常法向刚度下软弱夹层结构面剪切特性试验研究

Experimental study on shear characteristics of weak interlayer rock joint under constant normal stiffness

【目的】为研究常法向刚度条件下软弱夹层对岩石结构面稳定性的影响,对不同充填度的结构面剪切特性进行试验研究。【方法】基于Barton经典形貌曲线的粗糙度系数(joint roughness coefficient,JRC),采用3D雕刻技术制作了15组岩石结构面上下盘,开展了不同法向刚度(K_(n)=10、20、40 kN/mm)及充填度(Δ=0.0、0.5、1.0、1.5、2.0)的结构面直剪试验。【结果】充填度为0.0时,结构面剪应力随剪切位移增加呈非线性振荡上升,且最大剪应力随法向刚度增大不断增大;同一法向刚度(K_(n)=20 kN/mm)条件下,充填度为0.5和1.0时,结构面剪应力随剪切位移增加呈非线性增长,充填度为1.5和2.0时,结构面剪应力随剪切位移增加而增加并趋于平稳;结构面最大剪应力随充填度增加呈非线性减小,且临界充填度介于1.5~2.0之间;软弱夹层结构面剪胀量随法向刚度增大而减小,且随着充填度继续增加,法向位移由剪胀逐渐转为剪缩,破坏模式也转为夹层剪切破坏。【结论】本研究结果为地下工程中软弱夹层围岩稳定性评价提供了试验依据。

[Objective]To study the influence of weak interlayer on the stability of rock joint under the constant normal stiffness condition,the shear characteristics of rock joint with different filling degrees were studied experimentally.[Method]Based on joint roughness coefficient(JRC)of Barton's classical morphology curve,15 sets of hanging walls and footwalls of rock joint samples were made by 3D engraving technology to carry out the direct shear tests of rock joint under different normal stiffnesses(K_(n)=10、20、40 kN/mm)and filling degrees(Δ=0.0、0.5、1.0、1.5、2.0).[Result]When the filling degree is 0.0,the shear stress of rock joint increases non-linearly with the increase of shear displacement,and the maximum shear stress rises with the increase of normal stiffness;under the same normal stiffness(K_(n)=20 kN/mm)condition,the shear stress of rock joint increases non-linearly with increasing shear displacement at filling degrees of 0.5 and 1.0,whereas it steadily increases at filling degrees of 1.5 and 2.0;the maximum shear stress of rock joint decreases nonlinearly with the increase of filling degree,and the critical filling degree is between 1.5 and 2.0;the dilatancy of weak interlayer rock joint decreases with the increase of normal stiffness,and as the filling degree continues to increase,the normal displacement gradually changes from shear dilatancy to shear contraction,and the failure mode becomes interlayer shear failure.[Conclusion]The results of this study provide an experimental basis for the stability evaluation of weak interlayer surrounding rock in underground engineering.