巷道开挖效应下围岩损伤演化规律及试验研究

为了研究巷道开挖卸荷引起的围岩损伤演化规律及力学响应机制,采用RMT-150试验机开展了白砂岩试件三轴加载-卸载-单轴再加载力学特性试验,建立了岩石三维损伤本构模型。根据损伤岩石单轴加载应力-应变曲线,分析其破坏模式,确定了单轴再加载强度、波速与初始轴压加载比的非线性关系。结果表明:(1)三轴应力作用下,岩石损伤演化过程分为5个阶段,即损伤稳定减小阶段、无损伤阶段、损伤稳定增长阶段、损伤加速增长阶段、损伤破坏阶段;(2)单轴再加载强度、波速与初始轴压加载比呈现3次非线性相关关系,从环向应变规律来看,损伤岩石表现出塑性硬化和塑性软化两种状态;(3)损伤岩石以张拉破坏为主,随着损伤变量值增加,破坏形式逐渐向剪切滑移破坏转化。通过对岩石损伤演化规律的研究,为工程围岩稳定性判别及预警提供理论依据。

Experimental Study on the Law of Rock Damage Evolution under the Effect of Roadway Excavation

In order to study the surrounding rock damage evolution law and mechanical response mechanism caused by roadway excavation unloading, the RMT-150 testing machine was used to carry out the triaxial loading-unloading-uniaxial reloading mechanical characteristics test of the white sandstone specimen, and the three-dimensional damage constitutive model of the rock was established. According to the stress-strain curve of the damaged rock under uniaxial loading, its failure mode is analyzed. The nonlinear relationship between uniaxial reloading intensity, wave velocity and initial axial compression loading ratio is determined. The results show that: (1)Under the action of triaxial stress, the rock damage evolution process can be divided into five stages: the damage steady reduction stage, the non-damage stage, the steady damage growth stage, the accelerated damage growth stage, and the damage failure stage; (2)Uniaxial reloading strength, the wave velocity and the initial axial load ratio show a third-order nonlinear correlation. Judging from the hoop strain law, the damaged rock exhibits two states: plastic hardening and plastic softening; (3)The damaged rock is mainly tensile failure. As the value of the damage variable increases, the failure mode gradually transforms to shear slip failure. Studying the law of rock damage evolution provides a theoretical basis for the identification and early warning of engineering surrounding rock.