Hydraulic Properties For Loess Deposit With Burrows

The abundance of burrows and other macropores（interstice）are common characteristics of loess deposite,the saturated and unsaturated hydraulic conductivity is an important parameter to obtain the hydraulic properties of the loess with burrows,and it has great practical significiance for the evaluation and prediction of slope stability and the evaluation of groundwater resources in the loess area.In this paper,the saturated and unsaturated hydraulic conductivity of loess with burrows were studied through means of laboratory test,field experiment and theoretical calculations in the typical loess area of China.The results of the study are as follows:（1）The soil-water characteristic curves（SWCC）of the loess with burrows has a larger specific water capacity in the high water content section,and this characteristic is exactly the manifestation of macropores on SWCC.In general,the SWCC of the loess with burrows can still be generalized by using the van Genuchten mathematical model.There have higher fitting accuracy when the model parameters m and n are independent variables.In addition,it can be seen from the pore distribution of the loess with burrows from the SWCC of the test samples that the pore distribution of various pore sizes is more uniform,which is in accordance with the measured characteristics of the SWCC.（2）The unsaturated hydraulic conductivity calculated by Mualem model is more consistent with van Genuchten model to the actual value.On the K_r（S_e）curve with a degree of saturation of 0.8-1,the more burrows,the smaller the relative hydraulic conductivity is when the same degree of saturation is applied,while the existence of pores among aggregates makes the loess medium have a larger relative hydraulic conductivity.（3）The vertical saturated hydraulic conductivity of loess with burrows is a double Gaussian distribution,the topsoil（0-20 cm）and subsoil（20-40 cm）are particularly obvious,while the horizontal saturated hydraulic conductivity is not affected by macropores such as burrows.This feature shows that the loess with burrows has strong anisotropy,and the anisotropy coefficient can reach up to 20.（4）The physical meaning of the parameters of van Genuchten mathematical model is also studied in this paper.The mathematical relationship between theαand the air entry value is verified,the mathematical expression of the matrix potential at inflection point（hi）is derived.In addition,the test method for determining the soil-water characteristic curves by hanging water column method is also improved,and makes the suction capacity of the method can reach 7 mH₂O.