Study On Permeability And Pore Characteristics Of Weak Expansive Soil Improved By Silty Soil In The Yellow River

Expansive soil is spread all over the world,and it is particularly widely distributed in China.Every year,the losses caused by engineering problems caused by expansive soil in China are as high as 100 billion yuan.There are many ways to solve the problems of expansive soil.In this paper,the silty soil in Yuanyang County,Henan Province are used to improve the expansive soil in the Huangfan area.The permeability of plain expansive soil with different dry densities and modified expansive soil with different amounts of sand are analyzed.Pore characteristic parameters,to explore the relationship between the permeability coefficients of plain expansive soil and improved expansive soil and their pore characteristic parameters,the conclusions are as follows:(1)The permeability of plain expansive soil with different dry densities and different silt contents and the improved expansive soil with different dry densities were studied.The results show that: for plain expansive soil,as dry density increases,Porosity reduction,the permeability coefficient gradually decreases,and the dry density has a good linear relationship with the permeability coefficient.For the improved expansive soil,at the same dry density,as the amount of silty soil increases,its permeability coefficient increases;at the same amount of silty soil,as the dry density increases,its permeability coefficient decreases;At the maximum dry density of each sand-mixing ratio,it increases with the increase of the silt soil content.(2)The pore characteristic parameters of plain expansive soil with different dry densities and modified expansive soil with different silt contents are studied.The results show that for plain expansive soil,as dry density increases,the cumulative pore volume gradually decreases,The pore distribution curve changes from a multi-peak curve to a three-peak curve and finally to a bi-peak curve.At the same time,the total pore volume,total pore area,average pore diameter,critical pore diameter and medium pore percentage decrease,and the percentage of small pores less than 10?m increases,and the large pore The percentage is almost unchanged;for the improved expansive soil,as the amount of silty soil increases,the cumulative pore volume gradually increases,and the pore distribution curve changes from an obvious double-peak curve to a triple-peak curve and becomes multi-peak after 20% sand mixing ratio.At the same time,the total pore volume,average pore size,critical pore size,percentage of medium pores and percentage of large pores increase,the total pore area gradually decreases and rebounds at 40% sand mixing ratio,and the percentage of small pores less than 10 ?m decreases,and the percentage of macropores has the strongest correlation with permeability coefficient.(3)The relationship between the permeability coefficient and pore characteristic parameters of plain expansive soil under different dry densities and modified expansive soil with different silt contents is shown.The results show that for plain expansive soil,its permeability coefficient and total pore volume medium correlation with average pore size,strong correlation with total pore area,percentage of small pores less than 10?m,percentage of medium pores and percentage of large pores;for improved expansive soils,its permeability coefficient is weakly related to percentage of small pores less than 10?m,which is related to the remaining pores.The characteristic parameters are strongly correlated.In actual engineering construction,the percentage of large pores can be used as an index to evaluate the permeability of the soil.