Macroscopic Crack Propagation Research Articles

Failure Mechanism and Control Mechanism of Intermittent Jointed Rock Bridge Based on Acoustic Emission (AE) and Digital Image Correlation (DIC).

Deep foundation pit excavation is an important way to develop underground space in congested urban areas. Rock bridges prevent the interconnection of joints and control the deformation and failure of the rock mass caused by excavation for foundation pits. However, few studies have considered the acoustic properties and strain field evolution of rock bridges. To investigate the control mechanisms of rock bridges in intermittent joints, jointed specimens with varying rock bridge length and angle were prepared and subjected to laboratory uniaxial compression tests, employing acoustic emission (AE) and digital image correlation (DIC) techniques. The results indicated a linear and positive correlation between uniaxial compressive strength and length, and a non-linear and negative correlation with angle. Moreover, AE counts and cumulative AE counts increased with loading, suggesting surges due to the propagation and coalescence of wing and macroscopic cracks. Analysis of RA-AF values revealed that shear microcracks dominated the failure, with the ratio of shear microcracks increasing as length decreased and angle increased. Notably, angle exerted a more significant impact on the damage form. As length diminished, the failure plane's transition across the rock bridge shifted from a complex coalescence of shear cracks to a direct merger of only coplanar shear cracks, reducing the number of tensile cracks required for failure initiation. The larger the angle, the higher the degree of coalescence of the rock bridge and, consequently, the fewer tensile cracks required for failure. The decrease of length and the increase of angle make rock mass more fragile. The more inclined the failure mode is to shear failure, the smaller the damage required for failure, and the more prone the areas is to rock mass disaster. These findings can provide theoretical guidance for the deformation and control of deep foundation pits.

A new nonlocal macro-micro-scale consistent damage model for layered rock mass

Layered rock mass exhibits transverse isotropic characteristics in deformation and strength, and the strength anisotropy is difficult to achieve in traditional local action modes. Therefore, in the framework of nonlocal macro–micro-scale consistent damage (NMMD) theory, this paper constructed a micro damage criterion suitable for layered rock, where both the critical elongation and the brittleness index of material bond are defined as an elliptic function of the bond angle. Next, based on the geometric damage reflecting continuity loss of material point, which is obtained by the weighted average of bond damages around the point, an energy degradation model of a transversely isotropic stiffness matrix is established to achieve localized damage propagation of macroscopic cracks in the layered rock mass. The reliability and advantage of the NMMD model for transversely isotropic material are verified by comparison with the experimental and phase field results through a three-point bending shale beam with different bedding orientations. Finally, the splitting mechanism and bearing capacity of the Brazilian disk with different bedding directions and different inclinations of notch are explored through the established NMMD finite element model. The model is easily implemented, enabling automatic tracing of cracks and accurate prediction of load–displacement curves.

Intrinsic mechanisms of shale hydration-induced structural changes

The interaction between a water-based working fluid and shale causes a change in shale structure, resulting in wellbore instability and greatly increasing drilling costs. On the basis of the black rock samples of the Longmaxi Formation, the structural change characteristics and internal mechanisms of shale hydration are investigated using scanning electron microscopy, fixed-point observation experiments, X-ray diffraction experiments, ion analysis, and energy spectroscopy analysis. In this study, the changes in the microscopic elements during the propagation of macroscopic cracks to hydration were studied and the ion exchange of brine and mineral hydration was analyzed. The results indicate that the interaction between water and shale leads to shale fracture along the bedding plane, the expansion of primary fractures, the generation of new fractures, and the occurrence of a high number of dissolution phenomena. The ion exchange cation precipitation of shale and the fluid is dominated by Ca2+, and the anion precipitated is mainly SO42−. Through the energy spectrum analysis of the whole-rock mineral composition changes and shale structural changes, it is believed that shale dissolution is mainly from carbonatite minerals, such as calcite. While the oxidation of pyrite in the aqueous environment provides a large amount of SO42− and H+ and fracture propagation mainly occurs in areas where non quartz inorganic minerals are distributed on the bedding plane. The intrinsic mechanism of shale hydration structural changes is revealed through the structural changes, mineral composition changes, and chemical reactions present during the water–shale interaction, which is significant for ensuring the wellbore stability of drilling.

