岩-土复合地层暗挖隧道施工引起地表沉降计算方法

Calculation Method of Surface Settlement Caused by Construction of Mining Tunnel in Rock-Soil Composite Strata

考虑岩层与土层2种介质力学性质的差异性,基于随机介质理论,建立双层介质计算模型,推导岩-土复合地层暗挖隧道施工引起地表沉降分步计算公式;明确椭圆形隧道断面不均匀收敛区域积分的上下限;计算岩-土分界面的沉降曲线,将曲线与岩-土分界面所围成的区域视为"不等厚开挖",确定该区域积分的上下限,并给出岩、土层中主要影响角及断面收缩半径的计算方法。以贵阳地铁2号线诚-观区间暗挖隧道为工程背景,对比分析分层计算值、不分层计算值与现场实测值之间的吻合度。结果表明:将隧道上覆地层划分为岩层和土层2部分的计算值与实测值较为吻合,其最大沉降值相对误差在10%以内;地表沉降曲线沿隧道中心线对称分布,且中心线处沉降值最大。

Considering the differences in the mechanical properties between rock and soil layers,a twolayer medium calculation model was established based on the stochastic medium theory,and a step-by-step calculation formula for the ground settlement caused by the construction of mining tunnel in rock-soil composite strata was derived.Firstly,the upper and lower limits of the integral in the non-uniform convergence area of elliptical tunnel section were clarified,and the settlement curve of the rock-soil interface was obtained.Then,regarding the area surrounded by the curve and rock-soil interface as"unequal thickness excavation",the upper and lower limits of the integral of the area were also clarified,and the calculation methods of the main influence angle and section shrinkage radius in rock and soil layers were given.Finally,the calculated values of dividing the overburden of tunnel into rock and soil layers and the calculated values of non-dividing and the observed data were compared and analyzed on the backdrop of the mining tunnel project in the section between Chengxin Road Station and Guanshanxi Road Station of Guiyang Metro Line 2.Results show that the calculated values of dividing the overburden into two parts,rock and soil,are in better agreement with the observed data;and the relative error of the maximum settlement value is within 10%;the surface settlement curve is distributed symmetrically along the center line of the tunnel,and the calculated settlement value at the center line is the largest.