不均匀地层地铁隧道拱顶荷载计算方法研究

Study on the Vault Load Calculation Method for Urban Metro Tunnels in Inhomogeneous Strata

对于断面内地层起伏的盾构隧道,其地层参数差异较大且地层分界线起伏变化,而计算参数的选取将影响荷载的计算精度。文章在经典太沙基松弛土压力公式的基础上,对起伏地层盾构隧道拱顶荷载的计算方法进行研究,分别推导了隧道断面内水平地层和倾斜地层拱顶荷载计算的修正方法。对于水平地层分界线情况,通过分析断面内上部地层所占比例,给出了滑移面宽度取值方法;对于倾斜地层分界线情况,在水平地层分界线情况的基础上,分别对隧道左右侧滑移面宽度进行分析并给了出取值方法。通过对某直径为6 m的起伏地层盾构隧道的侧向土压力进行现场测试,并与经典理论公式进行对比,其结果表明:修正公式计算结果与实测值吻合较好,验证了修正公式的适用性。文章提出的计算方法可为城市盾构隧道工程提供参考。

Due to the fluctuation of strata boundaries and a wide variation of parameters for strata passed through by a shield tunnel, the accuracy of load calculations is affected by the selection of calculation parameters. Based on Terzaghi＇s soil relaxation pressure formula, the vault load calculation method for a shield tunnel in fluctuating strata was studied. Correction methods for vault load calculations were determined by considering the conditions of hori- zontal and tilted strata. Regarding the boundary in a horizontal stratum, a method for sliding surface width value se- lection is given by analyzing the proportion of the upper strata in a tunnel section. Regarding the boundary in a tilted stratum, the sliding surface widths of the left and right sides of the shield tunnel were analyzed and value selection is given based on the experience with the horizontal stratum. A field test of the lateral earth pressure was conducted aiming at a shield tunnel with a diameter of 6 m in fluctuated strata, and the results are compared with those ob- tained by the classical theoretical formula; the two sets of results agree very well.