The Research On Seepage Characteristic And Stability Of The Unsaturated Soil Fill Subgrade Under The Condition Of Rainfall Infiltration

Rainfall infiltration is easy to cause instability of slope and landslide. Hence, the study of stability of the unsaturated soil fill subgrade under the condition of rainfall infiltration was quite meaningful. This paper summarizes the previous research about slope stability under rainfall conditions, and discusses unsaturated soil fill subgrade stability under rainfall infiltration combined with a under-running highway embankment engineering examples. The following tasks have been made:(1) This paper systematically discusses the mechanical properties of unsaturated soil, including composition of unsaturated soil,effective stress,matric suction,stress state variables, unsaturated soil strength theory, deformation theory of unsaturated soil,the relationship between shear strength and matric suction,strain and many other aspects changes caused by changing of matrix suction.(2) The seepage problem of fill subgrade under rainfall infiltration are analyzed in numerical simulation. Through the establishment of the fill roadbed model and the simulation of the changing rule of the soil seepage field under the rainfall, this paper analyzed the influence of rainfall intensity,rainfall duration,rainfall patterns and the impact on seepage field of subgrade brought by the change of permeability coefficient.(3) The analysis of displacement change of soil under rainfall conditions. By the numerical methods, the distribution of displacement and the law of development of fill subgrade under rainfall and action of seepage has been simulated.(4) The stability of fill subgrade under the rainfall infiltration has been studied. The finite element strength reduction has applied to unsaturated soil to calculate the safety coefficient and its change law under the corresponding cases.(5) By the analysis of the influence of different rainfall factors on fill subgrade, the laws of seepage of the fill subgrade and analysis results of slope stability under rainfall conditions are concluded and summarized. The results are used to guide the practical engineering design.