Experimental Study On The Capillary Effect In Unsaturated Campacted Loess

This paper takes the loess-like silt of Zao-zhuang, Taiyuan as the study object. Samples with different slenderness ratio were prepared through the control of dry density and initial soil water content. By using a one-dimensional soil column instrument, five capillary tests were conducted in which the initial density and initial soil water content were various. Following testing data were obtained as: volumetric water content of soil column at different positions; soil matrix suction of the corresponding position; the changing of wetting front over time.Using MATLAB, the test data were analyzed and fitted. Four kinds of curve were fitted, i.e.: soil-water characteristic curve(SWCC), the changing curve of volumetric water content over time; the changing curve of soil matrix suction over time; the changing curve of the wetting front over time. The relationship formula of capillary rise height and time is obtained by fitting the changing curve of the wetting front over time, and the change trend of capillaryrise rata over time is picked up by means of formula derivation and plotting method.Therefore, the conclusions are drawn out as follows :1.Water content increases with time. The speed of increment is faster at the very start, then slows down as time goes by. Final stable moisture content becomes smaller and smaller from the bottom of soil column to the top of soil column.2.Matrix suction decrease with time, and the speed of decrement is faster at the very start, then slows down as time goes by, which adapts to the negative correlation between water content and matrix suction.3.Gardner model fitting SWCC of compacted loess by using fminunc of MATLAB is convenient, stable and accurate.4.The residual water content and dry density show a negative correlation relationship.5.Difference in water supply system, initial dry density and slenderness ratio impact on the capillary rise.6.The relationship between rising height of capillary water and time is power function. The statistical formula of the rising height with time is set up for the unsaturated compacted loess.7. Based the statistical formula, the capillary rising rate for testing soil is obtained. The results show that the slenderness ratio impacts on the beginning capillary rising rate; the late capillary rising rate is a negative correlation withthe dry density.