretical and experimental foundations for mine dynamic disaster protection.

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This paper explores the mechanisms of energy transfer and failure zones in rock mass blasting. By combining theoretical derivation with numerical simulation, we examine the deformation, failure features, and source parameters of rock subjected to spherical charge blasting. Using the Mohr–Coulomb yield criterion, we classify the rock failure process into four zones: the cavity zone, fracture zone, radial fracture zone, and vibration zone. Additionally, we establish a dynamic partitioned model that considers explosion cavity expansion, compression wave propagation, and energy dissipation. Applying elastic failure conditions, we develop a calculation model for vibration parameters in each zone and use MATLAB programming to find numerical solutions for the radius of the failure zone, elastic potential energy, and the interface pressure over time. Verification with a granite underground blasting project in Qingdao shows the ratio of the spherical cavity radius to the charge radius is 1.49, and the crushing zone radius to the charge radius is 2.85. Theoretical results are consistent with the approximate method in magnitude and value, confirming the model’s reliability. The interface pressure sharply peaks and then decays exponentially. The growth of the fracture zone depends heavily on initial pressure, rock strength, and Poisson’s ratio. These findings support blasting engineering design and seismic effect assessment.

In response to the common issue of instability and failure of weak interlayers under load in geotechnical engineering, a discrete element simulation study plan consisting of 25 schemes was designed, with the inclination and thickness of the interlayer as variables. Based on the test results from a universal testing machine, the weak interlayer and adjacent rock mass simulation parameters were calibrated. A Fish program was developed to monitor the evolution of cracks, the number of tension and shear cracks, block elastic strain energy, and tension and shear strain energy throughout the uniaxial compression process. This study reveals the influence of the inclination and thickness of the interlayer on the evolution of the "main rupture crack morphology—changes in the number of tension and shear cracks—energy accumulation and dissipation" under uniaxial compression conditions, as well as the interrelationship among these three factors. The results show that (1) when the interlayer thickness is the same, as interlayer inclination increases from 0° to 60°, the strength of the specimen decreases by 38%-40%. Elastic strain energy is positively correlated with the peak strength of the specimen. When interlayer inclination angles are 0°, 15°, 30°, and 45°, the number of shear cracks and shear strain energy stored in the contact do not change significantly. However, when the interlayer inclination is 60°, compared to the specimen with the interlayer inclination of 45°, the number of shear cracks in the specimen decreases by 24.01% to 48.28%, and shear strain energy decreases by 35.06% to 50.35%. (2) When the interlayer inclination is the same, as the interlayer thickness increases from 4 to 12mm, the strength of the specimen decreases by 6.49% to 22.02%. The specimen’s total tension cracks increase by 38.1% to 143.52%, while tension strain energy decreases by 13.04% to 40%. The number of shear cracks and shear strain energy fluctuates, with increases being positive and decreases being negative, with ranges of -7.65% to 26.02% and -11.33% to 24.55%, respectively. (3) Under the influence of different interlayer thicknesses and inclinations, the number of shear fractures and their energies are significantly higher than those of tension fractures, and shear failure is the main reason for the failure and instability of weakly cemented interlayered rock mass. The research results can provide a reference for predicting and evaluating rock and soil mass failure modes and designing reinforcement schemes for projects with weak interlayers.

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The stability of rock masses in karst regions is critically influenced by the coexistence of karst caves and joints. This study investigates the mechanical behavior, energy evolution, and failure modes of large-scale (1 m3) rock-like specimens containing a 30 cm karst cave and joints at varying positions and dip angles (α). The results indicate that joint dip angles between 30° and 60° define a critical strength deterioration zone, with the minimum peak strength (44 MPa, 24.1% lower than the 0° specimen) occurring at α = 60°. Side-positioned joints induced greater strength weakening than top-positioned ones. Energy analysis revealed that α significantly governs energy accumulation and dissipation; the elastic energy minimum was also observed at α = 60°. Specimens with side-positioned joints exhibited higher energy dissipation efficiency, promoting extensive crack propagation. The research results suggest that in engineering, are as with joints inclined at 30–60° should be avoided as much as possible, and the energy-dissipating capacity of near-vertical (~90°) joints should be utilized to enhance the stability of the rock mass in karst tunnel engineering.

In the study of high-stress deep-buried tunnels, the creep phenomenon of the surrounding rock significantly affects tunnel stability. To address this, this paper establishes a creep constitutive equation for rock masses anchored by bolts (RMAB). A comparison between numerical methods and theoretical solutions reveals a high degree of consistency between the two. The study shows that as the Ek value increases, the initial displacement of the surrounding rock grows significantly. However, once Ek reaches a certain level, the rate of displacement increase gradually decreases, and the system stabilizes. Additionally, as ηk increases, the displacement of the surrounding rock decreases significantly, enhancing the rock's energy dissipation capacity and effectively suppressing deformation. The findings of this research provide important theoretical support and reference for the design of bolted support systems in deep-buried tunnels, with practical engineering value.

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ABSTRACT Conventional borehole drilling, analogous to in-situ torsional shear tests, enables rock quality evaluation via drilling responses. This study applied digital drilling technology to test homogeneous materials and jointed rock masses, analyzing thrust, rotational speed, torque, and drilling rate. A specific energy index (SEI) was proposed to quantify rock jointing/intactness: 2.5–4.0 for intact rock, 1.5–2.5 for bulky rock mass, and <1.5 for severely broken/void-bearing rock. Derived via normalized rock unit cutting energy (with quadratic/thrust and logarithmic/speed correlations), SEI correlates with rock mass integrity to obtain RQD. Compared to traditional methods, this approach reduces artificial borehole logging biases, yielding more objective results. HIGHLIGHTS Novel Specific Energy Index (SEI) for rock mass integrity assessment. Quadratic and logarithmic relationships identified in rock cutting energy. Objective RQD determination reduces logging bias in geological drilling.

In deep underground engineering, it is inevitable that portions of the rock mass will be subjected to the erosion and chemical corrosion of infiltrating water. A comprehensive study of the physical, mechanical, and energetic properties of rocks after hydrochemical corrosion is crucial for ensuring the stability of the rock mass. The novelty of this research lies in the detailed investigation of the macroscopic and microscopic morphologies of rocks exposed to various corrosive solutions, as well as the changes in various physical and mechanical parameters. Utilizing the weighting method, a scientific comprehensive evaluation system for deep rocks after hydrochemical corrosion has been established. The results indicate a pronounced sensitivity of the macroscopic and microscopic morphologies to pH values. The longitudinal wave velocity of the corroded rock decreases obviously, with the maximum decrease being 13.46%. As the pH value decreases (from 7 to 3), the compressive strength, elastic modulus, cohesion, and internal friction angle of the rocks all decrease significantly. The acidity of the solution significantly aects the changes in the three types of strain energy of the rocks, with higher acidity leading to weaker energy storage capability. Among the factors influencing the characteristics of strain energy variation in rocks, confining pressure has a higher priority than pH value. This study precisely evaluates the impact of hydrochemical corrosion on rock damage using a percentage-based scoring system, and found that granite’s score dropped from 81 to 16. The research findings provide valuable insights for the evaluation of rock mass stability under hydrochemical corrosion conditions.

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Studies of the spatial and temporal patterns of seismic activity development in the undermined rock mass have been performed at the Rasvumchorr Mine. The main cluster associated with generation of rock caving in the overhang part has been identified. It is established that caving was developing gradually from the depth of the rock mass towards the surface. The results are presented of estimating the quantitative parameters of the seismic process in the undermined rock stratum, i.e. the energy index and the cumulative apparent volume, which reflect the stress changes in the rock mass. Ranges of the stable state of the rock mass, when the overhang rocks do not cave, as well as the ranges of active fracturing and caving of the overhang rocks have been identified. Changes in these parameters for the studied area of the deposit reflect the loading and strength degradation stages in the rock mass. The results of this study correlate well with the data on actual caving of the undermined rock strata. This work is a continuation of the authors' research into the problem of identifying spatial and temporal patterns in the development of undermined rock strata cavings in the tectonically stressed Khibiny massif.

