Coupled Analysis Of The Effects Of Boundary Conditions On The Behaviour Of Excavated Soil Slopes

Nowadays, people has recognized the displace field, the stress field and thepressure field of the excavated slope inside with FEM, but pay less attention to theresearch of its boundary conditions. In fact, boundary conditions will affect its interiorbehavior greatly. Generally, for an excavated slope, existed three boundary conditions,they are load boundary condition, displace boundary condition and pore boundarycondition. While coupled flow & deformation finite element method take into accountof the interacting of the soil framework and the seepage of water, it will meet thenecessity of the analysis of the excavated slope under different boundary conditions.Biot consolidation theory is a most universal tool for Effective Stress Analysis. Inthis paper, in order to take hydrostatic pressure into account, based on Biotconsolidation theory, equations with variable of pore potential is derived, withDuncan-Chang constitutive relationship of soils, the coupled nonlinear finite elementflow-deformation-stability analysis method is used to analyse the distributions ofstresses field and displacements field . The solution to the equation is midpointincremental method. A Coupled Flow & Deformation Behaviors Nonlinear FiniteElement Analysis of Slope Stability(CFEASS)program is developed. According tothe results of finite element methods, the effective stress, pore pressure, critical slipsurface, and the minimum factor of safety at any time are figured out. Furthermore,the critical slip and the minimum factor of safety at the final minute can be deduced.The minimum factor of safety is defined as the ratio of the summed anti-slip forces tothe summed slip forces along the critical slip surface. Bisection or two-dividedmethod are adopted in searching for the critical slip surface of a slope.In this paper, slope's stress field and displacement field under different boundaryconditions are discussed. CFEASS which is based on the coupled flow & deformationbehaviors finite element analysis is obviously advantageous over Total StressAnalysis methods in that it can simulate the behavior of stress and strain of soils ,theprocesses of slope excavations and it can reflect the dynamic change of stress field,pore pressure and factor of safety, deciding the long-term safety factor.