基于现场直剪试验和强度软化的围岩压力解析

Analysis of Surrounding Rock Pressure Basedon Field Shear Test and Strength Softening

高地应力、强挤压软岩隧道在开挖前,隧道设计线路范围内的原岩就已处在塑性状态,隧道开挖后对支护有影响的围岩处于不同的塑性区范围内.就此,考虑到岩体的力学性能通过现场试验能较为全面地反映,对两座隧道高地应力软岩段的现场直剪试验曲线进行分析,并进行室内常规三轴压缩试验,得到了适用于塑性软岩隧道的简化本构关系曲线和应变软化模型.在此基础上对圆形塑性软岩隧道支护后的围岩应力状态和位移状态进行分析,在考虑围岩强度参数c-、φ-随应变软化的情况下,推导出了塑性软岩隧道的扰动区半径r_(d)和支护力p_(i)解析表达式,并建立了动态支护力p_(i)与动态隧道壁径向位移u之间的关系,研究成果可为高地应力、强挤压塑性软岩隧道的支护设计提供一定的参考.

Before the tunnel excavation,the high-stress and strong-extruded soft rock tunnels of design line range are in a plastic state.After tunnel excavation,the surrounding rock affected the support is in different plastic zones.In this regard,considering the field test of the rock mass can reflect the whole picture of the mechanical properties of the rock mass more comprehensively,the on-site direct shear test curve of the high ground stress soft rock section of the two tunnels is analyzed,and the indoor routine triaxial compression test is carried on,finally a simplified constitutive curve and strain softening model for plastic soft rock tunnels are obtained.Based on this,the stress state and displacement state of surrounding rock after circular plastic soft rock tunnel support are analyzed.Considering the strength parameters c- and φ- softening with strain changes,the analytical expression of the radius r_(d) and the supporting force p_(i) of the plastic rock tunnel is derived,and the relationship between the dynamic support force p_(i) and the dynamic tunnel wall radial displacement u are established.The research results can provide a reference for the design of high-stress and strong-extruded plastic soft rock tunnels.