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Deep caverns are frequently subjected to transient loading, resulting in different failure characteristics in the surrounding rock compared to those in shallow caverns. Previous research has rarely focused on the transient responses of non-circular caverns. To address this gap, a theoretical solution for the dynamic stress concentration factor around a U-shaped cavern under transient stress waves was derived based on elasto-dynamic theory and conformal mapping. The theoretical results were validated through simulations using the discrete element software PFC2D 7.0 (Particle Flow Code in two dimensions). Additionally, the energy evolution and failure pattern of the surrounding rock under coupled static–dynamic loading were investigated. The results indicated that, when the stress wave was horizontally incident, rockburst failure was more likely to be observed in the cavern floor, while dynamic tensile failure was prone to occur in the incident sidewall. Furthermore, when the incident direction of the stress wave aligned with the maximum principal stress, more violent rockburst occurred. Moreover, when the rising time of the stress wave was greater than 6.0 ms, the peak dynamic stress concentration factor converged to a stable value, and the surrounding rock could be considered to be in a quasi-static loading state. These findings provide insight into the failure mechanisms of deep caverns and could guide the design of cavern supporting structures. [ABSTRACT FROM AUTHOR]

In deep rock engineering, caverns are often disturbed by engineering loads from different directions. To investigate the dynamic response of deep U-shaped caverns under different incident orientations, a theoretical solution of the dynamic stress concentration factor along the cavern boundary was derived based on the wave function expansion and conformal mapping method, and the failure characteristics around the cavern were further investigated by PFC2D (Particle Flow Code in two dimensions). As the incident orientation increases from 0° to 90°, the dynamic compressive stress concentration area transforms from both the roof and the floor to the sidewalls, and the peak dynamic stress concentration factor of the roof decreases from 2.98 to −0.20. The failure of the floor converts from dynamic compression shear failure to dynamic tensile failure. Compared to a stress wave incident from the curved boundary, a stress wave incident from the flat boundary causes severer damage. When the stress wave is incident from the sidewall, the cavern with a larger height-to-width (h/w) ratio exhibits severer damage. Conversely, the cavern with a smaller h/w ratio tends to fail as the stress wave is incident from the floor. This paper provides a basic understanding of dynamic responses of the deep U-shaped cavern. [ABSTRACT FROM AUTHOR]

The instability of double-cavern structure subjected to dynamic disturbances is a key issue for deep rock engineering. To investigate the dynamic responses of deep double U-shaped caverns, comprehensive analyses are conducted by Particle Flow Code (PFC2D), and the influences of incident directions of stress wave, cavern clearances, and cavern height ratios are discussed. The results indicate that the decreasing cavern clearance aggravates the static stress concentration on the intermediate rock pillar. When the stress wave is horizontally incident, the presence of the incident side cavern reduces peak tangential stress and kinetic energy on the non-incident side cavern; the higher the incident side cavern, the less damage on the non-incident side cavern. A vertically incident stress wave causes more severe damage in the intermediate rock pillar compared to a horizontally incident stress wave; the smaller the cavern clearance, the more violent the rockburst in the intermediate rock pillar. Comparatively, the cavern with a lower height exhibits more severe failure at the adjacent sidewall compared to the cavern with a higher height. This work can provide guidelines for disaster prevention of deep double-cavern structures. [ABSTRACT FROM AUTHOR]

Excavation damaged zone (EDZ) widely exists in the surrounding rock of underground roadway due to blasting excavation, which can further change the surrounding rock property and deteriorate the stability of the roadway. In the presented research, a damaged roadway model was developed to investigate the dynamic stress concentration factor (DSCF) distribution around the damaged roadway under a transient plane P wave. The influencing factors on DSCF distribution were discussed, including the shear modulus (μe/μd) of the intact surrounding rock to that of the damaged surrounding rock, the thickness of EDZ (Rd/R0), and the wavelength of the incident stress wave. Results indicated that the damaged surrounding rock around the roadway belongs to stress‐relaxed zones, and the existence of EDZ can reduce the overall DSCF of surrounding rock. As the ratio of μe/μd is increasing, both the maximum compressive and tensile stress concentrations in the damaged zones decrease gradually, which is opposite to that in the intact surrounding rock. A larger EDZ can induce a higher DSCF in the damaged surrounding rock and a smaller DSCF in the intact surrounding rock. As the incident stress wave's wavelength is increasing, the peak value of DSCF grows first before declining, finally followed by a constant value. Furthermore, the maximum compressive and tensile stress concentrations are always found near the surrounding rock that is perpendicular to and along the incoming direction of stress waves, respectively. The stress concentration in both intact and damaged surrounding rock near the incoming side of stress waves is higher than that at the transmitted side. [ABSTRACT FROM AUTHOR]

