scholarly journals Failure Behavior and Constitutive Model of Weakly Consolidated Soft Rock

2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
Wei-ming Wang ◽  
Zeng-hui Zhao ◽  
Yong-ji Wang ◽  
Xin Gao
Keyword(s):  
Constitutive Model ◽  
Failure Mechanism ◽  
Triaxial Compression ◽  
Soft Rock ◽  
Confining Pressure ◽  
Western China ◽  
Failure Behavior ◽  
Correction Coefficient ◽  
Compression Tests ◽  
Mining Areas

Mining areas in western China are mainly located in soft rock strata with poor bearing capacity. In order to make the deformation failure mechanism and strength behavior of weakly consolidated soft mudstone and coal rock hosted in Ili No. 4 mine of Xinjiang area clear, some uniaxial and triaxial compression tests were carried out according to the samples of rocks gathered in the studied area, respectively. Meanwhile, a damage constitutive model which considered the initial damage was established by introducing a damage variable and a correction coefficient. A linearization process method was introduced according to the characteristics of the fitting curve and experimental data. The results showed that samples under different moisture contents and confining pressures presented completely different failure mechanism. The given model could accurately describe the elastic and plastic yield characteristics as well as the strain softening behavior of collected samples at postpeak stage. Moreover, the model could precisely reflect the relationship between the elastic modulus and confining pressure at prepeak stage.

scholarly journals Triaxial Compressive Failure Characteristics and Constitutive Model Study of Jurassic-Cretaceous Weakly Cemented Sandstone

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Jinlong Cai ◽  
Wei Zou
Keyword(s):  
Constitutive Model ◽  
Residual Strength ◽  
Triaxial Compression ◽  
Volumetric Strain ◽  
Ductile Failure ◽  
Mathematical Expression ◽  
Confining Pressure ◽  
Mining Area ◽  
Peak Strength ◽  
Correction Coefficient

A conventional triaxial compression test of Jurassic-Cretaceous typical weakly consolidated sandstone from a mining area in Ordos, China, was conducted using an MTS816 tester. Results showed that, before the peak, the rock had a distinct yield stage. When the specimen reached its peak strength, the strength decreased rapidly and showed an obvious brittle failure. When the confining pressure was increased to 15 MPa, the decrease of strength was slow and the rock tended toward ductile failure. With the increase of confining pressure, the cyclic strain initially increased slightly, whereas the volumetric strain increased greatly and the rock sample was in a compression state. When the load reached a critical value, the curve was reversely bent, resulting in volume expansion, whereas the peak strength, residual strength, and elastic modulus increased with confining pressure, and Poisson’s ratio decreased with the confining pressure. In the model based on macroscopic failure rock, the expression of the relationship between fracture angle and confining pressure provided a solid theoretical basis for the direction and failure mode of the macroscopic crack. Based on the rock strength theory and Weibull random distribution assumption of rock element strength, the damage variable correction coefficient was introduced when the residual strength was considered. Then, the mathematical expression of the 3D damage statistical constitutive model was established. Finally, the theoretical curve of the established constitutive model was compared with the triaxial test curve, which showed a high degree of coincidence.

scholarly journals Study on the Rheological Failure Mechanism of Weakly Cemented Soft Rock Roadway during the Mining of Close-Distance Coal Seams: A Case Study

2020 ◽  
Vol 2020 ◽  
pp. 1-20
Author(s):  
Wenkai Ru ◽  
Shanchao Hu ◽  
Jianguo Ning ◽  
Jun Wang ◽  
Qingheng Gu ◽  
...  
Keyword(s):  
Coal Seam ◽  
Failure Mechanism ◽  
Coal Pillar ◽  
Soft Rock ◽  
Western China ◽  
Creep Failure ◽  
Mining Areas ◽  
Geological Conditions ◽  
Residual Coal ◽  
Close Distance

