Time-Effect Analysis On Earth Berms Of Deep Excavations

Recently, Rheology is an important property of geomaterials, especially for soft clay, it has a critical influence on stability and deformation of engineering structures, which has become one of the important issues to be considered in the construction.With the rheological models of rock and soil having complex species and numerous parameters, how to identify rheological models and parameters becomes the urgent problem. Because of indoor creep experiments with more practical difficulties costing too much in man-power, material and money, and with test of soil rheology having no clear and complete procedures, creep test existing more casual results, the paper combines with the test results of soft clay in Tianjin area, uses regression methods to determine the appropriate constitutive model and the model parameters, and proves the validity of regression by numerical computing software.For large-scale excavation of soft soil foundation, larger area, deadline, cost and construction difficulty usually result in difficulties in applying for supports. According to a recent project example, the method, which is reserving earth berm in the range around foundation pit supporting, can obtain good economic benefits. Previous studies of earth berm focus on the role of the retaining structure and pay no attention to the stability deformation and deformation features inside and outside the excavation pit. The paper explores and analyses the influence of earth berm's section property on stable deformation of pit and its support structure by finite element calculation.In the process of excavation earth berm of deep foundation pit, which affected by various construction parameters, this paper establishes a basic example by a finite element analysis software, analyses the influence of earth berm's section properties, constitutive model of soil, the excavation's speed, the seepage of groundwater, soil stress history and other factors on the time effect of earth berm system, and reflect the mechanism of earth berm's time effects, and guide the engineering practice.Finally, the paper combines with the first phase in the practical engineering of Tianjin JiaHai, builds the finite element calculation model, discusses the time effect of earth berm without supporting system, further confirms the time effect of reserving earth berm in the process of deep foundation pit construction in soil area, analyses the stress and the deformation characteristic of non-support retaining structure, warns that we should give full attention to spatial and time effects of excavation in the actual construction.