Experimental Study On Water Retention Characteristics And Permeability Characteristics Of Remolded Loess With Different Degree Of Compaction

In recent years,infrastructure projects in the Loess Region have been carried out in large numbers in response to national strategies such as the “Belt and Road” and“Western Development”.Typical projects include Yan'an New District and Lanzhou City.During its construction and operation,it encountered more and more engineering problems.For example,the settlement deformation of the remolded loess filling area in the Yan'an Shancheng city-building project has not been stabilized.At the same time,due to the difference in construction levels,some areas have insufficient compaction and there is a problem of potential collapse of the foundation.The process of loess foundation humidification is related to the water-retention and permeability characteristics of the soil.This paper further explores the water retention and permeability of unsaturated loess on the basis of the existing.The research results contained in this article mainly include the following:(1)In order to study the water retention curves of remolded loess with different degrees of compaction,the self-made low suction test device,tensiometer and GDS unsaturated soil triaxial instrument and other instruments were used to determine the water retention curves of reshaped loess with different degrees of compaction,and VG was applied The model and the water retention curve model based on the VG model considering the deformation effect fit the single compaction retention curve and all compaction retention curves,respectively,to obtain model parameters and analyze the prediction accuracy.The results show that the method of testing the water retention curve by multiple methods is feasible;the air intake value changes in the fitting function of the loess VG model with different degrees of compaction,and n controlling the rate of change of the water retention curve is very high except for the high pressure solidity.It is close to provide a test basis for the function form of the water retention model considering the deformation effect;the water retention curve model considering the deformation effect based on the VG model has sufficient accuracy in predicting the water retention curve of different compaction degrees,and can be used for different compaction Prediction of water retention curve in degree loess fill.(2)The variable water head method and the normal water head method were used to measure the saturation permeability coefficient of remolded loess withdifferent compaction degrees,and a comparative analysis was conducted to find that the saturation permeability coefficient gradually decreased from low pressure to high pressure.Within a certain degree of compaction,the acceleration decreases as the degree of compaction increases.(3)According to the indoor one-dimensional vertical soil column immersion saturation and water infiltration test,combined with the improved infiltration wetting front advancing method,the unsaturated permeability coefficients of different compacted remolded loess under different suctions are obtained,which are calculated based on the VG model indirect method,The permeability coefficient function of the unsaturated soil can predict the relationship between the unsaturated permeability coefficient and the suction under the high-pressure solid degree,and there is a certain error in predicting the relationship between the unsaturated permeability coefficient and the suction of the low-pressure solid degree sample.The saturated permeability coefficient and relative permeability coefficient of Yangling loess under low pressure are predicted by using the saturated permeability coefficient equation and relative permeability coefficient equation based on soil pore distribution proposed by Zhai and Rahardjo(2015).