剪切过程中锚杆轴力和剪力演化规律研究

Variation of Axial and Shear Forces of the Ground Anchor During Shearing

针对加锚结构面剪切过程中锚杆轴力与剪力演化及贡献的问题,基于FLAC3D软件开展了加锚结构面直剪实验。用pile单元代替传统的cable单元模拟锚杆,研究剪切过程中锚杆轴力、剪力的分布及演化特征,并分析了锚杆直径、锚杆倾角、围岩强度对锚杆轴力与剪力的影响。结果表明:(1)结构面处锚杆剪力与轴力达到最大值,在两端很小,剪力在位移较小的情况下就达到一个较大的值,轴力的发挥则相对滞后,锚杆在结构面两侧约5D范围内形成两个“塑性铰”点,塑性铰点间锚杆存在变形剧烈的“拉剪区”。(2)结构面加锚后峰值剪切强度提升约70%,锚杆对结构面的加固作用可以等效为增加了结构面的粘聚力。(3)随着直径的增加,锚杆的剪力有明显的提升,轴力反而减小;锚杆倾角为60°时,轴力与剪力换算得到的结构面等效抗剪强度最大;相比较软岩,硬岩更有利于锚杆轴力与剪力的发挥。

This paper presents the evolution and contribution of axial and shear forces of the ground anchor during the shearing process of anchored joint interface.A numerical simulation of the direct shear test on the anchored joint interface was performed by using the FLAC3D software.The“pile”element is used instead of the conventionally used“cable”element to simulate the ground anchor.The distribution and evolution characteristics of both the axial and the shear forces of the anchor are studied during the shearing process.The effects of the ground anchor diameter,anchor inclination,and surrounding rock strength on the axial and shear forces of the bolt are analyzed.The results show that:(1)The shear force and the axial force of the ground anchor at the joint reach the maximum value,which are small at both ends,the shear force reaches a large value with a small displacement,and the exertion of the axial force is relatively lagging,two“plastic hinge”points appeared on the bolt within a range of about 5D on both sides of the joint,and there is a“pull-shear zone”in which the bolt deforms sharply between the plastic hinge points.(2)The peak shear strength of the joint is increased by about 70% after the anchoring,and the reinforcing effect of the ground anchor on the joint can be equivalent to increasing the cohesion of the joint.(3)With the diameter increases,the shear force of the anchor increases significantly,but the axial force decreases.When the inclination of the bolt is 60°,the maximum equivalent shear strength of the joint converted from the axial force and the shear force is obtained;Compared with the soft rock,hard rock is more conducive to the exertion of the bolt's axial and shear forces.