In this study, mode I fracture tests on cracked straight-through Brazilian disc (CSTBD) and notched semi-circular bend (NSCB) shale specimens with different sizes were conducted to investigate the difference between maximum tangential stress fracture criterion and the size effect law (SEL) model in predicting apparent fracture toughness (Ka) of shale. In addition, the effects of specimen size and geometry on the Ka and the selection of fracture criterion on the prediction of the inherent fracture toughness (KIc) were also studied. The results show that the Ka increases with the increase of specimen size, and the difference between KIc of shale specimens with different sizes predicted by the fracture process zone length determined by the further improved maximum tangential stress (FIMTS) criterion is the smallest. For the prediction of Ka of NSCB specimen, the results predicted by the FIMTS criterion are the closest to the tested fracture toughness. However, the effect of SEL model applied to the prediction of Ka of NSCB specimens is poor. The effective establishment of SEL model requires high accuracy for test data, especially for the configuration with large variation of the dimensionless stress intensity factor (Y*) with normalized crack length (α). Highlights: Fracture toughness is closely related to the size and configuration of the specimen, which is ultimately attributed to the inconsistent tangential stress distribution at the crack tip. The further improved maximum tangential stress criterion has the best effect on apparent fracture toughness prediction, and higher-order terms of the Williams expansion should be considered in apparent fracture toughness prediction of small-size specimens. The fracture criterion for determining the fracture process zone length should be consistent with the prediction criterion of apparent fracture toughness. The effective establishment of size effect law requires high accuracy tested data, especially for the configuration with large variation of the dimensionless stress intensity factor with normalized crack length. [ABSTRACT FROM AUTHOR]

Deep borehole cores are an important material basis for understanding deep stress conditions and rockburst risk; however, the complex environment of deep boreholes poses many challenges to traditional core orientation techniques, thus limiting the application of cores in fields such as in situ stress measurement. A technical method of restoring the original spatial attitude of nonoriented geological cores on the ground was proposed based on the inherent "trajectory projection consistency" relationship between the borehole and the corresponding core. A prototype machine of core ground reorientation was developed. Using this method and machine, ground reorientation was performed on cores drilled from the deepest shaft in China. Subsequently, the reoriented core acoustic emission (AE) method was conducted to identify the in situ stress within the project area. Meanwhile, measurement accuracy was verified by the stress relief method. The results show that the in situ stress distributions, including the azimuth and the trends in principal stresses by the two methods, are in good agreement and indicate that the historical maximum principal stress in the case of the mine has little abrupt variability with that of the present day. The research results can be used as the design basis for the safe construction of the deepest shaft. [ABSTRACT FROM AUTHOR]

• Tangential stress distribution around U-shaped caverns were calculated. • Failure process around the U-shaped cavern was simulated by PFC2D. • Height-to-width ratio and principal stress direction effect failure characteristic. • Failure mechanism of caverns with different height-to-width ratios were discussed. Understanding the stress distribution and failure characteristics around a U-shaped cavern is vital to the stability analysis of rock structures such as tunnels and roadways. In this study, the stress distribution around a U-shaped cavern with different height-to-width (h/w) ratios under biaxial compression was first analyzed based on the complex variable theory. Then, numerical simulations were conducted using PFC2D to study the failure process and energy evolution around a U-shaped cavern with different h/w ratios. Theoretical solution shows that the maximum stress concentration factor occurs at the bottom corner of the U-shaped cavern. With the h/w ratio increasing from 0.75 to 3.0, the stress concentration factor around the sidewall shows a declining trend, while the opposite trend is observed in the vault and floor. Numerical results show that when the maximum principal stress is parallel to the vertical direction, the thin slab buckling occurs in the sidewall of the cavern with low h/w ratios (h/w = 0.75 and 1.0), accompanied by the release of relatively high kinetic energy. Instead, the wedged-shaped slab spalling occurs in the sidewall of the cavern with high h/w ratios (h/w = 1.5, 2.0 and 3.0), which can be considered as a static process. Although the U-shaped cavern with low h/w ratios has higher integrity after failure, more stain energy is accumulated in the remaining surrounding rock, which is likely to cause rockbursts under a higher stress state or dynamic disturbance. When the maximum principal stress is horizontal, the rock slab separates from the cavern floor and presents a reverse trend with the increasing h/w ratio. The above results indicate that the h/w ratio and the direction of maximum principal stress should be considered comprehensively in the design of the support system of U-shaped caverns. [ABSTRACT FROM AUTHOR]

