Deformation Process Of Rock Research Articles

Damage characteristics and energy-dissipation mechanism of frozen–thawed sandstone subjected to loading

To reveal the energy-dissipation mechanism of the rock deformation and destruction process under the influence of freeze–thaw cycles and investigate the essence of rock freeze–thaw damage, the evolution characteristics of the total strain energy, elastic energy, and dissipated energy in the sandstone failure process are analysed according to the energy principle, number of freeze-thaw cycles, and uniaxial compression. The results reveal that: (1) the evolution behaviours of the total strain energy, elastic energy, and dissipative energy of sandstone under different numbers of freeze–thaw cycles are similar; that is, the total strain energy and elastic energy gradually increase with the increasing strain, and the elastic energy decreases sharply after reaching the peak limit. The dissipative energy gradually increases and thereafter remains stable; finally, it rapidly increases. (2) With increasing freeze–thaw cycles, the growth rates of the total strain energy, elastic energy, and dissipated energy gradually decrease, whereas the energy value at the peak first increases and then decreases. The energy distribution during rock loading is affected by the number of freeze-thaw cycles (defined as N). When N is <30, the proportion of dissipation energy in the compacting section first increases and then decreases linearly; the decreasing rate decreases gradually with an increase in N. When N is larger than 30, the dissipation energy ratio linearly decreases as the strain increases, and the decreasing rate increases as N increases. (3) According to the dissipative energy ratio evolution characteristics of rock failure, the peak strength and peak strain damage evolution models of frozen−thawed rocks are established. The fitting results indicate that the model has a good correlation with the experimental data and can accurately reflect the peak strength and peak strain evolution of frozen−thawed rocks.

On the Kaiser Effect of Rock under Cyclic Loading and Unloading Conditions: Insights from Acoustic Emission Monitoring

The Kaiser effect reflects the memory of the loaded rock to the irreversible damage and deformation. The stress level, loading rate and lithology are the main factors affecting the Kaiser effect of the rock. To identify the accurate stress point of the Kaiser effect, the MTS 816 rock mechanics testing system and the DS5-A acoustic emission testing and analysis system were adopted. The uniaxial cyclic loading–unloading and acoustic emission characteristic test of 90 rock specimens from three types of rocks under different stress level and loading rate was carried out. The evolution of acoustic emission under uniaxial compression of the rock corresponds to the compaction stage, elastic stage, yield stage and post-peak stress drop stage of the rock deformation and failure process and is divided into the quiet period, transition period, active period and decay period of the acoustic emission. The larger the hardness of rock is, the earlier the stress point of the Kaiser effect appears. The loading stress level (σA) has appreciable influence on the Kaiser effect of the rock. When σA ≥ 0.7σc, the Kaiser effect disappears. Usually, the dilatancy stress (crack initiation stress) does not exceed 70% of the uniaxial compressive strength (σc) of the rock, and the stress point can be the threshold to determine whether the Kaiser effect occurs. The influence of loading rate (lr) on Felicity rate (FR) is relatively large when lr &lt; 0.01 mm/s, and FR rapidly grows with increase of the loading rate. When lr ≥ 0.01 mm/s, the influence of the loading rate on FR is relatively small. The findings facilitate the future application of the Kaiser effect and improvement of the accuracy of the acoustic emission data interpretation.

Elastic potential energy in linear poroelasticity

Biot’s theory of linear poroelasticity dates back to the mid-20th century and is still currently the backbone for understanding deformation processes in fluid-saturated porous rocks with applications in geomechanics, hydrogeology, reservoir engineering, and exploration geophysics. Therein, the elastic potential energy is the critical concept to derive the macroscopic stress tensors and constitutive equations. The potential energy is taken as the single function that forms an exact differential in macroscopic strains of the solid and fluid phases. This choice intrinsically implies a reciprocal interaction between the compressive stresses of the two phases. However, it leaves out the possibility that the phases can interact in a nonreciprocal manner, which is sometimes inferred from experimental observations. The limited scope of the Biot theory is overcome by upscaling the pore-scale governing equations using volume averaging aided by the physical argument that the conservation of mass, momentum, energy, and principle of equivalence must hold at all scales. This upscaling reveals that the proper measures of deformations are not only the deformation gradient terms but also a porosity change term that accounts for the emergent pore-interface kinematics at the macroscale. It also reveals that the elastic potential energy of a porocontinuum is the sum of the potential energies of the solid and fluid phases, which are functions of their so-defined respective measure of deformation only. Such potential energy is no longer limited to only the reciprocal interaction of the compressive stresses of the phases, but it enables us to capture nonreciprocal interactions still within the realm of linearity. A nonreciprocal interaction arises whenever the potential energy density is not uniformly distributed at the pore scale but partially localized in the vicinity of pore interfaces or within the bulk part of the phases. A direct consequence is that the coupling coefficients in the linear constitutive equations are expected to be different.