Acid-assisted subcritical blunt-tip crack propagation in carbonate rocks

AbstractSubcritical crack propagation in stressed carbonate rocks in a chemically reactive environment is a fundamental mechanism underlying many geomechanical processes frequently encountered in the engineering of geo-energy, including unconventional shale gas, geothermal energy, carbon sequestration and utilization. How a macroscopic Mode I crack propagates driven by a reactive fluid pressurizing on the crack surfaces with acidic agents diffusing into the rock matrix remains an open question. Here, the carbonate rock is modeled as an elasto-viscoplastic material with the mineral mass removal process affecting the rock properties in both elastic and plastic domains. A blunt-tip crack is considered to avoid any geometrically induced singularity problem and to allow a numerical analysis on the evolution of the chemical field being linked to the micro-cracking activities in front of the crack tip, affecting the delivery of acid. The model is capable of reproducing an archetypal three-region behavior of subcritical crack growth in a reactive environment. The crack propagation exhibits a prominent acceleration in Region III due to a two-way mutually enhancing feedback between mineral dissolution and the degradation process, which is most pronounced in front of the crack tip. With the consideration of initial imperfections in the rock, the macroscopic crack propagation is further accelerated with a secondary acceleration arising due to self-organization of micro-bands inside the chemically enabled plasticity zone.

An investigation on fracture toughness predictions from mini-sized uniaxial tensile specimens with global and local approaches

This study provides investigations on whether the fracture toughness can be accurately predicted from mini-sized uniaxial tensile specimens with existing global and local approaches. The critical toughness model, based on classical fracture mechanics, and the energy release rate (ERR) model, based on damage mechanics, were used as the two representative global approaches. While the finite element simulated compact tension (CT) specimen implemented with Gurson-Tvergaard-Needleman model was used as the local approach. Specimen size effect was judged through the viewpoints of stress–strain relationship and damage development. It was proved that the specimen size has no significant influence on stress–strain relationship, and has little influence on damage developments when the thickness reaches 1.0 mm. Fracture toughness predictions were conducted on four metals, including two steels (SA508Gr.3Cl.1 and 18MnMoNbR), one aluminum alloy (6061-T651), and one titanium alloy (TC4). For TC4 exhibiting brittle cleavage features on the fracture surface of CT specimens, neither the global nor the local approach can accurately predict its fracture toughness. For 6061-T651 exhibiting both ductile and brittle features on the fracture surface of CT specimens, there exists significant macroscopic crack propagation at the moment of conventional fracture toughness determination. The existence of significant macroscopic crack is inconsistent with the “equivalent crack” assumption in the ERR model, leading to a failure in its fracture toughness prediction. For two steels following the “equivalent crack” assumption, the ERR model and the local approach yield more accurate predictions (with the maximum error around 10 %) than their critical toughness counterpart (with the maximum error around 30 %).

Study on Fatigue Life of Aluminum Alloy 6061-T6 Based on Random Defect Characteristics.

A certain number of hole-like defects will occur in aluminum alloys under cyclic loading. The internal holes will reduce the strength of the material and cause stress concentration, which will aggravate the development of fatigue damage. A classification method of defect features based on X-ray CT damage data is proposed. The random hole distribution model is established through the linear congruence method and the region division method. The hole parameter is introduced as the intermediate variable of the 3D reconstruction model of internal defects. In the mesoscopic stage, the function relationship between the distribution of random holes and the fatigue life is established based on the coupling relationship between the number and proportion of pores and the fatigue life. In the macroscopic stage, the relationship between the random holes and the macroscopic crack growth life is established by taking the crack length as the damage variable. The crack propagation rate decreased with the increase in the number of holes. The prediction model of the whole life stage is established using the life function from microcrack initiation to macroscopic crack propagation. Finally, the validity of the whole stage fatigue life prediction model is demonstrated through the comparison and verification of experiments, which provides a certain engineering value for the life estimation of 6061-T6 aluminum alloy materials.

