Numerical Analysis On Moisture Field Of Loess Foundation Under Trench Seepage

The loess engineering field measures the advantages and disadvantages of the field and makes engineering countermeasure generally according to the saturated soaking collapse settlement of foundation's total or partial collapsible soil layer, which is different from the practical engineering. In fact, loess foundation collapse accidents mostly relate to underground trench seepage. Trench and other line source infiltration make local water content of loess foundation increase. The local soil layer of the foundation reach different moistening water content along width and depth direction, which brings uneven moistening collapse deformation. The reason of collapse accidents in loess foundation is great collapse difference rather than big collapse settlement. To study the moistening collapse deformation under trench seepage, the first step is determining the change of the moisture filed of loess foundation under trench seepage, that is, it needs to determine the moistening area and moistening extent of loess foundation, and then compute and analyze the moistening collapse deformation of loess foundation. The research of the subject is deficient. Based on this, the paper studies the change of the moisture filed of loess foundation under trench seepage.Based on the trench leakage in practical engineering and taken initial water content and void ratio of the loess foundation, hydrops pressure in trench, etc. into account, the paper establishes the finite element model of two-dimension unsaturated loess foundation under trench seepage, determine model parameters and program software to compute and analyze the moisture filed of loess foundation under trench seepage. The paper gets change process of the moisture filed of homogeneous loess foundation with infiltration over 3 years. Hydrops pressure in trench is considered in the form of non-pressure, full water and in-pressure. The value of initial water content of the foundation soil is 15% and 20%. The void ratio is 0.7, 0.9 and 1.1. The results showed that the moistening area is much wider if initial water content, void ratio and infiltration velocity are bigger, but the diffusion of infiltration water enhances. The saturation area decreases. On the other hand, the moistening area is much narrower if initial water content, void ratio and infiltration velocity are smaller. All those show the strong prevent water action of the low-saturated compacting soil. The moisture concentrated around the trench because of the moisture difficult infiltration and weak diffusion, but the saturation area increases. The infiltration range increases with the time going. The water in the trench can easily flow into underground when the water in the trench and groundwater connect and infiltration channel comes into being., but the moistening area decreases. Hydrops pressure in trench has great influence on water infiltration of loess foundation, the more the hydrops pressure, the more the infiltration velocity and the moistening area.