Numerical Investigation On Unsaturated Water Flow And Stability Of A Lateritic Embankment In Rwanda Under Rainfall Infiltration

Rainfall infiltration process based on different rainfall intensities,types and duration causes the instability of the lateritic embankment.This work summarizes the previous researches related to the unsaturated water flow and stability analysis of embankment and discusses the unsaturated water flow analysis of lateritic embankment under rainfall.The rainfall infiltration causes a reduction of soil suction and decreases the shear strength;and then when the shear strength of the soil decreases the possibility of failure increases rapidly.The UMAT(User Material)was used to determine the failure formation and the FOS(Factor of Safety)of the embankment under rainfall infiltration.Based on this case,the numerical investigation was made as follows:1.The lateritic embankment was used as the model in numerical simulation to study the seepage problem with the rainfall infiltration.Based on the test of the lateritic soil and the antecedent rainfall distribution,the pore pressure and the saturation distribution were presented.The basic parameters like rainfall intensity,type and duration were studied.And the results are showing these parameters have a great impact on the embankment.2.The new proposed model has been used to study the effect of the tensile-shear strength coupling by using the own user material subroutine UMAT as a function of the second development that expands the constitutive models in ABAQUS;while the ABAQUS itself does not take into account the tensile shear strength of the soil.The validation of the new proposed model was made through the comparison of the laboratory test results and the model predictions,as well as the new model that combines tensile-shear and compressive-shear strength of the soil.3.The stability of the lateritic embankment under the rainfall infiltration was analyzed through the numerical simulation.It was the way to apply the new model proposed of tensile-shear strength with the advantage of presenting the development of failure of the embankment and to determine the FOS of the embankment.The analysis results are showing the toe of the embankment is under critical.