饱和沙土中土压盾构开挖面极限支护力

为了避免土压平衡盾构在含水砂层中掘进时出现支护压力不足的现象,将渗流作用引入上限分析,以评估支护力对开挖面稳定的影响,得到土压平衡盾构在饱和沙土中掘进时的支护力方程.通过支护力方程各项系数比较以及敏感性分析,表明盾构直径与渗流作用对支护力影响显著.随着地下水位的升高,渗流因素在支护力中所占的比重提高;在高水头状况下,渗流作用大幅降低支护力,是造成开挖面前方土体失稳的最主要因素.给出较直观的支护力方程,采用简洁方法来分析在渗流作用下盾构支护力设置的安全性,结合地铁工程实例,分析开挖面失稳事故原因,给出合理的开挖面支护压力.

Supporting pressure for earth pressure balance tunnel face stability when tunneling is implemented in saturated sandy soil

Seepage application was considered in upper bound analysis to evaluate the seepage effect on face stability in order to avoid insufficient supporting pressure when earth pressure balance shield(EPB) is tunneling through aquifer sand stratum.Supporting pressure formula was proposed for EPB tunneling in saturated soil.Comparison and sensitivity analysis on coefficients of the supporting pressure equation indicated a slight effect of shield depth but obvious effect of shield diameter on face stability.Seepage factor takes larger portion in support pressure determination and becomes the most critical controlling factor with underground water level increasing.Stability equation deduced in the thesis gives out a straightforward criterion of support pressure determination.Case studies on the subway line show rational results from where important conclusions are obtained.