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Mode I fracture toughness, as a key index to reflect rocks' resistance to crack propagation and failure, which is significantly affected by temperature, plays an important role in accident prevention in underground engineering. In this work, a temperature‐damage‐dependent fracture surface energy model of rocks was developed first. Then, the theoretical characterization model of the temperature‐dependent mode I fracture toughness of rocks was proposed according to the relationship between the fracture surface energy and fracture toughness. All obtained experimental results are used for verification, and the predicted values are in good agreement with the experimental results. The temperature‐dependent mode I fracture toughness model of rocks established in this study not only provides a new method to predict the fracture toughness of rocks at different temperatures conveniently but also provides the theoretical basis to the research on stability analysis, monitoring, warning, and disaster control of underground rock engineering. Highlights: A new temperature‐dependent mode I fracture toughness model of rocks is proposed.The temperature‐dependent mode I fracture toughness model has no fitting parameters.The predicted results of this model are in good agreement with the experimental data. [ABSTRACT FROM AUTHOR]

Accurately and conveniently acquiring the tensile fracture strength of rocks at different temperatures is vital no matter for the security or economical design of deep underground engineering projects. Extensive testing in the laboratory, assisted with fitting approaches, is the main method to obtain the high-temperature tensile fracture strength in the available literature. However, the high-temperature destruction test is difficult to conduct and requires numerous time and resources. In this work, considering the main physical mechanisms such as phase transition and thermal damage that affect the tensile fracture strength of rocks at high temperatures, theoretical models for predicting their temperature-dependent tensile fracture strength (TDTFS) are established based on the Force-Heat Equivalence Energy Density Principle. The presented models achieve great prediction on the different variation trends of tensile strength below and above the phase transition temperature, as well as the corresponding sudden change of strength. For rocks without phase transition, the presented model only needs some physical parameters tested at room temperature can get a good prediction capacity on the TDTFS. Moreover, a new theoretical characterization model of the equivalent thermal damage parameter was presented and take a comparison with the previous model. Finally, the potential applications and limitations of the TDTFS model are further discussed. The application threshold of the presented TDTFS models is relatively low, and they may therefore be suitable as a method for providing a rapid and preliminary evaluation of strength at a large temperature range for rock engineering. [ABSTRACT FROM AUTHOR]

The effect of in-situ reservoir conditions (high temperature and pressure) on the fracture characteristics (aperture, asperities) and behaviour of fluid through the fractures is a very niche study area for varied energy fields like (i) enhanced geothermal energy systems (ii) nuclear energy storage (iii) CO2 sequestration, (iv) petroleum engineering and (v) storage of liquified natural gas. Keeping this in view many researchers have conducted studies to understand the heat and mass transfer processes occurring in the fractures. Along the same lines Tan et al., 2023 published the paper Thermal Effects Promotes Non-Darcian Flow in Heated Rock Fractures to understand the effect of fluid flow through rock fractures at high temperatures. However, the data presented in the paper by Tan et al., Rock Mech Rock Eng 2023 related to (i) the fracture closure, (ii) the time required for the changes along the fracture, (iii) the thermal expansion effect, and (iv) changes to the phase of water while heating requires further explanation and will otherwise result in the dissemination of incomplete information if not taken care of. The same has been further elaborated in the discussion that follows. [ABSTRACT FROM AUTHOR]

To date, many numerical studies on rock fractures are based on complete models with simple geometric parameters, ignoring the effects of microstructures on the strength and fracture properties of rocks. It is difficult to incorporate the influences of microstructures in simulations of crack initiation, propagation and coalescence by these numerical models. Thus, to explore the fracture and failure processes of rocks under the accumulation of stress, the influences of microstructures should be considered in establishing a numerical model. Spatial data about the internal microstructures and mechanical parameters of porous sandstone are obtained by computed tomography (CT) and triaxial compression experiments. Due to the limitations of the observation range of CT, a novel continuous reconstruction method is proposed to study the failure mechanisms of rocks on the microscale. The main difference between this continuous reconstruction method and our previous reconstruction method is the continuity of the microstructures in the reconstruction process. In addition, the definitions of the probability functions are completely different. The rock model is reconstructed based on the spatial information about microstructures. With the reconstruction model and mechanical parameters, the fracture processes of rocks in the triaxial test are analysed while considering microstructures. In the generation of the rock model, the meshes and elements are optimized regarding skewness, aspect ratio, and tetrahedral collapse value, which improves the calculation efficiency. The fracture properties of the reconstructed model are investigated by a coupled finite element–smoothed particle hydrodynamics (FE–SPH) method. Based on the numerical results, the failure mechanisms of sandstone are analysed through their microstructures. The numerical and experimental results are compared to validate the proposed reconstruction method. Highlights: A novel continuous reconstruction method is proposed to generate a numerical porous rock model. The generated rock models preserve the unique characteristics of the microstructures in rocks. Spatial correlation functions are employed to characterize the porous microstructures of coarse-grained sandstone. The mechanical and fracture properties of pore microstructures are analysed by the generated rock model. [ABSTRACT FROM AUTHOR]

Abstract—A computer model of fracture in heterogeneous materials (including rocks) is proposed to study evolution of the defect structure (cracks) during deformation process. The model is based on the Discrete Element Method (DEM), which, in contrast to the methods relying on continuum mechanics, naturally simulates the formation and evolution of cracks. We used the bonded particle model (BPM), which is widely used in various modifications to study the fracture process. The material is modeled by a set of spherical particles (simulating polycrystalline grains), connected by bonds placed at particle contact points, which simulate grain boundaries. In the BPM model, crack initiation is determined by the breakage of bonds, and its propagation is provided by the coalescence of a numerous set of broken bonds. Computer experiments were performed with different material parameters (different mechanical properties of grains and grain boundaries, different grain sizes) to determine their effect on the local stress patterns, defect formation, and fracture source nucleation and development. The calculations were performed in the open-source DEM simulation software MUSEN. Samples were modeled by cylinders filled with spherical particles of the same or different radii packed up to reaching the void ratio 0.35–0.37. The materials simulating grains and bonds (grain boundaries) were specified with mechanical parameters corresponding to granite, quartz, orthoclase, oligoclase, and glass. The sample was placed in a virtual press in which a bottom plate was fixed and a top plate was moved towards the lower plate at a constant rate until the sample failed. The maximum local stress calculations have shown that homogeneous materials yield more heterogeneous spatial distributions of local stresses and vice versa—material heterogeneity leads to more uniform stress distributions. Comparison with the results of laboratory rock deformation experiments has shown that the proposed model of polycrystalline materials realistically describes some features of fracture in these materials when the main processes occur along the grain boundaries. These features include the brittle type of fracture in homogeneous materials and the presence of nonlinear elasticity (plasticity) revealed for more heterogeneous materials based on the stress-strain diagrams, as well as the time behavior of "acoustic emission rate" (or acoustic activity)—the number of bonds broken per unit time. For heterogeneous materials, the model shows a two-stage pattern of the fracture process with uniform defect accumulation throughout the sample at the first stage and the formation and growth of fracture nucleation sites at the second stage. [ABSTRACT FROM AUTHOR]

