考虑土体小应变刚度的地表堆载对隧道影响数值分析

随着城市地下空间的进一步开发,交通隧道、地下车站和地下商铺等建筑(构筑)物不可避免地变得越来越密集,既有隧道周围会频繁存在堆载的情况。采用数值方法分别研究摩尔-库伦(M-C)本构模型及考虑土的小应变特性的硬化本构模型(HSS)情况下基坑开挖地表堆载尺寸、堆载大小及隧道埋深对既有顶管隧道变形的影响规律。计算结果表明:在相同堆载大小及堆载宽度的情况下,HSS本构得到的土体受堆载影响范围明显低于M-C(Moore-Coulomb)本构计算结果。当堆载大小为100 kPa时,M-C本构的侧边和深度影响范围达到了75 m,而HSS本构下侧边及深度影响范围仅有35、30 m左右;当堆载宽度为25 m时,M-C本构的侧边和深度影响范围达到了75 m,而HSS本构下深度影响范围不超过35 m,侧边则不超过40 m。基于数值计算结果,对实际工况提出严禁在既有隧道的正上方进行堆载的建议。

Numerical Research on the Influence of Ground Heaped Load on Disturbation Deformation of Existing Tunnel

With the further development of urban underground space, traffic tunnels, underground stations, underground shops and other buildings (structures) inevitably become more and more dense, so there is often a phenomenon of heaped load near existing tunnels. In this paper, the influence of heaped load on disturbance and deformation of existing pipe jacking tunnel is discussed through finite element calculation with Moore-Coulomb (M-C) constitutive model and the hardening constitutive model (HSS) considering the small strain characteristics of soil. The results show that under the same loading size and width, the influence range of the soil under HSS constitutive model is much lower than that under M-C constitutive model. When the loading size is 100 kPa, the influence range of the side and depth of M-C constitutive model reaches 75 m, while the influence range of the side and depth under HSS constitutive model is only 35 m and 30 m. When the loading width is 25 m, the side of M-C constitutive model is only 35 m and 30 m. The influence range of edge and depth is75 m, while that of HSS constitutive model is less than 35 m and that of side is less than 40 m. At the same time, based on the results of finite element analysis, the suggestion of forbidding loading directly above the existing tunnel is put forward.