As the key indicators to evaluate drilling efficiency, mechanical rate of penetration (ROP) and mechanical specific energy (MSE) are affected by many uncertain factors. In the actual drilling process, it is often necessary to adjust the parameters to achieve speed and efficiency. A dual-objective model is established considering the maximization of ROP and the minimization of MSE. Which combined with the theory of mechanical specific energy and the principle of multi-objective optimization, the model parameter weights are determined by the feature importance in the random forest regression model, and the value range of rock breaking parameter is optimized, realize the fusion of physical model and data model. The results show that, in the four strata of well X, the average ROP of T2k1 stratum is increased by 48.6% and the average MSE is decreased by 26.6%, the average ROP of T1b3 stratum is increased by 89.9% and the average MSE is decreased by 33.8%, the average ROP of the T1b2 stratum was increased by 41.3% and the average MSE was decreased by 39.0%, the average ROP of the T1b1 stratum was increased by 29.2% and the average MSE was decreased by 37.3%, which met the dual objectives of maximizing the ROP and minimizing the MSE. Compared with the traditional single-objective optimization method, the established dual-objective model is more in line with the needs of complex drilling engineering, and the fusion of physical model and data model can reduce certain human error.

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The mechanical rock-crushing efficiency is directly influenced by rock properties and joint structure. Tipped-hob is widely used in the construction of shafts. By analyzing the motion of tipped-hob and the mechanical properties of granite and sandstone, numerical rock samples with different mechanical properties were built to investigate the influences of rock properties and joint structure on rock-crushing efficiency using a single ring of tipped cutter. The results revealed correlations between compressive strength, tensile strength, hardness, brittleness, specific energy consumption, and the vibration of thrusting forces. It was suggested that the spacing, dip angle, and continuity of joints have a significant impact on the failure patterns and crack propagation in the process of rock fragmentation, as well as on the vibration frequency and amplitude of breaking-force of cutter and the specific energy consumption. This research is crucial for controlling the stability of drilling machine during shaft sinking by drilling method.

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Large-diameter pressure relief boreholes are one of the primary measures for preventing coal mine rockburst. However, the implementation of these boreholes disrupts the original support structure of the roadway surrounding rock, leading to conflicts with surrounding rock control. Therefore, the pressure relief and energy dissipation behavior of variable-diameter boreholes in roadway surrounding rock was studied. Using a typical rockburst-prone coal mine as the engineering background. Based on elastic–plastic mechanics theory, the elastic solution for the stress distribution around the borehole and the extent of the pressure relief zone are analyzed. Numerical simulation software was used to study the effects of variable diameter drilling parameters (deep reaming diameter, deep reaming depth, and deep reaming spacing) on the pressure relief of roadway surrounding rock, energy dissipation in the roadway, and roadway deformation. The research results indicate that the distribution range of the pressure relief zone is influenced by the vertical stress, lateral pressure coefficient, cohesion, and internal friction angle of the coal body. The maximum radius of the pressure relief zone increases with the borehole diameter. As the deep reaming diameter increases and the borehole spacing decreases, the stress concentration in the surrounding rock of the roadway shifts more significantly toward the deeper region, making it easier to form a dual-peak stress zone. This enhances the pressure relief and stress transfer effect on the surrounding rock of the roadway, leading to greater energy dissipation. From the perspective of energy dissipation, it is concluded that the optimal location for the variable-diameter borehole should be within the peak vertical stress zone of the surrounding rock that has not been relieved. This study provides guidance for the prevention and control of dynamic disasters in deep coal and rock.

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An in-depth understanding of the pre-peak mechanical damage and energy-evolution characteristics of typical hard-rock in a diversion tunnel under cyclic load is of great significance to promote the safe and efficient construction of the diversion tunnel and the stability of surrounding rock. To study the pre-peak mechanical characteristics and the competition mechanism between energy storage and energy dissipation of typical hard-rock in a diversion tunnel under cyclic loading-unloading, combined with the internal drilling and blasting excavation of the actual engineering rock mass and the external vehicle cyclic load environment of the diversion tunnel, the cyclic loadingunloading tests of typical granite and tuff in diversion tunnel were carried out. Based on the analysis principle of mechanics and energy, the strain variables, modulus variables, energy variables and damage variables of granite and tuff under cyclic loading-unloading test were defined. The cyclic mechanical properties and energyevolution characteristics of granite and tuff under pre-peak load were analyzed. The competition mechanism between pre-peak energy storage and pre-peak energy dissipation of granite and tuff and the evolution law of strain damage variable and energy damage variable were revealed. The selection principle of rock sample size and the limitation of the test scheme were further discussed. The study of the damage evolution of rocks close to failure (pre-peak stage) under cyclic load is helpful to better understand the damage and failure mechanism of rocks in practical engineering problems. Keywords: Diversion tunnel, Cyclic loading-unloading, Granite/Tuff, Blasting cyclic load, Energy evolution.

Rock engineering achieves the secondary stress balance through rock mass structure adjustment, where energy conversion is throughout and associated closely with rock deformation and damage. In this study, a series of triaxial compression tests were conducted on red sandstone to investigate these features. The results showed that the damage state of red sandstone specimens presented five stages under different confining pressure, corresponding to the multistage evolution characteristic of the energy conversion. In the case of the dissipation energy conversion ratio (η), it showed five stages: a gradual increase, decreasing gradually and reaching a minimum value, increasing gradually, increasing with growth rate, and accelerated growth, therein the strong nonlinearity reflected the stability and instability of the internal structure of the rock and had the basic characteristics of the mutation theory, therefore the damage state warning model was established on just that. The relation between the η and time fitted by a four‐rank potential function had a fitting parameter (R2) larger than 0.9, and the bifurcation set of the η calculated by the damage state warning model had twice stages less than 0. The second stage, which occurred near the minimum value of the η and run through the plastic deformation stage, could be used to predict rock damage and fracture, and it was proven feasible by acoustic emission (AE) precursor and better than AE warning. This research can enrich the methods for identifying rock damage state and provide reference for revealing the occurrence and development mechanism of various rock instability disasters.

In order to investigate the mechanical properties and energy evolution patterns of composite rock masses with structural planes of different inclinations, this study selected composite rock samples made from coal and sandstone, with structural plane inclinations of 0°, 30°, 45°, 60°, and 90°. Uniaxial compression tests were conducted, and energy theory was applied to analyze the energy transformation characteristics during the deformation and failure process. The results show that the structural plane inclination significantly influences the compressive strength, peak strain, and elastic modulus of the composite rock masses. The compressive strength exhibits a “U-shaped” trend, first decreasing and then increasing, with the minimum at 45° and the maximum at 90°. The peak strain decreases monotonically as the angle increases, while the elastic modulus increases exponentially. The energy evolution process can be divided into four stages: compaction, elastic deformation, plastic deformation, and failure. The total peak strain energy and elastic energy percentages exhibit a pattern of first decreasing and then increasing with changes in the inclination angle. A piecewise damage constitutive model considering the compaction stage was established based on the experimental results. The model curve aligns well with the experimental data and can accurately characterize the stress-strain evolution characteristics of composite rock masses with structural planes of different inclinations. The findings of this study provide theoretical insights for disaster prevention and control in deep mines, as well as the stability analysis of composite rock masses.