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Purpose. Development of a digital model of the stress-strain state of a rock mass during the extraction of coal by an underground method to predict the displacement of the earth’s surface. Methodology. The proposed technique is based on modeling the stress-strain state of a rock mass using the finite element method. Computer simulation of the stress-strain state of the rock massif was carried out in the area of lavas worked out in previous years in layers with the index K of the Karaganda suite of the mine named after Kostenko of the Karaganda coal basin, where instrumental surveying measurements were previously made to monitor the vectors and numerical values of the displacements of the earth’s surface undermined by mining. Findings. The reliability of the obtained finite element model of a rock mass for predicting the process of displacement of rocks and the earth’s surface is confirmed by the results of full-scale instrumental mine surveying measurements on the earth’s surface. Originality. For the first time, a method has been proposed for predicting the shifts of points on the earth’s surface, taking into account the physical and mechanical properties of rocks, based on a finite element model of a rock mass. A new approach was applied to assess the reliability of the model of the stress-strain state of a rock mass based on a comparison of the results obtained with the data of instrumental mine surveying. Practical value. A technique for computer simulation of the stress-strain state of a rock mass during the extraction of hard coal at the mine named after Kostenko, owned by one of the world’s leading steel producers, JSC ArcelorMittal. For modeling, a site was chosen in the area of lava mining along the coal seams of the Karaganda Formation of seams, starting from the K18 seam to the K10 seam, that is, a rock mass with a depth of more than 700 m. Previously, within this area a series of instrumental surveying observations was carried out of the displacement of the earth’s surface during the working out of these lavas using the method of roof management – complete collapse. The obtained values of vertical displacements of a point on the earth’s surface according to the results of computer simulation of the stress-strain state of a rock mass correspond to the data of field mine surveying observations of displacements of the same point, which confirms the reliability of the constructed model. [ABSTRACT FROM AUTHOR]

Transparent physical models of real rocks fabricated using three-dimensional (3D) printing technology are used in photoelastic experiments to quantify the evolution of the internal stress and deformation fields of rocks. Therefore, they are rendered as an emerging powerful technique to quantitatively reveal the intrinsic mechanisms of rock failure. The mechanical behavior of natural rocks exhibits a significant size effect; however, limited research has been conducted on whether transparent physical models observe similar size effects. In this study, to make the transparent printed models accurately demonstrate the mechanical behavior of natural rocks and reveal the internal mechanism of the size effect in rock mechanical behavior, the size effect in 3D printed models of fractured and porous rocks under uniaxial compressive loading was investigated. Transparent cylindrical models with different sizes that contained different fractured and porous structures were printed using the fracture and porous characteristics extracted from natural coal and sandstone. The variation in uniaxial compressive strength and elastic modulus of fractured and porous models for increasing model sizes were obtained through uniaxial compression experiments. Finally, the influence of internal discontinuous structural features, such as fractures and pores, on the size effect pertaining to the mechanical behavior of the model was analyzed and elaborated by comparing it with the mechanical properties of the continuous homogeneous model without fractures and pores. The findings provided support and reference to analyze the size effect of rock mechanical behavior and the effect of the internal discontinuous structure using 3D printed transparent models. [ABSTRACT FROM AUTHOR]

Seismic prediction of natural fractures is essential for the characterization of unconventional reservoirs because fractures provide seepage paths for fluid migration and storage space for hydrocarbon accumulation. However, it remains challenging to robustly estimate anisotropic parameters for fracture characterization based on seismic inversion methods. We propose an improved inversion scheme for the robust and accurate estimation of anisotropic parameters using PP-wave azimuthal amplitude differences incorporated with a hybrid optimization algorithm. Modeling analysis indicates that by removing the effect of isotropic terms, azimuthal amplitude differences are more sensitive to anisotropic parameters than the traditional azimuthal reflection coefficient; this can avoid possible instabilities in anisotropic parameter estimates that may occur in conventional methods due to unbalanced weighting coefficients between isotropic and anisotropic terms. Meanwhile, the proposed hybrid algorithm takes advantage of the global optimization ability of the simulated annealing algorithm and the fast convergence characteristics of the particle swarm optimization algorithm. Synthetic data tests indicate that the hybrid algorithm achieves reliable and stable estimates of anisotropic parameters with higher computational accuracy and efficiency than traditional methods. The improved inversion method is applied to characterize fractures in volcanic gas reservoirs. Based on azimuthal amplitude differences obtained after estimating fracture orientation using the Fourier series method, anisotropic parameters are computed and converted to weakness properties, which is more meaningful in terms of the fracture properties. Our results indicate that the obtained fracture tangential weakness exhibits an apparent correspondence with well-log permeability, thus justifying the applicability of the proposed method for fracture prediction. [ABSTRACT FROM AUTHOR]

To investigate the influence of loading rate and confining pressure on the mechanical behavior and energy evolution characteristics of hard and soft rock, high strength sandstone and low strength granite were subjected to triaxial compression tests with different loading rates. The results show that significant differences exist in the stress-strain curves for sandstone and granite. The confining pressure has a significant effect on the stress-strain curve, while the loading rate has a smaller effect on the stress-strain curve. As the confining pressure increases, the peak axial strain, peak axial stress, total energy, elastic energy and dissipated energy of sandstone and granite increase, the proportion of dissipated energy to total energy of sandstone and the proportion of elastic energy to total energy of granite are reduced. As the loading rate goes up, the peak axial stress, total energy and elastic energy increase in both sandstone and granite. The ultimate failure pattern of sandstone is a typical single inclined plane shear failure, while the ultimate failure pattern of granite consists of a single inclined plane shear failure and a vertical split failure. The loading rate has no significant effect on the macroscopic failure pattern, the elastic and dissipated energies are proportional to the total energy of sandstone and granite [ABSTRACT FROM AUTHOR]

