基于三维数字地质的深基坑排桩支护渗流耦合稳定性数值分析

Seepage coupling stability numerical simulation of deep foundation pit row pile support based on three-dimensional digital geology

建筑深基坑支护工程中地下水渗流作用是影响支护稳定的重要因素,准确进行渗流应力耦合计算是解决深基坑排桩支护稳定性的关键。以某商业综合楼建筑深基坑为研究对象,设计双排桩加3排预应力锚索复合支护试验方案,筛选有效数字地质参数,利用PLAXIS有限元软件构建基于渗流应力耦合作用的有限元模型,研究在不同开挖深度与不同支护参数下深基坑支护稳定性。结果表明:在不同开挖深度下,深基坑支护水平位移受渗流应力、开挖深度影响较大,开挖深度越深,支护水平位移和承受弯矩越大,基坑稳定性也随之变差;在不同支护参数下,通过增加支护桩嵌固深度、增加支护桩桩径,可减小支护的水平位移与弯矩,提升支护的稳定性。综合考虑开挖深度与支护参数,采用渗流应力耦合有限元模型数值模拟结果表明,当支护桩嵌固深度为10m,桩径为1.1m,双排桩加3排预应力锚索复合支护结构稳定性最优,支护最大水平位移与最大弯矩,均满足上限值要求;当支护双排桩最大排距超过4.0m,前后排桩的连接性变差,支护整体性能及稳定性降低。

Groundwater seepage is an important factor influencing the stability of deep foundation pit supporting engineering,accurate calculation of seepage stress coupling is the key to solve the stability problem of deep foundation pit supporting.Taking the deep foundation pit of a commercial complex building as the research object,this paper designs a composite support test scheme of double-row piles and three rows of prestressed anchor cables and screens effective digital geological parameters.The finite element model of seepage stress coupling is constructed by PLAXIS to study the stability of deep foundation pit support based on seepage stress coupling model under different excavation depths and different support parameters.The test results show thatthe horizontal displacement of deep foundation pit support is greatly affected by seepage stress and excavation depth,the deeper the excavation,the greater the horizontal displacement and bending moment of the supporting structure,the worse the stability of the supporting structure.Under different supporting parameters,the horizontal displacement and bending moment of supporting can be reduced and the stability of supporting can be improved by increasing the embedded depth and diameter of supporting pile.Considering the excavation depth and supporting parameters,the numerical simulation results of seepage stress coupling finite element model show that:when the embedded depth of supporting pile is 10m and the diameter of supporting pile is 1.1m,the stability of composite supporting structure with double-row piles and three rows of pre-stressed anchor cables is the best,and the maximum horizontal displacement and bending moment of supporting meet the requirements of upper limit;when the maximum row spacing of supporting double-row piles exceeds 4.0 m,the connectivity of front and rear piles becomes worse,and the overall performance and stability of supporting decrease.