Rock Crack Research Articles

Study on the Effect of Negative Temperature Change on the Fracture Morphology of Granite under Impact

SHPB test system was used to conduct dynamic impact experiments on frozen granite under different negative temperatures. The fracture surface of granite under impact load was found via scanning electron microscope (SEM). The micromorphological characteristics of rock fracture under negative temperature are analyzed to explore the influence of negative temperature on the rock fracture morphology, and a practicable explanation is given for the mechanical property changes of rock under different temperatures. Research results showed that low temperatures (<-20°C) caused “frostbite” in granite, leading to a sharp decrease in the rock dynamic mechanical strength under a high strain. Fracture morphology analysis indicated that the lower negative temperatures resulted in the formation of cracks among the mineral particles in the granite. These cracks have poor plastic deformation ability and are easy to destabilize and expand under a high strain rate. Moreover, the coupling effect of impact and negative temperature will cause the cleavage of some crystalline minerals, eventually resulting in the low-stress brittle failure of granite. It is considered that the nucleation of cracks in negative temperature rock under impact load is mainly caused by crystal deformation, which can be divided into three types: the nucleation of cracks resulted from elastic incompatibility between the grains, the nucleation of cracks caused by interface slip, and the nucleation of cracks caused by plastic deformation in crystalline solid.

Research on Crack Propagation of Deep Geologic Mass Disturbed by Excavation Based on Phase Field Method

In recent years, the phase field fracture model has been widely studied and applied. It has good convergence in crack propagation simulation. Comparing with other methods, the phase field method has advantages in simulating crack intersection, bifurcation, and three-dimensional propagation. Based on the phase field method, the influence of excavation disturbance on crack initiation of rock mass is realized in this paper. The phase field fracture variational model is built by using user-defined element interface (UEL) and user material subroutine (UMAT) in ABAQUS. Firstly, the prefabricated crack propagation simulation is carried out to verify the algorithm. The fracture initiates in a butterfly shape and then expands along the horizontal direction. The results show that the maximum support reaction decreases with the gradual increase of l , which is compared with the results obtained by Miehe et al. The result proved the correctness and reliability of the algorithm. In this paper, the phase field fracture model of a flat plate with a reserved small hole under the upper tension is established. The results show that the crack finally produces a crack in the lower left and upper right directions of the square hole and continues to extend to the model boundary, which proves the feasibility of crack independent initiation and propagation by the phase field method. The stress formed a butterfly region until the fracture occurs. And the butterfly stress distribution was still present at the end of crack propagation. The maximum vertical stress was 1.7 × 103 MPa. Based on the South-to-North Water Transfer Project, the simulation of tunnel crack propagation under excavation disturbance is realized for the first time, which is based on the phase field method. The results show that the influence area of excavation disturbance will increase after considering crack development. Comparing the simulation results without considering crack propagation with the simulation results considering crack propagation, it is found that the stress level in the excavation disturbance area around the tunnel is greatly affected by cracks. When the crack is not considered, the maximum vertical stress is 2.16 × 105 Pa, and the maximum horizontal stress is 9.35 × 105 Pa, which occurs at the waist of the tunnel on the horizontal axis. When the crack is considered, the maximum vertical stress is 2.53 × 105 Pa, and the maximum horizontal stress is 1.10 × 106 Pa. It shows that the stress at the dome increases greatly. The vertical stress reaches 3.68 × 105 Pa, and the horizontal stress is up to 3.07 × 103 Pa. For the rock mass far away from the excavation disturbance area, because part of the elastic strain energy is absorbed by the surface crack, the stress level considering the crack is lower than that without the crack. But it is basically similar, indicating the accuracy of the phase field fracture model. This paper realizes the simulation of crack propagation under excavation disturbance and provides a way for the application of phase field fracture model in rock mechanics. This paper proves that phase field method has broad prospects in simulating rock crack propagation and provides the possibility for the popularization of phase field method.

Pre-peak acoustic emission characteristics of tight sandstone failure under true triaxial stress

In this study, experimental investigations were conducted on low-porosity sandstone specimens to reveal their pre-peak cracking characteristics under constant mean stress (σm, 100 MPa) and varying stress Lode angles (θσ, −30° to +30°). The acoustic emission (AE) characteristics 50 s before specimen failure, as well as the strengths and fracturing surface networks, are presented and discussed. The results show that the values of the three principal stresses when the specimen failure occurs change linearly with increasing θσ, in which the maximum principal stress linearly decreases. The AE energy distribution exhibits three ranges, which can be speculated as the different stages of rock cracking propagation. The AE peak frequency is distributed unevenly in seven bands, in which over 90% of the AE signals are located in the 75–95 kHz and 96–130 kHz ranges, which correspond to the tensile and shear cracks, respectively. The RA-AF dynamic evolution curves reveal that the ultimate failure is driven by shear fractures under 3D stress states (for all θσ). The pattern of macrocrack networks shows the “double-X″ through-going mode, and clear tensile and shear areas were directly observed on the fracturing surfaces. These findings are deemed essential for determining the failure mechanism of deep engineering rock masses.

