明挖公路隧道基坑钢支撑轴力监测与数值模拟分析

Axial Force Monitoring and Numerical Simulation of Steel Supports in an Open-cut Expressway Tunnel Foundation Pit

为研究深基坑开挖过程中钢支撑轴力的变化情况,以沈阳市南北快速干线隧道深17.8 m基坑工程支护体系中横向钢支撑为研究对象,对基坑开挖过程中的轴力变化值进行现场实时监测,并采用有限元软件MIDAS/GTS对不同工况下的钢支撑轴力进行模拟研究,得出各道钢支撑的轴力云图及变化规律。结果表明:1)随着基坑开挖深度的增加,坑壁主动土压力逐渐增大,使得每道钢支撑轴力在短期内均呈线性增长趋势;2)同一断面钢支撑全部架设完成后轴力有所衰减,其原因之一是连续墙后的土体发生了流变现象,使得土体应力重新分配并达到新的平衡。

In order to study the variation laws of steel support axial force during excavation of a deep foundation pit of Shenyang North-South Expressway Tunnel with burial depth of 17. 8 m,the axial force of horizontal steel supports of the supporting system is studied. And then the real-time monitoring of axial force variation during excavation of foundation pit is conducted. Finally,the axial force of steel supports under different conditions is simulated by finite element software MIDAS/GTS,and the axial force nephograms and variation laws of every steel support are obtained. The results show that：（ 1） With the increase of excavation depth of the foundation pit,the active earth pressure on the foundation pit wall increases gradually,which makes the axial force of every support increase linearly in a short period.（ 2） The axial force of every steel support in a same cross-section attenuates after the whole erection of the steel supports,whose cause lays on soil stress redistribution-caused balance after rheology behavior of soil behind underground diaphragm wall.