Numerical Simulation Study on Shear Properties of Rock Joint Under CNS Boundary Conditions

IF 1.7 Q3 ENGINEERING, GEOLOGICAL
Guansheng Han, Zhijing Chen, Jiahao Xiang, Yuan Gao, Yu Zhou, Qiongqiong Tang, Weiqiang Chen
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Abstract

Abstract In this study, the shear mechanical property of rock joints under constant normal stiffness (CNS) boundary conditions was investigated by the PFC discrete element software. The effects of joint roughness coefficient (JRC), initial normal stress ( σ n0 ), normal stiffness ( k n ) and shear rate ( v ) on shear stress ( τ ), shear dilation (normal displacement, δ v ), and normal stress ( σ n ) were quantitatively investigated. The stress evolution and damage process inside the samples during the CNS shearing process of rock joints were analyzed. The test results showed that the increase of JRC significantly improved the shear performance of rock joints. Meanwhile, shear stress, normal displacement, normal stress and the number of tensile cracks of samples were significantly increased. Excessive initial normal stress (greater than or equal to 4 MPa) will cause irreversible failure of the joints. The protrusion of the joints is sheared or ground and detached from the samples, which leads to shear shrinkage of the sample. The increase of normal stiffness and shear rate will restrain the shear expansion of the joints, which will also aggravate the failure of the samples. Three empirical formulas for predicting shear stress, normal stress, normal displacement of rock joint samples under CNS boundary conditions are proposed and laboratory tests were carried out to verify them. The four factors involved above and shear displacement ( δ h ) are considered in the prediction model. The calculated results of the prediction model are in good overall agreement with the laboratory test results, and the error decreases with the increase of shear displacement.
CNS边界条件下岩石节理剪切特性的数值模拟研究
摘要采用PFC离散元软件,研究了岩石节理在恒法向刚度(CNS)边界条件下的剪切力学特性。定量研究了节理粗糙度系数(JRC)、初始法向应力(σ n0)、法向刚度(k n)和剪切速率(v)对剪应力(τ)、剪胀(法向位移,δ v)和法向应力(σ n)的影响。分析了岩石节理CNS剪切过程中试样内部的应力演化和损伤过程。试验结果表明,JRC的增加显著改善了节理的抗剪性能。同时,试样的剪切应力、法向位移、法向应力和拉伸裂纹数量均显著增加。过大的初始法向应力(大于等于4mpa)会导致接头的不可逆破坏。接头的突出部分被剪切或磨碎,脱离试样,导致试样的剪切收缩。法向刚度和剪切速率的增加会抑制节理的剪切膨胀,同时也会加剧试件的破坏。提出了3种预测CNS边界条件下岩石节理试样剪应力、正应力、法向位移的经验公式,并进行了室内试验验证。预测模型考虑了上述4个因素及剪切位移(δ h)。预测模型计算结果与室内试验结果总体吻合较好,且误差随剪切位移的增大而减小。
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来源期刊
Geotechnical and Geological Engineering
Geotechnical and Geological Engineering ENGINEERING, GEOLOGICAL-
CiteScore
3.70
自引率
5.90%
发文量
298
期刊介绍: Geotechnical and Geological Engineering publishes papers in the areas of soil and rock engineering and also of geology as applied in the civil engineering, mining and petroleum industries. The emphasis is on the engineering aspects of soil and rock mechanics, geology and hydrogeology, although papers on theoretical and experimental advances in ground mechanics are also welcomed for inclusion. The journal encompasses a broad spectrum of geo-engineering although several areas have been identified which will be given particular priority: Soil and rock engineering; Foundation engineering; Applied geology for design and construction; Geo-environmental engineering; Earthquake engineering and dynamic behavior of soils and rocks; Geohazards and mitigation; Mining engineering; Geotechnical aspects of petroleum engineering; Information technology applications in geo-engineering; Novel geotechnical construction techniques; Case histories describing important geo-engineering projects. Geotechnical and Geological Engineering publishes contributions in the form of original and review papers, or as short technical notes.
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