Impact Analysis of Microscopic Defect Types on the Macroscopic Crack Propagation in Sintered Silver Nanoparticles

Impact Analysis of Microscopic Defect Types on the Macroscopic Crack Propagation in Sintered Silver Nanoparticles

Macroscopic and microscopic mechanical characteristics and crack propagation behavior of sandstone-like samples with single cracks under freeze–thaw cycles: Experimental and numerical simulation

In permafrost regions, rock engineering projects inevitably suffer from the effects of freeze–thaw (F-T) cycles under complex geographical and climatic conditions. Under F-T cycles, the damage and deterioration of macro- and microdefects, such as joints and cracks, in the rock will reduce the structural stability of the rock and even lead to frost damage in rock engineering. In this study, through indoor F-T cycle tests, uniaxial/triaxial compression tests, acoustic emission monitoring, and discrete element method (PFC 3D) modeling, the macro/microscopic mechanical characteristics and crack propagation behavior of sandstone-like samples with single cracks under F-T cycles were investigated. The results show that the compressive strength of sandstone-like samples with single cracks tends to decrease and then increase with an increasing crack angle and exhibits a stable decreasing trend with increasing F-T cycles, indicating a significant crack angle effect and F-T deterioration effect. Additionally, the confining pressure has an inhibiting effect on the F-T deterioration of samples, and there is a mutual inhibition relationship between the F-T deterioration effect and the crack angle effect. The characteristics of the acoustic emission signals during the loading process of sandstone-like samples with single cracks show good consistency with the stress–strain curves. The analysis of fracture mechanisms based on rise time/amplitude (RA) and average frequency (AF) is consistent with the macroscopic failure modes observed in the experiments. Moreover, with an increase in the number of F-T cycles, the number of tension cracks in the sandstone-like samples with single cracks increases, while the number of shear cracks decreases. The crack propagation behavior of sandstone-like samples with single cracks obtained through discrete element simulations (PFC 3D) is mainly divided into four stages: Stage I - initial calm stage, Stage II - crack initiation stage, Stage III - crack propagation stage, and Stage IV - failure stage. The simulated mechanical properties and failure modes agree well with the experimental results, and five crack propagation modes of sandstone-like samples with single cracks under F-T cycles were proposed: direct tension (DT), relative tension (RT), shear-tension (ST), direct shear (DS) and relative shear (RS).

Cohesive Zone Modelling and the Fracture Process of Cement-Based Composites

Computational modelling of quasi-brittle fracture in cement-based composites needs to cover both i) the damage caused by micro-fractured zones, referring to some nonlocal strain-stress relations, respecting quite different behaviour of such composites in tension and compression, and ii) the initiation and propagation of macroscopic cracks, exploiting the cohesive zone model, handled by some modification of the finite element technique, together with the discretization in time. A fundamental issue for such model is the introduction of a traction-separation (stress-displacement) relationship. This contribution pays particular attention to the design, identification and estimation of material parameters for the traction separation law suitable for predicting the deformation behaviour of samples of materials and structures.