Summary: In actual geotechnical and civil engineering, dynamic stress concentrations around cavities generated by wave sources widely exist. In this study, based on the complex variable theory and Fourier transform method, the expression of the dynamic stress concentration factor (DSCF) around a circular cavity in infinite homogeneous media subjected to transient waves with arbitrary waveform is obtained. The relationships between both steady‐state and transient DSCF and their waveform parameters are investigated quantitatively. The results indicate that a relatively large tensile stress is generated with low Poisson's ratio under steady‐state incidence. Under the condition of transient incidence, the position of the wave peak has a minor effect on the DSCF in the case of small wavenumber, but it has a significant effect in the opposite case. It is found that when the wavenumber is high, such as 0.5, the stress response lags behind the stress wave. In addition, the closer the wave peak to the center of the waveform, the greater the potential damage of the transient incidence. [ABSTRACT FROM AUTHOR]

A theoretical model was first established in order to evaluate the physical possibility of a dynamic response occurring around an existing tunnel under conditions of unloading wave incidence. Based on the steady state solution of the wave expansion approach, transient solutions subjected to unloading waves with different unloading times were obtained. A three-dimensional numerical model was then constructed in order to simulate dynamic responses around an existing tunnel under unloading disturbance forces. In the simulation, dynamic unloading was carried out through a new excavation after stress redistribution had been finalized in the examined tunnel, and parametric studies were then conducted for various unloading times, stress levels and tunnel spacing configurations. The results show that dynamic effects are induced around an existing tunnel under high levels of initial stress and at high unloading rates. The results of the dynamic analysis show that the PPV of unloading-induced microseism can be as high as that of an explosion-induced wave, and damage can be inflicted on existing tunnel walls (especially on the incident side of a tunnel). This dynamic effect diminishes dramatically with an increase in tunnel spacing and unloading times. [ABSTRACT FROM AUTHOR]

To achieve a smooth fracture plane with minimal damage to a rock block or remaining rock mass, a water-coupling cutting blasting technique was applied in a granite quarry. The mechanism of water-coupling cutting blasting is demonstrated with the specification of prerequisites for crack growing and arresting. Using the LS-DYNA program, the maximum principal stress distribution and rock damage evolution process were observed, and the validity of crack extension till coalescence was verified by comparing the calculated and theoretical water pressure needed to induce fracture. The optimum blasting parameters for achieving the best cutting blasting performance were obtained by simulations under different coupling ratios and blasthole spacings. The successful water-coupling cutting blasting practice in the granite quarry has great potential to be applied in other similar engineering. [ABSTRACT FROM AUTHOR]

Stress conditions around deep underground mine openings can significantly influence rock fragmentation and stability, and thus the cuttability of the targeted rock. In this study, rock breakage experiments and associated regression analyses indicate nonlinear rock cuttabilities (decreasing followed by increasing) with increases in the differences between biaxial confining stresses and the values of uniaxial confining stresses. Rock breakages were found to be efficient and safe under low and no-stress conditions that require low indentation force and depth, cutting work and specific energy to completely split the rock wtih no rockburst risk. Stress concentration initially impeded rock breakage, although high uniaxial stress improved rock cuttability. Inducing high stress to fracture the rock and produce an excavation damage zone (EDZ) via stress release effectively transformed the stress condition into low confining stress or even the stress-free condition, improving rock cuttability significantly and preventing rockburst. Mining of rock in the EDZ around the pillar could be efficient, cost-effective and safe when using roadheaders, which showed high cutting efficiencies, low pick wear failures, high machine stabilities and no rockbursts. In addition, a binary linear regression model was proposed to determine the thickness variation of the EDZ correlated with the excavation span and a coupled index of rock properties and buried depth of opening. The results indicated that the thickness of the EDZ increases with increases in the buried depth of the opening, which can improve the applicability of non-explosive mechanized mining in deep mines. [ABSTRACT FROM AUTHOR]

