局部超挖对内支撑结构的施工效应

Construction effect of partial over-excavation on inner-support structure

为确定基坑开挖时局部超挖量以及控制局部超挖的施工效应,在分析实测数据的基础上,利用PLAXIS 3D数值分析软件,模拟不同局部超挖范围下支护结构的受力和变形特性,分析局部超挖对内支撑支护结构的施工效应影响范围,进而在基坑宽度固定的前提下,提出确定最适合局部超挖范围的方法。结果表明:局部超挖会对超挖区以及邻近非超挖区产生施工效应,主要体现在支护结构侧移、弯矩、支撑轴力上;局部超挖范围增大,相邻区域的内力和侧移也逐渐增大,影响范围与超挖范围存在一定关系;桩后土压力在超挖区内大幅减小,由于土拱及加载作用,邻近超挖段的非超挖区土压力会有小幅上升。

In order to determine the local over-excavation amount during excavation of foundation pits and control the construction effects of local over-excavation,based on the analysis of measured data,the PLAXIS 3D numerical analysis software is used to simulate and analyze the stress and deformation characteristics of the supporting structure under different partial over-excavation ranges,to study the construction effect range of partial over-excavation on the support structure.Then,on the premise of fixed foundation pit width,a method to determine the optimal local over-excavation range is proposed.The results show that,partial over-excavation will have obvious construction effects on the over-excavated area and the adjacent non-over-excavated area,including the lateral displacement,bending moment,and support axial force of the supporting structure.As the area of partial over-excavation increases,the internal force and lateral displacement of adjacent areas also gradually increase,and the range of influence has a certain relationship with the range of partial over-excavation.The earth pressure behind the pile is greatly reduced in the over-excavation area.For the effect of soil arching and loading,the earth pressure in the adjacent non-over-excavated area will rise slightly.