Cohesion correction coefficient.
<div><p>In order to study the shear mechanical properties of rock joint under different unloading stress paths, the RDS-200 rock joint shear test system was used to carry out direct shear tests on concrete joint specimens with five different morphologies under the CNL path and different...
محفوظ في:
| المؤلف الرئيسي: | |
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| مؤلفون آخرون: | , , , |
| منشور في: |
2024
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| الموضوعات: | |
| الوسوم: |
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| الملخص: | <div><p>In order to study the shear mechanical properties of rock joint under different unloading stress paths, the RDS-200 rock joint shear test system was used to carry out direct shear tests on concrete joint specimens with five different morphologies under the CNL path and different unloading stress paths. The unloading stress paths include unloading normal load and maintaining constant shear load (UNLCSL), unloading normal load and unloading shear load (UNLUSL), unloading normal load and increasing shear load (UNLISL). The results show that the peak shear strength, cohesion, internal friction angle, pre-peak shear stiffness and residual shear strength of concrete joints under CNL path increases with the increasing <i>JRC</i> and normal stress. Under the UNLCSL path, under the same initial shear stress τ<sub>1</sub>, instability normal stress σ<sub><i>i</i></sub> decreases with the increasing <i>JRC</i>, and normal stress unloading amount Δσ<sub>n</sub> increases with the increasing <i>JRC</i>. Under the same <i>JRC</i>, σ<sub><i>i</i></sub> increases with the increase of τ<sub>1</sub>, and Δσ<sub>n</sub> decreases with the increasing τ<sub>1</sub>. Under the same <i>JRC</i> and σ<sub><i>i</i></sub>, τ<sub><i>i</i></sub> is significantly smaller under the UNLCSL path than the CNL path. Under the same <i>JRC</i>, the cohesion under the UNLCSL path is less than the CNL path, and the internal friction angle is higher than that the CNL path. Under the same <i>JRC</i> and σ<sub><i>i</i></sub>, τ<sub><i>i</i></sub> is the largest under the path of CNL and UNLISL, followed by the UNLCSL path, and τ<sub><i>i</i></sub> under the UNLUSL path is the smallest. Compared with the CNL path, the variation range of the specimen internal friction angle is within 3% while the average decrease percentage of the specimen cohesion reaches 37.6% under the UNLCSL path, UNLISL, and UNLUSL. Therefore, it can be inferred that the decrease in cohesion caused by normal unloading is the main reason for the decrease in joint instability shear strength. After introducing the correction coefficient <i>k</i> of cohesion to modify the Mohr-Coulomb criterion, the maximum average relative error after correction is only 3.5%, which is significantly improved compared with the maximum average relative error of 56.9% before correction. The research conclusions can provide some reference for the accurate estimation of shear bearing capacity of rock joints under different unloading stress paths, which is of great significance to the stability evaluation and disaster prevention of rock mass engineering.</p></div> |
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