Study on the influence of mineral composition on the mechanical properties of granite based on FDEM-GBM method

The macroscopic mechanical properties and crack propagation of rocks are significantly affected by the micro-scale heterogeneity of rocks. In this study, a two-dimensional tensile/shear fracture model to simulate the nonlinear behavior of grain boundaries through a combined finite-discrete element method based on the grain model (FDEM-GBM). The purpose of this model was to investigate the effects of mineral composition on rock mechanical properties and fracture extension. To calibrate the micromechanical parameters of the cohesive elements within the numerical rock model, the Plackett–Burman design and response surface method were employed. Furthermore, the study analyzed the effects of different mineral compositions on the macro-mechanical characteristics of rocks and attempted to interpret the results from the perspective of fracture evolution. The results demonstrated that the PB design-response surface design-iterative optimization method successfully enabled the calibration of the required microscopic parameters in the FDEM-GBM model. Under uniaxial compression loading, damage primarily occurred inside the crystal, with a dominant mode of tensile failure at the stress peak. Additionally, an increase in feldspar mineral content generally led to a decreasing trend in the uniaxial compressive strength and elastic modulus of the rock model. This changing pattern may be associated with the greater presence of internal cracks within feldspar minerals and relatively fewer cracks in quartz minerals.

A novel damaged-based numerical manifold method to simulate the failure process of brittle rocks from damage evolution to crack initiation, propagation and coalescence

In addition to macroscopic crack propagation and coalescence, the nonlinear deformation of rocks also includes mesoscopic damage buildup and transformation to macroscopic crack. To accurately model the progressive failure process of rocks, a novel damage-based numerical manifold method (NMM) is proposed in this study. The damaged-based NMM incorporates the Weibull statistical distribution, and the exponential function material softening model to describe damage evolution and strength reduction of heterogeneous material. When the damage accumulation of adjacent manifold elements satisfies the failure threshold, a real macroscopic crack is initiated from these two manifold elements, accompanied by cutting off these two manifold elements. The Mohr-Coulomb criterion with a tension cut-off was used to evaluate fracture modes of cracks. To verify the proposed method, a series of numerical tests were conducted and the numerical results were compared with laboratory experiments and other numerical results. On this basis, the effect of heterogeneity on the failure process in rock specimens with a single crack is clarified. Results from this study show that the simulations satisfactorily capture the failure process of brittle rocks from damage evolution to crack initiation, propagation, coalescence and large displacement, implying that the method is an appropriate and robust tool to model the damage and fracture behavior of rocks.

High temperature creep property of a novel porous double layer cooling structure for gas turbine blades

This article investigates the high-temperature creep macroscopic and microscopic fracture mechanism of the porous double layer (PDL) cooling structure through experiments, and predicts the creep life of the structure using the back propagation (BP) neural network model based on the bone point stress method. The high temperature creep fracture of the PDL cooling structure is determined by the macro structure characteristics and the microstructure properties. Impingement holes and effusion holes, as stress concentration region, provide a place for crack initiation. The crack growth rate of effusion plate is greater than that of impingement plate. When the creep crack extends to a certain length, the effusion plate breaks first, and then the impingement plate breaks instantaneously. At the interface between carbide and matrix, microcracks are prone to occur due to stress concentration and inconsistent deformation, thereby promoting the initiation and propagation of macroscopic cracks. The BP neural network model based on the bone point method has a good prediction result for the creep life of the PDL cooling structure, and the maximum prediction error is 9%.

Strength Properties and Damage Evolution Mechanism of Single-Flawed Brazilian Discs: An Experimental Study and Particle Flow Simulation

Understanding the tensile strength properties and damage evolution mechanism in fissured rock is very important to fundamental research and engineering design. The effects of flaw dip angle on the tensile strength, macroscopic crack propagation and failure mode of symmetrical Brazilian discs of rock-like materials were investigated. A parallel bonding model was proposed to examine the damage of pre-flawed discs under splitting the load. The microscopic parameters of particles and bonds in the model that can characterize rock-like materials’ mechanical and deformation properties were obtained by calibrating against the laboratory test results. The crack development, energy evolution and damage characteristics of Brazil discs containing a single pre-existing flaw were studied at the microscopic scale. The results show that the flaw significantly weakens the strength of the Brazilian disc, and both the peak load and the initial cracking load decrease with increasing flaw angle. The failure modes of the rock-like specimens are mainly divided into three types: wing crack penetration damage mode, tensile-shear penetration damage mode and radial penetration failure mode. Except for the flaw dip angle 0°, the wing cracks generally sprouted at the tip of the pre-flaw, and the wing cracks at both tips of the pre-flaw are centrosymmetric. Crack coalescence was concentrated in the post-peak stage. Based on the particle flow code (PFC) energy partitions, the damage variables characterized by dissipation energy were proposed. The disc specimen’s pre-peak damage variables and peak damage variables decreased with increasing flaw angle, and the damage was concentrated in the post-peak phase.

