冻结岩石节理面峰值剪切强度准则研究

冻土区工程场地岩石节理作为力学薄弱面对工程的安全和耐久性有很大影响,因此研究冻结岩石的力学性质对冻土区工程建设有重大的意义。为了研究冻结岩石节理的剪切力学性质,试验选定青海省G214国道姜路岭路段4组不同粗糙度的凝灰岩天然耦合节理面,在设定温度下冻结后进行直剪试验。试验成果表明:冻结岩石节理面的峰值剪切强度与法向应力呈正比,与张开度和粗糙度呈反比。张开度大于节理面最大起伏差时,节理面以脱离破坏为主,其峰值剪切强度由冰与节理接触面的黏结力决定;当张开度小于节理面最大起伏差时,在较小法向应力下以冰层剪断破坏为主,在较大的法向应力下,冰层的剪断与节理面凸起的剪断同时存在,其峰值剪切强度由冰和节理面的剪切强度共同决定。研究推导出各破坏形式下的冻岩节理面峰值剪切强度准则,对分析岩石的边坡稳定性起着十分重要的作用。

Peak Shear Strength Criteria for Frozen Rock Joint Surface

In permafrost region,rock joint as a mechanical weakness has great influence on the safety and durability of engineering projects. Studying the mechanical properties of frozen rock is of great significance for engineering construction in permafrost regions.To investigate the shear mechanical performance of frozen rock joints,four sets of natural joint surfaces of tuff collected from G214 National Highway in Qinghai Province were selected for direct shear test after being frozen at given temperature. Results show that the peak strength of the frozen rock joint is pro-portional to normal stress,and is inversely proportional to opening degree and roughness. When the opening of joint surface is greater than the maximum fluctuation of joint, the joint surface is dominated by disconnection failure mode,and the peak shear strength is controlled by adhesive force between ice and contact surface;when the open-ing of joint surface is smaller than the maximum fluctuation,ice shearing failure is the dominant failure mode under small normal stress;while under large normal stress,shearing failure of ice and rock both exist,and the peak shear strength is determined by the shear strength of both ice and rock joint. Furthermore,the peak shear strength criteria for frozen rock joints with various failure modes were derived.