During the mining of the shallow-buried and close-distance multiple coal seam, the rheological failure of the surrounding weakly cemented soft rock of the roadway in the lower coal seam under the concentrated stress is very rare. However, the stress on the roof of the upper coal seam is transmitted down through the residual pillar, resulting in this situation. Taking the Gaojialiang coal mine which is located in the mining areas of western China as the research object, the failure mechanism of the roadway roof under the residual coal pillar in the shallow-buried and close-distance multiple seam is studied in combination with field monitoring and numerical simulation. Furthermore, suggestions on the roadway support under such geological conditions are proposed. The results show that the residual coal pillar in the working face of the lower coal seam gradually collapses during the mining of the shallow-buried and close-distance multiple coal seam. The concentrated stress transferred by the coal pillar increases further, which makes the roof stress of the lower coal seam roadway to increase continuously. In addition, the stress of the roadway roof also increases further due to the rotation of the broken rock above the goaf, and the peek region of stress moves to the nongoaf area. Combining the heavy concentrated stress and weakly cemented property, the shallow-buried surrounding rock shows rheological behavior and failure. Therefore, we must pay more attention on the creep failure of the roadway roof under the action of the residual coal pillar even in the shallow-buried coal seam.

scholarly journals Mechanical Properties and Numerical Analyses of Basalt Fiber Crumb Rubber Mortars in Soft Rock Roadways

2019 ◽  
Vol 2019 ◽  
pp. 1-13 ◽  
Author(s):  
Jun-Ling Qin ◽  
Wei-Guo Qiao ◽  
Deng-Ge Lin ◽  
Shuai Zhang ◽  
Ji-Yao Wang
Keyword(s):  
Constitutive Model ◽  
Triaxial Compression ◽  
Basalt Fiber ◽  
Soft Rock ◽  
Crumb Rubber ◽  
Compression Tests ◽  
Confining Pressures ◽  
Roadway Support ◽  
Uniaxial Compressive Stress ◽  
Triaxial Compression Tests

The strength of crumb rubber mortars can be improved by the addition of basalt fibers. However, limited studies have been conducted on basalt fiber crumb rubber mortars (BF-CRM), and the constitutive model is still very immature. In this paper, uniaxial compressive stress-strain curves are obtained for several groups of BF-CRM specimens with different contents. By comparison with the GZH model, modified GZH parameters that can be used in a BF-CRM constitutive model are obtained. Then, taking the support scheme of the main substation of a mine as the background, FLAC3D is used to simulate the roadway support, BF-CRM replaces the ordinary mortars in the original support, and triaxial compression tests are performed at different confining pressures. In this way, the application of BF-CRM in roadway support is studied and analyzed.

scholarly journals Study on Mechanical Behavior of Jurassic Frozen Sandstone in Western China Based on NMR Porosity

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Maoyan Ma ◽  
Yishun Huang ◽  
Guangyong Cao ◽  
Jian Lin ◽  
Shiliang Xu
Keyword(s):  
Mechanical Properties ◽  
Growth Rate ◽  
Low Temperature ◽  
Rock Strength ◽  
Tracking System ◽  
Triaxial Compression ◽  
Confining Pressure ◽  
Western China ◽  
Compression Tests ◽  
Rock Mechanical Properties

Study of frozen rock mechanical properties is necessary for safe application of the artificial ground freezing method in excavation of Chinese western water-rich soft rock layers. Triaxial compression tests and NMR test for samples from the western Jurassic sandstone were performed to investigate rock mechanical properties affected by low temperature and confining pressure. The results show mechanical parameters such as peak strength, cohesion, internal friction angle, residual strength, and elasticity modulus increased with the decreasing temperature under stable pressure, and the above parameters increased with the increasing confining pressure at a certain temperature. In particular, the growth rate of the rock strength would decline when the temperature was below −10°C in this study. Strength attenuation coefficients increased with the decreasing temperature, which indicated higher brittleness, whereas plastic characters got more obvious with the increasing confining pressure at a stable temperature. Furthermore, during the first two freezing stages, porosity decreased sharply with obvious increase of pore (crack) ice content, while porosity varied little at the third stage, which was the reason for the growth rate of rock strength declining with continuous low temperature from microcosmic point of view.

scholarly journals Mechanical properties and constitutive analyses of basalt fiber crumb rubber mortars in soft rock roadways

