Effect of High Temperature on the Permeability Evolution and Failure Response of Granite Under Triaxial Compression

2022 ◽  
pp. 405-437
Author(s):  
Sheng-Qi Yang
Keyword(s):  
High Temperature ◽  
Triaxial Compression ◽  
Permeability Evolution

scholarly journals Experimental Investigation of Thermal Cracking and Permeability Evolution of Granite with Varying Initial Damage under High Temperature and Triaxial Compression

2018 ◽  
Vol 2018 ◽  
pp. 1-9 ◽  
Author(s):  
Xiangxi Meng ◽  
Weitao Liu ◽  
Tao Meng
Keyword(s):  
High Temperature ◽  
Critical Temperature ◽  
Waste Disposal ◽  
Sharp Increase ◽  
Triaxial Compression ◽  
Thermal Cracking ◽  
High Level Waste ◽  
Permeability Evolution ◽  
Initial Damage ◽  
High Level

Thermal cracking and permeability evolution of granite under high temperature and triaxial compression are the key to designing high-level waste disposal sites. In this paper, uniaxial compression tests of granite specimens with different axial compression are designed, and then a solid-head-designed coupling triaxial testing system is applied to study thermal cracking and permeability evolution of granite specimen with different damage at different inlet gas pressures (1, 2, 4, and 6 MPa) and temperatures (ranging from 100 to 650°C). The test results show that granite, nearly impermeable rocks, can show a striking increase of permeability by heating beyond the critical temperature. When the initial axial pressure is 60% or 70% of the uniaxial compressive strength, the growth of granite permeability exhibits three stages during 100∼650°C heating process. Permeability increases by two orders of magnitude, but it does not reach the maximum value (i.e., a network of interconnected cracks is not fully formed in the specimen). With increasing initial damage, permeability shows a sharp increase. Permeability increases by three orders of magnitude, it is in equilibrium state, and a network of interconnected cracks is fully formed in the specimen. Permeability of granite has a critical temperature at which permeability increases sharply. When the temperature is lower than the critical temperature, the magnitude of permeability is 10−18 m2 with a slight increase. When temperature is higher than the critical temperature, the magnitude of permeability is 10−15 m2 with a sharp increase. The critical temperature is related to the initial damage of specimen, and the critical temperature is smaller with the initial damage going larger. Therefore, studying thermal cracking and permeability evolution of granite with different initial damage under high temperature and triaxial compression is expected to provide necessary and valuable insight into the design and construction of high-level waste disposal structures.

scholarly journals Experimental Investigation on the Evolution of Damage and Seepage Characteristics for Red Sandstone under Thermal-mechanical Coupling Conditions

2021 ◽  
Author(s):  
Haopeng Jiang ◽  
Annan Jiang ◽  
Fengrui Zhang
Keyword(s):  
High Temperature ◽  
Triaxial Compression ◽  
Confining Pressure ◽  
Effect Of Temperature ◽  
Permeability Evolution ◽  
Red Sandstone ◽  
Permeability Characteristics ◽  
Mechanical Coupling ◽  
Coupling Conditions ◽  
Rock Stability

Abstract Rock masses in underground space usually experience the coupling of high-temperature field, stress field and seepage field, which gives them complex mechanical behavior and permeability characteristics. In order to study the mechanical properties and permeability characteristics of red sandstone under different temperature environments, a seepage test under high temperature and triaxial compression is carried out based on the RLW-2000 multi-field coupling tester. The results show that the plastic flow of red sandstone at the stress peak under the same temperature is more obvious with the increase of confining pressure. In addition, as the confining pressure gradient increases, the permeability decreases and the trend becomes slower. And the higher the operating temperature, the easier to produce seepage channels inside the rock sample. The development of fissures is rapidly developed under the effect of temperature, so the seepage channels are widened and increased, and the permeability is greatly increased. The constitutive model of rock statistical damage considering the interaction of high temperature and osmotic pressure was constructed based on the experimental data and combining theoretical methods to reveal the characteristics of permeability evolution induced by thermal damage of rocks. The research results can be used as a reference for monitoring rock stability during geological engineering projects involving thermal-seepage-stress coupling conditions.

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.

