Failure Mode Of Rock Research Articles

THE MECHANICAL PROPERTIES AND FAILURE MODE OF SIMULATED LUNAR ROCK BY IN SITU TEMPERATURE REAL-TIME ACTION OF LUNAR-BASED

To achieve in situ condition-preserved coring of the lunar surface and deep lunar rocks and a return mission, it is necessary to explore the mechanical properties and failure modes of simulated lunar rocks that have physical and mechanical properties approximately equivalent to those of mare basalt under simulated lunar temperature environments ([Formula: see text][Formula: see text]C to 200[Formula: see text]C). To this end, real-time uniaxial compression tests were conducted on simulated lunar rocks under corresponding in situ temperature conditions, and the mechanical properties, deformation characteristics, micromorphology, and failure modes were analyzed. Based on the macroscopic analysis, as the environmental temperature decreases, the uniaxial compressive strength, peak strain, and peak strain duration of simulated lunar rocks exhibit a nonlinear increasing trend, with maximum increases of 33.00[Formula: see text], 36.16[Formula: see text], and 49.25[Formula: see text] from those at room temperature, respectively. Based on microscopic analysis, the intergranular fractures run through the entire samples under the environmental temperature. As the environmental temperature increases, intergranular and transgranular fractures coexist, and layered fractures appear at high temperatures. At the same time, some samples exhibit undulating and stepped morphologies caused by shear stress. For the fractal dimension of a simulated lunar rock main fracture surface, the fractal dimension of the actual angle and the corrected angle increase first and then decrease with increasing environmental temperature, and the maximum error of the two is only 1.84[Formula: see text]. The overall fractal dimension ranges from 2.02 to 2.28, and the fractal dimension under real-time high-temperature conditions is higher than that under real-time low-temperature conditions. In addition, the failure mode of the simulated lunar rocks under real-time in situ temperature changes is a combined tensile–shear failure mode with shear failure (primary) and tensile failure (secondary). The above research results are expected to be applied to in situ condition-preserved coring in extreme lunar environments and provide a scientific basis for the design and development of in situ condition-preserved coring robot systems for the extreme environment of deep space.

Experimental and numerical study of disk specimen with rough structural plane under splitting test

To study the effects of the anisotropic matrix and structural planes on the splitting strength and failure mode of rocks, Brazilian splitting tests were carried out with seven different loading angles on specimens of rock-like materials with rough structural planes. The surface strains of the samples during the failure process were monitored and analysed with the help of a high-speed camera and digital image correlation (DIC) technology. The test results showed that the Brazilian splitting strength (BSS) decreased gradually with an increased loading angle. According to the crack morphology, the samples showed three failure modes, and the structural plane and the loading angle (θ) had an important effect on the failure mode. When θ < 75°, the sample failure was mainly affected by the matrix, and when θ > 75°, the sample failure was mainly controlled by the structural plane. The numerical simulation of the sample with a structural plane was carried out by the PFC2D particle flow program, the micro parameters were calibrated using a back propagation (BP) neural network model. The internal cracks of the sample under a splitting load were mainly matrix tensile microcracks and structural plane shear microcracks, and the tensile microcracks in the side with the weak matrix appeared significantly earlier than those in the side with the strong matrix. With increasing loading angle, the proportion of tensile microcracks in the matrix increased, while the proportion of shear microcracks in the matrix decreased, especially in the weak matrix. The microcracks at the structural plane mainly changed from tensile microcracks to shear microcracks, and the development degree of microcracks along the structural plane was more significant than that on the weak matrix with increasing loading angle. The results of the study can provide a reference for rock stability evaluation and utilization.

Numerical Study on the Damage Characteristics of Layered Shale Using 3D DEM

Layered shale is a kind of rock with obvious anisotropy, which is significantly influenced by the inclination angle of the rock. In this study, the influence of bedding dip on the strength characteristics, failure mode, and internal fracture evolution of layered shale was investigated through laboratory triaxial compression tests and three-dimensional discrete element numerical simulations. Results show that the numerical model of layered shale constructed using the bonded block model can simulate the layered shale in terms of U-shaped strength variation and failure modes very well. Based on the distribution of cracks and failure characteristics of layered rocks, the failure modes of layered rocks are classified as follows: Shear failure across the bedding plane, slip failure along bedding planes, combined tensile splitting and shear failure. The development of microcracks damage in the slip failure model is controlled by interlayer joints, while in other failure modes, it is jointly controlled by the rock matrix and interlayer joints. The relationship between microscopic joint parameters and the variations of Young's modulus and peak strength has been proposed.

