深基坑双排桩支护体系及土体受力变形分析

以某双排桩支护基坑为工程背景,通过三维有限元和现场监测数据对比分析,探讨了双排桩桩身变形、桩身受力、坑外土体沉降,以及坑内、桩间、坑外土体的土压力变化规律。结果表明:双排桩前后桩身位移变化曲线基本相似,上部位移变化率大,下部变化率小;无论前后桩,桩身两个侧面轴向受力性状相反,桩身上半段内侧受压,桩的外侧受拉,向内受弯;下半段的内侧受拉,外侧受压,向外受弯;桩间土压力随深度先减小后增大,同时随开挖深度加深,土压力值增大;坑内和坑外土压力随基坑开挖深度增大,都基本呈线性单调变化,但坑内增大、坑外减小;分层沉降在基坑开挖面以上较大;沉降由双排桩水平位移和软黏土固结沉降引起;坑外总沉降量随离基坑距离增大先迅速增大后减小。

Stress and deformation analysis of double-row pile supporting system and soil in deep foundation pit

Under the engineering background of a deep foundation pit supported by double-row piles, deformation and stress of the double-row piles, subsidence of soil outside the pit, and the soil pressure variation at outside and inside of the pit and the interval of double-row piles are discussed through the comparative analysis of data obtained by three-dimensional finite element software and on-site monitoring. The results show that the displacement curves of the front pile and rear pile are similar and the displacement variation rate of the upper part is larger than that of the lower part. The two sides of the front and rear piles are under opposite axial forces in that the internal side is compressed and the external side is tensioned at the upper part of the piles while the lower part of the piles in reverse. The soil pressure between piles first decreases and then increases with the excavation. The soil pressure inside and outside the pit registers a linear variation in that the former increases and the latter decreases with the pit excavation. Stratified subsidence is relatively large on the excavation surface. The subsidence is caused by horizontal displacement of the double-row piles and consolidation of soft clay. The total subsidence outside the pit first rises sharply and then drops with its distance from the pit.