Mechanical behaviours of sandstone containing intersecting fissures under uniaxial compression

Predicting rock cracking is important for assessing the stability of underground engineering. The effects of the intersecting angle α and the distribution orientation angle β of intersecting fissures on the uniaxial compressive strength and the failure characteristics of sandstone containing intersecting fissures are investigated through laboratory experiments and two-dimensional particle flow code (PFC2D). The relationship between the mechanical properties of sandstone and the intersecting angle α and the distribution orientation angle β is analysed. Crack initiation forms and the final failure modes are then categorised and determined via empirical methods. In addition, the cracking processes of intersecting fissures with different α and β values are discussed. The results show that variations in the peak stress, peak strain, average modulus, and crack initiation stress of sandstone containing intersecting fissures show a “moth” shape in the space of the α-β-mechanical parameters. Two crack initiation forms are identified: inner tip cracking (usually accompanied by one outer tip cracking) and only outer tips cracking. Two failure modes are observed: (1) the main fracture planes are created at the inner tip and one outer tip, and (2) the main fracture planes are formed at the two outer tips. Two main crack evolution processes of sandstone containing intersecting fissures under uniaxial compression are found. Approaches for quickly determining the crack initiation form and the failure mode are proposed. The combination of the determination equations for the crack initiation form and the failure mode can be used to predict the crack evolution. The approach for determining the crack evolution processes is hence proposed with acceptable precision.

Disturbance Effect of Blasting Stress Wave on Crack of Rock Mass in Water-Coupled Blasting

The disturbance of a blasting stress wave on rock crack propagation directly affects blasting efficiency. This study aimed to explore the disturbance effect of water-coupled blasting using experimental and theoretical analyses. First, a model of crack instability under a blasting stress wave was analyzed. Next, experiments were conducted to study the characteristics of the blasting stress wave disturbance loads. Finally, blasting disturbances in different coupling media were compared. Following a blasting stress wave, explosive-source-penetrating (ESP) and explosive-source-nonpenetrating (ESNP) cracks underwent tensile failure and compression-shear or tension-shear cracking, respectively. In ESP cracks, the blasting stress wave disturbance load included direct and indirect explosive loads; in ESNP cracks, only the disturbance load was transmitted through rock mass. The differences in the disturbances of blasting with different coupling media were primarily due to the peak explosion pressure of hole wall and the wave-attenuation law in coupling medium. In water-coupled blasting, the disturbance effects transmitted indirectly and directly to the ESP crack tip exceeded those in air-coupled blasting by 1.19 and 3.80 times, respectively. In ESNP cracks, the disturbance effect in water-coupled blasting was equal to or greater than 1.32 times that in air-coupled blasting. The results of this study provide a theoretical basis for improving the design of water-coupled blasting.

Research on Rock Crack Classification Based on Acoustic Emission Waveform Feature Extraction Technology

Abstract Rock fracture mode has practical significance for the prediction and prevention of engineering disasters, and the inversion of fracture mode by the waveform signal not only reduces the experimental error of the mechanical strength measurement but also simplifies the type and quantity of disaster prediction source data. For the relationship between crack mode and mechanical strength, the acoustic emission (AE) waveform signal is studied. Six coarse-grained sandstone samples were tested by uniaxial compression, AE, and scanning electron microscopy. The results show that the number of microhole cracks in rock is positively correlated with tensile-shear cracks and negatively correlated with mechanical strength. The quadratic function regression curve of the proportion of shear cracks and mechanical strength is more realistic. When crack ratio is less than 0.31, the number of shear cracks is positively correlated with the mechanical strength and vice versa. The waveform mutation coefficient k is defined as the overall change description. It is found that the increase of signal mutation has a positive impact on the mechanical strength of rock. The fitting function of crack and the signal mutation near the peak of rock can be divided into six risk zones in a two-dimensional plane. In addition to these exciting results and discoveries, the determination of the number of tensile-shear cracks and its relationship with mechanical strength provide innovative methods and ideas for crack pattern discrimination and rock burst risk assessment of roadway surrounding rock.