A new hybrid inversion methodology for petrophysical properties (porosity, water saturation, and volume of clay) based on partially stacked seismic angle gathers was presented. The innovation of this method is that it combines the advantages of high efficiency of analytical and semianalytical multistep petrophysical estimation with the advantages of spatial continuity and high resolution of geostatistical direct inversion of reservoir parameters. A trace-by-trace linearized amplitude versus offset (AVO) inversion and semianalytical petrophysical estimation approach could efficiently achieve a preliminary estimation of reservoir parameters under some assumptions and approximations. These laterally unconstrained preliminary estimation results are able to provide effective information for finer-resolution geostatistical simulation and improve the computational efficiency of stochastic optimization. The 3-D fast Fourier transform moving average (FFT-MA) geostatistical cosimulation and the stochastic optimization by gradual deformation method (GDM) improve the resolution and spatial continuity of the preliminary estimation results. At the same time, stochastic inversion overcomes the assumptions in the analytical inversion algorithm that the parameters need to conform to the logarithmic Gaussian distribution and the linear approximation of the Zoeppritz equation. The method was tested on a synthetic case and a real case. The results show that compared with the analytical and semianalytical methods, this hybrid inversion can obtain results with finer resolution and better spatial continuity, and the computational efficiency is significantly improved compared with the geostatistical direct inversion of reservoir parameters. Uncertainty evaluation can be obtained by performing statistical analysis on the multiple realizations of stochastic inversions. [ABSTRACT FROM AUTHOR]

This paper concerns the results of research into the influence of the composition of rock inclusions on the fracture response of cement-based composite specimens. Specially designed specimens of the nominal dimensions 40 × 40 × 160 mm with inclusions in the shape of prisms with nominal dimensions of 8 × 8 × 40 mm were provided with an initial central edge notch with a depth of 12 mm. These specimens, which were made of fine-grained cement-based composite with different types of rock inclusion - amphibolite, basalt, granite, and marble - were tested in the three-point bending configuration. Fracture surfaces were examined via scanning electron microscopy and local response in the vicinity of rock inclusions was characterized via the nanoindentation technique. The aim of this paper is to analyse the influence of the chemical/petrographic composition of rock inclusions on the effective mechanical fracture parameters of cement-based composites, as well as on the microstructural mechanical parameters of the interfacial transition zone. The results of this research indicate the significant dependence of the effective fracture parameters on the petrographic and related chemical composition of the rock inclusions. [ABSTRACT FROM AUTHOR]

A complex and changeable water environment is a key factor for safe rock engineering. Variations in water distribution and pressure pose serious challenges in evaluating rock properties and failure modes. To investigate the effect of real water‒rock interactions on rock mechanical behavior, the self-developed hydraulic loading test equipment was designed. A series of mechanical experiments (unjacketed) were carried out on three representative types of rocks under different water pressure environments, and the jacketed test was also performed for the saturated rocks. The experimental results showed that with increasing water confining pressure, the stress‒strain curve of the saturated rocks increased, while that of the dry rocks first decreased and then increased, and that of the sandstone became more obvious. Furthermore, when the water confining pressure increased, the peak stress and elastic modulus of the saturated rocks increased linearly, and those of the dry rocks first decreased and then increased more sharply. Interestingly, the water confining pressure weakened the local tensile failure and aggravated the shear failure. The relationship between the water confining pressure and strength also indicated that the change of saturated rocks more slowly when in contact with the water confining pressure. From the above results, the pore water pressure correction coefficients (μ) of sandstone, marble and granite were 0.98, 0.96 and 0.93, respectively, in the water pressure environment and rock connection. The failure mechanism of saturated rocks is similar to that of rocks without confining pressure due to the balance of the water confining pressure and pore water pressure, and pore water pressure mainly acts as piestic water. For dry rocks, the penetration of pore water firstly weakens the mechanical properties of rocks when pore water pressure is smaller. A greater confining pressure enhances the role of traditional confining pressure for granite and dry rocks. [ABSTRACT FROM AUTHOR]

The inversion of reservoir elastic parameters and fracture parameters is of great significance to oil and gas production. In shale reservoirs with inclined fractures, using the reflection coefficient equation of vertical fractures or horizontal fractures under the vertical transverse isotropy (VTI) background has certain limitations. For this reason, based on the linear-slip model, this article establishes the approximate stiffness matrix of the monoclinic medium with a set of inclined fractures under the background of VTI and combines the Born scattering theory to further derive the PP-wave linear reflection coefficient equation of the monoclinic medium. The equation includes parameters, such as Young’s modulus, Poisson’s ratio, density, fracture weaknesses, and bedding weaknesses. Then, a rock physics model that comprehensively considers horizontal bedding and inclined fractures is established, and the influence of the inclination of the fractures on the reflection coefficient is analyzed. Finally, taking the advantage of Bayesian theory, the fracture weakness inversion method based on the azimuth amplitude difference is established, and the inversion accuracy is improved by adding Cauchy constraints and smoothing model regularization terms. Then, take the fracture weaknesses as inputs to invert the parameters, such as Young’s modulus, Poisson’s ratio, density, and bedding weaknesses. The inversion results of theoretical data show that the method can invert the fracture information well, and it can also be effectively applied to low-to-medium signal-to-noise ratio (SNR) data. The inversion results of theoretical and actual data prove that the inversion equation derived in this article can be used to obtain more accurate elastic and fracture parameters in fractured shale reservoirs. [ABSTRACT FROM AUTHOR]

In situ observations and laboratory experiments showed that slow deformation waves widely exist in geomedia under loading conditions. Slow deformation waves' behavior exhibits some similarities in media ranging from the scale as large as the Earth's crust to the scale as small as the laboratory test samples. However, the mechanism underlying their generation has not been clarified yet. In this research an experimental study was performed on small-scale red sandstone samples subjected to uniaxial compression at the displacement rates of 0.1, 0.5, and 1 mm/min. Slow deformation waves under different loading rates were analyzed by speckle photography for microscopic characterization combined with the digital image correlation (DIC) technique. The Luders deformation bands were predominantly observed in the flow channels formed at the stage of macro-elastic deformation. The spatial-temporal heterogeneity of the rock sample surface was quantified, and the deformation waves' propagation velocities under different loading rates were obtained. The linear relationship between the propagation velocities of slow deformation waves and the loading rates was determined. The research findings shed some new light on the evolutionary characteristics of the slow deformation waves. [ABSTRACT FROM AUTHOR]

The article describes the main mechanisms of deformation of rock masses of the Paleozoic basement of the Tien Shan complementary to plicative bending of its surface in the process of alpine tectogenesis. Mechanisms of volumetric deformation of various types are characterized with the example of specific geological structures: mélange, plastic deformation, cataclastic flow, dynamic recrystallization, etc. It has been determined that on the territory of the Tien Shan, the deformation of Pre-Mesozoic and younger surfaces of the leveling and overlying plate-orogenic sedimentary cover is associated primarily with 3D mobility (Reid flow) of mountain masses of the Paleozoic basement. Assumptions are made regarding the physics of the process, based on advances in the mechanics of block-granular media and fracture mechanics. [ABSTRACT FROM AUTHOR]

