The Anisotropy And The Scale Effect Of Hydraulic Conductivivty For The Loess In Baoji City, Shannxi Province

The permeability of the loess directly affects the stability of loess slope and groundwater recharge by rainfall infiltration in loess area, and hydraulic conductivity is the main parameter to characterize this permeability. Therefore, the research of hydraulic conductivity for the loess is significant for loess slope stability evaluation and groundwater resources evaluation and management in loess area. This paper chooses the hills region of the loess in front of the Qinling Mountain in the Baoji city, Shannxi Province, to demonstrate properties of hydraulic conductivity(K). In this study, standpipe method, double ring method and pumping method were used to determine the hydraulic conductivity of the loess sediments. Based on hydraulic conductivities of the loess were measured, the spatial variation, anisotropy and scale effect of hydraulic conductivity(K) were disscussed. The results showed that:(1) the spatial variation of hydraulic conductivity for the loess is very strong, and the upper K is greater than the lower K in shallow loess.(2) The vertical hydraulic conductivity(Kv) of loess is greater than horizontal hydraulic conductivity(Kh) of loess in study area. The anisotropy ratios of hydraulic conductivity(Kv/Kh) were less than 1, which indicate that the anisotropy of K is distinct and the main direction of seepage is vertical.(3) When measurement scale between 16 cm and 85 cm, the geometric mean of Kv is decreasing with the increasing of scale. Scale effect of Kh is inapparent. In the shallow loess, Kv increase with the increasing of scale on a small scale, but scale effect of Kh is inapparent. This research attempts to provide theory solution to determine the value range of hydraulic conductivity of aquifer and to provide the reasonable parameters for constructing landslide model of the loess and numerical simulation of groundwater.