Investigation of shear slip in hot fractured rock

This paper presents the results of a shear slip experiment in hot rock and its simulation and analysis using 3D coupled thermo-poromechanical model with the aim of assessing the role of pore pressure and temperature change on shear slip in granitic rock. The test is carried out in a triaxial system at representative reservoir pressure and temperature using right circular cylindrical specimens of Westerly granite with a 30° precut and ground surface. After the pore pressure and temperature were stabilized, the differential stress and absolute pore pressure were systematically varied to produce different effective stress states to evaluate the shearing response of the saw-cut fracture. The key objective of the experiment is to test the cooling effect on the fracture slip. The experimental results were then analyzed using a newly developed 3D thermo-poromechanical finite element model which uses traditional 4 node tetrahedron elements for intact rock deformation and transport processes. Zero thickness contact interface element is employed to capture the closure and slip on the fracture surface. The stick/slip state of fracture is determined by the Mohr-Coulomb criterion. Simulation results show that the convective cooling effects on rock/fracture surface promote deformation and slip of the fracture. The cold fluid cools the surrounding rock material and results in normal stress reduction that causes portions of the fracture surface to undergo stick/slip state changes, and induces irreversible slip. The experimental work along with modeling provides a physics-based understanding of the role of coupled processes on shear stimulation phenomenon.

Experimental Research on Precursory Characteristics of Macroscopic Deformation of Coal and Rock Failure

The research on precursory characteristics of coal and rock failure is of great significance for monitoring and early warning of disaster of surrounding rock. In this paper, the macroscopic deformation process of coal and rock under uniaxial compression is tested, and the evolution rule of the quantity, velocity and acceleration of their deformation is studied. The relationship between specimen surface damage and macroscopic deformation is investigated by image processing and analysis method. The research indicates that the macroscopic deformation indexes of coal and rock failure zones have significant changes before cracking, showing regular dynamic deformation characteristics, which could be precursory information of coal and rock failure.

Study on energy properties and failure behaviors of heat-treated granite under static and dynamic compression

The material testing machine and the split Hopkinson pressure bar (SHPB) were adopted, respectively, to conduct the static and dynamic compression tests on granite specimens heat treated by different temperatures. The effects of strain rate and heat-treatment temperature on the mechanism of energy evolution of the specimen during deformation and failure process were studied. The results show a significant strain rate effect on the granite, with the energy dissipation density increasing with increasing impact velocity (or strain rate), regardless of the treatment temperature. The specimens heat treated at 300 °C and 700 °C have the minimum and maximum energy dissipation densities, respectively. The specimen in the SHPB tests easily broke into pieces or even powder; while under static compression, only macroscopic fracture surfaces and spalling phenomenon on the specimen were detected. The energy dissipation density is inversely proportional to the compressive strength of the specimen. The rate of energy dissipation change is defined, which can be used to identify the stages in the deformation process of rock and to determine the position of the failure point in the stress-strain curve. For both the dynamic and static compression tests, the value of energy utilization ratio is relatively low, with a maximum value of about 35%.

Energy Evolution and Mechanical Features of Granite Subjected to Triaxial Loading‐Unloading Cycles

Energy evolution varies during the whole process of rock deformation, and mechanical parameters are markedly altered under cyclic loading and unloading. In order to investigate the effects of confining pressure on energy evolution and mechanical parameters, cyclic loading and unloading experiments were performed for granite under six different confining pressures. The experiment revealed the confining pressure effect on variation and allocation pattern of energy and mechanical characteristics. Four characteristic energy parameters, namely, storage energy rock, storage energy limit, energy storage ratio, and energy dissipation ratio, were proposed to describe energy storage and dissipation properties of rock. Elastic modulus and dissipation ratio presented a downward “U” and “U”‐shaped trends, respectively, with loading and unloading cycles, while Poisson’s ratio increased linearly at the same time. Elastic energy was accumulated mainly before peak stress, while the energy dissipation and release were dominant after the peak strength. As the confining pressure increased, efficiency of energy accumulation and storage limit improved. An exponential function was proposed to express the relationship between the energy storage limit and confining pressure. Dissipation energy increased nonlinearly with the strain, and the volume dilatancy point defined the turning point from a relatively slow growth to an accelerated growth of dissipation energy. The dilatancy point can be used as an important indication for the rapid development of dissipation energy.

