Stability Analysis Of Soft Soil Embankments Reinforced By Drainage Consolidation Method

Soft soils are generally characterized by high natural water content,large void ratio,high compressibility,poor permeability,low strength and bearing capacity,etc.The drainage consolidation method is a reliable means of soil improvement for soft soil embankment.During staged construction,the vertical drainage body and sand cushion joint to form a drainage system,leading to the shear strength improvement of soil.However,its characteristics go further than that.It has been shown in theory and measurements that sand cushion and staged construction homogenize the embankment loads and affect the additional stresses in the foundation.Therefore,in order to reasonably assess the stability of embankments treated by drainage consolidation,it is necessary to conduct a comprehensive study in terms of the characteristics of the drainage consolidation method.At present,the stability analysis of embankment treated by drainage consolidation method focuses on the strength growth of soil resulting from consolidation,but the effective consolidation stress method and its derived stability analysis methods still have problems.First,they fail to reflect the triaxial stress state of soil.Second,they ignore the strength growth of certain areas.Third,they ignore the change of shear stress during construction.In addition,the stability analysis ignores the characteristics of embankment load diffusion,which leads to overlooking the additional stresses and shear strength of the foundation.In response to the above problems,the work accomplished and the results obtained in this paper are as follows:(1)A simplification calculation method of subgrade pressure is proposed for embankment load diffusion.The homogenization phenomenon of subgrade pressure is explained from the perspective of stress diffusion.Based on the measured data of subgrade pressure and the theory of stress diffusion of double-layer foundation,the simplified calculation method of embankment load is proposed.(2)The degree of foundation consolidation is obtained from the back analysis of engineering settlement monitoring data.Combined with an engineering case of embankment foundation treatment by drainage consolidation method,the degree of consolidation was obtained by the curve fitting method of s-t curve.This confirms the necessity of considering soil consolidation for stability analysis.(3)The strength growth and stability calculation method based on the actual stress state is proposed.According to the additional stresses under the embankment load,the shear strength and shear stress increment of the foundation can be considered by the soil isotropic stress state.(4)The verification and analysis of the calculation cases were realized by the program.The analysis parameters were selected by integrating the engineering characteristics of the embankment treated by the drainage consolidation method.The effects of soil strength index,embankment load diffusion,slope and reinforcement tension on the stability were discussed respectively.Serval engineering suggestions are proposed.(5)The similarities and differences between the embankment reinforcement project and the road widening project are compared.The effect of drainage consolidation method for reinforced embankment foundation treatment on the overall stability enhancement is analyzed,and it is suggested that this method should be used cautiously in the reinforced embankment project from the perspective of stability enhancement.