2021 ◽  
Vol 303 ◽  
pp. 01023
Author(s):  
Qiao Wei-Guo ◽  
Vladimir Pershin ◽  
Qin Jun-Ling ◽  
Zhang Shuai
Keyword(s):  
Mechanical Properties ◽  
Constitutive Model ◽  
Compressive Stress ◽  
Triaxial Compression ◽  
Basalt Fiber ◽  
Soft Rock ◽  
Confining Pressure ◽  
Crumb Rubber ◽  
Roadway Support ◽  
Uniaxial Compressive Stress

Uniaxial compressive stress-strain curves of several groups of basalt fiber crumb rubber mortars (BF-CRM) with different contents are tested. By comparing with the GZH model, the improved values of the parameters of the BF-CRM constitutive model based on the GZH model are obtained. Then, taking the supporting scheme of main substation of the mine as the background, using FLAC3D to simulate the roadway support, using BF-CRM to replace the ordinary mortars in the original support, and combining with the triaxial compression test of different confining pressure, the application effect of BF-CRM in roadways support is studied and analyzed.

scholarly journals Study of statistical damage constitutive model of layered composite rock under triaxial compression

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Yong-Sheng Liu ◽  
Zhuan-Zhuan Qiu ◽  
Xue-Cai Zhan ◽  
Hui-Nan Liu ◽  
Hai-Nan Gong
Keyword(s):  
Constitutive Model ◽  
Axial Strain ◽  
Triaxial Compression ◽  
Confining Pressure ◽  
Layered Composite ◽  
Model Parameters ◽  
Compression Tests ◽  
Fitting Method ◽  
Confining Pressures ◽  
Curve Fitting Method

Abstract The layered composite rock was subjected to triaxial compression tests under constant confining pressure and the stress–strain curves under different confining pressures were obtained. Based on the continuous damage theory and statistical strength theory, it is assumed that the strength of rock microelements obeys Weibull distribution by taking the defects such as random micro-cracks in the rock into account. The statistical constitutive model of layered composite rock with damage correction is established by taking the axial strain of rock as a random distribution variable of microelement strength. The model parameters were determined by the curve fitting method and referring to some test parameters. By comparing the experimental data and the constitutive model curve, the rationality and feasibility of the model are verified.

Experimental Investigation on Mechanical Properties of Soft Rock under Instantaneous Triaxial Compression

2012 ◽  
Vol 594-597 ◽  
pp. 218-221
Author(s):  
Yu Wang ◽  
Feng Liu
Keyword(s):  
Mechanical Properties ◽  
Shear Failure ◽  
Triaxial Compression ◽  
Deformation Modulus ◽  
Soft Rock ◽  
Confining Pressure ◽  
Test System ◽  
Compression Tests ◽  
Confining Pressures ◽  
Failure Angle

Using the RMT-150C rock mechanics test system, the instantaneous triaxial compression tests for muddy siltstone were carried out under different confining pressures, and the instantaneous mechanical properties of soft rock were obtained. The results show that the strength parameters of sample have a positive linear relation with the confining pressure, and the sensitivity of peak strength on the confining pressure is higher than that of residual strength. The elastic and deformation modulus of sample linearly increase with the confining pressure going up, and the elastic modulus is more sensitive to the confining pressure. The soft rock sample shows typical ductility failure characteristic, while the damage characteristic is mainly shear failure and the shear failure angle linearly decreases with the confining pressure going up.

scholarly journals Permeability Characteristic and Failure Behavior of Filled Cracked Rock in the Triaxial Seepage Experiment

2019 ◽  
Vol 2019 ◽  
pp. 1-12
Author(s):  
Xinyu Liu ◽  
Zhende Zhu ◽  
Aihua Liu
Keyword(s):  
Growth Rate ◽  
Rock Mass ◽  
Failure Modes ◽  
Peak Stress ◽  
Confining Pressure ◽  
Strength Characteristics ◽  
Failure Behavior ◽  
Compression Tests ◽  
Secondary Cracks ◽  
Safety And Stability