A non-linear damage rheological constitutive model and its application to a giant slow-moving landslide

Generation of a landslide is a typical aging process of rock and soil deformation. Therefore, it is a basic method and also a difficult problem to build constitutive models that reflect the deformation process of landslides and furthermore to use the models for prediction. However, many classical rheological models can only be used to describe the first and second creeping stages and are unable to describe the third accelerated stage. Base on the non-linear and aging characteristics of the slip zone soil during the shear creeping development and the damage theory, this paper attempts to construct a non-linear damage rheological constitutive model by combining a non-linear damage visco-plastic element with the CVISC rheological model built-in FLAC3D, namely the modified CVISC model. For implementing this modified CIVSC model in 3D numerical simulations, its 3D difference equations are developed. The numerical codes for the difference equations are programmed following the roles of the FLAC3D’s user interface program. This model is applied to simulation of the Xieliupo landslide, which is a long-term slow-moving landslide with intermittently intense movement. The results show that the modified CVISC model can disclose accelerated creeping of the landslide, which is roughly consistent with the movement history of the landslide. This gives an indication of the validity of the modified CVISC model based on non-linear damage theory.

Energy Analysis of the Deformation and Failure Process of Sandstone and Damage Constitutive Model

The damage theory was introduced to clarify and simulate the strain softening property of rocks. On the basis of the theory, an energy method was utilized to portray the rock mechanical properties from microscopic perspective. Firstly, from the perspective of rock microstructure, damage variable (expressed as D) was redefined by dividing the rock into three portions: undamaged materials, damaged materials and micro-defects, and an impact factor was introduced as the connection between the damaged material and the micro-defects. Meanwhile, the method for determining the impact factor was presented. Secondly, the damage variable was redefined in light of energy dissipation, then damage evolution analysis was conducted based on triaxial tests. An improved rock damage constitutive model was further obtained in another expression to reflect the energy change law. Subsequently, the relationship between D and the deformation and failure process of rocks was analyzed on account of the damage evolution equation formularized by fitting to a logistic function, which can measure the influence of energy dissipation on the propagation of micro-defects. By comparing between experimental results and theoretical results of illustrative examples, the effectiveness of the improved model was validated, and the its application was also discussed.

Thermal damage constitutive model for rock considering damage threshold and residual strength

With the gradual depletion of mineral resources in the shallow part of the earth, resource exploitation continues to move deeper into the earth, it becomes a hot topic to simulate the whole process of rock strain softening, deformation and failure in deep environment, especially under high temperature and high pressure. On the basis of Lemaitre’s strain-equivalent principle, combined with statistics and damage theory, a statistical constitutive model of rock thermal damage under triaxial compression condition is established. At the same time, taking into account the existing damage model is difficult to reflect residual strength after rock failure, the residual strength is considered in this paper by introducing correction factor of damage variable, the model rationality is also verified by experiments. Analysis of results indicates that the damage evolution curve reflects the whole process of rock micro-cracks enclosure, initiation, expansion, penetration, and the formation of macro-cracks under coupled effect of temperature and confining pressure. Rock thermal damage shows logistic growth function with the increase of temperature. Under the same strain condition, rock total damage decreases with the rise of confining pressure. By studying the electron microscope images (SEM) of rock fracture, it is inferred that 35.40 MPa is the critical confining pressure of brittle to plastic transition for this granite. The model parameter F reflects the average strength of rock, and M reflects the morphological characteristics of rock stress–strain curves. The physical meanings of model parameters are clear and the model is suitable for complex stress states, which provides valuable references for the study of rock deformation and stability in deep engineering.