Current computer techniques provide new modern utilization and approaches in processes that have not been used. One of such possibilities is a design of models for optimization of rock excavation process. The qualities of the model derived from conventional energy theory of rock drilling are compared to the qualities of non-standard model obtained by scanning of the acoustic signal as an accompanying effect of environment in the rock drilling process. The paper focuses on the signal energy, as one of type energy transformed by rock drilling process. The acoustic signal was registered on the laboratory drilling stand at the Institute of Geotechnics SAS in Košice.

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This study focuses on tunnel construction in fault fracture zones and systematically investigates the energy evolution and damage catastrophe mechanisms of surrounding rock during excavation, based on energy conservation principles and cusp catastrophe theory. A tunnel instability prediction and support optimization framework integrating energy damage evolution and intelligent optimization algorithms was developed. Field tests, rock mechanics experiments, and Discrete Fracture Network (DFN) numerical simulations reveal the intrinsic relationships among energy input, dissipation, damage accumulation, and instability under complex geological conditions. Particle Swarm Optimization–Back Propagation (PSO-BP) is applied to optimize tunnel support parameters. Model performance is evaluated using the Mean Absolute Error (MAE), Mean Squared Error (MSE), Mean Absolute Percentage Error (MAPE), and R-squared (R2). The results show that upon reaching structural mutation zones, the system damage variable (ds), displacement, and dissipated energy increase abruptly, indicating critical instability. Numerical simulation and catastrophe feature analysis demonstrate that energy-related damage accumulation is effectively suppressed, the system damage variable decreases significantly, and crown stability is greatly enhanced. These findings provide a theoretical basis and practical reference for optimizing tunnel support design and controlling instability risks in complex geological settings.

The measurement-while-drilling (MWD) method of roof bolter plays an important role in characterizing the structure of roadway roof, especially the soft hard relationship of rock layers. One of a key factor for the MWD method of roof bolter is to ensure the accuracy of monitoring, which greatly depends on the optimized selection and matching of indexes. Therefore, this study first analyzed the source of monitoring indexes data to see how they relate to normal distribution, and then evaluated their reliability for subsequent feedback. After that, the receiver operating characteristics (ROC) quantitative calculation and analysis method was used to obtain the specific accuracy values of some commonly used individual indexes and the comprehensive index of specific energy. The quantitative results showed that the performances of individual thrust and torque indexes were relatively excellent, and unexpectedly exceeded that of the comprehensive index of specific energy. The research results have important reference value for the subsequent selection of MWD indexes for roof bolter. It is necessary to use indexes with better feedback results to comprehensively reflect the medium, and to furthermore improve the accuracy of feedback.

There are a large number of tunnel projects in the construction of national infrastructure. The water and mud inrush disaster of the tunnel seriously limits the construction process. Due to the unclear geological body in front of the tunnel face and the fact that the survey data can not completely and accurately reflect the geological situation in front of the construction, it brings great blindness to the on-site construction. Therefore, unpredictable geological disasters often occur, including sudden collapse, water and mud inrush Rock burst and harmful gas, the engineering disasters caused by tunnel excavation are non selective, diversified, difficult to treat and sudden. In view of the above problems, this paper puts forward the fine identification method of tunnel geological digital drilling, explores the relevant skillful indicators between dip parameters and formation information as the main line, takes the drillability index, drilling energy and drilling parameter data as the core, and based on the setting up of parameter acquisition system and data conversion, so as to realize the identification of formation interface, identification of adverse geological bodies and classification of surrounding rock, It has been f tested and applied in engineering practice, and a series of innovative research results have been obtained. This paper studies how to strengthen the application basis of artificial neural network technology and improve its practicability in system modeling, calculation and prediction, especially in tunnel geological calculation and prediction.

Investigative drilling (ID) is a modern measurement while drilling (MWD) technique that has been effectively used in site investigations for several long corridor projects in Australia. The drilling data collected through the ID method has provided clients with valuable in situ strata verification for earthworks and footings. However, the use of drilling data from ID has been primarily qualitative. This paper presents a preliminary assessment of the ID method’s potential for quantitative site characterisation through case studies involving soils and rocks. Comparative analysis with conventional boreholes demonstrates that ID data provides significant insights into ground conditions and can be used to characterise soil and rock properties. Specifically, the penetration rate, as a single drilling parameter, proves effective in identifying rock fractures, while compound indices such as the soil-rock resistance, Somerton index, and drilling energy correlate with the standard penetration test (SPT) values and rock strength. Despite the promising results, further rigorous testing is necessary to validate these findings, given the inherent uncertainties in subsurface conditions and conventional testing results.

Measurement While Drilling technology (MWD) is a technique used to monitor and record the mechanical response of a drilling system. The measured parameters in geotechnical engineering typically include down pressure, torque, rotation speed, and penetration rate. These drilling parameters can then be combined using different physics-based or empirical equations to form compound parameters. One of the goals of MWD technology is to use these combined parameters for subsurface characterization and correlate the combined parameters to different engineering and index properties of the subsurface material. These correlations depend on the drilling rig type, the drilling operational procedure, and the geomaterial type (geology). In this study, the results of the MWD data from four different boreholes (drilled using a mud rotary method with tricone bits) in the state of Nebraska, USA were used to investigate the correlations between different compound parameters and SPT-N values. The soils encountered in these boreholes were low-plasticity and high-plasticity silts and clays.  Specific energy (), drillability (), Somerton index (), soil-rock resistance (, alteration index (AI). The results showed that there are good correlations between these compound parameters and the SPT-N values. The main challenges in developing these correlations included preprocessing the data, dealing with the SPT refusal tests, correcting the SPT values for overburden pressure, and choosing the correct interval for calculating the average compound parameters. All these challenges and the solutions to overcome them are discussed in detail in this paper.

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Abstract The anisotropic characteristics of rock have important value for construction safety and evaluation of rock properties. The purpose of this article is to study the variation law of drilling parameters in different rocks and their anisotropy characteristics. This article investigates drilling characteristics by conducting digital drilling experiments on six different types of rocks in three different directions. The variation law of drilling parameters (drilling speed, torque, rotational speed, thrust force) and the special energy with drilling depth are analyzed as well as the anisotropy variation of six types of rocks. The influence of anisotropy on the specific energy of six types of rocks is investigated. A special energy index f is proposed to characterize the anisotropy for evaluating different rocks. The test results show that the anisotropy of granite, slate, gneiss, red sandstone, argillaceous sandstone, and sandstone is weakened accordingly by using the special energy index f. The specific energy index after data normalization can better judge the anisotropy difference for different rocks, such as granite, slate, gneiss, and red sandstone.

Discontinuous structures in coal mine roadway roofs, such as rock interfaces and joint fractures, are critical factors leading to surrounding rock instability. The use of Measurement While Drilling (MWD) technology to identify geological formations has become a growing trend. However, there is still a lack of rock structure recognition methods that offer high accuracy, efficiency, and strong generalizability. Therefore, this study acquired four drilling parameters including thrust, torque, modulation specific energy (SEM), and rock drillability assessment (RDA) through drilling experiments. By leveraging the Bayes algorithm, which has high precision, efficiency, and low cost, a change point detection model for drilling parameters was established, and a multi-parameter fusion criterion was proposed for identifying rock structures. The results show that for single rock interface identification, the errors of thrust, torque, SEM, and RDA were 13.3 mm, 4.6 mm, 4.4 mm, and 18.3 mm, respectively. For multiple rock interface identification, the recognition rates were 83.3%, 100.0%, 66.7%, and 83.3%, respectively. Moreover, the absolute value of the magnitude index (SLP) at the interface location was generally the highest among all change points. In multi-change-point detection, the SLP threshold should be set at ± 0.2. It is worth noting that the SLP value is correlated with data fluctuation intensity; greater fluctuation leads to higher SLP values at change points. This study contributes significantly to enabling intelligent perception of rock structures and improving the quality of rock mass control.