Characterization of Carbon Fibre Reinforced Polyphenylene Sulfide Composite Under Interlaminar Shear Strength

Aerospace industry is seeking thermoplastic composites materials due to several advantages over thermoset material and one of them is mechanical properties. Mechanical properties of thermoplastic composite materials are found to be superior compared to thermoset materials. High strength fibre composites parts are made of several plies with different fibre orientation with a designed balanced of lay-up sequence. Interlaminar Shear Strength (ILSS) is an essential consideration when designing laminated structures exposed to transverse stresses. It is to predict quality and strength of laminate levels of composite due to, composite failure cannot be observed directly to the propagation of single macroscopic crack when subjected to cyclic loading. This test is employed to evaluate both the interfacial adhesion of the matrix and the influence of the reinforcement on the mechanical characteristics of the composite. This study provides the understanding of ILSS test of 2 different thickness for 6 and 8 plies Carbon Fibre Reinforced Polyphenylene Sulfide (CF/PPS) according to the testing standard EN 2563. The results show that 8 plies have higher ILSS properties compared to 6 plies. The fractography of the CF/PPS composite under Scanning Electron Microscope (SEM) shows good agreement with the experimental values which was recorded 8 plies can withstand to shear strength of 79 MPa with maximum load applied was 2.738kN while, 6 plies recorded 75 MPa on shear strength with load of 1.971kN. More damage/cracks on 6 plies specimen compared to 8 plies.

Coupled thermo‐viscoplastic fracture model for ductile‐brittle failure of amorphous glassy polymers with phase‐field approach

AbstractAmorphous glassy polymers have an extensive use in the industrial sectors including micro‐electronics, medical industry and aerospace, therefore their design and usage have become a significant task nowadays. The fracture response of these polymers may vary from ductile to brittle depending on several factors such as entanglement density, temperature level and external loading rate. The ductile response is driven by diffuse shear zones exhibiting volume–preserving inelastic deformations while the brittle response is manifested by very small crack‐like defects composed of a sequence of fibrillar bridges separated by micro‐voids, thereby connotating void formation consisting of nucleation and propagation steps. The presents study is focused on the description of shear yielding and crazing phenomenon in terms of their respective evolution equations. In addition, an extension towards the modelling of the fracture is employed via the crack phase–field approach, considering ductile and brittle failure simultaneously. This is provided by the novel failure criterion that features a critical amount of plastic strain and void volume fraction. Since the proposed approach unitedly models the macroscopic crack initiation and propagation for ductile or brittle failure, it is asserted to be more physically grounded compared to present models in the literature. Constitutive formulations for shear yielding, crazing, and void volume fraction are derived with their specific forms starting with the local and conductive component of the dissipation inequality. The performance of model is evaluated after developing the local and global Newton–type update algorithms for the dissipative internal and primary field variables, respectively and it has been analysed by fitting of several experimental data of homogeneous and inhomogeneous tests. The findings reveal the remarkable temperature dependency on the type of failure as well as the interaction between loading rate and temperature change owing to dissipative heating in the solid.