Acoustic emission characteristics of a fine-grained marble with different thermal damages and specimen sizes

Acoustic emission (AE) is a technique which has been widely used in geomechanics to study the progressive micro-cracking behavior of rocks in response to different loadings. However, the study of the combined effects of thermal damage and specimen size on the performance of rocks using the AE technique is still limited, which needs further investigation. This study experimentally investigated the AE characteristics of a fine-grained marble with different thermal damages and specimen sizes. The variation of AE counts in response to the rock deformation can divide the stress−strain relation into several stages. The AE activity is limited in the initial deformation stage and multiplies at a stress level about 0.7 to 0.8 times the peak stress. However, the AE signals in the initial stage become more prominent as the treatment temperature increases. The accumulated AE parameters (i.e., AE counts, AE hits, and AE energy) are found to decrease with the increase in the treatment temperature. The b-value, which generally decreases as the stress approaches the peak strength, correlates well with the stress−strain relation. It is also found that the b-value generally increases as the treatment temperature gradually increases, which is mainly attributed to the initially generated thermal micro-cracks in the rock specimen. The real-time spatial distribution of AE events is in considerable agreement with the failure mode observed in laboratory tests. Overall, the results in this study reveal that the AE technique is capable of studying the micro-cracking behavior involved in the deformation process of rocks possessing different degrees of thermal damage and with different specimen sizes.

Evolution of the shape parameter in the Weibull distribution for brittle rocks under uniaxial compression

Applying the statistical damage theory based on the Weibull distribution to describe rock deformation and failure processes is an important development in rock mechanics. The shape parameter of the Weibull distribution, m, determines the basic shape of the distribution curve; additionally, it also represents a physical characteristic which can be applied when constructing rock constitutive models. To study the evolution of m during rock failure when applying the Weibull distribution to rock mechanics, uniaxial cyclic loading tests of shale specimens were conducted and previous rock mechanics experiments under different temperatures and loading rates were reviewed. The results indicate that m varied with the accumulation of damage but was almost constant between the volume expansion point and the peak strength point of each specimen. Combined with previous studies about the accelerated failure behavior of rocks, we conclude that between the volume expansion point and the peak strength point, the mechanical behavior of the rock fracture process did not change significantly. Based on the characteristics of m at different damage stages during the rock failure process, ranges of m values at different damage stages are proposed. The conclusions reached in this study may be used as an important reference for theoretical research on rock mechanics.

An experimental investigation on deformation and failure behavior of carbonaceous Garau shale in Lurestan Basin, west Iran: Application in shale gas development

The safety and efficiency of commercial shale gas development strategies are tightly related to accurate evaluation of rock deformation and brittle failure processes. In contrast to extensively developed siliciclastic shale gas resources in the world, the mechanical behaviors of the carbonaceous shales and their causal mechanisms are not thoroughly understood. In this study, a geomechanical characterization program including unconfined and confined deviatoric compression experiments together with complementary compositional and microstructural analyses was therefore carried out to explain the stress-strain behaviors of the carbonaceous organic-rich Garau shales in Iran. Deformation and progressive fracturing process of the collected rock samples at varying confinement states were evaluated and discussed in terms of well-established mechanistic concepts and theoretical models. In addition, the applicability of some of widely used expressions for assessing rock brittleness was also investigated. According to the obtained results, in spite of substantially varying deformation and failure characteristics, all collected samples over the range of applied confinement states up to 40 MPa follow the typical brittle failure process. However, the degree of brittle failure in terms of brittleness is considerably variable and dependent to the established definition. Furthermore, the diagnosed range of stress-strain characteristics are dominantly correlated with variations of carbonate depositional textures. Accordingly, as the stiff fine-grained micritic fabric of a carbonaceous shale gradually transforms to relatively large sparitic texture, rock generally tends to fail at relatively lower strength but higher degree of brittleness. This relation can be advantageous to an accurate determination of the relative brittleness successions in carbonaceous shale gas layers for practical field operations.

A coupled thermo-mechanical damage model for granite

With the increasing demand for mineral and energy resources, deep underground operations in mining, oil and gas industries become more frequent. This also resulted in problems associated with high temperature and pressure (HTP) that rock is exposed to in deep underground conditions. It is therefore imperative to understand and correctly model the coupled thermo-mechanical (TM) behavior of rocks for better and safer designs. For this purpose, based on the Weibull distribution and Lemaitre's strain-equivalent principle, a framework for the coupled thermo-mechanical (TM) damage model for granite is developed to simulate the deformation and failure process of rock under the high temperature and pressure (HTP) conditions. The thermal damage caused by the temperature change and the mechanical damage caused by high pressure were analyzed, and a nonlinear coupled total damage parameter is proposed in this study. The Weibull distribution parameters involved in the damage model are derived by combining the geometric conditions obtained from the conventional triaxial compression tests. In order to compare the performance of the proposed damage model, Drucker-Prager failure criterion is used as an example in the nonlinear TM damage model. For the validation of the proposed model, test results for granite samples at various temperature and confining pressures were compared in which the theoretical results are found to be in a good agreement with the experimental results. The proposed coupled TM damage model can be used in conjunction with any other failure criteria to account the damage evolution under HTP conditions.

