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法向卸荷条件下含单裂隙砂岩剪切强度与破坏特征试验研究 被引量:14

Experimental investigation on shear strength and failure characteristics of sandstone with a single preexisting flaw under unloading normal stress
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摘要 在地下工程及边坡开挖和河谷下切等人为和自然因素作用下,岩体应力将沿至少某一个方向卸荷,造成复杂的岩体应力重新分布。这种卸荷易诱发岩体工程灾变,其中法向应力卸荷诱发岩体剪切破坏尤为突出。采用法向应力逐渐卸荷而剪切应力保持恒定的直剪试验方法,模拟开挖卸荷诱发岩体剪切破坏的力学机制。研究法向应力卸荷条件下,裂隙与剪切方向的夹角(后面简称夹角)及应力水平对单裂隙砂岩试样剪切变形、强度及破裂演化的影响规律。随着夹角从0°向180°增加,破坏模式依次表现为剪切破坏、张拉破坏、张剪混合破坏及剪切破坏的过渡。卸荷过程中法向位移和剪切位移均随初始法向应力的增大逐渐增大,而随初始剪应力的增大均逐渐减小。卸荷过程中法向位移随夹角的增大呈现先减小后增大的变化,而剪切位移对夹角不敏感。破坏时法向应力卸荷量随初始法向应力的增大逐渐增大,随初始剪应力的增大逐渐减小,随夹角的增大先减小后增大,夹角为60°时试样最容易发生破坏。通过对破裂面的应力状态分析,从力学机制的角度解释了破坏模式与夹角的相关性。研究成果丰富了卸荷岩体力学基础理论,为岩体工程开挖灾害防治提供理论支撑。 Under the influence of anthropogenic and natural factors such as underground engineering,slope excavation and valley cutting,the rock mass stress will release at least in one direction,which induces complex stress redistribution of rock mass.Such unloading easily induces rock mass engineering disasters,and the shear failure due to normal stress unloading is particularly prominent.The direct shear test with gradually unloading the normal stress but keeping the shear stress constant was performed to simulate the shear mechanical behavior of rock mass induced by excavating and unloading.The influences of the angle between the flaw and the shear direction and the stress level on deformation,strength and fracture evolution of single flaw sandstone under unloading normal stress were studied.It is revealed that,with increasing the angle from 0°to 180°,single flaw sandstone in sequence shows shear failure,tension failure,mixed tension-shear failure and shear failure.In the process of unloading,the normal and shear displacements increase with increasing the initial normal stress but decrease with rising the initial shear stress.The unloading normal displacement decreases firstly and then increases with increasing the angle,while the unloading shear displacement is not sensitive to the angle.The unloading amount at failure respectively increases,decreases,and decreases firstly and then increases with increasing the initial normal stress,the initial shear stress and the angle.The specimen is most prone to unloading shear failure when the angle is 60°.The correlation between the failure mode and the angle was presented based on the analysis of the stress state of the crack surface.The research results enrich the basic theory of unloading rock mass mechanics and have reference value for the prevention and treatment of excavation disasters in rock mass engineering.
作者 黄达 郭颖泉 朱谭谭 张永发 HUANG Da;GUO Yingquan;ZHU Tantan;ZHANG Yongfa(School of Civil and Transportation Engineering,Hebei University of Technology,Tianjin300401,China;State KeyLaboratory of Coal Mine Disaster Dynamics and Control,Chongqing University,Chongqing400044,China)
出处 《岩石力学与工程学报》 EI CAS CSCD 北大核心 2019年第7期1297-1306,共10页 Chinese Journal of Rock Mechanics and Engineering
基金 国家自然科学基金资助项目(41472245,41672300,41807279)~~
关键词 岩石力学 裂隙岩体 法向卸荷 直接剪切 裂隙夹角 破裂模式 rock mechanics fissure rock mass unloading normal stress direct shear flaw angle failure pattern
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