分级循环加卸载作用下花岗岩变形破坏研究

以地下深部花岗岩为试验材料,利用GAW-2000微机控制电液伺服岩石单轴试验机进行分级循环加卸载试验,研究在同一递增荷载幅度条件下,试件的抗压强度、变形、破坏特征、残余应变以及弹性模量的变化趋势。结果表明：在单轴分级循环加卸载试验作用下,岩样的峰值强度随着每级循环次数的增加呈现递减趋势,且单调荷载应力-应变曲线包络住循环荷载应力-应变曲线;岩样破坏特征主要以剪切破坏为主,随着循环次数增加,破坏裂纹更加分散;岩样在加载过程中,岩体内部的结构在不断地调整,导致结构面变得密集与裂隙间更加闭合,卸载时回弹变形有滞后现象,加载起点与卸载终点不重合;轴向弹性、残余应变与环向弹性、残余应变随循环次数变化的规律具有相似性,岩样弹性模量曲线的趋势以“波浪形”的规律交替变化。

Research on Deformation and failure of Granite Under Staged Uniaxial Cyclic Loading and Unloading

Using underground deep granite as the test material, the GAW-2000 microcomputer controlled electro-hydraulic servo rock single-axis testing machine was used to carry out the grading cycle plus unloading test. The changes of compressive strength, deformation, failure characteristics, residual strain and elastic modulus trend of the specimens under the same increasing load amplitude were studied. The results show that under under staged uniaxial cyclic loading and unloading, the peak strength of rock samples decreases with the increase of cyclic times of each stage, and the stress-strain curve of monotone load envelops the stress-strain curve of cyclic load. The failure characteristics of rock samples are mainly shear failure. With the increase of the number of cycles, the failure cracks become more dispersed. Sample in the process of loading, the inside of the rock mass structure is adjusted ceaselessly in, lead to more closed structural plane become dense and crack, unload the springback deformation hysteresis, load starting point and unload the finish is not coincidence. The laws were similar to axial elastic, residual strain and toroidal elasticity and residual strain change with cycles, rock"s elastic modulus curve trend to the rule of "waves" variations.