Experimental Simulation on the Stress Disturbance Mechanism Caused by Hydraulic Fracturing on the Mechanical Properties of Shale Formation

Hydraulic fracturing is an indispensable technology for the development of shale oil and shale gas. Knowing the changes in the rock mechanical properties and failure modes during hydraulic fracturing is the key to improving the efficiency of hydraulic fracturing. Based on experiments and simulations, it can be concluded that the injection of fracturing fluid in the hydraulic fracturing caused deformation of the fracture surface, and the rock mechanical properties experienced degradation with a maximum reduction in the rock mechanical properties of 44.24%. As indicated in the experiments, the displacement of the measurement point was decreased with the distance increase between the injection point and the measurement point. According to the numerical simulations, tensile failure is the main failure mode in hydraulic fracturing, but the percentage of shear failure had an obvious increase with the increase in distance between the injection point and the measurement point. Comparing DDS #1 and DDS #5, the DDS #5 measurement point was farther away from the injection point, and the average percentage of shear failure increased from 21.94 to 52.72%. Meanwhile, the increase in the branch fractures also caused shear failure to occur. Comparing Sample 1 and Sample 3, in Sample 3, which had more branch fractures, the average percentage of shear failure increased from 33.12 to 37.58%. Due to the porous medium of the reservoir rock, the enormous pressure generated during the injection of fracturing fluid caused significant deformation of the fracture surface, leading to the tensile failure of the rock. The displacement of the fracture surface caused by the fracturing fluid injection also led to the deformation of the pore throat structure; thus, the shear failure increased when the measurement point was away from the injection point.

Experiment and particle flow simulation on mechanical properties and crack evolution mechanism of Brazilian discs containing two flaws

Abstract The mechanical behavior of fractured rock in tensile stress environment is a hot topic in underground mining engineering. Here, real surrounding rock of coal mine roadway was simulated by using rock-like materials and the tensile failure behavior of Brazilian discs with intermittent double fissures was investigated experimentally. The deformation response, fracture evolution, and failure mode of rock were analyzed. The fissured disc specimen's discrete element model was proposed in particle flow code (PFC2D). The microforce field, crack, and energy evolution processes of model specimens were discussed. The results showed that the load-displacement curves exhibit single-peak and double-peak types, corresponding to the splitting penetration and wing crack penetration damage modes of the specimen. The fissure angle or rock bridge angle showed a great influence on the evolution of main cracks and secondary cracks. The double-fissured Brazilian disc failed due to the initiation and transfer of microcracks in the stress concentration zone, combined with the continuous propagation and convergence of those microcracks. The splitting failure of the Brazilian disc is a continuous process of strain energy accumulation from the early stage of loading and instantaneous release of strain energy after obtaining the peak strength as the dissipative energy sharply rises.

Mechanical characterization of intermittent weak interlayer based on DIC and acoustic emission technique

Current research on intermittent structural surfaces tends to concentrate on intermittent joints, often neglecting the abundance of intermittent weak interlayers present in rock structures. To analyze the effect of intermittent weak interlayer on the mechanical properties of rock mass, specimens with varied interlayer thickness and dip angles were prepared and subjected to uniaxial compression tests using an acoustic emission system and Digital Image Correlation (DIC) technique. The results revealed an inverse relationship between the interlayer thickness (t) and dip angle (θ), and the uniaxial compressive strength. Through a nonlinear fitting method, an empirical strength equation for these interlayers was established. Acoustic emission (AE) counts and cumulative acoustic emission counts increased with loading, and the RA-AF values indicated that the specimens were dominated by shear damage, and the larger the thickness and dip angle of the interlayer, the higher the proportion of shear damage. In terms of failure mode, the greater the thickness of the interlayer, the lower the level of development of cracks other than the main crack, and the greater the dip angle of the interlayer, the fewer the number of wing cracks required for specimen failure and the lower the degree of wing crack development. The increase in interlayer thickness and dip angle resulted in a specimen structure that was more susceptible to damage. The actual crack initiation angles agree with the theoretically calculated angles based on the maximum tensile stress theory. These findings emphasize the critical role of these parameters in influencing the failure mode of rocks.

