Study On Characteristics Of Water Transport And Stability Of Loess Embankment

Loess is often unsaturated in nature.Under unsaturated condition,loess has very complex permeability and engineering characteristics.Rainfall infiltration is a saturatedunsaturated seepage process.When rainfall infiltration occurs,the soil moisture content will change with time and space,so rainfall is the main factor that leads to the deformation and even instability of unsaturated loess slope.Therefore,based on the saturated-unsaturated seepage theory,it is of practical significance to study the water infiltration characteristics of loess embankment and its influence on the mechanical properties of embankment.In this paper,the high-fill loess embankment slope formed by the newly-built project from the west of Sanmenxia to Henan-Shaanxi section of National Highway G310 is taken as the background.Based on the unsaturated seepage equation and its definite solution conditions,the seepage law of loess slope under rainfall infiltration condition is studied by finite element method,and the dynamic response of rainfall intensity and compaction degree to different positions of embankment slope and the analysis of slope stability under seepage-stress coupling action are carried out.The main research work and results are as follows:(1)The soil-water characteristic curves of loess with different compactness are measured by using the dynamic multi-step flow method of the improved pressure plate instrument,and the permeability coefficient of unsaturated loess is calculated,which provides model parameters for the subsequent finite element seepage calculation.(2)Exploring the internal relationship between the shear strength of unsaturated soil and the soil-water characteristics,and verifying the applicability of the shear strength formula of absorbing stress to loess in western Henan.(3)The finite element software Geostudio is used to analyze the two-dimensional embankment slope model under rainfall conditions.The infiltration law of slope is studied by SEEP/W module,and the influence of rainfall intensity and fill compaction coefficient on pore water pressure,wet front migration,infiltration rate change and transient saturation zone development of embankment slope is analyzed Two modules,SIGMA/W and SLOPE/W,are used to analyze the stress field and stability of slope under seepage-stress coupling.(4)The dynamic response affected by rainfall at the foot of slope is most obvious,and the influence on effective stress of embankment is mainly reflected in the shallow layer of embankment,and the influence on slope stability is lagging behind.