Stability And Deformation Analysis Of A Rebuilt Excavation Engineering In Soft Clay In Hangzhou

At present, as the urbanization develops quickly in china, utilizing of the underground space becomes more and more important. Consequently, a lot of deep excavations occur in the infrastructure construction, especially for the subway station construction and basement of the high-rise buildings. However, deep excavation collapses are frequently known from big construction projects, especially in soft clay area, and that cause life loss and large property damage. At the same time, the collapse would disturb the ground seriously and causes large displacement of the strata soils, and thus the properties of the strata soils would change greatly, which mainly perform in the aspects of lowering of the strength and modulus. After collapse, rebuilt of the excavation should be followed. And before the rebuilding of the excavation we should have known that the conditions of the site have changed greatly, and obtain the changed mechanic characteristics of the disturbed strata soils of the ground through detailed site investigation, including field tests such as cone penetration tests (CPT) and filed shear vane tests, and still including a lot of triaxial tests and oedometer tests, making sure that the safety of the rebuilt of the excavation.This paper sets in the rebuilding project after the collapse of N2excavation, a deep excavation of the Xianghu subway station in east Hangzhou, and following aspects about the rebuilding of the deep excavation are studied. Firstly, the site condition and excavation construction process of the original N2excavation are reviewed. Secondly, the soil properties of the undisturbed soil and disturbed soil at site are studied through filed and laboratory tests. The influence of the strength and modulus of the soils caused by disturbance are mainly considered. And the different disturb degree zones around the original N2excavation are defined by the disturbance degree research of the strata soils. Thirdly, based on the limit equilibrium theory, the push in stability and base stability of the rebuilt excavation are analyzed by classic methods, and the stability of the rebuilt excavation is evaluated. At last, a simplified analysis model of the rebuilt N2excavation is established in using the FEM commercial soft program Plaxis, and the deflection of the retaining sheet piles and ground deformation during the construction are studied, and the results are compared with the field data. Besides, the strength reduction ration method is used in the Plaxis analysis to evaluate the stability of the excavation.