不同渗漏盾构隧道渗透特性及地表沉降研究

Study on seepage properties and ground settlement caused by different seepage conditions in shield tunnel

渗水是盾构隧道长期运营阶段的常见病害,这可能引发严重的地表沉降从而诱发灾害。以南宁市轨道交通一号线下穿粘土、粉土、砂土及圆砾土四种典型土层为工程背景,建立三维数值分析模型,考虑环缝和纵缝的渗水影响,在四种不同渗漏条件下对不同土层中的渗透特性及地表沉降进行分析。研究发现:环缝渗水对地表沉降、孔压分布及渗水流量的影响远大于纵缝渗水;土层的渗透系数不影响最终沉降量,但影响沉降达到稳定的时间,二者成反比;沉降稳定后的孔压分布主要由渗漏条件决定,不随土层变化;沉降稳定后的渗水流量与土层的渗透系数成正比。在同一规范限值渗水流量下,渗透系数越小的土层地表沉降越大,因此单独以规范流量限值是不能有效控制地表沉降的。

Seepage of shield tunnel is a common disease during the long-term operation period,which may lead to serious ground settlement and result in disasters.Based on Nanning Rail Transit Line 1,which passed through four typical soil layers,namely clay,silt,sand and gravel soil,a 3D numerical analysis model is built.The seepage properties and ground settlement in the different soil layers are analyzed respectively under four different seepage conditions,which consider both the circumferential and the longitudinal joints.The results show that the seepage of the circumferential joint has a larger influence than the longitudinal joint on ground settlement,pore pressure distribution and tunnel seepage inflow.The permeability coefficient of soil layer does not affect the final settlement,but it is inversely proportional to the settling time.The distribution of pore pressure is mainly determined by the seepage conditions and does not change with the soil layer.The final tunnel seepage inflow is proportional to the permeability coefficient of the soil layer.Under the same code limited seepage inflow,the smaller the permeability coefficient is,the greater the ground settlement is.Therefore,the ground settlement can not be effectively controlled by only using the code limited seepage inflow.