Energy characteristics of sandstones with different crack angles under true triaxial cyclic loading and unloading

AbstractThe effect of crack angle on energy evolution during sandstone failure subjected to true triaxial cyclic loading and unloading is of great concern. However, the energy consumed in the crack initiation and compaction process is generally referred to the dissipated energy, which is inaccurate. To reveal the energy law in the breaking process of sandstone, a complex cyclic loading and unloading test is carried out on precast angled sandstone samples by employing the triaxial test system. The area integral methodology is exploited to evaluate the evolution of total energy density, elastic energy density, dissipated energy density, and plastic energy density of the rock samples of different crack angles. The variations of these four energy density levels in terms of the number of loading and unloading cycles and the upper limit of stress are explained and discussed. The obtained results reveal that during the entire cycle of loading and unloading, the variations of the above‐mentioned factors of the rock sample fairly do not rely on the crack angle. The energy density increases with the number of cycles, and the total energy density and elastic energy density significantly increase faster than the consumption mode. The growth rate of the dissipative energy density is greater than that of the plastic energy density. Additionally, the aforementioned four energy quantities grow in a quadratic manner as a function of the upper limit of the loading stress. The releasable elastic energy gradually magnifies by increasing the upper limit of the loading stress. The plasticity density first decreases and then increases, reflecting the change law of the irreversible plastic deformation caused by newly developed cracks in the rock sample. The elastic energy density, the fitting coefficient of the dissipated energy density, and the total energy density are employed to define the characteristic coefficients of the rock energy storage and energy dissipation. The results indicate that the larger the rock crack angle, the stronger the energy storage energy and the weaker the energy dissipation capacity. It also explains that how the strength of the rock sample becomes higher as the crack angle increases.

The Pullout Mechanical Properties of Shrub Root Systems in a Typical Karst Area, Southwest China

Roots play a major role in reinforcing and stabilizing soil. The pullout mechanical characteristics of soil reinforcement and slope protection of the root systems of dominant shrub species (Pyracantha and Geranium) were estimated by in-situ pullout tests in a karst area, in which roots were pulled out from soil to reliably test the pulling force. The goals of this study were to discover the pullout mechanical properties of roots in karst areas and to try to analyse the impact of the root system on landslide control. The F–s curves were multipeak curves with a noticeable main peak and main double peaks. The curves showed a linear increasing trend at the initial stage of drawing and decreased rapidly after reaching the peak. The F–s curves of root systems inserted into rock cracks showed secondary fluctuations in the later stage of drawing, and rock cracks stimulated the tensile efficiency of the root system more effectively. Field in situ pullout results indicate that tree roots fail progressively rather than simultaneously. The maximum pulling force had a linear relationship with the increase in soil thickness and a disproportionate increasing trend with the increasing number of broken roots. The displacement of the maximum peak was different between the two tree species and was concentrated at 5–15 cm and 5–25 cm for Pyracantha and Geranium, respectively. The maximum pulling force of Geranium was 1.29 times that of Pyracantha, and the root system of Geranium had strong pullout resistance. We concluded that the peak distribution of the F–s curves was affected by broken roots and rock cracks, while soil thickness and the number of broken roots had positive effects on the maximum pulling force, all of which is helpful in understanding the effect of root pullout mechanical properties on landslides in karst areas.

A coupled thermo-mechanical bond-based smoothed particle dynamics model for simulating thermal cracking in rocks

A smoothed particle dynamics (SPD) method was proposed for crack propagation analysis. The computational efficiency of this method was significantly better than the traditional smoothed particle hydrodynamics (SPH) method. In the SPD method, the motion equations were approximated by a Lagrange kernel determined by the coordinates of the material in the initial configuration. A coupled thermo-mechanical bond-based smoothed particle dynamics (TM-BB-SPD) model was proposed for simulating the thermal cracking process of rocks. In the SPD program, the thermal cracking behaviors of rock, such as crack initiation and propagation, were dynamically tracked by capturing the damage state of virtual bonds. The robustness and accuracy of the proposed SPD method and TM-BB-SPD model were verified using two benchmark examples. The numerical results were in good agreement with the experimental results and analytical solutions. In addition, the effects of the thermal expansion coefficient and homogeneity index on the mode of thermal cracking in the rock disc were also investigated. The numerical results were also in good agreement with previous experimental observations. Moreover, the numerical results showed that with an increase in the homogeneity index, the mode of crack propagation in rock gradually changed from non-smooth to smooth types of fracture.