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Catastrophic dynamic rock failure is one of the most challenging problems existing in the fields of civil tunneling and mining. It occurs in complex environments of geology, stress and excavation, and there is no one set of circumstances that is responsible for the phenomenon. However, a major contributing factor is believed to be energy storage and release. This paper studies and quantifies the energy release concept to advance the understanding and control of dynamic rock failures. The impacts of energy sources within rock masses on dynamic rock failures are assessed. The energy sources include strain and potential energy, the pressure energy of free and adsorbed gas and radiated seismic energy related to rock fracture or faulting. A new time-based coupled model is developed to estimate the ejection velocity when dynamic rock failures occur. Two burst scenarios are demonstrated using the proposed coupled model, i.e., a burst in the development heading of an unsupported face, and a ribside burst in a supported rib. The coupled model results show the superiority of bolts with a capacity for greater plastic elongation. Conveniently from the design perspective, maximum mesh tension is governed entirely by bolt capacity and mesh rupture strain. In addition, a rockburst hazard classification is proposed by examining a broad range of studies conducted in various disciplines to classify the relationship between injury severity and impact velocities. The hazard profile of dynamic rock failures caused by various mine layouts, structural domains, gas environments and geological sequences can then be estimated on the basis of the quantitative analysis. The energies within rock masses contributing to dynamic rock failures are quantitatively assessed. A new time-based coupled model was proposed to estimate the ejection velocity in coal faces considering energy components involved in dynamic rock failures. The interactions between ground support elements and the surrounding rock mass are examined in the time-based explicit coupled model. The hazard profile of dynamic rock failures can be estimated on the basis of the quantitative analysis. The energies within rock masses contributing to dynamic rock failures are quantitatively assessed. A new time-based coupled model was proposed to estimate the ejection velocity in coal faces considering energy components involved in dynamic rock failures. The interactions between ground support elements and the surrounding rock mass are examined in the time-based explicit coupled model. The hazard profile of dynamic rock failures can be estimated on the basis of the quantitative analysis.

Rockburst disasters in deep-buried roadways significantly threaten mine safety. To uncover the evolutionary laws of energy zoning, this paper employs analytical theory and numerical modeling to investigate the static distribution characteristics and dynamic energy evolution in deep-buried roadway surrounding rock. The near-field energy storage model for roadways is established, and the large-diameter drillhole pressure relief measures based on energy zoning is designed. The results are as follows: (1) After the formation of deep-buried roadways, the roof on both sides and the coal mass of the elastic zone in the deep region became energy storage zones, while the coal mass in the shallow plastic area became energy release zones. Rockbursts release stored elastic energy, causing crack propagation and kinetic energy transfer. (2) The surrounding rock was divided into release, transitional, and energy storage zones during roadway excavation. Exceeding energy storage limits triggered the instantaneous release of elastic energy, leading to rockbursts. (3) The large-diameter pressure relief drillhole parameters designed based on the energy zoning range of roadway surrounding rock can effectively destroy the energy storage zone of roadway surrounding rock, improve the safety of working face mining, and have important engineering guiding significance for rock burst prevention.

To reveal the rock burst mechanism, the stress and failure characteristics of coal-rock strata under different advancing speeds of mining working face were explored by theoretical analysis, simulation, and engineering monitoring. The relationship between energy accumulation and release was analyzed, and a reasonable mining speed according to specific projects was recommended. The theoretical analysis shows that as the mining speed increases from 4 to 15 m/d, the rheological coefficient of coal mass ranges from 0.9 to 0.4, and the elastic energy of coal mass accumulation varies from 100 to 900 kJ. Based on the simulation, there is a critical advancing speed, the iteration numbers of simulation are less than 15,000 per mining 10 m coal seam, the overburden structure is obvious, the abutment pressure in coal mass is large, and the accumulated energy is large, which is easy to cause strong rock burst. When the iteration number is greater than 15,000, the static force of coal mass increases slightly, but there is no obvious rock burst. Based on engineering monitoring, the mining speed of a mine is less than 8 m/d, and the periodic weighting distance is about 17 m; as the mining speed is greater than 10 m/d, and the periodic weighting distance is greater than 20 m; as the mining speed is 3–8 m/d, and the range of high stress in surrounding rock is 48 m; as the advancing speed is 8–12 m/d, and the high-stress range in surrounding rock is 80 m. Moreover, as the mining speed is less than 8 cut cycles, the micro seismic energy is less than 10,000 J; as the mining speed is 12 cut cycles, the micro-seismic energy is about 20,000 J. In summary, the advancing speed is positively correlated with the micro seismic event; as the mining speed increases, the accumulated elastic energy of surrounding rock is greater, which is easy to cause rock burst. The comprehensive analysis indicates the daily advance speed of the mine is not more than 12 cut cycles.

When tunnels in underground hard rock mines experience strainbursts, the effective shape of the tunnel suddenly changes as part of the rock fails, notches form and the broken rock bulks inside the strainburst volume. For circular tunnels, this dynamic rupture and bulking process causes a shape change with associated displacements and velocities in the surrounding elastic rockmass and at the excavation walls. This process can be approximated for circular tunnel bursting in elastic rock by a shape change from circular to elliptical and Maugi’s solution [1] can be adapted to estimate related displacements and average ground velocities. If these velocities are imposed on a volume of rock or shotcrete with a given mass, the mass can be ejected, and the corresponding kinetic energy can be estimated. When combined with the sudden bulking of the fractured rock, displacements and velocities are magnified between the elliptical shape and the pre-burst (circular) shape of the tunnel. This study focuses on the effect of the combined excavation response with elastic and bulking deformations to assess frequently observed excavation damage processes involving ‘shotcrete rain’ and heave of floor slabs caused by these shape changes. An analytical solution is presented for circular tunnels to estimate the elastic and bulking displacements, the resulting velocities, and energy demands.

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Fractured rock masses are susceptible to stress-induced disturbances, which can lead to severe geological disasters. In recent years, the shear deformation and failure characteristics of fractured rock under cyclic shear loading have become a frontier issue in rock mechanics and engineering. A thorough understanding of the failure mechanism of fractured rock masses is of great significance for the scientific evaluation of their long-term stability in engineering applications. In this study, experiments were conducted on marble specimens with artificial fractures under constant normal stress using the RDS-200 rock mechanics shear test system. The results reveal the following three key findings: First, the residual shear displacement increases linearly with cycling numbers, and the fractures demonstrate memory functions under pre-peak tiered cyclic shear loading, with shear displacement exhibiting hysteresis effects. Second, significant differences were observed between tiered cyclic shear (TCS) and direct shear test (DST) outcomes in terms of peak shear stress and failure patterns. The peak shear strength under TCS was 17.76–24.04% lower than under DST, with the strength-weakening effect increasing with normal stress. The fracture surfaces showed more severe damage and debris accumulation under TCS compared to DST, with the contour area ratio decline rate correlating with both normal stress and initial surface conditions. Third, energy evolution analysis indicates that as cyclic shear stress increases, the elastic energy release rate exceeds the dissipation rate, and the elastic energy index progressively rises through the loading cycles. The findings of this research contribute to a better understanding of the shear instability of rock fractures under pre-peak tiered cyclic shear loading with constant normal stress.

