某深基坑桩锚支护的数值模拟及优化设计

Numerical simulation and optimization design of pile-anchor supporting structure for deep foundation pit

为了增强深基坑桩锚支护方案的安全性,提高经济效益,根据某勘察设计院提供的地质资料和监测数据,通过有限元分析软件MIDASGTS建立支护结构的三维模型。提取支护体系4个监测点位的变形值与实际监测值进行对比,对比结果显示此模型具有可行性。结果表明:基坑的最大水平位移随着桩径增大而减小,随着桩间距减小而减小,但增加桩径或减小桩间距到一定程度后位移减小已不明显。锚杆锚固段轴力随锚固段长度减小,最小可达到0。根据计算模型对基坑支护方案做出如下优化:桩径由0.8m增加至1.2m,桩间距由1.2m增加至1.4m,锚索MS2与MS5的锚固段长度由10m减少至6m,MS3与MS6的锚固段长度由10m减少至8m。优化后,在总造价基本相同的前提下,基坑的最大水平位移从32.63mm减少至25.41mm,兼顾了经济性和安全性。

In order to improve the safety and economic benefit of pile-anchor supporting structure in deep foundation,three-dimensional model of the structure was established by the finite element analysis software MIDAS GTS(Geo-Technical Analysis System).The deformation value of four monitoring points in the supporting system was compared with the actual monitoring value.The comparison results show that the model is reasonable.The results show that the maximum horizontal displacement decreases with the increase of pile diameter and the decrease of pile spacing.However,the decrease of horizontal displacement is no longer obvious when increasing the pile diameter or decreasing the distance to a certain extent.According to the results of the model,the following optimization is made for the foundation pit supporting structure:the pile diameter was increased from 0.8 m to 1.2 m.The pile spacing was increased from 1.2 m to 1.4 m.The length of anchorage section of MS2 and MS5 was reduced from 10 m to 6 m.The length of anchorage section of MS3 and MS6 was reduced from 10 m to 8 m.After optimization,the maximum horizontal displacement of the foundation pit decreased from 35.64 mm to 25.41 mm.Besides,the total cost has not increased,which means that the optimization balances economics and safety.