法向动载条件下粗糙岩质节理面剪切力学特性试验研究

Experimental study on the shear mechanical behaviors of a rough rock joint surface under dynamic normal load boundary condition

为探究地震荷载作用下岩石节理的承载特性,开展不同法向动载应力边界条件下岩质节理面剪切试验,分析法向动载幅值和频率对节理面强度参数、变形参数以及破坏特征的影响规律。结果表明:(1)随着动载幅值由增大,峰值剪切强度呈线性趋势降低48.27%~55.59%,而动载频率对峰值剪切强度影响较小;进入稳定残余阶段,剪切应力幅宽随幅值的增大呈线性趋势增大1.24~2.83倍;动载频率由0.2 Hz增大至0.5 Hz,剪切应力幅宽迅速减小36.28%~40.61%,在频率大于0.5 Hz后缓慢降低。(2)峰前剪切刚度呈现法向应力依赖性,随动载幅值和频率的增大剪切刚度和剪胀性均明显降低。(3)法向应力于剪切应力波峰存在明显相位偏移,相位偏移随着动载幅值和频率的增大而降低,且在频率达到2.0 Hz后无明显相位偏移。(4)当频率低于0.5 Hz时,节理面磨损面积占比迅速增加了36.10%~69.37%,而当频率大于0.5 Hz时,其磨损面积占比近似呈线性增加了5.17%~10.18%。

To explore the load-bearing characteristics of the rock joints under seismic loads,the shear experiments about the mechanical behaviors of a rough joint surface under the dynamic normal load stress were carried out.The influence of the amplitude and frequency of the dynamic normal load on the intensity parameters,morph parameters and failure characteristics of the joint surface were obtained.The results show that:(1)Increasing the dynamic load amplitude results in a linear decrease of 48.27%to 55.59%in the peak shear strength.The dynamic load frequency has less impact on the peak shear strength.In the stable residual stage,the shear stress amplitude width increases linearly by 1.24 to 2.83 times with increasing the amplitude,and the dynamic loading frequency increases from 0.2 Hz to 0.5 Hz,resulting in a rapid decrease of 36.28%to 40.61%in the shear stress amplitude.This decline continues gradually after the frequency exceeds 0.5 Hz.(2)The shear stiffness in the pre-peak stage is a normal stressdependent.And,both the amplitude and frequency of the dynamic normal load decrease the shear stiffness in the pre-peak stage and dilatancy in the post-failure stage.(3)A significant phase shift between the shear stress and normal stress occurs.The phase offset decreases with the increase of the amplitude and frequency of the dynamic normal stress.When the frequency reaches 2.0 Hz,the phase shift becomes negligible.(4)When the frequency is below 0.5 Hz,the proportion of the joint surface wear area increases sharply by 36.10%to 69.37%.Conversely,when the frequency exceeds 0.5 Hz,the wear area proportion shows an approximately linear increase of 5.17%to 10.18%.