摘要
在层状岩体中掘进隧洞后,围岩破裂碎胀大变形机制与各向同性围岩存在很大差异。对于无支护隧洞而言,其破裂模式可归结为复合破裂、V型凹槽破裂和层间剥落,不同破裂模式受控于岩体自身物理力学特性、地应力和隧洞断面形状等因素。采用有限元-离散元法(finite-discrete element method,简称FDEM)耦合数值模拟研究了水平层状围岩破裂碎胀大变形机制,并研究了岩体强度参数(如黏聚力、内摩擦系数和抗拉强度)、变形参数(如弹性模量)、地应力和隧洞跨度对水平层状围岩破裂模式的影响。研究结果表明,复合破裂为层状岩体基本破裂模式,其机制为水平集中应力产生的共轭剪切裂隙F3在隧洞中心线附近不断向围岩深处扩展,同时产生平行于层理面的剪切滑移裂隙F1,由此产生中央破碎、两端相对完整的板块岩块;左右两侧板状岩块相互挤压向隧洞内翻转运动产生垂直层理面的拉伸裂隙F2。随着岩体强度的升高、侧压系数的增大或隧洞跨度的减小,F1裂隙消失、F2裂隙与层理面斜交,从而产生V型凹槽破裂。当岩体强度进一步升高或侧压系数进一步增大时,F3裂隙在层理面交界处受阻,进而产生了层间剥落破裂。
For the tunnel excavated in layered rock mass, the failure mechanism of surrounding rocks is different from that of isotropic surrounding rocks. For unsupported tunnel, the failure mode can be summarized into mixed failure, V-shaped notch breakout failure and spalling of bedding. The failure modes are controlled by multiple factors such as the physico-mechanical properties of the rock mass, in situ stress, and the shape of the tunnel. In this study, the combined finite-discrete element method(FDEM) is used to understand the failure mechanism of horizontally layered rock mass, including the influences of strength parameters(such as cohesion,internal friction coefficient and tensile strength), deformation parameters(such as Young’s modulus), in situ stress and tunnel span.The study results show that the mixed failure is the basic failure mode of the layered rock mass, and its failure mechanism is the conjugate shear fractures F3 generated by the horizontally concentrated stress continuously propagate into the surrounding rocks near the centerline of tunnel;at the same time, shear-slip fractures F1 parallel to the bedding plane are generated, resulting in slab-like rock fragments. The tensile fractures F2 perpendicular to the bedding plane are generated due to the contact squeezing effect between the left and right slab-like rock fragments and thus flip to the tunnel. With the increase of the rock mass strength, the increase of the lateral pressure coefficient or the decrease of the tunnel span, the fractures F1 disappear, and the fractures F2 are oblique to the bedding plane, resulting in V-shaped notch breakout. When the rock mass strength or the lateral pressure coefficient is further increased, the fractures F3 are blocked at the junction of the bedding planes, resulting in spalling of bedding.
作者
邓鹏海
刘泉声
黄兴
潘玉丛
伯音
DENG Peng-hai;LIU Quan-sheng;HUANG Xing;PAN Yu-cong;BO Yin(School of Civil Engineering,Wuhan University,Wuhan,Hubei 430072,China;State Key Laboratory of Geomechanics and Geotechnical Engineering,Institute of Rock and Soil Mechanics,Chinese Academy of Sciences,Wuhan,Hubei 430071,China)
出处
《岩土力学》
EI
CAS
CSCD
北大核心
2022年第S02期508-523,574,共17页
Rock and Soil Mechanics
基金
国家自然科学基金资助项目(No.41941018)。
关键词
水平层状岩体
破裂碎胀大变形
FDEM数值模拟
围岩破裂模式
圆形隧洞
horizontally layered rock mass
buckling failure
finite-discrete element method(FDEM) numerical simulation
failure mode of surrounding rocks
circular tunnel