Abstract A modified Hopkinson pressure bar system with coupled static and dynamic disturbance is used to study the failure characteristics of a granite specimen with a cavity. Different coupled static pre-stress and dynamic loading experiments are conducted. The dynamic failure processes and characteristics of the granite specimen with a cavity under the test conditions are summarised. High speed camera images showed that moderate static pre-stresses of 27 MPa and 36 MPa coupled with moderate dynamic loading of 168 MPa lead to violent rock failure, which is the same as rock-burst. In addition, the coupled static pre-stress and dynamic loading processes are simulated, and the dynamic stress concentration factors (DSCFs) and strain energy density (SED) around the cavity under different coupled loads are investigated. The simulation results show that violent rock failure occurs at a higher DSCF and SED. The experimental and numerical setup used in this study provides useful results for investigating the characteristics of rock failure under coupled static and dynamic stress conditions. [ABSTRACT FROM AUTHOR]

Understanding the stress distribution, deformation and fracture behavior around a circular hole or inclusion is critical for the stability assessment of rock structures such as tunnels and backfilled openings. In this study, the analytical solutions of stress and displacement distribution around a circular inclusion of different elastic properties were first derived based on the theory of elasticity. Then prismatic sandstones with a circular hole in different filling modes were prepared and tested in uniaxial compression tests. Progressive deformation and fracturing behavior around holes were analyzed by digital image correlation technique. Moreover, the energy evolution characteristics of specimens were studied to reveal its deformation and failure mechanism. The results show that after filling, the radial and tangential stress and displacement of the inclusion increase, while the stress and displacement around the surrounding rock of the hole decreases, thereby improving the strength and deformation properties. In addition, the crack types and initiation positions around the unfilled and filled holes are quite different due to the stress redistribution. Based on the energy evolution characteristics and the major principal strain fields, the stress-strain behavior is divided into five stages. It is found that the inclusion not only has passive supporting and energy absorption effects on the surrounding rock, but also has a similar crack arrest effect on the initiation and propagation of new cracks. Finally, the effects of inclusion elastic properties and lateral stress coefficient on the stress concentration characteristics around the filled hole were discussed. [ABSTRACT FROM AUTHOR]

Natural or artificially disturbed rocks containing massive fillings are frequently subjected to various sophisticated temperature and stress perturbations. To investigate the effects of temperature and filling angle on the dynamic mechanical characteristics and fracture patterns of red sandstone, thermal treatments at 25°C, 200°C, 400°C, 600°C, and 800°C were conducted on red sandstone samples containing single fracture filling angles at 0°, 30°, 60°, and 90°. Subsequently, the dynamic mechanical information and crack evolution of specimens after thermal treatment were tested and recorded utilizing a modified split Hopkinson pressure bar (SHPB) test system integrated with a high-speed camera, and the crack expansion modes were identified and analyzed. Meanwhile, X-ray diffraction (XRD), scanning electron microscopy (SEM), simulation and one-dimensional stress wave theory were employed to analyze and discuss the thermal damage and failure mechanism of the specimens in detail. The results demonstrate that temperature and filling angle have conspicuous effects on the elastic modulus, thermal expansion, mineral composition, dynamic compressive strength, strain rate effects, and crack expansion modes of the specimens. Tensile cracks dominate the fracture of the specimen during dynamic loading, while shear cracks tend to appear in thermal stress concentration area. Moreover, thermal damage, wave impedance and stress wave propagation path are the critical factors controlling the fracture evolution and dynamic mechanical properties of the specimens. • Effects of thermal treatment on the dynamic behavior of fissure-filled red sandstone. • Fracture patterns of the specimen after the effect of temperature and filling angle are exhibited. • Damage parameters and simulation are employed to characterize the thermal damage. • Wave impedance and stress wave path control the dynamic mechanical response of the specimen. [ABSTRACT FROM AUTHOR]

In this study, the Hoek Brown criteria is primarily employed to calculate the distribution of excavation damaged zone (EDZ) around the cavity buried at 500 m, 1000 m, and 2000 m based on the variation of the in-situ stress and the mechanical properties of the rockmass. Then, the simulation scheme Spectral Element Method (SEM) is applied to investigate the dynamic responses of the excavation-damaged cavity that subjected to the dynamic disturbance, including peak particle velocity (PPV), particle vibration frequency (PVF), particle displacement, and dynamic stress concentration factors (DSCF). Three two-dimensional (2D) models embedding a circular hole with different shapes of EDZ are prepared to numerically study the dynamic responses of the underground cavity, finding the influencing factors, such as the shapes of EDZ, the incident direction of the dynamic disturbance, and the dynamic source frequency. The cavity that is surrounded by EDZ has resembled as the one with a series of low-velocity areas. The results indicate that the underground cavity and EDZ become a scatter to the incoming stress waves that correspondingly produce high amplitude scattered waves. The influencing factors to the dynamic response of the cavity are summarized to be the shape of EDZ, the angle of stress disturbances, and the wavelength of incoming stress waves. We also find that the amplitude of stress disturbance around the cavity is proportional to the areas of EDZ and the frequency of the incident waves. In particular, only the tensile stress concentrates around the cavity that is surrounded by EDZ. [ABSTRACT FROM AUTHOR]

