Abstract:

According to the research status of construction spatial effects in large-long-deep foundation pit that is mainly focusing on the numerical simulation, but theoretical research is not too many till now. A simplified method for calculating the construction spatial effects of large-long-deep foundation pit in cohesive soil was advanced. The soil layers around deep foundation pit were equal to cohesionless isotropic soil mass by introducing the concept of equivalent internal friction angle. And then, by means of limit equilibrium analysis method combined with soil plasticity upper bound theory and associated flow rule, the spatial effects of two 3D failure modes: tension crack-shear and pure shear in deep foundation pit were studied concretely; and the corresponding formulas of spatial effects coefficient were put forward; also two examples were analyzed. The research results indicate that the method, which can complete by hand-calculation, avoids the defects of low efficiency, high cost and long period in numerical simulation, and the distribution characteristics and value size of spatial effects coefficient could be obtained directly from its calculation results, which can be used as guidance for the supporting structure, construction scheme design and the test points or sections choice in process of information monitoring.

Key words: large-long-deep foundation pit, spatial effects, simplified calculation, soil plasticity upper bound theory, associated flow rule, equivalent internal friction angle, limit equilibrium analysis method