Determination Of Soil Parameters For Numerical Simulation Of Excavations

Numerical analysis is an excellent mean to estimate the response caused by excavation and the determination of soil parameters is the key of it. One of the main distinctions between geomaterials and other engineering materials is the spatial variation of their properties in different directions. To account for non-uniformity and uncertainties in soil parameters, geotechnical engineering practice has seen an increasing emphasis on analysis of the design soil parameters that can apply to numerical simulation.In this paper, an inverse analysis method of deep excavation based on the Pareto multiobjective optimization is proposed, combined respectively with 2-D continuous medium finite element method and 3-D elastic foundation beam method, and applied to multiple well-instrumented deep excavations in Shanghai. The main research findings are summarized as follows:(1) A multiobjective optimization algorithm multialgorithm genetically adaptive multiobjective method(AMALGAM) is implemented in ABAQUS invoked by MATLAB to identify soil parameters based on multiple types of field observations, combined with 2-D continuous medium finite element method, and applied to multiple well-instrumented deep excavations in Shanghai. The results show that the inverse-analyzed soil parameters of the compromise solution from the biobjective inverse analysis can reasonably simulate both the wall deflection and ground surface settlement. The prediction effect showed an obvious improvement on accuracy between one Stage and the next Stage, one Stage at enough depth and subsequent Stages. Multi-objective inverse analysis had obvious advantages and could be wide used in excavation engineering.(2) The ratio of the reverse-analyzed and geological soil parameters were analyzed and the range of the ratio is proposed. The result also showed that the ratio follow normal distributions, standard values of ratios was proposed by analogy with reliability degrees of structural.(3) The AMALGAM proposed is combined with 3-D elastic foundation beam method, and applied to a well-instrumented deep excavation in Shanghai. The results show that the soil parameters of the compromise solution from the multi-objective inverse analysis can reasonably simulate the wall deflection of both the width and height of the rectangle excavation. The inverse-analyzed “m” value were presented.