富水软岩隧道破碎带围岩稳定性及预留变形量优化研究

Study on surrounding rock stability and reserved deformation optimization in fracture zone of water-rich soft rock tunnel

为了掌握穿越富水断层破碎带隧道围岩大变形规律及改善支护参数。首先推导渗流力作用下圆形洞室弹塑性解析表达式,并且引入Caquot公式和Kastner公式,得到考虑渗流力条件下的围岩形变压力和松动压力与围岩变形之间的关系,确定围岩特征曲线。根据隧道支护方式,得到隧道支护特征曲线。并通过现场监测,验证理论分析正确性,优化破碎带围岩预留变形量值。研究结果表明:考虑渗流力、围岩塑性形变压力和松动压力共同作用下围岩变形规律与现场监测结果比较接近。考虑渗流力、围岩形变和松动压力求出的围岩压力大于不考虑渗流时得到的结果,考虑渗流力、围岩形变和松动压力时地层与支护结构达到平衡时的变形量比不考虑渗流时大0.15 m。根据围岩-支护相互作用全过程规律曲线,通过曲线交点,得到预留变形量理论值,对比隧道大变形段的监测结果,确定破碎带围岩最优预留变形量为300 mm。研究结果能准确表征渗流效应、围岩形变和松动压力对富水软弱破碎带围岩大变形影响规律,对类似工程的支护设计优化有明确的指导意义。

In order to grasp the large deformation law of surrounding rock of tunnel crossing the water-rich fault fracture zone and improve the supporting parameters,the elastic-plastic analytical expression of circular cavern under seepage force was derived,and the Caquot formula and Kastner formula were introduced to obtain the relationship between the deformation pressure and loosening pressure of surrounding rock and the deformation of surrounding rock under the condition of seepage force.The characteristic curve of surrounding rock was determined,and according to the tunnel support method,the characteristic curveof tunnel supportwas obtained.Through on-site monitoring,the correctness of the theoretical analysis was verified,and the reserved deformation value of the surrounding rock in the fracture zone was optimized.The results show that the deformation law of surrounding rock under the combined action of seepage force,plastic deformation pressure and loosening pressure of surrounding rock is close to the results of on-site monitoring.The surrounding rock pressure obtained by considering the seepage force,plastic deformation pressure and loosening pressure of surrounding rockis greater than the result without considering the seepage,and the deformation when the stratum and the supporting structure reach equilibrium considering the seepage force,plastic deformation pressure and loosening pressure of surrounding rockis 0.15 m larger than that without considering.According to the whole process law curve of surrounding rock and support interaction,the theoretical value of reserved deformation is obtained through the intersection of curves.By comparing the monitoring results of large deformation section of tunnel,the optimal reserved deformation of surrounding rock in fracture zone is determined to be 300 mm.The research results can accurately characterize the influence of seepage effect,surrounding rock deformation and loosening pressure on the large deformation of surrounding rock in water-rich soft fracture zone,and have clear guiding significance for the optimization of support design of similar projects.