The investigation of localized deformation in rocks at the laboratory scale can yield valuable insights into the internal structures and mechanisms of shear zones and compaction bands that impact the permeability characterization and failure mechanisms of rocks. Combined with high-resolution X-ray computed tomography and in situ loading, the digital volume correlation (DVC) technique is an effective tool for mapping the deformation in rocks. This technique is mainly divided into two categories: subset-based local DVC (L-DVC), used for rocks because of its straightforward implementation and high efficiency, and finite-element-based global DVC (G-DVC), which usually offers better accuracy because of the continuity among element nodes. In this study, we compared the accuracy and precision of these two DVC approaches for five rocks and discussed two factors important for accuracy, namely element/subset size and microstructure. The results show that performance of the G-DVC is better than that of the L-DVC, albeit at the expense of computational efficiency, especially for smaller subset sizes. An indentation test on red sandstone was performed to further demonstrate the feasibility of the two methods. This study aims to supplement the lack of research on the two DVC approaches for rocks and provides a reference for subsequent related research. [ABSTRACT FROM AUTHOR]

The Discrete Element Method (DEM) is increasingly used to study the failure behavior of rock. Despite DEM's intrinsic capability to capture the mechanical behavior of discontinua, there remains several open questions that include the numerical modelling of the meso-fracture evolution and behavior of brittle rock bodies. A Cohesive Fracture Model (CFM) designed explicitly for polyhedral shaped DEM particles is proposed for the simulation of the fracture and behavior of brittle rock bodies. A rock body is discretized into a series of rigid polyhedral blocks which are bonded along the boundary faces along the normal and shear directions. A cohesive criterion dictates the normal and shear break strengths of the bonds for the CFM. The computational efficiency of the CFM for polyhedral shaped DEM simulations is enhanced by parallelization over multiple graphical processing units (GPUs) in the Blaze-DEM framework. A series of numerical and laboratory tests are conducted. For marble, these include three-point bending and uniaxial tests to investigate the relationship between the meso-mechanical parameters and macro-mechanical behavior. Following a sensitivity analysis of the meso-mechanical parameters, an inversion procedure is established to estimate the numerical meso-mechanical parameters of the CFM model. Two different failure modes for different rocks are proposed. Unlabelled Image • A Cohesive Fracture Model (CFM) used for blocky DEM is proposed. • A GPU DEM code for CFM is developed to improve the computational efficiency. • Relationships between CFM parameters and macro behaviors of rock have been studied. • An inversion procedure is provided for the numerical parameters of CFM. [ABSTRACT FROM AUTHOR]

In view of the unsymmetrical large deformation and failure phenomenon that often occurs after the excavation and support of the roadway in steep seam with weak structural plane, the numerical simulation analysis and engineering application research on the deformation and failure characteristics of its surrounding rock are carried out. The results show that the key position of asymmetric deformation is near the weak structural plane and the intersection of the roadway section and the inclined direction of the rock. On this basis, the "unsymmetrical high prestress pressure relief coupling control technology" is put forward, and the industrial test is carried out. The practice shows that the unsymmetrical coupling support technology can not only effectively solve the differential deformation of the surrounding rock but also ensure the coordinated deformation of the support structure and the surrounding rock, thus improving the overall stability of the roadway, greatly reducing the repair rate of the roadway, and saving the support cost. [ABSTRACT FROM AUTHOR]

Based on the similarity theory, sandstone was taken as the prototype, and rock-like specimens were made with the strength ratio of 1 : 1. Single "X" fracture and double "X" fractures were prefabricated in rock-like specimen, and crack propagation was studied through the compressive test. An improved discontinuous deformation analysis method (DDARF) was adopted to simulate on the cracking process. Further, other factors should not be ignored such as confining pressure and temperature, which were considered: rock's crack propagations under loading and unloading with different confining pressures were studied; influences of temperature from 20°C to 300°C on crack propagation were analyzed. [ABSTRACT FROM AUTHOR]

The focus of this work is toward an investigation of the mechanical response of a variety of rocks to indentation loading as a close condition to drilling application. A rock classification method is introduced based on the mechanical response of the rock when loaded by a spherical indenter. Spherical shape is selected for the indenter as a common geometry, which to some extent represents most of the new or worn inserts in drill bits. Both of the force–penetration and fragmentation responses are studied and the results are categorized accordingly. Indentation loading of a quasi-brittle medium like rock contains a complex three-dimensional stress state, in which the compressive strength, tensile strength, compaction behavior and the brittleness of the rock all together are reflected in its mechanical response. Therefore, depending on the type of the rock and its properties, this response is also very diverse for different rocks. Eight types of rocks are investigated and the results from the force–penetration and fragmentation responses are summarized into three different classes. [ABSTRACT FROM AUTHOR]

The strength of rock under combined compression and shear loading has been paid more and more attention, but still lacks a theoretical model that incorporates both compression–shear characteristics and influence of dip angle to estimate the strength of the rock. This work is aiming to solve the issue by combining experimental and theoretical methods. First, in the laboratory, 112 rock samples with different sizes were applied to obtain the dip effect characteristics of strength via combined compression–shear tests. The ratio of compression–shear strength to uniaxial compression strength is called the compression–shear coefficient, which is used to characterize the degree of dip effect. Second, according to the compression–shear load characteristics of inclined rock samples, a strength model was established considering both compression–shear characteristics and dip angle by the Mohr–Coulomb failure theory. This strength model is an extension of the Mohr–Coulomb criterion and was verified by experimental data. The verification results are consistent with experimental results. Finally, the mechanism of dip effect on strength was explained from the resistance to the sliding and stress path of the rock sample. The results show that the dip effect is an inevitable strength weakening characteristic of rock materials under combined compression–shear loading. Compared with the vertical rock sample loaded under pure pressure, the resistance to the sliding of inclined rock samples decreases and the stress path is changed, which reduces the ability of the rock sample to resist external loads, resulting in the decrease of strength. [ABSTRACT FROM AUTHOR]