Understanding the brittle fracture behavior of rock is crucial for engineering and Earth science. In this paper, based on acoustic emission (AE) and laser Doppler vibration (LDV) monitoring technology, the staged damage behaviors of rock-like materials with different brittleness degrees under uniaxial compression are studied via multiple parameters. The results show that the brittleness degree determines the fracture mode. As the specimen’s brittleness degree increases, the tensile failure increases and shear failure decreases. AE activity is enhanced at the crack damage point. With an increasing specimen brittleness degree, different instability precursor information is shown during the unstable crack growth stage: the AE b value changes from the fluctuating to continuously decreasing state, and the natural frequency changes from the stable fluctuation to upward fluctuation state. The AE b value near the stress drop is the smallest, and it decreases with an increasing brittleness degree. The natural frequency reduction indicates the rock-like fracture. The natural frequency is a symbolic index that reflects staged damage characteristics and predicts the amount of energy released by brittle failure. These findings provide guidelines for rock stability monitoring and provide support for better responses to stability evaluations of rock slopes, rock collapses, and tunnel surrounding rock in engineering.

In order to better apply the drilling method to underground mines, rock drillability classification and identification in situ by drilling process monitoring technology is a convenient and effective method to achieve the rock mass drillability. In this study, a database was established based on 188 groups of drilling parameters, drillability parameters and rock mechanics parameters. By analyzing the correlation between mechanical parameters and drillability parameters, rock drillability was classified using the TOPSIS-RMR method. Then, drilling force (F), torque (T), rotation speed (N), rate of penetration (V), specific energy (SE) and drillability index (Id) were used as machine learning input variables to predict drillability grades. Finally, the machine learning classification models include SVM, ELM, BPNN, RBF, RF and LSTM are compared to select the optimal model. The efforts and results can be used to evaluate the rock mass drillability and provide support for the design optimization of drilling and blasting method. It can effectively protect the safety and improve efficiency of underground mining.

This paper proposes a formation hardness grading method based on a coupled axial-torsional dynamic model of the drill-string. Initially, the bit-rock interaction parameters were identified through genetic algorithms using the coupled dynamic model, obtaining mechanical characteristics of the drilled formations (including the Coulomb friction coefficient and intrinsic specific energy). By integrating these parameters with uniaxial compressive strength-based rock hardness criteria, a weighted fusion evaluation system was established. The method was validated using field drilling data collected from coal mine tunnel operations, with experimental results demonstrating that the proposed hardness classification model achieves superior accuracy in characterizing formation hardness.

Drilling is one of the most important and expensive geological survey processes. The wear of drill bits is closely related to the specific energy that expresses the energy consumption of the drilling process and significantly affects the total cost of drilling. In this article, the correlation between the wear intensity and the specific energy was examined. For the purpose of obtaining the necessary information, a series of experiments were performed on a horizontal laboratory drilling rig with the use of 8 types of rocks and 5 diamond-impregnated small-diameter core drill bits with synthetic diamonds of various qualities. The selected drilling mode was the mode with a constant rotation speed and an increasing thrust force. Results of the experimental measurements indicated that relatively high rotation speeds were preferred for the tested drill bits for the purpose of efficient drilling. The lowest amount of the specific energy required for drilling was observed for sandstone and andesite, i.e. the rocks in which radial cracks were formed around the chipped-off crater during the drilling. A simple linear regression between the intensity of wear of the drill bits and the specific energy was found. The evaluation of the results of this experimental research also showed that the quality of the used diamonds significantly affected the wear intensity.

Rock-breaking specific energy model of bit is the key foundation of evaluation and optimization of downhole drilling condition, while some necessary parameters for the existing models is difficult to measure directly while drilling. Aiming to improve the accessibility and accuracy of the model, this study proposes and illustrates an improved method by combining field tests and logging while drilling. The improved model was used to distinguish the inefficient drilling conditions and then to optimize drilling parameters. The results of application cases show that, the necessary parameters for the improved model could be obtained in time and the improved model helps to distinguish the reasons of stick–slip, whirling, load transfer difficulties in different horizontal wells. Based on the proposed model, the drilling parameters were evaluated and optimized, and then the rate of penetration get improved by 90.5% with higher energy efficiency. The proposed model and method could facilitate to realize automated and intelligent drilling. An improved rock-breaking specific energy model is presented to evaluate and optimize the drilling efficiency. This model could also facilitate to optimize drilling parameters and select better drilling technology and bit. The model lays some foundation for intelligent drilling. An improved rock-breaking specific energy model is presented to evaluate and optimize the drilling efficiency. This model could also facilitate to optimize drilling parameters and select better drilling technology and bit. The model lays some foundation for intelligent drilling.

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As oil and gas exploration progresses to ultradeep and 10 000-m depths, insufficient energy supply during rock breaking by downhole polycrystalline diamond compact (PDC) bits presents a critical challenge. Quantifying the energy consumed in PDC cutter/rock interactions is therefore essential for enhancing bit efficiency and minimizing nonproductive energy losses during drilling. Consequently, for this study, we analyzed and calculated the mechanical work and energy consumption associated with cutter/rock interactions in the rock-cutting process of PDC cutter. First, through indoor single-cutter rock-cutting experiments and methods such as high-speed camera real-time observation and 3D morphology analysis of cuttings, the single-cutter rock-cutting mechanism was revealed, and the pivotal role of the rock crushing zone ahead of the cutter in force transmission during single-cutter cutting was clarified. Based on the rock-cutting mechanism, an improved calculation model for rock-cutting mechanical specific energy (MSE) during single-cutter rock cutting was derived, which comprehensively considered the essential force interactions of PDC cutters. Furthermore, starting from the principle of MSE calculation for full-scale drill bits, the same calculation result was derived, achieving mutual validation between the rock-cutting mechanism and mathematical derivation. Finally, the effectiveness of the improved rock-cutting energy calculation model in evaluating the efficiency of single planar cutters and the rate of penetration (ROP) of full-scale drill bits was verified through indoor single-cutter cutting experiments and full-scale bit rock-breaking experiments using two planar cutter profiles. The findings of this work are of significant reference value for the rational application of PDC bits and technological innovation in ROP improvement.

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Axial–torsional coupled impact drilling (ATCID) technology represents a promising solution for overcoming the drilling challenges posed by conglomerate formations, which are characterized by strong heterogeneity, high abrasiveness, and poor drillability. However, the optimal parameter matching relationships and their influence patterns on mechanical specific energy (MSE) remain unclear. This study employed self-developed true triaxial impact rotary rock breaking equipment with conglomerate cores from the Junggar Basin to systematically investigate the effects of weight on bit (WOB), rotational speed (RPM), axial impact frequency, and torsional impact frequency on MSE through orthogonal experimental design. The results demonstrate that the parameter influence ranking on MSE is as follows: torsional impact frequency > WOB > RPM > axial impact frequency, with torsional impact frequency exhibiting the largest range value (87.5 MPa). ANOVA reveals that the interaction between axial and torsional impact frequencies is the dominant controlling factor, contributing 22.8% to MSE variation with high statistical significance. The optimal parameter combination yields the minimum MSE (103 MPa): 19 kN WOB, 20 r/min RPM, 20 Hz axial impact frequency, and 20 Hz torsional impact frequency, representing a 69.1% reduction compared to the maximum value. Response surface analysis revealed that increasing WOB significantly reduces MSE, RPM exhibits positive correlation with MSE, and synergistic effects occur when both impact frequencies reach high values simultaneously. A nonlinear MSE prediction model incorporating main effects, quadratic terms, and interaction effects was established with R2 = 0.8240 and a mean absolute percentage error of 9.26%. The research findings provide an essential theoretical foundation for parameter optimization and engineering applications of ATCID technology, offering significant implications for enhancing drilling efficiency in conglomerate and other challenging hard rock formations.