Effect of real-time high temperature and loading rate on mode I fracture toughness of granite

An in-depth understanding of the effect of real-time high temperature and loading rate on the fracture toughness of rocks is highly important for understanding the fracture mechanism of Hot Dry Rock (HDR). Three-point bending tests on notched semi-circular bending (NSCB) samples at the real-time temperatures (25, 100, 200, 300, 400 and 500 ℃) and different loading rates (0.1, 0.01 and 0.001 mm/min) were performed to characterize the temperature and rate dependence of the mode I fracture toughness. Besides, the characteristic of the fracture surface morphology was investigated by scanning electron microscope (SEM) and crack deviation distance analysis. Results show that the temperature has a significant effect on the development of intergranular and transgranular cracks. The fracture toughness and peak load are similarly influenced by temperature (i.e., they both decrease with increasing temperature). At the loading rates of 0.1 mm/min and 0.01 mm/min, from 25 to 400 °C, the fracture toughness decreases slightly with decreasing loading rates. However, at a loading rate of 0.001 mm/min, the fracture toughness values above 200 °C are very similar, and the fracture toughness does not strictly follow the law of decreasing with decreasing loading rate. Especially at 500 °C, fracture toughness and loading rate are negatively correlated. Our study also indicates that the effect of loading rate on macroscopic crack propagation path at real-time high temperature is not obvious. This study could provide an important basis for evaluating the safety and stability of geothermal engineering.

Experimental Study on Uniaxial Compression Fracture Process of Marble Specimens with Circular Holes with Different Diameters

After a long period of geological tectonic action, the rock mass develops defects such as pores and fissures of different sizes and scales. The mechanical properties of the rock are largely affected by these discontinuous structures, and there will be obvious stress concentration at the edge of the hole inside the rock. Under the action of concentrated stress, cracks initiate, expand, and penetrate from the edge of the hole to form the final fracture surface and cause instability and failure of the rock mass. In practical engineering, due to the limitation of various factors, it is impossible to conduct uniaxial compressive strength test for each geotechnical engineering. Therefore, the rock in the weak part of the project can be selected as the test specimen before the indoor physical tests. In this paper, the static uniaxial compression test of specimens with circular holes with different diameters is carried out. Digital Image Correlation (DIC) monitoring system is used to observe the test process in real time; then, the data from uniaxial compression test and DIC monitoring test are obtained. At the same time, the macroscopic failure characteristics and crack propagation law of rock specimens are obtained, and the evolution law of strain field during the failure process of rock specimens is also obtained. Meanwhile, Realistic Failure Process Analysis (RFPA) is carried out to verify the accuracy of static uniaxial compression physical tests numerically. Physical tests show that the uniaxial compressive strength of marble specimens with circular holes and the dispersion of measured peak stress data decrease with the increase of hole diameter. The main failure type of marble specimens with circular holes is tension shear failure; the macroscopic failure zone of the sample, the strain field localization zone, and the maximum shear stress field of the numerical test are distributed in a semi-“X” shape with the hole as the center. The localization zone of the strain field on the specimen is usually the region of crack initiation, propagation, and penetration on the surface of the marble specimens. It also shows that specimen breaks in the radial direction along the y -axis of the circular hole, and cracks connecting both ends of the circular hole and the specimen are generated on the specimen. It is of great theoretical value and practical significance to the influence of the cavities in the rock specimens on the stress and strain characteristics and the initiation, propagation, and penetration modes.

Phase-field modeling of 3D fracture in elasto-plastic solids based on the modified GTN theory

An appropriate failure model of ductile materials needs to consider complex phenomena at the microscopic level, such as the nucleation, growth, and coalescence of microvoids and the final fracture at the macroscopic level. A recent popular continuous phase-field method based on the regularization of sharp crack discontinuities can easily model macroscopic cracks. In this work, we developed a coupled model to predict the crack law when materials undergo ductile fracture. The coupling model combined the ductile phase-field fracture model of the material with the shear-modified GTN model to illustrate the microscopic damage accumulation caused by the growth of voids and the macroscopic crack initiation and propagation. In addition, a modified phase-field degradation function was established, combining phase field, void volume fraction, and shear damage. This paper also considers the crack propagation law when the materials undergo ductile fracture under different stress triaxialities. In this study, we used the subroutines UEL and UMAT in the commercial finite element software Abaqus to give the staggering solution algorithm for ductile phase-field fracture of the materials. The shear-modified GTN model was written by the subroutine UMAT, while the ductile phase-field fracture model was written by the subroutine UEL. The results of the numerical simulations showed good agreement with the experimental damage failure mechanisms and the load–displacement curves.

