Study On The Displacement Of The Surrounding Soil Mass In Foundation Excavation Engineering

The exploration of underground space and construction of tall buildings in the city result in a large number of deep excavation engineering. In general, the deep excavation projects in the city are located in dense building complex. As a result, the construction site is small and its nearby buildings impose more strict requirements on deformation. The existing design theory (intense control design) would hardly meet the environmental requirements proposed by the buildings around the construction site. In recent years, though many scholars have conducted abundant researches on the deformation control of foundation pit engineering, many significant problems in the relationship and rules among the deformation of support construction, the ground surface displacement around the foundation pit and the deformation of nearby buildings are still to be solved.This paper relies on the research project"Studies on the Impact of Exploration of Urban Underground Space on its nearby Buildings and Control Technology"by the Foundation Institute of China Academy of Building Research. By means of indoor model tank test and digital photography technology, a research on the displacement of the soil behind the retaining structure for sandy soil pit and clay soil pit when support structures have different types of deformation has been carried out. Furthermore, during the process of excavation in the project"Ginkgo Jinchuan"in Yunnan, the soil displacement and settlement around the foundation pit are observed, by using multi-spot measurement equipment which is based on rope measuring. Through a comprehensive analysis on these two tests, the following conclusions are formed.1. Under the circumstances that support structures are in the same deformation types, the curves of ground surface settlement are the same. The ground surface settlement is increasing as the whole displacement of support structure is increasing. The impact of the deformation of the support structure on the ground surface settlement is negligible.2. Under the circumstances that support structures are in the same deformation types, the maximum ground surface settlement is in direct proportion to the displacement area of support structure, as the latter is changing. However, the maximum displacement does not change.3. For different kinds of soil (i.e. sandy soil and clay soil in the test), when support structures'displacement types are the same, sandy soil's ground surface settlement is larger than that of clay soil, and its influence is smaller than that of clay soil. For sandy soil, the distance between the maximum spot and the baffle is smaller, compared with that of clay soil. However, the curve of clay soil's ground surface settlement is smoother than the curve for sandy soil.4. This paper suggests a calculation method, which can forecast the ground surface settlement after the initiation of excavating the foundation pit by determining 3 unknown parameters.This paper conducts the research by indoor model tank test and field test. The conclusions are helpful and beneficial to some extent for predetermining the deformation of the soil around the foundation pit and the soil deformation's impact on its nearby buildings.