Evolutionary Analysis of Heterogeneous Granite Microcracks Based on Digital Image Processing in Grain-Block Model.

Rocks are natural materials with a heterogeneous microstructure, and the heterogeneity of the microstructure plays a crucial role in the evolution of microcracks during the compression process. A numerical model of a rock with a heterogeneous structure under compression is developed by digital image processing techniques and the discrete element method. On the grain scale, the damage mechanism and microcrack characteristics of a heterogeneous Biotite granite under compression fracture are investigated. First, the process of constructing a digital image-based heterogeneous grain model is described. The microscopic characteristics of geometric heterogeneity, elastic heterogeneity, and contact heterogeneity are all considered in the numerical model. Then, the model is calibrated according to the macroscopic properties of biotite granite obtained in the laboratory, and the numerically simulated microcrack cracking processes and damage modes are obtained with a high degree of agreement compared to the experiments. Numerical simulations have shown the following: (1) Microcracking occurs first at the weak side of the grain boundaries, and the appearance of intragranular shear cracks indicates that the rock has reached its peak strength. (2) The stress concentration caused by the heterogeneity of the microstructure is an essential factor that causes rock cracks and induces rupture. Intragranular cracks occur successively in quartz, feldspar (plagioclase), and biotite, with far more intragranular cracks in quartz and feldspar (plagioclase) than in biotite. (3) Microcracking in quartz occurs as clusters, fork and fracture features, and in feldspar (plagioclase) it tends to cause penetration microcracking, which usually surrounds or terminates at the biotite. (4) As the confining pressure increases, the tensile break between the grains is suppressed and the number of shear cracks increases. At the macro level, the rock failure mode of the numerical model changes from split damage to shear destruction, which is consistent with the law shown in laboratory experiments.

Stable Crack Propagation Model of Rock Based on Crack Strain

The establishment of a rock constitutive model considering microcrack propagation characteristics is an important channel to reflect the progressive damage and failure of rocks. The prepeak crack strain evolution curve of rock is divided into three stages based on the triaxial compression test results of granite and the definition of crack strain. According to the nonlinear variation characteristics of crack strain in the stage of rock crack stable propagation, rock deformation is expressed as the sum of matrix strain and crack strain. Then, the exponential constitutive relationship of rock crack stable propagation is deduced. The axial crack strains of the rock sample and its longitudinal section are equal. Thus, the longitudinal symmetry plane of the rock sample is abstracted as a model containing sliding crack structure in an elastic body, and the evolution equation of crack geometric parameters in the process of stable crack propagation is obtained. Compared with the experimental data, results show that the rock crack stable propagation model based on crack strain can adequately describe the evolution law of crack strain and wing crack length. In addition, the wing crack propagates easily when the elastic body with small width contains an initial crack with a large length and an axial dip angle of 45° under compressive load. This study provides a new idea for the analysis of the stable propagation characteristics and laws of rock cracks under compressive load.

Crack propagation characteristics and fracture toughness analysis of rock-based layered material with pre-existing crack under semi-circular bending

Fracture initiation, fracture propagation, and their interactions with the interlayer interface in rock-based layered material are important in assessing the stability of rock-based structures such as lined tunnels. A numerical model based on the inserted cohesive zone model (CZM) method is established, and further verified against the semi-circular bending (SCB) test to simulate the complex crack initiation and propagation behavior in a rock-based layered semi-circular disk with pre-existing rock crack at different angles. From the results, three typical crack propagation modes are identified: interface fracture, wing fracture from crack tip and wing fracture not from crack tip. At a small crack inclination angle, interfacial crack is formed, while at a larger crack inclination angle, wing crack which initiates deviating from the crack tip appears. It is found that the crack propagation mode is also controlled by the interface strength, and the interface crack is always formed in SCB specimens with lower interface strength. By increasing the interface strength, the length of interface crack gradually decreases and wing crack presents. When the pre-existing rock crack inclines greater than 45° and the interface strength is larger, the wing crack initiating far away from the crack tip merges with the interface crack to be connected propagating path, and the initiation position of wing crack gradually moves toward the crack tip with the further increasing of interface strength. Moreover, it is also found that the crack length ratio and the support span ratio are important influencing factors for crack propagation mode. Increasing the crack length ratio can suppress the formation of interfacial crack. When the crack inclination angle is more than 45°, the wing crack tends to originate at the tip of pre-existing crack as the support span ratio increases. In addition, the effects of crack length ratio, support span ratio, crack inclination angle and Young’s modulus ratio on the fracture toughness of layered SCB specimen under different loading modes are also investigated and the corresponding results indicate that these factors remarkably control the fracture mode and fracture resistance of rock-based layered material.