Fracture and deformation behaviors of saturated and dried single-edge notched beam sandstones under three-point bending based on DIC

It is of great significance to study the fracture and deformation characteristics of rock with different moisture conditions for the safety assessment of “fragile surface with cracks” in rock engineering such as dams and underground chambers affected by groundwater. Therefore, in this work, three-point bending tests were conducted on single-edge notched beam sandstone specimens with different moisture conditions (natural condition, dried condition, and saturated condition) under complex stress environment. Additionally, the digital image correlation (DIC) method was used to quantitatively research the fracture parameters and deformation behavior of specimens during pure mode I fracture and mixed mode I-II fracture. The results show that (1) the average peak load of dried sandstone is 42.18–116.08% higher than that of saturated sandstone. (2) By increasing the offset distance of the pre-notch (0–72 mm), the specimen is transformed from pure mode I fracture to mixed mode I-II fracture, with an increase in average peak load of 152.83–284.24%. (3) When the pure mode I fracture occurs in saturated sandstone, the fracture toughness is 66.74% of that natural sandstone, which is 46.28% of that dried sandstone. (4) In the mixed mode I-II fracture, the effective fracture toughness of sandstone with a consistent moisture condition is 1.05–1.70 times that of the pure mode I fracture. (5) The fracture toughness of saturated sandstone is most significantly affected by the loading mode. When the offset distance of pre-notch increases from 0 to 72 mm, the average effective fracture toughness increases from 4.324 MPa·mm0.5 to 7.357 MPa·mm0.5, increasing by 70.14%. Besides, according to the trend of the ap, which was calculated by the DIC method, the post-peak macroscopic crack propagation is divided into two stages: the post-peak stable propagation stage and the post-peak unstable propagation stage.

Experimental study of the shear failure of granite based on full-field-strain monitoring using digital image correlation

Shear failure is a common failure form of engineering rock mass. As a typical engineering rock mass, granite is widely present in reservoir dams, mine slopes, mine roadways, and other projects in China. Therefore, in this study, the direct shear testing of granite was conducted by taking granite as the research object and using an RLW-3000 shear creep biaxial testing machine. The complete process of shear failure was monitored by using digital image correlation non-contact full-field strain measurement technology, and the spatial evolution of the shear-failure process of granite was assessed by analyzing the main strain nephogram in combination with the main strain–time variation curves. The spatiotemporal evolution of strain during the shear-failure process of granite was studied to reveal the shear-failure mechanism of the material. Results show that the strain nephogram of granite during shear failure could be divided into four stages: uniform strain distribution, strain-localization band generation, strain band expansion, and strain-band expansion acceleration. Strain localization is an important feature of the shear failure of a rock mass; it is characterized by the uneven distribution of strain on the surface of the specimen and the appearance of strain-concentration bands, which indicate the initiation and propagation of macroscopic shear cracks. According to the principal strain–time curve obtained, the principal strain curve exhibits a sharp upward trend when strain localization occurs, and the stress is approximately 76%–79% of the peak stress. The space–time evolution characteristics of the above strain reflect the spatiotemporal variations in the stress field on the surface of the specimen, and the spatial extension of the banded strain-concentration area corresponds to the formation and development of shear failure in the rock. Therefore, the direction of the spatial development of shear microfractures can be predicted by capturing the spatial development of strain-localization bands. The results of this work provide an important theoretical basis and guidance for reservoir dam seepage prevention, highway and mine slope support, and goaf face instability early-warning systems.