During excavation of foundation pit, soils of different sites may undergo different unloading paths. This study focuses on the tangent modulus of soil under different stress paths and provides theoretical basis for the deformation calculation of soil. In this paper, conventional triaxial compression test and 0 consolidation unloading test were conducted with mucky soil and silty clay to obtain the deformation characteristics of soils under different stress paths. Experiment results show that the soil samples exhibit distinct stress-strain characteristics under different stress paths, but they all show nonlinearity. The initial tangent modulus increases as the consolidation confining pressure intensifies. Then, based on the test data, the power function relationship between initial tangent modulus and confining pressure under unloading was verified. Simultaneously, a hyperbola function to express stress-strain relation of soils under the 0 consolidation unloading condition was proposed and proved. Finally, the formulas of the tangent modulus under 0 consolidation unloading were established referring to the derivation of that in Duncan-Chang model. The theoretical calculation results agree well with the test results. It can expand the use of the Duncan-Chang model and improve its application to engineering practice.

Abstract. Based on the investigation of the distribution of strata in the downtown area of Guangzhou City, simulating the stress path of excavating foundation, the triaxial pressure tests on isotropic consolidation and K0 consolidation conditions, the lateral unloading tests and the axial unloading tests on mucky soil and silty clay were performed by using SLB-1 stress-strain controlled triaxial shear penetration apparatus, in order to research the loading and unloading deformation properties of foundation soil, and change rules with strain and strength properties of pore water pressure under different stress paths. The results show that there exist different characters of stress-strain curves of the soil under different stress paths, mucky soil and silty clay are different in mechanical properties, while the stress-strain curves of them present obvious nonlinear type; the failure model of soil under normal triaxial compression conditions, K0 compression conditions and lateral unloading conditions presents compression-shear type, and under the axial unloading conditions presents longitudinal stretch type; change rules of stress-strain curves of the soil are influenced by average consolidation stress, plastic index and confining pressures; change rules of pore water pressure are also influenced by average consolidation stress, stress path and properties of the soil, which can be fit by exponential decay function; stress-strain curves of pore water under K0 compression-axial unloading conditions can be fit by quadratic parabolic equation.

Used the program, ANSYS, finite element model of the rung-shape long-span tensile cable-membrane structure in Foshan Century Lotus Stadium was conducted to investigate its dynamic characteristics and its mechanics performance under seismic loading. Results indicate that the natural frequencies of the structure are all lower and concentrate in a small range, and its jumping phenomenon isn't in evidence. The structure's vibration is mainly vertical vibration, and its lateral stiffness and torsional rigidity is well. To ensure that the modal mass participating coefficient is not less than 90%, the contribution of the former 140 modes are should to consider when the analysis of response spectrum is done. Because the earthquake action can greatly influence the internal force of the upper compression ring, the lower compression ring, and the truss web, it should be calculated in the load combination. When the earthquake waves load on the structure from different directions, the internal force and displacement of the structure have significant difference. So the effects of the different direction of the waves and their combination should be considered together.