围压卸载条件下岩石的变形特性及渗透演化的试验研究（英文）

Experimental investigation on deformation characteristics and permeability evolution of rock under confining pressure unloading conditions

在应力释放条件下岩石的变形行为及水力性质是影响岩石工程开挖及使用安全的两个主要因素,鉴于此,本文以探寻卸荷条件下岩石的变形行为和渗透特性并提供一些表征岩石卸荷性质的参数为研究目标。首先,进行了一组加载路径为应力峰值前卸载围压的三轴试验,在试验中进行渗透率测试及声发射实时信号监测。然后,基于试验结果对整个应力–应变过程中岩石的变形行为及渗透演化情况作了深入分析。结果表明:在围压卸载条件下,岩石的应力–轴向应变曲线、渗透率–轴向应变曲线以及声发射事件分布情况具有很好的对应关系;在围压卸载之后,径向应变发展速率较轴向应变快,从而导致体积应变也迅速增大;所有的卸围压破坏均表现为具有一个宏观破裂面的剪切破坏;随着围压卸载过程中变形模量的不断降低,损伤变量呈不断增加趋势,表明围压卸载过程是一个累积损伤及强度劣化的过程;从整个加载和卸载过程来看,渗透率与体积应变存在一定的正相关关系。

Deformation behavior and hydraulic properties of rock are the two main factors that influence safety of excavation and use of rock engineering due to in situ stress release.The primary objective of this study is to explore deformation characteristics and permeability properties and provide some parameters to character the rock under unloading conditions.A series of triaxial tests with permeability and acoustic emission signal measurement were conducted under the path of confining pressure unloading prior to the peak stress.Deformation behavior and permeability evolution in the whole stress–strain process based on these experimental results were analyzed in detail.Results demonstrate that,under the confining pressure unloading conditions,a good correspondence relationship among the stress–axial strain curve,permeability–axial strain curve and acoustic emission activity pattern was obtained.After the confining pressure was unloaded,the radial strain grew much faster than the axial strain,which induced the volumetric strain growing rapidly.All failures under confining pressure unloading conditions featured brittle shear failure with a single macro shear rupture surface.With the decrease in deformation modulus during the confining pressure unloading process,the damage variable gradually increases,indicating that confining pressure unloading was a process of damage accumulation and strength degradation.From the entire loading and unloading process,there was a certain positive correlation between the permeability and volumetric strain.