邻近建筑物基坑开挖变形的特性分析及控制

Analysis of the deformation feature and control measures of the deep excavation close to existing buildings

本文以重庆市某医院防治中心深基坑工程为背景,采用商业有限差分软件FLAC;对最危险剖面进行了基坑开挖全过程的数值模拟,基于数值模拟结果分析了邻近建筑物时基坑开挖过程中周围土体及支护结构的变形情况。数值计算结果及实测数据表明:开挖过程中,由于卸荷量以及土体临空面不断增大,坑侧土体不断向基坑内倾斜,地表产生沉降;随着邻近基坑的建筑荷载逐渐增大,荷载对基坑变形的影响呈先有利后急剧不利的趋势;随着基坑的开挖,桩身的变形模式由内凸式过渡为悬臂式,最终稳定为复合式;对基坑采用锚索桩板挡墙支护后,土体变形满足规范关于变形控制的要求,表明该支护系统可有效地控制基坑变形。监测点地表沉降的数值结果与实测数据较为接近,证实了数值模型的可靠性。研究结果可为类似工程制定有效的支护与监测措施提供理论依据及工程借鉴。

A deep excavation project in a hospital in Chongqing is simulated with FLAC;to analyze the deformation of the surrounding soil and retaining structure in the most dangerous section. The numerical simulation result and actual monitoring data show that the side soil inclines to the excavated pit continuously with the soil unloading and excavation scale increases in the excavation process, and the surface settlement occurs correspondingly;as loading of adjacent building increase gradually, the effect of surcharge on the deformation of excavated pit is favorable firstly and then becoming unfavorable suddenly;with the excavation depth increases, the deformation mode of pile shaft is transformed from inner convex to cantilever and finally stabilized to composite form;if prestressed anchor and soldier pile is used, the soil deformation could be satisfied with the code requirements, which indicates the excavation deformation can be controlled effectively by the supporting system. The numerical results of surface subsidence are close to the monitoring data, which confirms the reliability of the numerical model. The study results can provide a theoretical basis and reference for similar projects on supporting design and monitoring plan.