Study On Numerical Simulation And The Soil Constitutive Model Of A Deep Excavation Retaining In Haikou

During the excavation, the deformation of excavation is very important for itself and surrounding environment. How to forecast the deformation of excavation is the emphasis and difficulty in excavation engineering, numerical analysis is an effective method to solve this problem at present. Constitutive model of rock and soil is the core of geotechnical plastic mechanics, as well as cornerstone of numerical simulation. The core of numerical simulation is to select constitutive model and model parameters. This paper studies on the scope of the part of geotechnical constitutive model and the selection of model parameters.MC model, MCC model, HS model and HSS model are selected in this paper, the constitutive model parameters of the undisturbed soil are determined by conventional laboratory soil test and the triaxial test, a set of suitable parameter selection scheme for the four kinds of constitutive models combined with the Investigation Report of excavation engineering has been established, then the constitutive model parameters of the relevant layer are obtainted. Using Plaxis program simulates excavation engineering, the simulation results that obtained using four numerical constitutive model are compared with the actual results, then the following conclusions are obtained.(1) The elastic modulus E of soil can be5Es or more; The modified Cambridge model parameters λ and x, can be calculated according to the plasticity index provided by the Investigation Report and the derived formula; Consolidation modulus Eoed can be Es, secant modulus E50can be2Es, unloading and reloading modulus Eur may be taken as5E50; Small strain parameters Go can be taken as2Eur, which directly affects the results of numerical simulation, the numerical simulation results are closer to the actual results with the increasing value of Go, the value of γo.7fluctuates within a narrow range, γo.7can be2E-04.(2) The simulation results of MCC and HS and HSS model show that ground settlement performances groove type, which matches with the engineering experience; The deformation of the retaining pile show that abdomen prominents to the inside of excavation and presents parabolic, the maximum deformation occurs near the surface of excavation.(3) The most ideal simulation results is HSS model, the second ideal is the HS model and MCC model, simulation results of MC model is not ideal. So the finite element analysis of excavation engineering should be preferred to constitutive model firstly which can reflect the shear hardening and compression hardening and distinguish the difference of stiffness between loading and unloading and small strain behavior. It is suggested that HSS model should be adopted to carry on numerical analysis of excavation engineering in Haikou. (4) The selection of parameters are optimized, the deformation curve of retaining pile is closer to the actual results after the optimized HSS model are adopted, the change trend and values are closer to the actual results too. The optimization of parameters for HSS model is that the value of stiffness parameters and the value of reference shear modulus can be incressed properly.