Impacts of Cyclic Loading and Unloading Rates on Acoustic Emission Evolution and Felicity Effect of Instable Rock Mass

Uniaxial cyclic loading‐unloading compression experiments with schemes of six loading rates and six unloading rates were carried out on the combined testing platform. Impact of loading and unloading rates on rock AE characteristics was revealed. Results show that increasing loading and unloading rates resulted in decreasing total AE rings in the entire rock deformation and failure process. Increasing loading rate decreased the AE rings at loading stages, and increasing unloading rate decreased the AE rings at unloading stages in the same cycle. Total AE counts had a negative linear relationship to the loading and unloading rates. The loading stage was the active period of the AE phenomena, and impacts of the loading rate on the AE characteristics were more apparent. Especially when the loading rate was greater than 2.0 kN/s, brittle failure of rock specimens became noticeable. After the cyclic load reached the uniaxial compressive strength of 1/3∼1/2 times, the rock Felicity effect became more obvious. With the increase of the loading rate, the Felicity ratio decreased in the elastic stage and increased a little in the plastic stage, whereas with the increase of the unloading rate, the Felicity ratio decreased gradually in the elastic stage and remained almost the same in the plastic stage.

Deformation-Electromagnetic Relations in Lithospheric Activity Manifestations

It has been shown that dipole radiation of accelerated charges, described by Larmor relation, is the basis of the known mechanic-electromagnetic processes of rock deformation. Comparison of crust deformation acceleration with natural electromagnetic field parameters of ELF-VLF range showed good relation. It manifests in the maxima of occurrence frequency density of synchronous deformation-electromagnetic events on two dimensional histograms. The data of a laser strain-meter and a recorder of natural electromagnetic radiation of ELF-VLF range, recorded in a zone of increased seismic activity (Kamchatka, Karymshina site), were used. The authors made an assumption on the existence of stationary regions of deformation process and mechanic-electromagnetic transformations corresponding to regions with different mechanic properties and rock petrographic composition.

Study and Analysis of the Failure Mechanism of Tuff Rock based on Laboratory Tests and Three-Dimensional Numerical Modeling

Summary Failure mechanism is different due to stress conditions and rock types, and it is very important to stability of structures. One of the investigations of failure mechanism’s techniques is using triaxial compression test. The aim of the research is determination of failure plane and failure mechanism of Rhyolite Tuff experimentally in different confining pressures and then investigating failure mechanism numerically using three-dimensional finite difference method in details. From the experimental results it was found that with increasing confining pressure, failure angle changes from vertical to oblique. Then numerical model was calibrated with laboratory data and analyzed the details of failure process, which could not be investigated experimentally. Investigations showed that failure process, started with plastic strains at the center of the sample and continued to achieve shear failure plane. Moreover, the results showed that the numerical model is in good agreement with the laboratory tests. Introduction Given the increasing production of minerals, the need to expand and deepen mines is inevitable. With deeper mining, sustainability issues have become more important. All of underground structures have been constructed in rock and the recognition of the rock mechanics issues in relation to the stability of these structures is very important. One of the main topics of rock mechanics, which plays a significant role in the stability of structures, is the rock failure mechanism. Since these structures are located deep in the ground and the behavior of rock failure in different conditions of stress is different, recognizing the rock deformation process under stress conditions can provide a better picture of rock behavior in real conditions .When the distribution and turbulence of the stress creates an imbalance in the rock mass, rock failure occurs by the distribution and interconnection of the micro cracks. Still, there are ambiguities about how rocks are really broken and how the cracks begin to spread. Therefore, prediction of models for fracturing of rocks is very complicated, and it is impossible to predict the failure of rocks with simple models. Therefore, fundamental studies are needed to evaluate the failure process and damage of rocks in different stages of stress. Methodology and Approaches By using uniaxial and triaxial tests, a stress-strain graph was drawn for a rhyolite rock sample. Analyzing the experimental results, it was observed that, with increasing lateral stress, rock resistance increased, and the direction of the fracture plane was maximally illuminated and more angular than the direction of the main stress. It was also found that the behavior of rock with the Mohr Columb's failure criterion is good. For numerical modeling of laboratory experiments, cohesion parameters, internal friction angle, shear modulus, volume modulus and specific gravity were used. To calibrate the model, the meshes and the rate of application applied to the top of the specimen were changed to see the fracture and ultimate strength similar to the laboratory sample in the numerical model. After calibrating the model, the details of the failure stages were carefully examined. Results and Conclusions In numerical models with increasing lateral stress, the angle of deflection compared to the original stress was increased. Tensile plastic strains were formed at the beginning of the loading at the center of the sample. As the loading steps progressed, shear plastic strains started from the corners of the sample and proceeded to the center of the sample. This condition continued until the complete failure of the model and the creation of the plane shear failure. Also, with increasing lateral stress, the initiation of plastic strain occurred in higher stresses and later formed in the sample. Plastic tensile strains appeared at the center of the sample at the beginning of the loading. In the following, the strain began from the two corners of the sample and extended towards the center of the sample. It then extended its path until a plane was formed. Shear and tensile strains were formed in the form of shear-n and (tensile-n) in the sample. These strains may create a shear failure sheet. In fact, joining these strains continuously created a failure plane in the model. The final shear plane was the result of shear-n joining of the shear strains.