Simulation and experimental research on ultrasonic vibration high temperature rock

Ultrasonic vibration technology as a new type of auxiliary lithotripsy technology, a lot of research on this technology. However, at present, the effect of rock temperature on ultrasonic vibration of rock breaking has not been studied. Therefore, with the help of numerical simulation software, nuclear magnetic resonance detection and penetrant testing methods, it is necessary to complete the numerical simulation and laboratory testing of granite at different temperatures under ultrasonic vibration with granite as the research object. The main results are as follows:1. Under ultrasonic vibration, the number of rock cracks will increase with increasing temperature. And the fracture azimuth intensity in the rock model is 90°concentrated. 2. As the temperature increases, the accumulated thermal damage will promote the large number of expansion and connection of certain internal cracks, resulting in the macroscopic destruction of the rock sample and the increase in crack volume. 3. With the increase of temperature, the increase of porosity of rock samples under ultrasonic vibration has a staged characteristic. And 150 °C is the threshold. The significance of this research is to provide theoretical and technical support for the application of ultrasonic vibration technology in the future hard rock geological exploration and deep resource mining.

Excavation-induced deep hard rock fracturing: Methodology and applications

To analyze and predict the mechanical behaviors of deep hard rocks, some key issues concerning rock fracturing mechanics for deep hard rock excavations are discussed. First, a series of apparatuses and methods have been developed to test the mechanical properties and fracturing behaviors of hard rocks under high true triaxial stress paths. Evolution mechanisms of stress-induced disasters in deep hard rock excavations, such as spalling, deep cracking, massive roof collapse, large deformation and rockbursts, have been recognized. The analytical theory for the fracturing process of hard rock masses, including the three-dimensional failure criterion, stress-induced mechanical model, fracturing degree index, energy release index and numerical method, has been established. The cracking-restraint method is developed for mitigating or controlling rock spalling, deep cracking and massive collapse of deep hard rocks. An energy-controlled method is also proposed for the prevention of rockbursts. Finally, two typical cases are used to illustrate the application of the proposed methodology in the Baihetan caverns and Bayu tunnels of China.

Main features of the latest geodynamics of the North-West and Central Caucasus

Structural-geomorphological and morphometric analyses of the North-West and Central Caucasus (to the meridian of Elbrus) and adjacent areas of the foothills and the Black Sea basin, supplemented by computer statistical processing of field fracturing measurements, revealed the longitudinal and transverse zonal of the latest dislocations, which is inherited from ancient stages of development. The distribution of earthquakes is subordinate to the neotectonic zonal. It has been established that the cracking of different age rocks determines the orientation of the modern erosion network, and the lines of its elongation, built with the help of the LESSA program, correlate with the field of tectonic stresses. Morphometric analysis showed a high degree of statistical correlation between the density of earthquakes and the magnitude of the vertical dissection of the relief, the speed of modern vertical movements, which makes it possible to recommend these parameters for forecasting seismicity.

Evolution of tensile and shear cracking in crystalline rocks under compression

We performed laboratory-scale unconfined compression experiments on Barre granite specimen with a single pre-existing flaw to study the evolution of tensile and shear cracking that occurs during different stress levels. Moment tensor inversion of acoustic emission (AE) events in combination with the nonelastic strain component obtained through the 2D digital image correlation (DIC) technique are used to track the changes in the source mechanisms of the stress-induced cracks. The mode of deformation computed from the image based strain profiles, enables visual comparison of the nucleation, growth and interaction of the tensile and shear cracks with the microseismic source mechanism observed by moment tensor inversion of the AE events. Comparing the results obtained from the two techniques on the same dataset demonstrates a quantitative correlation between the acoustic and visual observations in terms of the cracking mechanisms obtained at different stages of cracking from crack initiation at the flaw tips to the failure of the rock specimen.

