某高速铁路明挖隧道黄土深基坑变形规律分析

Analysis of Deformation Law of Loess Deep Foundation Pit in Open-cut Tunnel of a High-speed Railway

依托实际工程,对某高速铁路明挖隧道黄土深基坑施工过程中钻孔灌注桩桩顶及桩身水平位移、钢筋混凝土内支撑轴力以及基坑周边山体边坡的沉降开展实时监测,研究基坑的变形规律,阐释发生机理。结果表明:钻孔灌注桩桩顶的水平位移随基坑开挖深度增加而增加;整个桩身的水平位移最终大致呈“倒S”形曲线变化,最大水平位移为8.87 mm;内支撑轴力随基坑的开挖逐渐增大而后趋于稳定;距离基坑越近,基坑周边山体边坡的沉降越大,最大沉降量为9.63 mm;利用“钻孔灌注桩+钢筋混凝土内支撑”支护结构可有效的控制基坑变形,但安全储备较大,设计上存在可优化空间。

Based on the actual project,the horizontal displacement of bored pile top and pile body,the axial force of reinforced concrete inner support and the settlement of mountain slope around the foundation pit are monitored in real time during the construction of deep foundation pit.The deformation law of foundation pit is studied and the occurrence mechanism is explained.The results show that the horizontal displacement of bored pile top increases with the increase of excavation depth.The horizontal displacement of the whole pile body finally changes in an‘inverted S’shape curve,and the maximum horizontal displacement is 8.87 mm.The axial force of the inner support gradually increases with that of the excavation of the foundation pit and then tends to be stable.The closer to the foundation pit,the greater the settlement of the mountain slope around the foundation pit,the maximum settlement is 9.63 mm;the supporting structure of‘bored pile+reinforced concrete inner support’can effectively control the deformation of foundation pit,but the safety reserve is large,and there is room for optimization in design.