Shear behavior of Beishan granite fractures after thermal treatment

Zhao, Zhihong; Zhang, Dou; Xu, Haoran; Liu, Zhina

doi:10.1016/j.engfracmech.2019.04.012

Cited by 70 publications

(9 citation statements)

References 22 publications

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“…According to Zhao et al (2019), surface with higher value of Z 2 is rougher. We have calculated the relation between Z 2 and perturbation of R 2 as shown in Figure 2.…”

Section: Methodsmentioning

confidence: 99%

Roughness Effects of Crack Surfaces on the Elastic Moduli of Cracked Rocks

Han

et al. 2021

Front. Earth Sci.

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Crack surfaces are usually rough on various scales, and are sensitive to loading stresses and hence significantly affecting the mechanical properties of cracked rocks. We design a number of dry- and fluid-saturated numerical cracked samples to investigate the roughness influence of crack surfaces on the elastic stiffness. The fracture surface roughness is characterized by non-uniform fracture radii. We calculate the elastic moduli of cracked samples by finite-element simulation. Comparisons with the theoretical predictions by Gassmann and C&S (Ciz and Shapiro) (Ciz and Shapiro, Geophysics, 2007, 72(6), A75–A79) substitution equations demonstrate that the rough crack surfaces for both dry- and fluid-saturated samples can induce a stress concentration around the crack that reduces the elastic moduli and decreases the stiffness of rocks. For the fluid/solid-saturated cracks under the normal (shear) loading stresses, because the stress-concentration can induce shear (normal) strains around fracture, shear (bulk) modulus of the filling material will have contributions to the effective bulk (shear) modulus of rocks. The extra contribution, however, makes the Gassmann equation and C&S equation invalid.

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“…According to Zhao et al (2019), surface with higher value of Z 2 is rougher. We have calculated the relation between Z 2 and perturbation of R 2 as shown in Figure 2.…”

Section: Methodsmentioning

confidence: 99%

Roughness Effects of Crack Surfaces on the Elastic Moduli of Cracked Rocks

Han

et al. 2021

Front. Earth Sci.

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“…The temperature-dependent shear behavior of different rock types is controlled by two main mechanisms, physical and chemical mechanisms 45 , 46 . The physical mechanism includes the growth of thermal fractures due to the difference in the thermal expansion coefficient of constituent minerals and the evaporation of absorbed water.…”

Section: Resultsmentioning

confidence: 99%

Extensive experimental investigation on the effect of thermal treatment and lateral pressure on the shear behavior of intact mudstone

Alneasan

Alzo’ubi

2023

Sci Rep

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The coupling environment of temperature (T) and lateral pressure at great depths promotes intact rocks to shear failure, posing a serious threat to underground engineering. Temperature effect on shear behaviour is of particular importance due to the possible mineralogical alterations in mineral composition, especially in clay-rich rocks such as mudstone that has a great affinity for water. Accordingly, the effect of thermal treatment on the shear behaviour of intact mudstone was investigated, in this study, using the Short Core in Compression (SSC) method. Three temperatures of RT, 250 and 500 °C, and four lateral pressures of 0.0, 0.5, 2.0, and 4.0 MPa were adopted. Numerical and experimental observations showed that the resulting fractures in SCC samples are shear and by increasing the lateral pressure, shear failure is promoted. Compared with other rock types such as granite and sandstone, shear properties in mudstone have only one positive trend with temperature increase up to 500 °C, by increasing T from RT to 500 °C, mode II fracture toughness, peak friction angle, and the cohesion increased by about 15 to 47%, 4.9%, and 47.7%, respectively. The bilinear Mohr–Coulomb failure criterion can be used to model the peak shear strength behaviour of intact mudstone before and after thermal treatment.

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“…However, at temperatures from 100 to 150°C, the thermal stress between the mineral particles gradually increases and exceeds the particle cohesion, reducing the rock strength and stiffness to a small degree (Ghassemi et al, 2011;Zhao et al, 2017;Sepúlveda et al, 2020). In conclusion, when the temperature of granite varies from room temperature (25°C) to 200°C, the fractures in the rock mass are not obvious, and the strength of the rock does not change significantly (Zhao et al, 2019;Yang et al, 2020;Zhang et al, 2020). Therefore, the reservoir temperature has a negligible effect on the rock mechanical properties and can only affect the rock fracture process indirectly during EGS reservoir construction.…”

Section: Introductionmentioning

confidence: 99%

Hydraulic Conductivity Characteristics of Hot Dry Rocks under Different Fracture Modes

Liu

Feng

Liu

et al. 2021

Acta Geologica Sinica (Eng)

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Enhanced geothermal system (EGS) is an effective method for developing and utilizing hot dry rock (HDR). The key to the effectiveness of EGS is the construction of an artificial fracture network. The permeability of fractures has severe effects on the heat transfer efficiency and sustainability of geothermal energy. However, the evolution characteristics of hydraulic conductivity under different failure modes have not been adequately studied for HDR. To clarify this, rocks with different failure modes were investigated by conducting thermal triaxial compression experiments, and the fluid seepage related to different rock failure modes was comprehensively investigated. The results showed that the characteristic stresses and crack surface roughness of the rock increased as the confining pressure increased. The permeability in the composited failure mode was the largest (11.4 μm2), followed by that in the Y‐shaped shear failure mode (9.7 μm2), and that in the single‐shear failure mode was the smallest (7.2 μm2). The confining pressures had an inhibitory effect on permeability. As the confining pressure increased from 5 to 30 MPa, the permeability decreased by 88.8%, 88.4%, and 89.9%, respectively. In contrast, the permeability was significantly enhanced by 128.3%, 94.6%, and 131% as the flow rate increased from 3 to 7 mL/min.

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Shear behavior of Beishan granite fractures after thermal treatment

Cited by 70 publications

References 22 publications

Roughness Effects of Crack Surfaces on the Elastic Moduli of Cracked Rocks

Roughness Effects of Crack Surfaces on the Elastic Moduli of Cracked Rocks

Extensive experimental investigation on the effect of thermal treatment and lateral pressure on the shear behavior of intact mudstone

Hydraulic Conductivity Characteristics of Hot Dry Rocks under Different Fracture Modes

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