In the present research, two real-time rock strength determination models based on the drilling parameters were studied. Firstly, a discrete element software named Particle Flow Code in 2 Dimensions (PFC2D) was used to analyze the applicability of rock drillability index and drilling specific energy, in which graded particle assemblies were created to simulate the rock behaviour. In the numerical models, Weibull distribution was used to randomize the bonds between particles and make the assembled rock model with different heterogeneity. The drilling process of a PDC (polycrystalline diamond compact) cutter was modelled in two steps: horizontal linear rock cutting and vertical pressing-in progress. From the horizontal linear rock cutting process, the peak cutting forces were obtained and vertical pressing-in process outputs the relationship between normal force and cutting depth. Subsequently, the methods for calculating rock drillability index and drilling specific energy were proposed in the discrete element model. Then, the relationship between the calculated indexes and rock strength was investigated (supported with the regression analysis). Moreover, the effect of rock heterogeneity, along with error comparison between the above two indexes, were discussed. The results showed that the rock drillability index is more accurate than drilling specific energy in rock strength assessment (The error is about 10% smaller).

During the drilling process of the top rock layer with a roof bolter, monitoring certain resultant signals can provide feedback on different rock lithology and thickness parameters of the roof, which can optimize support parameters and evaluate the risk of roof fall. This study analyzed and studied the complexity feedback degree of individual indexes (thrust, torque, and propulsion speed) and specific energy index for revealing different rocks while maintaining a certain rotation rate in order to provide basic data reference and obtain more optimized feedback indexes for measurement-while-drilling (MWD) technology of roof bolter. More importantly, the study analyzed and discussed the composition and feedback degree of torque energy and thrust energy in the specific energy index based on measured feedback level analysis. The results showed that the feedback of torque energy was relatively better, and its weight for indicator contribution should be increased, which can provide a basis for optimizing the specific energy index in the later stage.

Current rock engineering design in drill and blast tunnelling primarily relies on engineers' observational assessments. Measure While Drilling (MWD) data, a high-resolution sensor dataset collected during tunnel excavation, is underutilised, mainly serving for geological visualisation. This study aims to automate the translation of MWD data into actionable metrics for rock engineering. It seeks to link data to specific engineering actions, thus providing critical decision support for geological challenges ahead of the tunnel face. Leveraging a large and geologically diverse dataset of 500,000 drillholes from 15 tunnels, the research introduces models for accurate rock mass quality classification in a real-world tunnelling context. Both conventional machine learning and image-based deep learning are explored to classify MWD data into Q-classes and Q-values, examples of metrics describing the stability of the rock mass, using both tabular and image data. The results indicate that the K-nearest neighbours algorithm in an ensemble with tree-based models using tabular data, effectively classifies rock mass quality. It achieves a cross-validated balanced accuracy of 0.86 in classifying rock mass into the Q-classes A, B, C, D, E1, E2, and 0.95 for a binary classification with E versus the rest. Classification using a CNN with MWD-images for each blasting round resulted in a balanced accuracy of 0.82 for binary classification. Regressing the Q-value from tabular MWD-data achieved cross-validated R2 and MSE scores of 0.80 and 0.18 for a similar ensemble model as in classification. High performance in regression and classification boosts confidence in automated rock mass assessment. Applying advanced modelling on a unique dataset demonstrates MWD data's value in improving rock mass classification accuracy and advancing data-driven rock engineering design, reducing manual intervention.

The geomechanical characteristics of a drill formation are uncontrollable factors that are crucial to determining the optimal controllable parameters for a drilling operation. In the present study, data collected in wells drilled in the Marun oilfield of southwestern Iran were used to develop adaptive network-based fuzzy inference system (ANFIS) models of geomechanical parameters. The drilling specific energy (DSE) of the formation was calculated using drilling parameters such as weight-on-bit (WOB), rate of penetration (ROP), rotational speed of drilling string (RPM), torque, bit section area, bit hydraulic factor, and bit hydraulic power. A stationary wavelet transform was subsequently used to decompose the DSE signal to the fourth level. The approximation values and details of each level served as inputs for ANFIS models using particle swarm optimization (PSO) algorithm and genetic algorithm (GA). As model outputs, the Young’s Modulus, uniaxial compressive strength (UCS), cohesion coefficient, Poisson’s ratio, and internal friction angle were compared to the geomechanical parameters obtained from petrophysical logs using laboratory-developed empirical relationships. Both models predicted the Young’s modulus, UCS, and cohesion coefficient with high accuracy, but lacked accuracy in predicting the internal friction angle and Poisson’s ratio. The root mean square error (RMSE) and determination coefficient (R2) were lower for the ANFIS-PSO model than for the ANFIS-GA model, indicating that the ANFIS-PSO model presents higher accuracy and better generalization capability than the ANFIS-GA model. As drilling parameters are readily available, the proposed method can provide valuable information for strategizing a drilling operation in the absence of petrophysical logs.

The precise detection of stratum interfaces holds significant importance in geological discontinuity recognition and roadway support optimization. In this study, the model for locating rock interfaces through change point detection was proposed, and a drilling test on composite strength mortar specimens was conducted. With the logistic function and the particle swarm optimization algorithm, the drilling specific energy was modulated to detect the stratum interface. The results indicate that the drilling specific energy after the modulation of the logistic function showed a good anti-interference quality under stable drilling and sensitivity under interface drilling, and its average recognition error was 2.83 mm, which was lower than the error of 6.56 mm before modulation. The particle swarm optimization algorithm facilitated the adaptive matching of drive parameters to drilling data features, yielding a substantial 50.88% decrease in the recognition error rate. This study contributes to enhancing the perception accuracy of stratum interfaces and eliminating the potential danger of roof collapse.

The Mechanical Specific Energy (MSE) model is used widely in the drilling industry. However, its use has been questioned in a two-part series in the SPE-IADC Drilling Conference, "Mechanical Specific Energy (MSE): Claims and Implications – Facts, Fallacies, and Pitfalls" (Samuel and Mensa-Wilmot, 2023 SPE 212508, 2024 SPE 217727). This paper will independently develop the theory of the MSE, leading to an improved understanding and an appraisal of the conclusions in the two papers. This paper develops the theory underlying the MSE from fundamentals and explains its applications and constraints. The theoretical development uses the concept of instantaneous mechanical power, which it transitions to drilling energy and then to drilling energy per a specific volume of rock, the MSE. The development pays particular attention to physical units. Of special interest is the relationship of the MSE to rock parameters, and its use in defining mechanical efficiency, and limits, of the drill bit. The paper further examines the validity of the Samuel and Mensa-Wilmot claims. The MSE is a valid method for describing the amount of energy delivered by the drilling system to the drill bit to destroy rock. It is calculated as specific to a certain volume of rock, which in physics relates to the strain energy density (SED) of the formation. That is, the concentration of mechanical energy required to catastrophically fail (destroy) a volume of rock. Comparison between the MSE and the SED of the formation describes the mechanical efficiency of the drill bit in converting input mechanical energy to output energy. Hydraulic energy applied at the drilling workface can both improve (e.g., clean, kerf) or impede (e.g., increase pressure overbalance) energy transfer at the workface. It is, therefore, considered separately. Current oilfield measurement capabilities, and theoretical misunderstandings, introduce simplifications and errors in the MSE. It is important to understand this when using the MSE. Several of Samuel's and Mensa-Wilmot's deprecating claims about the MSE are questionable. The paper examines these claims and describes why they are incorrect. However, they do advocate a holistic approach to drilling process management—essentially an operational approach—which has merit. Understanding of the MSE is important in that approach. This paper details the theoretical development of the MSE from a concept of instantaneous drilling power. This places the MSE on a firm theoretical basis and leads to an understanding of its limitations, and valid application. The relationship of the MSE to the energy density of the formation shows that the MSE should not be compared to the compressive strength of the formation, which leads to an improved understanding of drill bit mechanical efficiency.

