松散堆积体隧道围岩空间位移特征分析

为研究松散堆积体隧道施工引起围岩空间位移的变化,采用弹塑性非线性有限元法对隧道开挖过程进行仿真模拟,将空间位移分为地表沉降、周边围岩位移和掌子面挤出变形3部分进行分析,并与既有理论和现场测试数据进行对比。数值计算结果表明:隧道开挖引起的围岩变形具有明显的三维特性,掌子面前后方影响范围均约为20m,横向沉降槽呈明显的"深沟"形,沉降槽宽度较小,与塞形曲线拟合度最高;周边围岩拱部下沉和隧底隆起范围与量值均较大,水平收敛较小,下台阶支护封闭成环后变形趋于稳定;上台阶掌子面挤出变形呈中间大、周围小的"圆形放射状",下台阶掌子面挤出变形总体较小;与现场测试值相比,拱顶下沉和净空收敛偏大,地表沉降两者基本一致。

Space displacement characteristics of surrounding rock for tunnel constructed through loose deposits

To research the space displacement of surrounding rock induced by tunnel construction in loose deposits, the process of tunnel excavation was simulated by using the elasto-plastic non-linear finite element method. Space displacement, divided into ground settlement, displacement around the tunnel and extrusion deformation of tunnel face, was compared with the theory and in-situ test results. Numerical results show that deformation of the surrounding rock induced by tunnel excavation has obvious three-dimensional characteristics, with the affected area of vertical section about 20 m, and that ground traverse settlement trough shows "deep gully" type with small width in accordance with plug-shaped curve. Settlement at the arch part and upheaval deformation at the bottom of tunnel are respectively large, horizontal convergence is small, and the tunnel deformation tends to be stable when the primary support structures are closed. The extrusion deformation of the upper bench face has the shape of "round-shaped radiation" where the center is biggest, which is respectively larger than that of the lower bench. Compared with in-situ test, vault settlement and horizontal convergence are slightly larger, and the ground settlement is basically consistent.