• The porosity effects on dynamic response of water-saturated sandstone was obtained. • Stress distribution characteristics on the fracture surface and inter-particles were analyzed. • Dynamic mechanical model was established considering pore water pressure and Stephen effect. • Effect mechanism of the porosity and water saturation on water-saturated sandstone was revealed. The dynamic response of sandstone to porosity and the amount of water are crucial to understanding the role of these physical parameters on the dynamic behaviour of rock. This study used four different types of sandstone, selected based on a microscopic analysis, for experimental tests and an analytical evaluation. During the experimental tests, dynamic compressive examination was employed on these types of sandstone under both water-saturated and dry states. The ratio of dynamic mechanical parameters of water-saturated sandstone to those of dry sandstone was focused on to eliminate the effect of the self-properties of the sandstone. The results indicate that the effect of water saturation on the dynamic mechanical properties of sandstone significantly affected by the porosity and the weakening degree of water saturation to sandstone positively correlates with the porosity. This effect is intuitively expressed in the features of the fracture propagation as recorded by a high-speed camera and dominated by the micromechanics between the pores and microfracture. This is microscopically attributed to the effect of the pore water pressure and the Stefan effect between the fracture surface and water on the fracture initiation and propagation. In addition, the dynamic mechanical model was further established and applied to discuss the effect mechanism of porosity on the dynamic behaviour of water-saturated sandstone. These insights can contribute significantly to improving the safety and cost-effectiveness of water-saturated rock engineering. [ABSTRACT FROM AUTHOR]

• Hard rock fragmentation using a conical pick under high uniaxial confining stress was performed. • Rockburst triggered by pick penetration was reproduced in laboratory. • A process model was established to shed light on the rockburst mechanism. • Size statistics of the rock fragments produced in rockburst were analyzed. • Correlations between rockburst performances and rock properties were illustrated. High excavation-induced stress concentration and strong mining/tunneling disturbance are prominent conditions in deep excavations, and often present a coupled process to induce rockbursts. This study aims to reproduce and shed light on the rockburst process triggered by hard rock fragmentation using a conical pick. A true triaxial test apparatus was used to apply confining stress and pick force on cubic rock specimen, where the real-time values of the stresses and pick forces were recorded. A high-speed camera system was equipped to shoot the processes of rock fragmentation and rockbursts. The size of fragments produced in rockburst was analyzed via image processing approach. The results show that the cuttability and the rockburst susceptibility of hard rock under high confining stress are correlated with strength parameter and brittleness index of the rock material. Rockburst process consists of three progressive steps: surface slabbing triggered by pick penetration, rapid ejection and violent burst of chips powered by high confining stress, and final shear failure. The mean size of fragments produced in rockbursts decreases as the rock brittleness increases, which suggests that higher rock brittleness will induce more intense rockbursts. Therefore, the precautions, such as timely backfilling of the adjacent mined-out areas, flexible and energy-absorbing rock supports, and pre-destress ahead of excavation, should be taken to prevent rockbursts in peninsula- or island-type hard rock pillar under high excavation-induced stress. [ABSTRACT FROM AUTHOR]

Abstract: In mining engineering, dynamic stress concentrations around cavities generated by wave sources widely exist. To obtain the influence of wave curvature on the dynamic response around the circular cavity, the dynamic stress concentration near the cavity caused by a cylindrical P-wave scattering was investigated based on the wave function expansion methods and Fourier transform. A three-dimensional numerical finite element model was subsequently established to simulate the dynamic damage and its influencing factors, including the peak rising time of the incident wave and the initial lateral pressure coefficient, around the underground cavity subjected to cylindrical P-wave. The results indicate that an obvious dynamic stress concentration occurs around the cavity under dynamic stress disturbance. The dynamic stress concentration factors (DSCFs) caused by the cylindrical P-wave was obtained. Furthermore, the failure characters of the cavity under different initial static stresses and dynamic incident loadings are simulated using the software LS-DYNA, indicating that the dynamic failures are related to the initial static pressure coefficients, peak rise time (t0) of incident wave, and incident wavefront curvature. Keywords: tunnel; transient loading; DSCF; wave function [ABSTRACT FROM AUTHOR]