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To address the low rock-breaking efficiency of milled-tooth rolling cutters used for shaft sinking via drilling methods in the Jurassic strata of Western China, this study conducted rotational cutting tests using a mechanical rock-breaking test platform. The rock-breaking mechanisms and efficiency of the cutter were systematically investigated. First, rock-like material specimens were prepared based on the physical and mechanical properties of the weakly cemented sandy mudstone from the Jurassic system. Second, rotational cutting tests on Jurassic sandy mudstone-like materials were conducted on a mechanical rock-breaking test platform using a milled-tooth rolling cutter, a tool commonly employed in shaft sinking by drilling methods. Finally, the rock-breaking phenomena and modes of the milled-tooth rolling cutter were described in detail. Furthermore, the effects of penetration and rotational speeds on the rock-breaking force, cutting coefficient, rock drillability index, rock-breaking specific energy, and coarseness index were thoroughly discussed. The main findings are as follows. (1) The average rock-breaking force exhibited a positive linear correlation with both the penetration and rotational speeds of the rolling cutter. (2) When the penetration exceeded 1.5 mm and the rotational speed was below 0.19 rps, the drillability of the rock improved. (3) The milled-tooth rolling cutter achieved the highest efficiency at a penetration range of 2.0 and 3.0 mm. These findings could provide theoretical support for selecting rock-breaking cutting tools for shaft sinking by drilling methods in weakly cemented Jurassic strata in Western China and for optimizing the power parameters of drilling rigs under such conditions.

The term "toughness” refers to a rock's resistance to excavation and indentation from boring or cutting tools. It is evaluated in relation to the ductile properties of rocks, which show visible plastic deformation. Various indices exist for evaluating toughness, which is the opposite of brittleness. In this study, 24 samples from three types of rocks (igneous, metamorphic, and sedimentary) were selected to evaluate the toughness indices. The toughness indices were assessed based on existing methods such as strain, energy, strength, and specialized tests such as the Brittleness Value ( S 20 ), Sievers' J Value ( S J ), Punch Penetration Test ( BI ), and Porosity ( n ). The best toughness index by using entropy and Gini split from Iterative Dichotomiser 3 algorithm decision tree was found to be S J =18. By using the Sievers' J Value and rock tensile strength is proposed a new rock toughness index which is related to specific energy. A new toughness index was presented as the S J Drillability Coefficient Toughness ( T SDC ). The value of T SDC = 5 (N/mm 3 ) was found to be a good threshold for indicating the energy consumed during drilling and rock excavation. The results showed that the energy required to excavate toughness rocks is more than brittleness rocks.

This paper deals with rotary drilling into andesite in laboratory conditions, conducted on an experimental horizontal drilling rig. The processing of experimental data after the experiments contributed to the application and verification of mathematical models of penetration depth and torque as a function of the thrust force. The output is the identification of intervals of the applied thrust force levels for the efficient drilling zone. Designing of an optimisation algorithm for controlling the rock drilling process and monitoring the tool condition was based on changes in the thrust forces level at which specific energy reached minimum values. The criterion applied was the monitoring of the penetration depth, which together with the theoretical value of the torque defined the calculation of the specific energy values.

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In the drilling exploitation of hot dry rock for geothermal energy, whirling is one of the main low efficiency conditions that affect the efficiency of PDC bit in horizontal well drilling. Realizing automatic and real-time identification with whirling is of great significance to save non-productive time and ensure drilling safety and benefit. In this paper, we firstly constructed a real-time drilling mechanical specific energy model (MSE) combined with while-drilling testing to reflect the real-time drilling conditions. The MSE model is used to normalize multi-source parameters. Secondly, we constructed a BP artificial neural network, and then the normalization effect verification, optimization of network parameters, and identification effect verification of whirling were carried out. The final results show that the established MSE model has favourable effect on data normalization, which could also reduce the complexity of the required network model, and shorten the training time by 20-30 s/step. The optimal algorithm is Trainscg, whose optimal number of hidden layer nodes is 5, and the optimal maximum number of iteration steps is 1000. The established artificial neural network model can accurately identify whirling based on MSE, the accuracy is about 0.94, and the average relative error is 1.3%. The method established in this paper provides a reference for automatic identification of various low efficiency conditions based on MSE.

Application of the drilling energy intensity indicator to determine the rock mass hardness ratio makes it possible to quickly assess areas with insufficient previous geomechanical studies, which contributes to optimization of the drilling and blasting operations. This is achieved by standardizing the drilling parameters at the design stage and subsequently adjusting them in accordance with the expected physical and mechanical properties of the rocks, in order to ensure the required size of the muck pile fragments. The authors propose an innovative approach based on the automated processing of telemetry data obtained from drilling rigs in real time. The study provides a detailed examination of the stages of statistical data filtering to eliminate anomalous values, calculation of the energy consumption while drilling using calibration coefficients, and the construction of block models that represent distribution of the energy consumption and the rock hardness. Based on the research conducted, it was found that the use of a floating correlation factor allows combinig telemetry data collected from different types of drilling rigs, which in turn makes it possible to maintain a single telemetry database, ensuring high detail in zoning the rock mass by the energy intensity. In the future, the energy intensity of blast hole drilling may be used to calculate the optimal specific consumption of explosives per blast hole, ensuring the required process-specified size of the muck pile fragments with a minimum amount of explosives, which will increase the economic efficiency of the drilling and blasting operations.

The article is devoted to the analysis of energy consumption in the process of drilling wells in karst rock blocks. The paper presents the results of experimental and analytical studies of the drilling process and energy consumption for the destruction of rock massifs with a complex structure characterized by the presence of karst cavities. The operation of the drilling machine during the drilling of the karst rock block was monitored. In the article, the use of the criterion of energy intensity of the well drilling process is proposed to assess the level of energy consumption by the drilling rig. On the basis of the conducted research, the dependence of the rotary power of the drilling machine on the productivity of drilling wells was established, and the dependence of the specific energy intensity of rock drilling on the drilling productivity was determined. The results of the conducted analytical and experimental studies on the determination of the geological structures of well columns by the energy intensity of their drilling process allow the development of designs of well charges for effective and safe destruction of complex rock massifs.

The diamond core drilling operation is very essential in the preliminary stage of mineral extraction in the mining industry. The energy required to remove a unit volume of the rock mass (specific energy) is discussed in the present investigation. Estimation of the specific energy is the essential key parameter for tunneling, excavation, and other allied industries. It helps in reducing the time-consuming and cost of the project. For that, the laboratory experimental work was carried out on a laterite rock using CNC drilling machine BMV45T20. Using a multiple regression analysis reasonable mathematical equation was established among specific energy and dominant frequencies through diamond rock core drilling operations. The established prediction model could be utilized at the preliminary stage of the excavation projects for estimation of the specific energy in tunneling, excavation and petroleum industries.The diamond core drilling operation is very essential in the preliminary stage of mineral extraction in the mining industry. The energy required to remove a unit volume of the rock mass (specific energy) is discussed in the present investigation. Estimation of the specific energy is the essential key parameter for tunneling, excavation, and other allied industries. It helps in reducing the time-consuming and cost of the project. For that, the laboratory experimental work was carried out on a laterite rock using CNC drilling machine BMV45T20. Using a multiple regression analysis reasonable mathematical equation was established among specific energy and dominant frequencies through diamond rock core drilling operations. The established prediction model could be utilized at the preliminary stage of the excavation projects for estimation of the specific energy in tunneling, excavation and petroleum industries.