A complex analysis of stress intensity factors for two asymmetric and unequal collinear cracks in rocks subjected to compressive and shear loads

Crack in the rocks is an important factor of landslide disasters, and cracks may be interconnected to form a large gap under compressive and shear loads. Therefore, it is necessary to study the stability of cracks. In order to study the interaction between multiple cracks, a plane containing two asymmetric and unequal collinear cracks under compressive loads, shear loads and internal pressure was investigated. Complex functions were applied to derive the stress intensity factors (SIFs) of crack tips. The numerical simulation by using the ABAQUS code was conducted to validate the correctness of theoretical solutions, and the numerical results were in good agreement with the theoretical solutions. Then, the effects of outer shear stress, internal pressure, crack distance, crack surface friction and crack length on stress intensity factors of mode II were discussed. We thus can conclude that internal pressure will reduce the friction effect on the crack surface and cause the crack to initiate more easily; the maximum value of KII increases with the outer shear stress increase; the SIFs of internal crack tips are more easily affected by the distance of cracks than that of the external crack tips.

MLS-Based Numerical Manifold Method for Modeling the Cracked Rock Considering the Contact of the Crack Surface

To simulate the moving boundary problems, the moving least square–based numerical manifold method, abbreviated as MLS-based NMM, was proposed. The MLS-based NMM has been applied successfully to open crack problems, which exhibits the high accuracy and strong robustness. In this study, we extend the MLS-based NMM to simulate the cracked rock considering the contact of the crack surface. Simultaneously, in order to simulate the progressive failure of the cracked rock, an improved strength-based criterion is proposed. The criterion is based on the Mohr–Coulomb criterion and maximum tensile stress criterion. Because rock can be regarded as a quasi-brittle material, a characteristic distance is used to calculate the crack tip stress and correct the crack propagation direction which avoids the phenomenon of “Zig-zag” for the crack propagation path based on the fracture mechanics criterion. The proposed strength-based criterion can acquire the crack tip stress and propagation direction and also realize the automatic determination of the crack propagation length in each step of the crack growth. A Brazilian disc problem and a rectangular plate problem are adopted to verify the numerical model. At last, the numerical model is applied to study the progressive failure process of the rock slope. The results indicate that the proposed method can deal with the crack propagation in the rock and the opening/sliding of rock blocks along discontinuities in a natural way.

Research on Evolution Characteristics of Shale Crack Based on Simultaneous Monitoring of Multi-Parameters

Meso-crack evolution mechanism of shale is a key factor affecting the mechanical properties of shale. In order to explore evolution laws of cracks in shale during loading, a meso-crack monitoring system, loading test equipment and an automatic ultrasonic data acquisition system were set up. On this basis, a set of experimental apparatus simultaneous monitoring multi-parameters of shale micro-crack was designed, and destruction experiments of shale samples with different bedding angles were carried out to find out evolution characteristics of cracks. The results show the following: (1) The designed apparatus can monitor ultrasonic, mechanical and video information simultaneously of crack evolution in the entire process of shale destruction under load to provide information for analyzing acoustic and mechanical characteristic responses of crack propagation at key time nodes. (2) With an increase in load, shale will undergo four stages of destruction: crack initiation, propagation, penetration and overall failure. In the course of these stages, acoustic characteristics and mechanical characteristics are in good agreement, which proves the validity of predicting rock mechanical parameters with acoustic data. (3) During the loading process of shale, the main amplitude of acoustic wave is more sensitive than mechanical parameters to the change of rock cracks. Research results have important theoretical reference value for evaluating wall stability of shale gas horizontal well with ultrasonic data.

Investigation of Cement Prepared with Microencapsulated Microorganisms.

Cracks in underground rock masses cause gas leakage, seepage, and water inflow. To realize calcium carbonate deposition and mineralization filling in rock cracks, microencapsulated bacterial spores were prepared by an oil phase separation method. To optimize the microorganism growth conditions, the effects of microcapsules with various pHs, particle sizes, and amounts on microcrack self-healing were investigated through an orthogonal test, and the best conditions for repairing the cracks using microencapsulated Bacillus sphaericus were obtained. Infrared analysis and scanning electron microscopy were used to observe the morphological characteristics and coating performance of the microcapsules. The results showed that the microcapsules contained functional groups in the core and wall materials. The surfaces of the microcapsules prepared by the test were rough, which was beneficial for adhesion onto the fracture surface. X-ray diffraction analysis, X-ray photoelectron spectroscopy, and thermal analysis were conducted. The results showed that the microcapsules with pH = 8 and a particle size of 100 μm had the highest thermal decomposition temperature and the best thermal stability. The elements of the core and wall materials were detected in the microcapsules, and the coating had a beneficial effect. The compression and acoustic emission tests of the specimens embedding microbial capsules with different contents under different working conditions revealed that the two fractures of the specimen were due to the rupture of the microcapsule and the rupture of the rock specimen, indicating the best mechanical triggering properties and compressive properties of the microcapsule.