Highlights • Microseismic source location identification is conducted in deep mines. • Convolutional Neural Networks and Deep Learning algorithm are used. • The accuracy and performance are validated with blast experiment in a deep mine. Abstract Recent years have witnessed a clear trend to develop deeper and longer tunnels to meet the growing needs of mining. Micro-seismic events location is vital for predicting and avoiding the traditional mine disasters induced by high stress concentration, such as rock burst, roof caving, water inrush and slope landslide. Deep learning has become a research hotspot within the field of artificial intelligence in recent years, which has achieved significant progresses and applications in the areas of image recognition, speech recognition, language processing and computer vision. The biggest difference between the deep learning and the traditional back propagation training method is that the deep learning can automatically and independently learn the characteristics of a large amount of data without human intervention. This paper uses Convolutional Neural Network (CNN) and deep learning techniques to develop a method for identifying the Time Delay of Arrival (TDOA) and subsequently the source location of micro-seismic events in underground mines. The power spectrum and phase spectrum of cross wavelet transform calculated from the recorded seismic waves due to micro-seismic events are used as inputs to CNN. The amplitude and phase information of the cross wavelet transform power spectrum are parameters that are used without manual manipulation to build the complex mapping to predict TDOA by deep learning network. Experimental data from the in-field blast tests and simulation tests show that the proposed approach can well identify TDOA and hence detect the event source locations of the field blasting tests. It is demonstrated that the proposed approach with the CNN and deep learning techniques gives more accurate micro seismic source identifications with the recorded noisy waveforms from in-situ blast tests, as compared to several typical existing methods. [ABSTRACT FROM AUTHOR]

To investigate the effects of pre-fabricated holes with different geometries, including size, shape and inclination angle, on the strength and fracture behavior of rock materials, a series of uniaxial compressive tests were conducted on prismatic marble specimens containing a circular or an elliptical hole using a servo-hydraulic machine synchronized with a charge-coupled device (CCD) camera. Digital image correlation (DIC) was applied to record and analyze the deformation and fracturing process of marble. Experimental results combined with theoretical analysis indicate that the geometries of the internal hole are important factors affecting the strength of marble and also the boundary tangential stress distribution. The specimen with a higher tangential compressive stress concentration coefficient will have a lower UCS values. Observations show that the evolution of deformation and fracturing process of marble specimens can be visually displayed by the apparent displacement and strain fields. The propagation of cracks is a progressive development of high major principal strain zones, and the process of damage accumulation, crack initiation and propagation of rock at different stress stages can be well reflected by DIC. When the stress increases to 78.2% of peak value, critical cracks initiate in the tensile stress concentration zones. The progressive process of “open-close-reopen” of tensile cracks was quantitatively studied by the tensile strain of the specimens. It was found that the propagation of tensile cracks surrounding the hole in marble specimens was mainly affected by the nucleation and propagation of strain localization zones. [ABSTRACT FROM AUTHOR]

• The failure mode of samples with different hole sizes were carried out. • The dynamic failure characteristics of different circular tunnel radii were obtained. • The results showed that the initial stress promoted the compression-shear failure. • A theoretical solution including the stress state around of the hole was obtained. A modified Split Hopkinson pressure bar (SHPB) was used to carry out dynamic and static combined loading on prefabricated granite samples. Meanwhile, digital image correlation (DIC) technology was used to evaluate the failure mode of samples with different cylinder hole sizes under different loading conditions. In addition, the dynamic failure characteristics of different circular tunnel radii were obtained by numerical simulation software under impact loads. The influence of different normalized times and Poisson's ratio on the dynamic stress concentration factor (DSCF) distribution around the circular cavity was obtained theoretically. The experimental results show that with the increase in hole diameter and pre-stress, the hole edge damage changes from tensile damage to compression. Numerical simulation reveals the influence of 3D initial stress on the failure of a tunnel, the results showed that the initial stress promoted the compression shear failure and the increment of initial stress would restrain the tensile crack around the tunnel. Furthermore, a theoretical solution indicated that with the increase of Poisson's ratio, the tensile stress on the 0 and π direction increases; with the increase in normalized time, the tensile stress on the incident side decreases first, followed by an increase. When the normalized time increases to 6 ms or higher, the value of the DSCF on the tunnel rarely changes and the value of the DSCF at this time is close to the distribution of steady-state incidence. [ABSTRACT FROM AUTHOR]