Optimizing the drilling process is critical for the exploration of natural resources. However, there are several mechanic parameters that continuously interact with formation properties, hindering the optimization process. Rate of penetration (ROP) and mechanical specific energy (MSE) are considered two key performance indicators that allow the identification of ideal conditions to enhance the drilling process. Thus, the goal of this research was to analyze field data from pre-salt layer operations, using a 2D analysis of parameters as a function of depth, response surface methodology (RSM), and multi-objective optimization. The results show that the RSM method and multi-objective optimization provide better results when compared with 2D analysis of parameters as a function of depth. The RSM method can be used as a tool to analyze the effects of the independent drilling mechanical parameters (WOB, RPM, FLOW, and TOR) on the response variables (ROP and MSE) with a 95% confidence level. Through multi-objective optimization, it was possible to concomitantly achieve an ROP of approximately 22 ft/h and MSE of nearly 11 kpsi using the values of WOB, RPM, FLOW, and TOR of about 11 klb, 109 rev/min, 803 gpm, and 3 klb-ft, respectively. Using high WOB values, i.e., from the mean value up to the maximum value of approximately 43 klb, reflects a low ROP and most likely indicates an operation beyond the foundering point. High FLOW promotes a more efficient hole cleaning and higher rates of cuttings transport, thus preventing eventual in situ drill-bit sticking. Flow adjustment also ensures an adequate balance of dynamic bottom hole pressure, in addition to controlling the force impact force of the drilling fluid in contact with the rock being drilled, expressing importance in terms of efficiency and rock penetration. Finally, it is important to mention that the results of this research are not only applicable to hydrocarbon exploration but also to geothermal and natural hydrogen exploration. Values analyzed and presented with decimal precision should be logically focused as integers when in industrial application.

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In this research, in order to compare and select the optimum patterns, two parameters of specific charge and specific drilling are used. Two explosive substances, including ammonium nitrate and fuel oil (ANFO) and Amulet, are used to charge the holes located on the cross-section of the tunnels in order to advance by 3 meters. Also, the cross-section of the selected tunnels was 19, 28, 32, 40, 48, 50, 65, and 76 square meters with horseshoe, circle and D-shaped. The diameter of the explosive hole is 48 mm for the Norwegian method and 51 mm for the two energy balance models and the Swedish method to compare them. A total of 160 designs are prepared for three types of limestone, sandstone and marl. The results obtained for two parameters of specific charge and special drilling for the selected rock material are completely opposite. Also, in the Swedish methods, according to the Amulet, the values of the calculated parameters are close to the energy balance model. Finally, according to the geomechanical parameters of the rock, for the Swedish method and the energy balance model in charging with amulet explosives, the energy balance model and the Holemberg-Persson method are proposed in the optimal design for the tunnel drilling and blasting pattern. In addition, for the Norwegian method and the energy balance model in charging the holes with ANFO, the energy balance model is prior to the Norwegian method. The amount of stemming of holes in different parts of the tunnel face is less for the Swedish method than the Norwegian and energy balance models.

The Mechanical Specific Energy (MSE) is not so well known in coring as compared to conventional drilling. Teale (1965) first defined MSE for the full face-bit as an amount to energy spent to remove unit volume of rock. Pessier and Fear (1992) introduced MSE in its expanded form in O&G industry. At present MSE has been used widely to understand the mechanism of drilling, evaluate efficient drilling, and diagnose the root cause of in-efficiency. MSE is also used real-time for drilling performance evaluation (Dupriest et al., 2005; Pessier et al., 2016). These processes have saved Billions of dollars in the O&G industry. However, the MSE concept has not been transferred to coring operations. Current work examines the use of MSE and its adaptation in coring processes. Limited data published were reviewed, re-analyzed, and finally compared with field example of MSE in coring thereby explaining the mechanism of coring, its usefulness in getting a better recovery, and the best bore-hole quality. The MSE for coring can be expressed as MSE = (W/A) + 2pi N.T / (A.R). Where, W, the weight-on-bit, and T, the torque are available from drilling rig through some mechanical loss. The rate-of-penetration is R, number of core-bit revolutions per minute is N and the core-bit kerf area (A) is given by coring diameter (OD-ID). The unit of MSE in metric unit is MPa or psi in imperial unit. The limited published data obtained from laboratory-based coring do not give the clear picture of coring operation. The re-processed data and a careful analysis shows that the depth-of-cut, DOC, is a better indicator of R and N, higher DOC results in lower MSE; stronger rocks ends up having higher MSE, and efficient coring zones could easily be identified. A similar and consistent result is obtained in the present work. The coring operation was conducted in a test well in Oklahoma; the rock types encountered were sand, shale and the basement granite. This paper will discuss the coring operations results in detail. The role of axial and rotational energy will be analyzed and their influence on rock properties will be discussed. The efficient coring zone of linear weight-on-bit with DOC and torque with DOC will be presented and anomaly due to balling or undue vibrations will be discussed. Finally, the preliminary results show that the axial energy is proportional to hardness and rotational energy (nearly equal to MSE) is proportional to confined compressive strength.

Currently, the accurate prediction of tunnel boring machine (TBM) performance remains a considerable challenge due to the complex interactions between the TBM and rock mass. In this study, the research work is based on part of a metro tunnel project that covers 2,083.94 m. The Gaussian mixture model (GMM) and K-nearest neighbor algorithm (KNN) are used to classify and predict the rock mass drillability in the TBM excavation process. Drillability indexes are introduced to cluster and classify the rock mass, including the penetration (P), field penetration index (FPI), torque penetration index (TPI), and specific energy (SE). Statistical characteristics of the drillability indexes were analyzed, and it was found that their distributions did not conform to the normal distribution, with large variation coefficients. Clustering analysis was then conducted on the TPI and FPI within the training group using the Gaussian mixture model, and six drillability categories of rock mass were classified. Subsequently, the mapping relationship between the cutterhead speed, advance speed, total advance force, and cutterhead torque in the training group and the drillability of rock mass was established based on the KNN classification model. It was revealed that when the K-value is set to 4, the model has high macro-F1, macro-P, and macro-R. Validated by the testing group data, this method has been proven to be feasible and effective. The research results indicate that this method can effectively classify and predict the drillability of tunneling surrounding rock mass in shield construction, particularly when the rock mass at the shield face is uniform and homogeneous. This provides a theoretical basis and technical support for safe and efficient shield tunneling.

Reliably assessing the quality and mechanical properties of rock masses is crucial in underground engineering. However, existing methods have significant limitations in terms of applicability and accuracy. Therefore, a field measurement method that meets the real-time monitoring and safety requirements for the quality of engineering rock masses is needed. Firstly, the research findings of domestic and international scholars on the application of drilling process monitoring technology are comprehensively analyzed. Rotary cutting penetration tests are conducted on tuff rock masses containing fractures and joints. Various rock mass classification and evaluation standards are integrated with rotary penetration tests. Rotary cutting penetration tests are used to determine the residual strength of rock, based on this review. The rationality of the calculated mi parameter values is validated. The peak strength, residual strength, and errors of the rock are obtained based on the penetration method. The rock quality index rock quality designation from drilling (RQDd) is redefined, based on the drilling process monitoring apparatus (DPMA). Rock mass classification is conducted, based on the correlation between the standard deviation of rotary drilling energy and the rock quality designation (RQD). Additionally, a new relational formula is introduced to determine the RQD from variations in drilling energy, based on discontinuity frequency. This field measurement method undoubtedly provides a crucial scientific basis for rock design and construction, ensuring long-term safety in engineering applications.