双排桩支护下软土深基坑开挖的变形分析与控制

Analysis and Control of Deformation of Deep Foundation Pit Excavation in Soft Soils Supported by Double-row Piles

武汉市某双排桩支护基坑工程地处深厚软土地区,在基坑开挖过程中通过监测发现,支护结构出现较大变形,基坑周围地面和房屋开裂。为深入研究基坑开挖时双排桩支护结构的受力变形特性及变形控制,采用FLAC 3D有限差分软件对该工程的基坑开挖过程进行了数值模拟计算,通过观察对比实测值与计算值,分析了基坑开挖过程中支护结构的变形规律,提出了合理控制软土基坑变形大的方法。结果表明:支护结构变形以水平变形为主,最大水平位移发生在支护桩顶端,随着深度的增加变形逐渐减小直至趋于0;基坑土体位移以基坑侧壁水平位移和地表沉降为主,坑顶水平位移最大,基坑外侧建筑物基底处地表沉降最大;通过被动区加固可以明显减小基坑的水平位移、坑内隆起量和坑外地表的沉降量。

A foundation pit supported by double-row piles in Wuhan is located in a deep soft soil area.During the excavation of the foundation pit,it was discovered through monitoring that the supporting structure was deformed and the surrounding ground and houses cracked.In order to deeply study the stress and deformation characteristics and deformation control of the double-row piles supporting structure during the excavation of the foundation pit,the FLAC 3 D finite difference software was used to carry out the numerical simulation calculation of the foundation pit excavation process.By observing and comparing the measured value with the calculated value,the deformation law of the double-row piles supporting structure during the excavation of the foundation pit is analyzed,and a reasonable method to control the large deformation of the soft soil foundation pit is proposed.The results show that the deformation of the supporting structure is dominated by horizontal deformation,and the maximum horizontal displacement is at the top of the supporting pile.With the increase of depth,the deformation gradually decreases until it tends to zero.The soil displacement of the foundation pit is dominated by the horizontal displacement of the sidewall of the foundation pit and the ground settlement.The top of the pit has the largest horizontal displacement,and the largest ground settlement is at the base of the building outside the foundation pit.The use of passive zone reinforcement measures can significantly reduce the horizontal displacement of the foundation pit,the uplift in the pit and the settlement of the ground outside the pit.