Triaxial compression system for rock testing under high temperature and high pressure

2012 ◽  
Vol 52 ◽  
pp. 132-138 ◽  
Author(s):  
Yangsheng Zhao ◽  
Zhijun Wan ◽  
Zijun Feng ◽  
Dong Yang ◽  
Yuan Zhang ◽  
...  
Keyword(s):  
High Pressure ◽  
High Temperature ◽  
Triaxial Compression ◽  
Compression System ◽  
Rock Testing

Experimental Study on the Influence of Temperature on Shale Mechanical Properties under Conventional Triaxial Compression

2011 ◽  
Vol 250-253 ◽  
pp. 1452-1455 ◽  
Author(s):  
Lu Bo Meng ◽  
Tian Bin Li ◽  
Liang Wen Jiang ◽  
Hong Min Ma
Keyword(s):  
Mechanical Properties ◽  
Thermal Stress ◽  
Elastic Modulus ◽  
High Temperature ◽  
Poisson’S Ratio ◽  
Triaxial Compression ◽  
Poisson's Ratio ◽  
Influence Of Temperature ◽  
Conventional Triaxial Compression ◽  
Influence Of Temperature On

High temperature conventional triaxial compression test of shale are carried out by the MTS815 servo-controlled testing machine, based on the experimental results, the relationships between temperature and shale peak strength, elastic modulus, Poisson's ratio, cohesion, internal friction angle are investigated. Although the experimental results are discrete comparatively, the general law is obvious. When the confining pressure imposed on shale is constant and the temperature changes form 25°C to 120°C, with the increasing of the temperature, the triaxial compression strength, shear strength gradually increase, while average elastic modulus, Poisson's ratio has a slightly decrease. The thermal stress generated by the high temperature plays a role to accommodate the deformation and the function of preventing crack propagation, thus the bearing capacity of shale samples are strengthened. But the influence of temperature on shale mechanical properties mutates when the temperature is at 80°C. Shale peak strength dramatically decreased, average elastic modulus decreased slightly, and Poisson's ratio also increased slightly, which indicated that at 80°C, different thermal expansivity of mineral particles of shale may cause cross-grain boundary thermal expansion incongruous, creating additional thermal stress, thus the sample’s bearing capacity decreased.

scholarly journals Mechanical behavior investigation of Longmaxi shale under high temperature and high confining pressure

2019 ◽  
Vol 23 (3 Part A) ◽  
pp. 1521-1527
Author(s):  
Hui-Jun Lu ◽  
Dong-Feng Hu ◽  
Ru Zhang ◽  
Cun-Bao Li ◽  
Jun Wang ◽  
...  
Keyword(s):  
High Temperature ◽  
Triaxial Compression ◽  
Confining Pressure ◽  
Bedding Plane ◽  
Brittleness Index ◽  
Tensile Fracture ◽  
Pressure Condition ◽  
Failure Patterns ◽  
Longmaxi Shale ◽  
High Confining Pressure

Triaxial compression tests are conducted on Longmaxi shale under high temperature and high confining pressure condition corresponding to a depth of 3000 m for two typical bedding plane orientations (0? and 90?). It is found that the crack initiation stresses and crack damage stresses of the Longmaxi shale specimens with different vein orientations are different, reflecting that the inclination of the bedding plane has a non-negligible influence on the microcrack initiation and propagation. In addition, the brittleness index of the Longmaxi shale with a bedding plane orientation of 90? is greater than that with an orientation of 0?, which confirmed that the brittleness index is related to the structural orientation under a high temperature and high confining pressure condition. Concerning the failure patterns, both the shear and tensile fracture modes has been observed.

scholarly journals Mechanical Behavior and Permeability Evolution of Coal under Different Mining-Induced Stress Conditions and Gas Pressures

Energies ◽  
2020 ◽  
Vol 13 (11) ◽  
pp. 2677
Author(s):  
Zetian Zhang ◽  
Ru Zhang ◽  
Zhiguo Cao ◽  
Mingzhong Gao ◽  
Yong Zhang ◽  
...  
Keyword(s):  
Triaxial Compression ◽  
Volumetric Strain ◽  
Coal Mass ◽  
Gas Pressure ◽  
Stress Conditions ◽  
Permeability Evolution ◽  
Compression Tests ◽  
Induced Stress ◽  
Conventional Triaxial Compression ◽  
Gas Pressures

The gas permeability and mechanical properties of coal, which are seriously influenced by mining-induced stress evolution and gas pressure conditions, are key issues in coal mining and enhanced coalbed methane recovery. To obtain a comprehensive understanding of the effects of mining-induced stress conditions and gas pressures on the mechanical behavior and permeability evolution of coal, a series of mining-induced stress unloading experiments at different gas pressures were conducted. The test results are compared with the results of conventional triaxial compression tests also conducted at different gas pressures, and the different mechanisms between these two methods were theoretically analyzed. The test results show that under the same mining-induced stress conditions, the strength of the coal mass decreases with increasing gas pressure, while the absolute deformation of the coal mass increases. Under real mining-induced stress conditions, the volumetric strain of the coal mass remains negative, which means that the volume of the coal mass continues to increase. The volumetric strain corresponding to the peak stress of the coal mass increases with gas pressure in the same mining layout simulation. However, in conventional triaxial compression tests, the coal mass volume continues to decrease and in a compressional state, and there is no obvious deformation stage that occurs during the mining-induced stress unloading tests. The theoretical and experimental analyses show that mining-induced stress unloading and gas pressure changes greatly impact the deformation, failure mechanism and permeability enhancement of coal.

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