In this paper, an empirical relationship between the Unconfined Compressive Strength (UCS) of intact rock and the unit shaft resistance of piles penetrating rock is investigated. A growing number of civil engineering projects are utilizing steel piles driven into rock where a significant portion of the pile capacity is derived from the shaft resistance. Despite the growing number of projects utilizing the technology, little to no guidance is offered in the literature as to how the shaft resistance is to be calculated for such piles. A database has been created for driven piles that penetrate bedrock. The database consists of 42 pile load tests of which a majority are steel H-piles. The friction fatigue model is applied to seven of the pile load tests for which sufficient UCS data exists in order to develop an empirical relation. The focus of this paper is on case histories that include driven pipe piles with at least 2 m penetration into rock. [ABSTRACT FROM AUTHOR]

The deformation process and failure mechanism of rock mass with increased density of initial joints subjected to confined stress state are investigated in this study using discrete element method (DEM). A numerical model of standard size granite samples is developed and validated using experimental data for both intact and jointed rocks. The micro-parameters of the rock material are first determined, and the effects of the rock discontinuity on strength, deformability, stress–strain relationship, and failure modes are then investigated at the macro-scale level. Analyses are also performed to examine the tensile and shear crack distributions, fragmentation characteristics, particle kinematics, and energy dissipation to advance the current understanding of the deformation processes and failure mechanisms of jointed rock masses. The microscopic evolutions in the fabric and force anisotropy during loading and distributions of contact forces provide insights into the influence of increasing initial jointing on the macroscopic deformational behavior of the rock. The results show how the deceleration in the growth of fabric and contact force anisotropies develops and confirms that the increase in initial jointing and the associated changes in microstructure can restrain the development of anisotropy, thereby reducing significantly the strength of the rock samples. [ABSTRACT FROM AUTHOR]

Over the last few decades, pronounced changes of mountain environments during exceptionally warm summers have raised strong awareness towards changing cryospheric conditions in high mountain areas. Alpine regions are considered particularly sensitive to climate change, observations as well as projections report a significantly higher temperature rise in comparison to lowland areas. Rising sub‐zero temperatures were demonstrated to alter rock‐ and ice‐mechanical strength, namely compressive and tensile intact rock strength, friction, ice creep and fracturing of rock‐ice interfaces as well as elastic moduli. So far benchmark studies have only investigated the impact on rock masses irrespective of the interaction with high‐alpine infrastructure. This study investigates the interconnection between a high‐alpine cable car station and its permafrost‐affected surroundings. For engineering applications, the understanding of the state of natural systems is combined with numerical modelling of interactions between constructions and their frozen subsoil. This enables an improved design of high‐alpine infrastructures in the long run. [ABSTRACT FROM AUTHOR]

The crack stress thresholds of rocks have remained a focus in rock mechanics and engineering. Herein, a novel observation method uses Hooke's law to evaluate crack stress thresholds based on transition points in the equivalent elastic modulus. Unlike previous studies, this method considers confining pressure as a variable and involves a differential method to handle the variation of discrete data. To test the method, we compare it with the volumetric strain method and another observation method with respect to the crack stress thresholds of sandstone and granite. The results are within the boundary values presented in the literatures. For the sandstone and granite samples, the proposed method performs better than the other two methods. In summary, the results indicate that the proposed method can be practically applied with that a promising performance. In the future, we will further improve the method by considering more types of rocks with various confining pressures. [ABSTRACT FROM AUTHOR]

The Brazilian method experiments were applied to investigate effects of loading rate on tensile strength of gabbro-diorite, marble, granite. The tensile strength was measured over a wide range of loading rate, σ ˙ = 10 - 3 - 10 2 MPa s. Also the fracture toughness of marble, gabbro-diorite, dolerite were measured over a wide range of loading rate from 5 × 10−4 to 25 MPa m1/2/s by three-point bending of beams with a central narrow cut. The strength and fracture toughness of studied rocks are related to the loading rate by typical equations: σ = a + e ln σ ˙ and K 1 c = c + d ln K ˙ 1 in the range of loading rates of 10−3–102 MPa/s. A comparison of the characteristic fracture parameters for both types of tests showed the initial activation energy of fracture has the same values. The parameters of proportionality were compared on the basis of the integral strength criterion. The obtained parameters of the studied rocks allow extrapolating the results of measurements of strength and fracture toughness for longer periods, it is important for estimating the long-term stability of rock structures. The methodology for determining the characteristics of rock fracture from the loading rate in static fracture of rocks can be easily applied to other brittle materials. [ABSTRACT FROM AUTHOR]

The embedment depth of footings is an essential factor affecting the bearing capacity of base material. In most bearing capacity determination methods, the effect of the embedment depth was considered by applying an equivalent vertical stress to the ground surface. This simplifying assumption excludes the effect of the shear strength of the rock mass at the levels above the footing base. In the present paper, a bearing capacity equation was obtained for rock masses in which, the effect of the embedment depth of the footing was considered directly without replacing its equivalent vertical stress. Using the upper bound method, the Hoek–Brown failure criterion was employed for the rock mass. The results revealed that the incorporation of the embedment depth results in considerably greater bearing capacity than the cases in which, an equivalent surcharge was used. Therefore, it is important to consider the footing embedment depth for optimal design of foundations. [ABSTRACT FROM AUTHOR]

Due to the complexity of the environment in which the high geostress tectonic rock mass is located and the uncertainty of its influencing factors, the mechanical process and stability of the surrounding rock and the supporting structure are not accurate enough. On the basis of rock mechanics, the principle of joint support of "anchor and anchor" is analyzed, and the theory of force transmission bearing system of superimposed arch is proposed. According to the characteristics of surrounding rock of engineering, the mechanical model of superimposed arch bearing body and reliability theory are combined. Comprehensive consideration of influencing factors, establishes the limit equilibrium equation of the equivalent coupled surrounding rock after the secondary support of the chamber of the crushing station. The comparison and verification of the theory is carried out in combination with the project of Jinchuan III mine crushing station. The results show that the failure probability of chamber engineering support in the Jinchuan III mine crushing station is 5.87%. Monitoring data shows that the deformation of surrounding rock supported by overlap arch bearing body trend to be stable, and the convergence speed is less than 0.1 mm/day. [ABSTRACT FROM AUTHOR]

To deeply analyze the failure evolution of surrounding rock during excavation-induced unloading of the high-stress rock mass, a multistage failure model was established based on revealed failure patterns. The critical conditions for wing cracks were determined. The slab crack buckling analysis was carried out. The true-triaxial rockburst testing system was used for the miniature model test to study the fracturing evolution of surrounding rocks during excavation-induced unloading of the high-stress rock mass. The research results indicated that harder rock samples had higher compressive strength. Moreover, the smaller peak strains implied more obvious yield/plastic stages of harder rock samples with high confining pressures and softer rock samples with low confining pressures. V-shaped grooves appeared at the beginning of the surrounding rock's failure while spalling and splitting occurred as the stress increased. Finally, the entire sample's overall splitting failure was observed, and the borehole bottom bulged upward. The harder rock masses had fewer fractures and higher degrees of failure. There were obvious V-shaped grooves on both sides of the marble cave wall. The tensile failure occurred near the opening surface and shear failure at a far distance. The sandstone's overall failure was related to tensile cracking, and splitting failure occurred far away from the opening surface, which was similar to the in situ failure of surrounding rocks during excavation-induced unloading of the high-stress rock mass. The results obtained are instrumental in the construction safety control and prevention of underground engineering disasters. [ABSTRACT FROM AUTHOR]

