地下综合管廊CFG桩土复合地基条件下基坑围护结构受力性状研究

Research on mechanical properties of foundation pit enclosure under the condition of CFG pile-soil composite foundation of underground comprehensive pipe gallery

综合管廊明挖施工涉及到基坑开挖,管廊明挖施工过程中会破坏土体的原有平衡状态,引起支护结构变形、土体产生应力卸载效应并且发生位移变化,形成新的平衡状态,故需要施加CFG工程桩加固地基。在先施工工程桩再进行开挖的基坑工程中,有无CFG工程桩以及工程桩的长短以及布置情况对基坑围护结构有一定的影响。以贵州某地下综合管廊项目为依托,利用有限元计算软件MIDAS GTS NX模拟了基坑开挖的施工过程,研究了CFG桩长和桩布置对基坑围护结构受力及变形的影响规律。结果表明:管廊基坑开挖卸载下,工程桩对围护结构具有显著影响:围护桩的最大负弯矩、最大正剪力、最大水平位移要明显小于无工程桩的情况。桩长设置为6m是该断面基坑的最佳情况,桩长过短或者过长都不利于围护桩的变形且浪费财力。

The open-cut construction of the integrated pipe gallery involves the excavation of the foundation pit.During the open-cut construction of the pipe gallery,the original equilibrium state of the soil will be destroyed,causing the deformation of the supporting structure,the stress unloading effect of the soil and the displacement change,forming a new In the equilibrium state,it is necessary to apply CFG engineering piles to strengthen the foundation.In the foundation pit project in which the engineering piles are constructed first and then excavated,the presence or absence of CFG engineering piles and the length and arrangement of the engineering piles have a certain impact on the foundation pit enclosure structure.In this paper,based on an underground comprehensive pipe gallery project in Guizhou,the finite element calculation software MIDAS GTS NX is used to simulate the construction process of foundation pit excavation,and the influence of CFG pile length and pile arrangement on the stress and deformation of the foundation pit enclosure structure is studied.law.The results show that the engineering piles have a significant impact on the enclosure structure under the excavation and unloading of the tunnel foundation pit:the maximum negative bending moment,the maximum positive shear force and the maximum horizontal displacement of the enclosure piles are significantly smaller than those without engineering piles.Setting the pile length to 6m is the best situation for the foundation pit of this section.Too short or too long pile length is not conducive to the deformation of the enclosure pile and wastes financial resources.