卸荷对隧道掌子面渐进失稳坍方影响  

Influence of unloading level on progressive collapse of tunnel face

作　　者：安永林[1,2] 胡文轩[2] 岳健[1,2] 欧阳鹏博 AN Yonglin;HU Wenxuan;YUE Jian;OUYANG Pengbo(Hunan Provincial Key Laboratory of Geotechnical Engineering for Stability Control and Health Monitoring, Hunan University of Science and Technology,Xiangtan 411201,China;School of Civil Engineering,Hunan University of Science and Technology,Xiangtan 411201,China)

机构地区：[1]湖南科技大学岩土工程稳定控制与健康监测省重点实验室,湖南湘潭411201 [2]湖南科技大学土木工程学院,湖南湘潭411201

出　　处：《铁道科学与工程学报》2018年第9期2301-2307,共7页Journal of Railway Science and Engineering

基　　金：国家自然科学基金资助项目(51408216;51308209;41272324)

摘　　要：通过应力释放模拟卸荷的大小,结合强度折减有限元法分析卸荷对掌子面稳定性、坍方破坏形态与应力路径的影响,并同极限分析的结果作对比。研究结果表明:随着卸荷量增大,掌子面安全系数整体非线性降低,前期降低梯度较后期大,应重视早支护对稳定掌子面围岩的作用。低卸荷量下,掌子面前方无塑性区;随着卸荷的提高,塑性区首先发生在掌子面中心偏下方的小部分范围,并进一步扩展;塑性区形状类似于半个椭球体。掌子面呈现鼓出状态,其中心部位存在一个低应变区;随着卸荷量的增大,掌子面位移增大,并向地表逐渐扩展;掌子面最大位移所在位置逐渐向掌子面中下方转移,此部位是位移控制的重点。地表沉陷范围集中在掌子面上方对应的地表,隧道中线位置最大,向四周逐渐减小。平均应力随着应力释放的增大而减小;偏应力存在极值,呈现先增大后减小。数值模拟和极限分析的结果基本一致,差异与隧道断面形状及破坏模式有关。The unloading level was simulated by release of stress.The finite element method combined with strength reduction was proposed to study the influence of unloading level on the tunnel face stability,collapse failure pattern and stress path.The results were compared with limit analysis.The results show that with the increase of unloading level,the safety factor of tunnel face is reduced nonlinearly overall.The gradient reduction of early stage is greater than later stage,so the attention should be paid to the effect of early support on tunnel face stability.There is no plastic zone in front of tunnel face in the low level of unloading;with the increase of unloading level,the plastic zone is shown in the small range of center offset of tunnel face at first and further expanded;the shape of the plastic region is similar to the half ellipsoid.The tunnel face appeared bulging state and there is a low strain zone in the center;with the increase of unloading level,the displacement of tunnel face is increased and gradually extended to the surface;the location of maximum displacement in tunnel face is transferred to the lower part of tunnel face center,so this part is the focus of displacement control.The subsidence is centered on surface above the tunnel face.The value of subsidence is the largest in the mid-line of tunnel and gradually decreases to the circumference.The average stress decreased with the increase of stress release;there is an extreme value in deviator stresses,which is increased at first and then decreased.The results of numerical simulation and limit analysis agreed well.The difference is related to the shape of tunnel section and the failure mode.

关 键 词：隧道工程 掌子面稳定 卸荷量 应力释放 强度折减法 

分 类 号：U495.2[交通运输工程—交通运输规划与管理]