This paper explores a new approach for assessing the stability of a hazardous rock block on a slope using vibration feature parameters. A physical model experiment is designed in which a thermally sensitive material is incorporated into the potential failure plane of the hazardous rock, and the complete process of hazardous rock collapse caused by strength deterioration is simulated by means of constant-temperature heat transfer. Moreover, the vibration response of the hazardous rock is monitored in real time by laser vibrometry. The experimental results show that five vibration feature parameters, including the mean frequency, the center frequency, the peak frequency, the mean frequency standard deviation, and the root mean square frequency, are well-correlated with rock stability. Furthermore, through principal component analysis, the five vibration feature parameters are synthesized into a principal component factor (PCF) as a representative assessment parameter. The results of the analysis demonstrate that the variation in the PCF exhibits three characteristic stages, i.e., "stationary-deviation-acceleration," and can effectively identify the stability evolution trend and collapse precursor behavior of hazardous rock block. [ABSTRACT FROM AUTHOR]

Summary: To assess the influence of thermal stress on fracture deformation, a composite element algorithm of thermo‐mechanical coupling for fractured rock mass is developed based on the composite element method (CEM). This study aims to investigate coupled processes associated with the (i) effect of temperature on mechanical deformation and (ii) effect of fracture aperture on heat transfer. The composite element contains fracture segments exhibiting arbitrary shapes with variables that can be interpolated from their mapped nodal variables; the mapped variables can be determined using the governing equations derived from the variational principle or virtual work principle. The proposed coupling algorithm can simulate the discontinuity of fractures, with consideration of the heat transfer of rock blocks and fractures, together with heat exchange among fractures and the adjacent rock mass. A computational mesh is generated without restrictions by explicitly embedding the fractures into the mapped composite elements, substantially simplifying the pre‐process work. Analytic solutions to the transient temperature problem are examined to verify the proposed CEM algorithm. Two three‐dimensional numerical models are developed to perform thermo‐mechanical coupling analyses. These analyses are used to prove the advantage of the mesh handler and the reliability of the proposed algorithm. During coupling with the CEM model, the computational mesh requires no modification regardless of changes in fracture aperture. Results indicate that an increase in temperature leads to rock expansion, causing fracture deformation, which affects the general temperature of the fractured rock mass. [ABSTRACT FROM AUTHOR]

The growth of double cracks is the main factor leading to progressive rock failure under hydromechanical coupling. The initiation modes and interaction behaviors of double cracks were investigated by using laboratory tests, and the influences of water pressure were analyzed. The maximum energy release rate criterion was modified to determine the crack growth characteristics. A numerical model was established and then verified by the test results. Based on the simulation, the distribution of stress fields and key fracture parameters of double cracks was investigated. Then, initiation characteristics and interaction behaviors of parallel and nonparallel cracks were quantitatively analyzed. The results indicate that the increase in water pressure leads to the crack initiation being inclined to the original surfaces and the growth length along the crack fronts tending to be uniform; the small tensile stress zones are formed close to the crack tips, and significant compressive stress zones are formed at both sides of the crack surfaces; stress superposition and interaction occur when crack spacing is less than 2.5a; the interactive weakening effect is mainly present in the inner side (rock bridge zone) of cracks, while a certain degree of interactive enhancement effect exhibits in the outer sides; the cracks are much easier to initiate at the outer wing cracks when the spacing is less than the critical length (0.5a); and cracks with a dip angle of 45° are much easier to initiate at the endpoints of long axis. The research results provide certain theoretical guidance for the safety assessment of underground engineering. [ABSTRACT FROM AUTHOR]

Pore-like flaws, which are commonly encountered in brittle rock, play an important role in the engineering performance of structures constructed in or on rock. Experimental and numerical investigations of micro-cracking mechanism of rock containing a pore-like flaw can enhance our knowledge of rock damage/failure from a microscopic view. In this study, the influences of a two-dimensional circular pore-like flaw with respect to its diameter and position on the strength and micro-cracking behavior of brittle rock under uniaxial compression are numerically investigated. The results reveal that the strength and elastic modulus are significantly affected by the diameter and position in the pore. The uniaxial compressive strength and elastic modulus of the numerical model with a pore diameter of 15.44 mm located in the center of the model are found to decrease by 58.6% and 56.4% respectively when compared with those of the intact model without a pore. As the pore position varies while the porosity remains unchanged, the simulated uniaxial compressive strength and elastic modulus are also found to be generally smaller than those of the intact model without a pore. When a pore-containing numerical model is loaded, the micro-cracks are found to mostly initiate at the top and bottom of the pore, due to the local tensile stress increase. The simulation results of the early-stage micro-cracking process and stress distribution are in a generally good agreement with the analytical solution obtained from the Kirsch equations. The grain-based model used in this study can not only study the crack initiation on the boundary of the pore but also provide a convenient means to analyze and visualize the temporal and spatial micro-cracking process after the crack initiation, which accounts for the variations in the simulated strength and modulus satisfactorily from a micro-cracking view. [ABSTRACT FROM AUTHOR]

Firstly, an X-ray diffraction test is carried out to investigate brittle rock specimens' composition, and a triaxial compression test is conducted to study the deformation behaviors and mechanical properties. Then, assuming that the rock material is able to be divided into the elastic part satisfying the Hooke's law and the damage part where rock strength follows lognormal distribution, this paper determines a damage variable and establishes a damage constitutive model which effectively reflects the residual strength in the process of rock failure. Meanwhile, testing data are used to validate the reliability of the proposed model in this paper and the dependence of statistic parameters on the confining pressure. Finally, impacts caused by statistic parameters variation on compression strength are analyzed comprehensively, and we also conduct a comparison between this proposed model and other models from other literatures, thereby showing the reliability and rationality of this proposed model. In addition, the research outcomes presented in this paper also can effectively offer significant reference for the development of rock mechanics and rock engineering. [ABSTRACT FROM AUTHOR]

