非均匀收敛随机介质模型对浅埋隧道施工引起地表沉降预测研究

针对软弱土层中的浅埋大跨隧道在施工过程中出现的初支变形、断面底部隆起等现象,通过对原有的断面收敛模式进行修正,提出考虑初支变形与断面底部收敛的统一收敛模式,并以单洞及双洞椭圆隧道为例,推导出该种收敛模式下隧道施工中产生地表沉降的随机介质法预测公式,应用遗传-蚁群混合算法(GA-ACA)解决该预测模型的参数反演计算问题。为验证该模型对浅埋隧道地表变形预测的准确性,以乌鲁木齐地铁1号线三—新区间某典型断面为例,分别使用均匀收敛、底部为0、底部非0以及统一收敛模式等4种收敛模式进行参数反演,并将反演结果与现场监测结果做对比,研究结果表明:统一收敛模式与隧道断面实际变形规律更加吻合,其预测精度要比不考虑初支变形与断面底部收敛时的预测精度更高,即对浅埋、超浅埋隧道而言,初支变形以及底部隆起等现象对地表变形预测结果产生的影响不可忽略。

Study on Prediction of Ground Surface Settlement Caused by Construction of Shallow Buried Tunnel based on Non-uniform Random Medium Model

Aiming at the phenomenon of the initial support deformation and the uplift in the bottom of the shallow buried large-span tunnel in soft soil,a unified convergence model considering initial support deformation and the bottom of the cross section is proposed based on the modification of the original section convergence model. With reference to single-hole tunnel and double-hole elliptical tunnel,the formula for ground settlement prediction in stochastic medium method is derived based on the convergence mode in the tunnel construction,and the genetic and colony algorithm(GA-ACA) are used to solve the problem of parameter inversion in the prediction model. In order to verify the accuracy of the model,this paper refers to Urumqi Metro Line 1 in SAN-XIN district and uses 4 kinds of different convergence mode parameter inversions such as uniform convergence,the bottom 0,the bottom not 0 and a unified convergence mode. The inversion results and the measured values are compared,and the results show that the uniform convergence model is more consistent with the actual deformation law of tunnel section,and the prediction accuracy is higher than that without considering the deformation of the primary support and the convergence of the bottom section. As far as the shallow buried tunnel and ultra shallow buried tunnel are concerned,the effects of the initial deformation and the bottom heave on the surface deformation prediction should not be ignored.