Introduction of the method of finite-discrete elements into the Abaqus/Explicit software complex for modeling deformation and fracture of rocks

The paper has considered development of a model within the framework of the method of finite-discrete elements for describing processes of rock deformation and fracture. Analysis of the methods of mathematical modeling of geomechanical processes which makes it possible to take into account the medium damage or fracture was presented. A physical model of rock fracture was proposed. It considers the fracture process as formation of microcracks of separation and shear or their combination. Examples of numerical modeling of loading a rock sample by the scheme of uniaxial compression and splitting by compression along generatrixes and in conditions of volume compression were considered. Formulation and results of simulation of development of a stress-strain state in the vicinity of the rock outcrop within the framework of the method of finite-discrete elements were presented. Within the framework of the study, an algorithm of implementing the method of finite-discrete elements in the Abaqus/Explicit software complex for strength calculations including all main stages of forming the numerical model from generation of an elemental grid to specification of boundary conditions has been worked out. A software solution for generation of the elemental grid was developed and capabilities of the Abaqus/Explicit software complex were expanded. This solution allows one to generate elemental grids for bodies of arbitrary shapes taking into account presence of surfaces of weakening within the body, both in flat and spatial formulations. The capabilities of the Abaqus/Explicit software complex were expanded in the field of modeling rock strength under the conditions of volumetric compression. According to the results of the performed studies, it was established that modeling of fracture formation (formation of shear and separation cracks) at the microlevel has allowed us to reliably represent processes of rock deformation and fracture. The possibility of using the method of finite-discrete elements for prediction of development of geomechanical processes in the vicinity of underground structures was presented. The presented study results allow us to extend the scope of the method of finite-discrete elements to solve the problems of geomechanics and form the basis for application of this method in solving engineering problems

A damage model for modeling the complete stress–strain relations of brittle rocks under uniaxial compression

Based on the “elastic modulus method” derived from the hypothesis of strain equivalence and test data of complete stress–strain curves of marble, granite, and sandstone under uniaxial compression, a damage model in the form of Logistic equation is proposed to simulate the stress–strain relation of rocks. This model can describe the complete deformation process of rocks under uniaxial compression satisfactorily. The used mathematical function is simple with just four model parameters, and each parameter has distinct physical meaning. The validity of the model is demonstrated by a mathematical deduction analysis and the model is further verified using laboratory test data. In addition, this model provides a method for estimating the elastic modulus of undamaged rocks using uniaxial compression test results and it presents a reasonable explanation of the chaos phenomenon occurred in uniaxial compression test.

Modeling Deformation and Failure of Anisotropic Rocks nearby a Horizontal Well

The article describes modeling mechanical behavior of rocks, including selection of models of inelastic deformation process in anisotropic rocks, experimental determination of elastoplastic properties of rocks and calculation of stress states for specific design well bottoms. The research is carried out for the conditions of Fedorov oil reservoir. The scope of modeling embraces the situations of uncased well shaft and shaft with slotted holing.