Finite-element Analyses On The Property Of Soil-cement Mixing Pile Foundation Pit Support Structure

Soil-cement mixing pile support structure is a kind of support forms which is widely used in the area with soft soil. It is water-proof and the material need just cement, so it is economical. It came into use broadly in the last few years. Main computation methods include computation method, earthresistance method and finite-element method, among them, 3-D finite-element method is able to analyze the displacement and stress of support structure and soil in all. This paper summarized predecessors'research findings, established 3-D finite-element model and analyzed the property of mixing pile support structure roundly. And the analyses took into account the soft soil interlining. Primary coverage as follows:(1) In this paper, the soil adopted ideal elastoplasticity constitutive model-Drucker-Prager model which was staple in geotechnical engineering. The model was rest on broad sense Mises yield criteria considering hydrostatic pressure. The expansion angle of soil in this model reflected the soil's expansion due to shear gender. This paper used the increment iteration and iterate adopted tangent change rigidity iteration. This paper utilized ANSYS large scale computation software to complete non-linearity finite element computation, considered primary stress field, and adopted life and death unitary means to simulate excavation off load course.(2) It could be concluded from the become-pile theory and property of soil-cement mixing pile that, although intensity of support structure was improved, it still approached raw soil, so in this paper the constitutive model of mixing pile support structure also adopted Drucker-Prager model. The borderline of soil and soil-cement mixing pile was not obvious, moreover, the disparity of their module was small, so this paper didn't take account of interface unitary problem, regarded both support structure and soil as one whole, and regarded earth pressure acting at support structure as integral internal force.(3) According to the project in Quanzhou, this paper established 3-D finite-element model, soil layering followed project practice, the calculation model made use of foundation pit's symmetry. Compared the displacement outcome calculated by ANSYS software with the one measured outcome, then verified the calculation model's rationality.(4) Made use of the 3-D finite-element model to analyze the soil-cement mixing pile's displacement, vertical stress, shear stress and so on. The analysis included basic behavior and influence brought by floor heap carry size, it's holding position, support structure width, foundation pit width, foundation pit depth and excavation speed rate. Got a series of conclusions for practical design and construction reference.(5) Soft soil interlining impacted support structure's property notably, this paper made use of the calculation finite-element model to analyze the influence on support structure brought by soft soil interlining's location, thickness and quality of soil.(6) Soft soil interlining possessed definite rheological properties. This paper adopted a sort of practical computation method, fitted the timevariation of c andφduring the computational procedure through time-varying parameter, in order to achieve the purpose of considering soil's rheological properties, and verified parameter's rationality through the practical project. Then analyzed the timevariation of mixing pile'property and the influence on excavation step disposition brought by soft soil interlining's rheological properties. Got a series of innovative conclusions with practical meanings.