近邻浅基础建筑物深基坑变形特征的实测及数值分析

Numerical analysis and filed monitoring on deformation characteristics of deep excavation adjacent to shallow foundation building

基于某基坑工程现场实测数据和数值模拟方法,对近邻既有浅基础建筑物的深基坑变形特征进行了研究。建立了结构-基础-地基共同作用的数值模型,采用考虑土体加卸载路径的土体塑性硬化本构关系,能够较好地反映基坑开挖诱发的地层变形。通过基坑现场实测数据及既有经验曲线验证了所建立数值模型的正确性,在此基础上分析了既有建筑对基坑变形特征的影响。结果表明,基坑开挖主要影响区域内的地表差异沉降导致浅基础建筑物出现转动倾斜,引起建筑基础下地基附加应力重分布,进而加剧了差异沉降。对于基坑诱发变形的预测计算有必要考虑建筑物与地基的共同作用。忽视共同作用影响则有可能低估基坑开挖引起的建筑物差异沉降而造成潜在安全风险。

The deformation characteristics of a deep foundation pit excavation adjacent to the existing shallow foundation building in Changsha city were studied based on the field monitoring data and numerical simulation method.A numerical model that considers structure-foundation-ground interactions was established using the finite difference program FLAC.The plastic hardening constitutive model that can consider loading and unloading paths was adopted in the numerical model,which shows the capability in properly capturing the ground deformation induced by foundation pit excavation.The complete excavation and support construction process has been simulated numerically,and the simulation results have been verified by the field measurement data and the existing empirical curve.The support structures and parameters proposed in this paper can effectively limit the ground deformation and ensure the safety of the adjacent existing building.The proposed support design can provide relevant experience for deep excavation projects in similar ground conditions.The influence of the existence of existing buildings on the ground settlement characteristics of the excavation was further analyzed.The results show that the differential settlement of the ground surface in the main influenced area of excavation will cause the shallow foundation building to rotate,which leads to additional stress in the ground under the shallow foundation of buildings.The redistribution of additional stress may cause an increment in the differential settlement.The empirical curves of ground settlement induced by foundation pit excavation do not consider the influence of the interaction between existing building structure and foundation and are impossible to accurately predict the ground and building deformation.It is necessary to consider the interaction of existing buildings and the ground for the deformation prediction is performed.Ignoring the impact of the interaction effect may underestimate the differential settlement of the building caused by the excavation and lead to potential safety risks.