Theoretical and experimental investigation of a shear failure model for anisotropic rocks using direct shear test

This study proposes a theoretical model for predicting the shear strength of anisotropic rocks in which failure is dependent on the inclination of the inherent structural weak planes. For this purpose, triaxial and direct shear tests were conducted on dried and saturated shale samples. Samples were cored at different orientations (β) to the inherent structural weak planes, i.e., bedding planes. To verify the anisotropic behavior of the samples, triaxial tests were performed on samples with various inclinations of the bedding planes. The experimental results demonstrated a U-shape relationship between the compressive strengths and the inclination of the bedding planes, which is in accordance with Jaeger's model of the plane of weakness (JPW). Accordingly, apparent strength and elastic properties, such as Young's modulus, Poisson's ratio, cohesion, and internal friction angle were all observed to be dependent on β, which verified the mechanical anisotropy of the shale samples. Many of the existing failure criteria consider the impact of bedding inclination on failure strength based on uniaxial and triaxial conditions. However, it is also important that the failure modes of anisotropic rocks are evaluated during shearing. For this purpose, a theoretical model was derived to relate shear strength to β following the Coulomb-Navier criterion. The relationship between shear strength and β was plotted and illustrated in an Inverted-U shape. Direct shear tests were conducted to validate the proposed criterion. Plotted experimental data confirmed the shape of the geometry determined by theoretical analysis. From the results, the maximum shear strength occurred when β was between 30° and 60° in direct shear tests. To obtain a more comprehensive understanding, changes in the shear stress-displacement curve and dependence of the friction angle, to the bedding plane orientation, β, were evaluated and indicated shear anisotropy behavior.

The Deformation Behavior and Failure Modes of Surrounding Rock after Excavation: A Experimental Study

The deformation and failure of the surrounding rock during roadway excavation often determine the choice of supporting methods. To study the deformation behavior and failure modes of the surrounding rock after excavation under unloading stress, structural model tests were carried out with a novel experimental device. The present structural model test using partial hollow thick-walled cylinder cement mortar specimen φ200 mm × 280 mm with a horizontal central circular hole of 60 mm diameter and the hollow height of 160 mm was conducted to investigate the deformation, failure characteristics, and AE response of a whole testing process from excavation to postunloading state. Experimental results revealed that the amount of deformation behind the surface is significantly higher than that in front of the surface, and the radial strain increases with the increase of the distance from the surface within the range affected by unloading. Furthermore, the unloading rate has a little effect on the radial deformation of the surrounding rock in front of the surface, but has a substantial effect on the radial deformation behind the excavation surface. The peak value of the strain rate at the unloading rate of 2 MPa/s is much higher than that at the unloading rate of 0.1 MPa/s. According to AE results and the failure of opening the boundary, the increase of unloading rate triggers and exacerbates the damage of the specimen under high in situ stress conditions. The surrounding rock expanded to the inner hollow, accompanied by large dilation and volume changes, and it resulted in the shrinkage of the hole diameter. A large number of rock slices are generated at the opening curved free surface and then fell off, whose morphology is similar to the rock blocks that fell off after caving failure and rock burst in situ field. The results show that the system can accurately simulate the mechanical response and acoustic emission response of the excavated surrounding rock, which provides a new experimental method for further study of the unloading response of the surrounding rock.

Global Mapping of Fragmented Rocks on the Moon with a Neural Network: Implications for the Failure Mode of Rocks on Airless Surfaces

Failure modes of lunar boulders depend both on rheology and the erosion agents acting in the lunar surface environment. Here, we address the failure modes of lunar boulders and their variations at a quasi-global scale (60°N to S). We deploy a neural network and map a total of ∼130,000 fragmented boulders (width > ∼10 m) scattered across the lunar surface and visually identify a dozen different disintegration morphologies corresponding to different failure modes. Our findings suggest that before a boulder is catastrophically shattered by an impact, there is an internal weakening period with minor morphological evidence of damage at the rock scale at the resolution of the used imagery. We find that some of the rare pre-shattering morphologies (e.g., fractures) are equivalent to morphologies observed on asteroid Bennu, suggesting that these morphologies on the Moon and on asteroids are likely not diagnostic of their formation mechanism (e.g., meteoroid impact, thermal stresses). In addition, we identify new morphologies such as breccia boulders with an advection-like erosion style. We publicly release the produced fractured boulder catalog along with this paper.