The phenomenon of electromagnetic radiation (EMR) generated by rock fracture is relatively common. Due to different properties of rock, the variation laws and distribution characteristics of signals in time and frequency domain are significantly different. In this paper, the uniaxial compression experiments of four different kinds of rocks were carried out under the same loading conditions. EMR response characteristics during loading were studied, and the relationship between EMR signal statistics and mechanical parameters or quartz contents of rocks were analyzed. However, quartz content is not a decisive factor since quartz-free rock can also produce significant EMR signals when it fractures. Quartz content does not stimulate the activity and intensity of EMR signals generated by rock fracture. For the same kind of rock, specimen with larger elastic modulus tend to exhibit higher EMR signal intensity. Activity of EMR signals is not strictly proportional to the compressive strength of rocks but affected by complex stress-induced crack events during the loading process. With the continuous evolution of cracks, the dominant frequency of EMR signal shifts from a higher band to a lower frequency. As the quartz content decreases, the dominant frequency of EMR signal appears in a higher frequency band. [ABSTRACT FROM AUTHOR]

Grain size is an important consideration in the determination of the bulk chemistry of Martian rocks and unconsolidated materials in situ by the alpha particle X‐ray spectrometer (APXS), deployed on the NASA‐led Mars Science Laboratory mission. We used 2.5 MeV protons to emulate the particle‐induced X‐ray emission (PIXE) branch (5 MeV alphas) of the APXS. Seven polished rock slabs (igneous and sedimentary), ranging from fine‐ to coarse‐grained, were analyzed by PIXE in their original form, then milled to powders and pressed into pellets for further analysis. The summed area (160 mm2) over 10 interrogated regions on each slab is comparable to the area interrogated on the APXS; analysis of two pellets per rock, each using a 16 mm2 region, was found to be appropriate. The mean pellet/slab concentration ratio for Na, Mg, Al, Si, K, Ca, and Fe was close to 1.0 for fine‐grained samples, but changed by ±10% for the coarser cases. The variability among PIXE concentration values across the 10 rock regions increased monotonically with coarseness in the rock slabs. Comparison of overall PIXE concentrations with values measured by borate‐fusion WDXRF provides further quantitative support to the direct comparison of pellet and slab PIXE concentrations. This work affirms the use of the APXS on fine‐grained Martian materials but recommends larger interrogation areas (including rastering) when analyzing coarser‐grained materials. It also demonstrates that the presence of relatively large mineral grains (phenocrysts) or rock/mineral fragments within fine‐grained materials can contribute to greater error for specific elements associated with those phenocrysts/fragments. [ABSTRACT FROM AUTHOR]

The size reduction process of rocks in cone crushers is one of the most important issues, particularly for the secondary and tertiary stages of crushing operations. In this study, 17 different rock types were considered for the evaluation of their size reduction variations that occurred in a laboratory-scale cone crusher. Based on several mineralogical, physico-mechanical, and aggregate properties determined for each rock type, the crushability tests were performed. Before and after the crushability tests, particle size distribution (PSD) of the uncrushed (feed) and crushed (product) materials were determined by sieve analyses. On the basis of these PSDs, the degree of rock crushability (DRC) was attempted to quantify by simple approaches (i.e., size reduction ratio, SRR, and the theoretical square mesh aperture size that corresponds to the 10% of the cumulative undersize in the product, P10 (mm)). The crushability test results demonstrated that the DRC in cone crusher could be quantified by focusing on the variations in the SRR and P10. The SRR and P10 are associated with three important rock properties, Shore hardness (SH), Los Angeles abrasion loss (LAA, %), and Brazilian tensile strength (BTS, MPa). The textural and mineralogical features of rocks also have substantial impacts on the DRC for several rock types. It was concluded that the combination of the SRR and P10 could be considered together for the evaluation of DRC in cone crushers. Moreover, further research potentials on the DRC were also discussed in this study. [ABSTRACT FROM AUTHOR]

Cerchar Abrasiveness Index (CAI) is one of the commonly used methods for determining rock abrasiveness. The main parameters that affect abrasion are density, cementation, strength properties and amount of abrasive minerals in the rock etc. In this study, 15 different tests including uniaxial compressive strength (UCS) and CAI were performed on 35 different rocks with low-medium abrasive properties. UCS and CAI values of 35 rocks used in the study are ranged between 6.64 to 148.36 MPa and 0.68 to 2.67 respectively. All of the rocks are classified below the medium abrasiveness class according to CAI classification. The main purpose of the study is to estimate the UCS value which is known as the most commonly used rock feature by CAI values. For this purpose, it was tried to estimate UCS values by multiple regression method using CAI and other test parameters. The results of the study show that there are significant relationships between UCS and CAI. [ABSTRACT FROM AUTHOR]

Characterizing global mechanical behavior accurately is important for a detailed understanding of the deformation mechanism of rock material. In this paper, a new characterization model of the global mechanical behavior of rock is proposed, based on the structural characteristics of rock deformation. Uniaxial compression tests were carried out using the digital image correlation method and acoustic emission to obtain the interrelationship between mechanical behavior and deformation evolution. The test results show that the appearance of deformation localization leads to non-linear evolution of global mechanical behavior in a rock specimen. Further, due to the gradual evolution of deformation localization bands, the rock specimen evolves from a complete whole to a rock structure with a "weak interlayer". Thus, the global mechanical behavior of the rock specimen depends heavily on the structural evolution process, especially when close to failure. A simplified characterization model was established according to the deformation process. The finite element method was used to verify the rationality of the proposed structural model. The verification result showed that under uniaxial compression, the structural model can reproduce the global mechanical behavior evolution process of the rock specimen. [ABSTRACT FROM AUTHOR]

The electrical charge characteristic of rock materials under compression is an important index for predicting the development of rock fractures and the failure of engineering structures. However, the charge behaviours of a preexisting rock sample have not been studied in depth. In this study, sandstone samples with a single fabricated precrack at different angles of inclination are prepared. The uniaxial compression tests are performed to study the charge behaviours associated with the initiation and propagation of secondary cracks, the mechanical properties, and the progressive failure of stressed rock samples. An improved analytical model based on the maximum tensile stress failure theory for brittle materials is also proposed for determining the crack growth paths of the single precrack rock samples under uniaxial compression. The friction factors of crack surfaces are computed. The results show that the step functions on the curves of charge accumulation over time correspond to the fluctuation of stress, indicating the initiation of microcracks. The sample with a crack inclination angle of π / 4 shows the largest amount of both the first charge and the total accumulation. The analytical model shows a positive relationship between the crack face friction factors and the charge accumulation. The analytical solution of the crack development angles shows good agreement with the experimental results. This work may provide reference for the similar studies regarding the correlation of charging behaviours to the compressed rock materials. [ABSTRACT FROM AUTHOR]