Filling is commonly found in natural cracked rock mass. As the weakest part of the rock, the filling properties directly affect the rock deformation and strength, permeability, and so on and affect the safety and stability of the rock mass engineering. In this study, a single slit has been preset in sandstones and filled with different physical properties materials. Based on the laboratory triaxial seepage test, the permeability and strength characteristics of filled cracked sandstones are analyzed, and the failure modes are obtained. The main findings of this study are as follows: (1) The permeability coefficient peak value of the filled cracked rock appears before the stress peak. (2) At the same confining pressure growth rate, the peak stress growth rate of the filled cracked rock is generally higher than that of the intact rock and the strength growth rate of the cracked rock increases with the length of the fracture. The strength characteristics of the filling in the uniaxial compression tests and triaxial seepage tests are significantly affected by the hydraulic properties. (3) The strength and permeability coefficients of cracked rock filled with cement mortar are more sensitive to the change of confining pressure, while under the same condition, the ones of cracked rock filled with gypsum mortar are stable. (4) According to the failure mechanism, under the seepage stress, the secondary cracks can be divided into 3 types and the failure modes can be divided into 2 types.

scholarly journals Triaxial Testing of Geosynthetics Reinforced Tailings with Different Reinforced Layers

Materials ◽  
2020 ◽  
Vol 13 (8) ◽  
pp. 1943
Author(s):  
Fu Yi ◽  
Changbo Du
Keyword(s):  
Triaxial Compression ◽  
Friction Angle ◽  
Confining Pressure ◽  
Test Results ◽  
Compression Tests ◽  
Strength Index ◽  
Stress Strain ◽  
High Confining Pressure ◽  
Zhang Model ◽  
Triaxial Compression Tests

To evaluate the shear properties of geotextile-reinforced tailings, triaxial compression tests were performed on geogrids and geotextiles with zero, one, two, and four reinforced layers. The stress–strain characteristics and reinforcement effects of the reinforced tailings with different layers were analyzed. According to the test results, the geogrid stress–strain curves show hardening characteristics, whereas the geotextile stress–strain curves have strain-softening properties. With more reinforced layers, the hardening or softening characteristics become more prominent. We demonstrate that the stress–strain curves of geogrids and geotextile reinforced tailings under different reinforced layers can be fitted by the Duncan–Zhang model, which indicates that the pseudo-cohesion of shear strength index increases linearly whereas the friction angle remains primarily unchanged with the increase in reinforced layers. In addition, we observed that, although the strength of the reinforced tailings increases substantially, the reinforcement effect is more significant at a low confining pressure than at a high confining pressure. On the contrary, the triaxial specimen strength decreases with the increase in the number of reinforced layers. Our findings can provide valuable input toward the design and application of reinforced engineering.

scholarly journals A Thermal Damage Constitutive Model for Oil Shale Based on Weibull Statistical Theory

2019 ◽  
Vol 2019 ◽  
pp. 1-11 ◽  
Author(s):  
Guijie Zhao ◽  
Chen Chen ◽  
Huan Yan
Keyword(s):  
High Temperature ◽  
Constitutive Model ◽  
Oil Shale ◽  
Thermal Damage ◽  
Triaxial Compression ◽  
Strain Curve ◽  
Practical Significance ◽  
Compression Tests ◽  
Different Temperatures ◽  
Damage Constitutive Model

In this work, we first studied the thermal damage to typical rocks, assuming that the strength of thermally damaged rock microelements obeys a Weibull distribution and considering the influence of temperature on rock mechanical parameters; under the condition that microelement failure conforms to the Drucker–Prager criterion, the statistical thermal damage constitutive model of rocks after high-temperature exposure was established. On this basis, conventional triaxial compression tests were carried out on oil shale specimens heated to different temperatures, and according to the results of these tests, the relationship between the temperature and parameters in the statistical thermal damage constitutive model was determined, and the thermal damage constitutive model for oil shale was established. The results show that the thermal damage in oil shale increases with the increase of temperature; the damage variable is largest at 700°C, reaching 0.636; from room temperature to 700°C, the elastic modulus and Poisson’s ratio decrease by 62.66% and 64.57%, respectively; the theoretical stress-strain curve obtained from the model is in good agreement with the measured curves; the maximum difference between the two curves before peak strength is only 5 × 10−4; the model accurately reflects the deformation characteristics of oil shale at high temperature. The research results are of practical significance to the underground in situ thermal processing of oil shale.

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