Comparative analysis of quasi-static penetration characteristics of slotted granite and intact granite

The stress release method with rock slotting in the bottom hole by ultra-high-pressure water jet is proposed as a solution to the problem of increased rock strength due to high in-situ stress. However, the failure mode of rock with annular grooves under the simultaneous action of geostatic stress and hydrostatic pressure is still unclear. The failure characteristics, penetration force, failure mode and deformation characteristics of rock under geostatic stress are studied by numerical simulation. The results showed that the presence of an annular groove changes the rock failure mode. The radial crack propagation direction dominated by extrusion shear is deflected and will be connected to the peripheral area of the groove’s bottom. It becomes the primary crack propagation dominated by tensile shear, controlled by the crack formation zone and the stress concentration zone at the peripheral area of the groove’s bottom. The annular groove can significantly reduce the peak penetration force by about 72%. There is a critical value for the influence of groove depth on the peak penetration force. The presence of an annular groove changes the load-penetration curves from ductile failure to brittle failure mode. The groove modifies the stress propagation mode, altering the rock response and crack propagation zones. In addition, the annular groove decreases the radial force that restricts the extension of rock in the surrounding area, allowing the rock to expand more easily in the surrounding area. Therefore, this stress release method and the study’s findings are instructive for improving rock-breaking efficiency and gaining a deeper understanding of the technique.

Study on Damage Characteristics and Failure Modes of Gypsum Rock under Dynamic Impact Load.

The objective of this work was to investigate the damage characteristics and failure modes of gypsum rock under dynamic impact loading. Split Hopkinson pressure bar (SHPB) tests were performed under different strain rates. The strain rate effects on the dynamic peak strength, dynamic elastic modulus, energy density, and crushing size of gypsum rock were analyzed. A numerical model of the SHPB was established using the finite element software, ANSYS 19.0, and its reliability was verified by comparing it to laboratory test results. The results showed that the dynamic peak strength and energy consumption density of gypsum rock increased exponentially with strain rate, and the crushing size decreased exponentially with the strain rate, both findings exhibited an obvious correlation. The dynamic elastic modulus was larger than the static elastic modulus, but did not show a significant correlation. Gypsum rock fracture can be divided into crack compaction, crack initiation, crack propagation, and breaking stages, and is dominated by splitting failure. With increasing strain rate, the interaction between cracks is noticeable, and the failure mode changes from splitting to crushing failure. These results provide theoretical support for improvements of the refinement process in gypsum mines.

Investigation of fatigue failure and energy characteristics of rock exposed to complicated stress disturbance paths: Cyclic stress amplitude effect

AbstractTo deeply reveal the differences in geomechanical responses of rock during mining exposed to complicated stress disturbance of excavation unloading and cyclic loading conditions, cyclic triaxial fatigue loads with four cyclic stress amplitude (CSA) (60, 100, 130, and 160 MPa) were performed on deeply buried rock. Results show that rock deformation, energy evolution, and failure modes are all influenced by the CSA. Additionally, it is found that all the strain energy increases with increasing CSA during rock failure. Especially, the dissipated energy increases greatly at the confining stress unloading stage (CSUS) than the fatigue loading stage (FLS), indicating the influence of unloading on rock damage accumulation. Moreover, a damage evolution model reflecting a first slow and then quick increase pattern was established using the dissipated energy. Finally, a transition failure mode from the dominant tensile‐shear to pure shear is found. It is suggested that much more energy needs to be consumed to induce shear cracks than tensile cracks.

Effects of Heating and Liquid Nitrogen on Mechanical Characteristics and Rockburst Characteristics of Granite