Rock slope instability by earthquakes results in substantial economic and property losses. The calculation method of interlayer load and stability coefficient of horizontal complex layered rock slopes in high-intensity areas is established from material mechanics, fracture mechanics, and dynamics. The stability of horizontal layered dangerous rock is calculated after combining it with PFC simulation technology to verify the rationality of the calculation in the Wenchuan area of Sichuan Province. The dynamic response characteristics of dangerous rocks under different weathering degrees are also analyzed. The results show that both methods have an excellent early warning effect on earthquake dangerous rocks. Among the PGA amplification factors, Model 1 has a relatively uniform distribution, Model 2 has a zigzag distribution, Models 3 and 4 have a "U"-shaped distribution, and the most severe acceleration dynamic responses are 4-1 and 4-2 rock blocks. The dynamic acceleration response of mudstone is affected by the crack propagation process of the upper sandstone and exhibits a particular elevation amplification effect. The peak stress gradually decreases with the increase in weathering and elevation. The stress change of the inner chain No. 2 in the horizontal x and y directions is severe, and the stress response of the outer chain No. 1 in the vertical z-direction is severe. It recommends that earthquake disaster protection projects should pay attention to the impact of low-frequency (0–10 Hz) and high-frequency (250 Hz) earthquakes on slope stability. [ABSTRACT FROM AUTHOR]

Deep brittle rock exhibits characteristics of rapid stress dropping rate and large stress dropping degree after peak failure. To simulate the whole process of deformation and failure of the deep brittle rock under load, the Lemaitre strain equivalent theory is modified to make the damaged part of the rock has residual stress. Based on the damage constitutive model considering residual strength characteristics, a correction factor reflecting stress dropping rate is added, the Weibull distribution is used to describe the inhomogeneity of rock materials, and Drucker–Prager criterion is used to quantitatively describe the influence of stress on damage; a damage constitutive model of deep brittle rock considering stress dropping characteristics is established. According to the geometric features of the rock stress-strain curve, the theoretical expressions of model parameters are derived. To verify the rationality of the model, triaxial compression experiments of deep brittle rock under different confining pressures are conducted. And the influence of model parameters on rock mechanical behaviour is analysed. The results show that the model reflects the stress dropping characteristics of deep brittle rock and the theoretical curve is in good agreement with the experimental results, which indicates that the proposed constitutive model is scientific and feasible. [ABSTRACT FROM AUTHOR]

Under the triaxial compressive state, the compressive strain is supposed to happen in the direction of the maximum principal stress, but tensile strain happens in the direction of the minimum principal stress. Moreover, as the intermediate principal stress is not too high, the corresponding strain can also be tensile. If the brittle rock is assumed as linear elastic in the prefailure stage, a new strength criterion based on the sum of the two tensile strains was presented. The new criterion considers the differences in mechanical parameters (i.e., elastic modulus and Poisson's ratio) under tension and compression. The parameters of the criterion only include Poisson's ratio and uniaxial strength. And the effect of the intermediate principal stress σ 2 can be reflected. Certain featured failure phenomenon of rock material can be explained well by the proposed criterion. The results of conventional and true triaxial tests can verify the criterion well. Finally, the criterion is compared with the Mohr–Coulomb and Drucker–Prager criteria. [ABSTRACT FROM AUTHOR]

In the current paper, the deformation behaviours of rocks during compression are studied by testing 10 groups of sandstone samples with different porosity characteristics. According to the energy theory, the rock material was divided into two parts: solid skeleton and voids. A statistical damage-based approach was adopted to establish a nonlinear statistical damage constitutive model. The validity of the statistical damage constitutive model is verified by the test data. The statistical damage constitutive model performs well in each stage of rock compression before failure. For different types of rocks, different confining pressures, and different water contents, the statistical damage constitutive model fits well. This model can be applied to most types of rocks and in most engineering environments. [ABSTRACT FROM AUTHOR]

We present results from a series of thermal stressing experiments that used three igneous rocks of different composition, grain size, and origin and contemporaneously recorded acoustic emissions (AEs) with changing temperature. Samples were subjected to both a single heating and cooling cycle and multiple heating/cooling cycles to different peak temperatures. The vast majority of thermal crack damage is generated during heating in the coarser‐grained (quartz rich) rock but during cooling in the two finer‐grained (quartz poor) rocks. Our AE results also demonstrate the presence of a temperature‐memory effect, analogous to the Kaiser stress‐memory effect observed during cyclic mechanical loading, but only in the coarser‐grained rock. We suggest that the total amount of crack damage induced during either heating or cooling is dependent on the mineral composition and, most importantly, the grain size and arrangement, as well as the maximum temperature to which the rock was exposed. We use our laboratory‐scale results to suggest ways in which crustal‐scale geophysical data may need to be reinterpreted to provide more accurate estimates of total, accumulated damage and the approach to macroscopic failure in crustal segments hosting magma chambers and geothermal reservoirs. Plain Language Summary: We present results from a series of laboratory thermal stressing experiments using three igneous rocks of different composition, grain size, and origin: a Granophyre (SGP) from the Slaufrudalur pluton in Iceland, an Andesite from Santorini, Greece (SA), and a Basalt from the Seljadalur region of Iceland (SB), in which acoustic emissions (AEs) were recorded at the same time as the temperature of the samples was experimentally increased or decreased. Samples were subjected to both a single heating and cooling cycle and multiple heating and cooling cycles to different peak temperatures. The vast majority of thermal crack damage was generated during heating in the larger‐grained SGP but during cooling in the smaller‐grained SA and SB. Our AE results demonstrate the presence of a temperature‐memory effect in SGP, analogous to the Kaiser stress‐memory effect observed during cyclic mechanical loading, but no similar effect is observed in either SA or SB. We suggest that the total amount of crack damage is dependent on the mineral composition and, most importantly, the grain size and arrangement, as well as the maximum temperature to which the rock was exposed. The results should be considered in models that consider the distribution of damage in cyclically thermally stressed regions such as crustal segments hosting geothermal reservoirs and/or magmatic intrusions. Key Points: The majority of thermal crack damage is produced during heating in the coarse‐grained granophyre but during cooling in the finer‐grained andesite and basaltA temperature‐memory effect is exhibited during thermal cycling in the quartz‐rich granophyre but not in the quartz‐poor andesite or basaltInterpretation of prefailure seismicity in volcanic/geothermal settings needs to take account of damage accumulated in earlier deformation cycles [ABSTRACT FROM AUTHOR]