软土深基坑被动区超前加固变形控制效果研究

依托某实际工程,利用FLAC 3D软件建立了3种不同地层参数的基坑有限差分数值模型,验证了土体本构模型的硬化模型比摩尔-库仑模型更适用于基坑工程中,对比分析了裙边加固和满堂加固的加固效果,同时借鉴基坑底部被动区加固思路,提出了在软土深基坑中对开挖段进行超前加固,以控制基坑开挖过程中支护结构位移的方法。结果表明:裙边加固的合理加固宽度为0.5h(h为基坑开挖深度),合理加固深度则与坑底的地层条件密切相关; 满堂加固的合理加固深度可取0.3h,在某些基坑位移控制特别严格的情况下,满堂加固深度超过0.5h后,可考虑优先加固最后一道撑到坑底的土体; 开挖段的满堂超前加固可以使首道撑位置下移,为减少支撑道数提供了可行方案; 研究为同类工程设计提供了参考依据,进一步丰富了软土地区的深基坑变形控制措施。

Research on Deformation Control Effect of Passive Zone Reinforcement Before Excavation of Deep Foundation Pit in Soft Soil

Based on a practical project, three kinds of finite difference numerical models with different stratum parameters were established by using FLAC 3D software. It was verified that the hardening model was more suitable than the Mohr-Coulomb model in foundation pit engineering, and the effect of skirt edge reinforcement and full pit bottom reinforcement was explored. Besides, based on the idea of passive zone reinforcement at the bottom of foundation pits, advanced reinforcement of excavation section in deep foundation pits in soft soil was proposed to control the deformation of retaining structure. The results show that the hardening model is more suitable than the Mohr-Coulomb model in foundation pit engineering. The reasonable reinforcement width of skirt edge reinforcement is 0.5h(h is the excavation depth), and the reasonable reinforcement depth is closely related to the stratum conditions at the bottom of the pit. The reasonable reinforcement depth of the full pit bottom reinforcement is 0.3h. In some cases where the displacement of the foundation pit is strictly controlled, when the reinforcement depth is more than 0.5h, reinforcement priority can be given to the soil between the last brace and the bottom of the pit. The full pit bottom reinforcement can make the position of the first brace move down, which provides a feasible scheme to reduce the number of braces. This study provides a reference for similar engineering design and further enriches the control measures of deep foundation pit deformation in soft soil area.