Due to the depletion of shallow resources and the reduction of the space for human life and development, in recent years, human beings began to gradually expand to the deep underground. The increase of development depth will bring a series of safety problems, so it is particularly important to study and deal with rockburst. In this paper, based on laboratory tests, relevant literature, and research at home and abroad, the TAWD-2000 electrohydraulic servo rock mechanics testing machine and PIC-2 acoustic emission (AE) testing system are used. Uniaxial compression tests and AE monitoring tests were carried out on granite samples to analyze the property and AE characteristic parameters of granite under the action of liquid nitrogen (LN2) and to further study the fracture mode of granite. The following conclusions can be obtained: the LN2 cooling has a deterioration influence on the strength of rock, and the elastic modulus and peak stress of granite show a downward trend with the increasing number of cycles. With the cycle times of LN2 actions increasing, the AE ring count of granite and the frequency and amplitude of energy in each stage have an upward trend. When the rock reaches the failure stage, the energy at the catastrophe point increases, and the ring count also increases sharply. The RA-AF diagram of AE parameters can characterize two failure modes of rock, tensile failure and shear failure. In the process of fracture of granite samples, shear cracks dominate, leading to shear failure or compression failure of granite. Based on the method of elastic energy, the tendency index of rockburst of granite samples under different working conditions is calculated. The tendency of rockburst decreases with the decrease of elastic modulus. Under the repeated action of LN2, the tendency of rockburst of granite samples presents a downward trend, and the action of LN2 reduces the probability of rockburst to a certain extent.

Role of Rock Sections in Intermittent Joints in Controlling Rock Mass Strength and Failure Modes

Role of Rock Sections in Intermittent Joints in Controlling Rock Mass Strength and Failure Modes

Experimental studies on rock failure mechanisms under impact load by single polycrystalline diamond compact cutter

Percussive drilling shows excellent potential for promoting the rate of penetration (ROP) in drilling hard formations. Polycrystalline diamond compact (PDC) bits account for most of the footage drilled in the oil and gas fields. To reveal the rock failure mechanisms under the impact load by PDC bits, a series of drop tests with a single PDC cutter were conducted to four kinds of rocks at different back rake angles, drop heights, drop mass, and drop times. Then the morphology characteristics of the craters were obtained and quantified by using a three-dimensional profilometer. The fracture micrographs can be observed by using scanning electron microscope (SEM). The distribution and propagation process of subsurface cracks were captured in rock-like silica glass by a high-speed photography system. The results can indicate that percussive drilling has a higher efficiency and ROP when the rock fractures in brittle mode. The failure mode of rock is related with the type of rock, the impact speed, and the back rake angle of the cutter. Both the penetration depth and fragmentation volume get the maximum values at a back rake angle of about 45°. Increasing the weight and speed of falling hammer is beneficial to improving the rock breaking effects and efficiency. The subsurface cracks under the impact load by a single PDC cutter is shaped like a clamshell, and its size is much larger than the crater volume. These findings can help to shed light on the rock failure mechanisms under the impact of load by a single PDC cutter and provide a theoretical explanation for better field application of percussive drilling.

Macro and meso crack evolution of granite specimens with non-straight fissures: A comparison between two bond models

Various flaws in rock mass can weaken mechanical properties of the rock and pose a risk to the safety of underground engineering, with significant implications for design, construction and maintenance. A study of the strength and failure modes of rocks with non-straight fissures can provide a better understanding of fracture mechanisms of rocks. In this study, uniaxial compression tests were carried out on granite specimens with three types of fissures, including straight and arc fissures. The experiments showed that the stress–strain curves and failure modes of the granite specimens were influenced by pre-existing fissures. Compared to straight fissures, arc fissures had less influence on mechanical parameters of the specimens. In order to further investigate the effects of arc fissures, PFC models were constructed, based on calibrated PBM and FJM parameters. Stress–strain curves, mechanical parameters and failure modes of specimens with pre-existing fissures were simulated. The initial cracks around the arc fissure were shifted from the tip of the fissure to the highest point of the arc fissure. Finally, the dip angle of cracks, the stress distribution in the specimens and the local stress evolution around the fissures were further discussed, and the advantages and disadvantages of the two contact models were summarized.

Study on Calculation Method of Stability of Damaged Sliding Dangerous Rock on Reservoir Bank

The rapid destruction of dangerous rock produces a large amount of energy, causing heavy casualties and economic losses every year. There are various failure modes and stability calculation methods of dangerous rock. The common failure modes of dangerous rock are tipping mode, sliding mode and falling mode. For large tower pillar dangerous rock with degraded foundation, it is unreasonable to use conventional stability calculation methods to calculate the stability of dangerous rock. This paper takes Jianchuandong dangerous rock in Wushan County as the research background, considering the expansion of rock cavity of damaged dangerous rock base and the deterioration of rock mass in the base of large tower column reservoir bank, and establishes the stability calculation method of dangerous rock suitable for the damage deterioration of the base. It is innovative on the basis of the traditional stability calculation method of dangerous rock, which has important practical significance and theoretical basis for the calculation of the stability of unconventional dangerous rock.

