富水地层坑趾宽度对坑中坑支护结构变形影响研究

Study on Influence of Pit Toe Width of Water-rich Stratum on Deformation of Support Structure of Pit-in-pit

随着地下空间的不断开发,坑中坑在工程中越来越常见,但目前对坑中坑的研究尚不全面。以南昌艾溪湖隧道坑中坑工程为研究背景,利用Midas GTS/NX有限元软件,研究在富水地层中坑趾宽度对基坑围护结构变形规律的影响。通过将模拟计算结果与实测对比,证明了模型的正确性及考虑渗流条件的必要性。结果表明:增大坑趾宽度能有效减小外坑围护结构水平位移,且最大水平位移所在位置会逐渐上升;坑趾宽度的增加对减小内坑排桩水平位移有显著效果,该工程中坑趾宽度由2 m增大到12 m,最大水平位移减小了76%;随坑趾宽度的增大,地表沉降会逐渐减小。在工程场地条件允许的前提下,应该尽量增大坑趾宽度,以减小内外坑围护结构变形。

With the continuous development of underground space,pits in pits are more and more common in engineering,but the research on pits in pits is not comprehensive at present.Based on the research background of the pit in Aixihu lake tunnel in Nanchang,Midas GTS/NX finite element software was used to study the influence of pit toe width on the deformation rule of foundation pit retaining structure in water-rich stratum.The correctness of the model and the necessity of considering the seepage condition were proved by comparing the simulation results with the measured ones.The results showed that increasing the width of pit toe could effectively reduce the horizontal displacement of the outer pit envelope,and the position of the maximum horizontal displacement would gradually increase.The increase of pit toe width had a significant effect on reducing the horizontal displacement of pile rows in the pit.Pit toe width increased from 2 m to 12 m,and the maximum horizontal displacement decreases by 76%.With the increase of pit toe width,the surface settlement would gradually decrease.Under the conditions of the project site,pit toe width should be increased as much as possible to reduce the deformation of the inner and outer pit envelope.