复合土钉支护转角有利影响范围

基坑复合土钉墙转角处有明显的空间效应，受力变形较小，对支护结构有利，但不清楚转角定量的有利影响范围，目前设计中仍按照与基坑中部一样保守设计，为在此范围内降低土钉用量，避免保守设计，对水泥土搅拌桩复合土钉支护结构建立了全尺寸整体三维有限元模型，这种模型包含基坑的转角，能考虑基坑的空间效应，通过建立接触面单元，能考虑土体和搅拌桩、土体和土钉的相互作用，量化分析了基坑转角对支护结构受力和变形的有利影响范围，计算结果表明，基坑转角对开挖面水平位移、地表沉降、坑底隆起、土钉轴力的有利影响范围分别约为1.3、1、1、1.2倍的开挖深度。经与实际工程现场实测值对比，验证了该模型分析结果的可靠性，同时分析结果优于平面二维和局部三维有限元模型，结论为复合土钉支护结构的优化设计和安全施工提供了理论依据和研究方法。

Beneficial affected area of corner of composite soil nailed wall

Foundation pit corner of composite soil nailed wall has obvious spatial effect. Supporting structure near foundation pit corner is safer due to smaller stress and deformation, Whilst at present quantitative beneficial affected area of foundation pit corner to the supporting structure are not known and designs are the same in the middle and the corner of foundation pit. In order to reduce the material consumption and avoid overcautious design, the construction process of excavation and supporting of the composite soil nailed wall of soil nailing and cement-soil piles for deep foundation excavation was simulated through establishing a whole three-dimensional finite element model,which includes the corner of the foundation pit and can consider spatial effect of corner location and the interaction between soil nailing,cement-soil piles and soil through establishing interface elements. Beneficial affected area of foundation pit corner to stress and deformation of the supporting structure is analyzed and quantified. The calculation results show that beneficial affected area of foundation pit corner to the horizontal displacement of excavation face, the subsidence displacement of the ground beside the foundation pit,the bottom heave displacement and the axial forces of soil nails are about 1.3 times, 1 times, 1 times, 1.2 times of the excavation depth. Whole three-dimensional finite element calculation results are basically consistent with those of the field test data and are more reliable than two-dimensional or local three-dimensional. These conclusions can provide theory basis and research method for optimization design and safety construction of composite soil nailed wall.