Microscopic cracking behaviors of rocks under uniaxial compression with microscopic multiphase heterogeneity by deep learning

Cracking behaviors of rocks significantly affect the safety and stability of the explorations of underground space and deep resources. To understand deeply the microscopic cracking process and mechanical property of rocks, X-ray micro-computed tomography (X-μCT) is applied to capture the rock microstructures. The digital color difference UNet (DCD-UNet)-based deep learning algorithm with 3D reconstruction is proposed to reconstruct the multiphase heterogeneity microstructure models of rocks. The microscopic cracking and mechanical properties are studied based on the proposed microstructure-based peridynamic model. Results show that the DCD-UNet algorithm is more effective to recognize and to represent the microscopic multiphase heterogeneity of rocks. As damage characteristic index of multiphase rocks increases, transgranular cracks in the same grain phase, transgranular and intergranular cracks of pore-grain phase, intergranular and secondary transgranular cracks and transgranular crack between different grains propagate. The ultimate microscopic failure modes of rocks are mainly controlled by the transgranular cracks-based T1-shear, T3-shear, T1-tension, T2-tension and T3-tension failures, and the intergranular cracks-based T1-tension, T1-shear and T3-shear failures under uniaxial compression.

Experimental Evaluation of Conjugate Flaws on Rock Dynamic Fracturing

The fracture behaviors of rocks under dynamic loading are significantly affected by flaws. Understanding regarding this fundamental mechanism of flaw-induced dynamic fracturing could aid in reducing dynamic geohazards in deep rock engineering. In this study, a series of dynamic loading experiments are conducted on conjugate flawed white sandstone specimens to study the effect of the geometric configuration of flaws on dynamic fracturing. The results show that the geometry configuration of flaws and the loading conditions both strongly affect cracking and failure behaviors. Two types of shear cracks and three types of tensile cracks are observed, four coalescence patterns are identified, and the global failure modes of rock are usually coupled with two or more coalescence patterns. The inhibiting and enhancing mechanism of flaws in regards to potential shear fracture are obtained. These two failure mechanisms depend on the angular relationship between the flaws and the potential shear strain field. The “guiding effect” of the flaws results in the deviation and deformation of shear cracks. Moreover, it is found that the loading condition dominates the fracture tendency of rock macroscopically, while the geometric setting of flaws significantly affects the fracture behavior and failure mode locally.

Comparison of fracture characteristics of different PDC cutters penetrating carbonate rock

Carbonate rock is a very important reservoir rock in many parts of the world, but due to high temperature, high hardness, strong abrasiveness and other reasons, PDC (Polycrystalline Diamond Compact) bit is seriously worn and the efficiency of breaking rock is low. To solve this problem, a lot of research has been carried out on the cutting mechanism of PDC cutters, but less research has been done on the crushing mechanism of PDC cutters penetrating carbonate rock. Actually, effective penetration can increase the cutting depth and change failure mode of rock. Furthermore, the PDC cutter penetration process will also cause damage to the rock, which is conducive to improving the subsequent efficiency of cutting rock. Therefore, the study of PDC cutter penetrating rock characteristics can provide theoretical basis for drilling parameter optimization and PDC bit structure design. In this paper, the crushing mechanism of PDC cutters penetrating carbonate rock was studied. Based on the hydraulic servo experimental system and ST400 3D Profilometer, a series of experiments were carried out on conventional cutter, axe cutter and conical cutter penetrating carbonate rock at different back rake angles. The penetration force-penetration depth curve and surface topography of broken pits were analyzed. The results show that the failure mode of carbonate rock is affected by the back rake angle of cutter. Conical cutter has strong aggression when penetrating at a small back rake angle. The expansion of axe-shaped angle of the axe cutter exacerbates the failure of carbonate rock. Moreover, at the back rake angle of 10° and 20°, the maximum penetration depth and penetration efficiency of conical cutter were significantly greater than those of conventional cutter and axe cutter. At the back rake angle of 30° and 40°, the maximum penetration depth of axe cutter is greater than that of conventional cutter and conical cutter. The research results are expected to provide theoretical guidance for the optimized design of PDC cutter shape and back rake angle.