A Effective Stress Form Of Spencer Method For Soil Slope Stability Analysis

Spencer method is a strict limit equilibrium slice method to solve the problem of slope stability.As this method satisfies all the force balance and moment equilibrium condition,and the calculation is simple,so it has been widely used in engineering.Using the total force method is easier to derive mechanical analysis and balance equations then using the effective force method.Current Spencer method take the mixture of water and soil as research subjects.And using the soil skeleton as the object of study is relatively small.Forces act on soil body under phreatic line can be separate into effective stress from soil skeleton and buoyancy with pore-water pressure from pore water.The resultant of weight of water with same volume of soil under the phreatic line and pore-water pressure act on side of soil is seepage force.The forces acting upon soil slice were reanalyzed.A Effective Stress Form of inter-slice forces were founded.So the two equations of equilibrium in respect of effective stress and effective moments were rearranged and the safe factor with effective stress form was obtained.For seepage flow field of homogeneous isotropic soil slope,the streamline can be divided into three straight lines,which paralleling to slope crest,slope surface and slope base respectively.Two cases in Spencer's original paper were studied by the new method.The results show that the effective stress form of Spencer method for soil slope stability analysis is validated.The effective stress is dominated for strength and deformation of soil,so the effective forces form of Spencer method has significance in theory and application.