Experimental study of characteristics of swelling-shrinkage and permeability for Jingmen weak expansive soil

A series of tests for characteristics of swelling-shrinkage and permeability are carried out on Jingmen weak expansive soil under five different compactnesses and on the lime-treated soil.The test results show that the swelling pressure-dry density relation can be represented by a power function;while the relations between non-loaded swelling ratio,linear swelling ratio,volume shrinkage ratio and dry density are all non-monotonous.The expansive soil with the compactness of 95 % has the lower swelling ratio and volumetric shrinkage ratio,which is due to effects of coupled compaction and swelling.Therefore,the compactness should be selected as 95 % in weak expansive soil embankment construction.On the other hand,the lime treatment can reduce swelling and shrinkage of expansive soil,indicating by the fact that the swelling-shrinkage total ratio of the lime-treated expansive soil is only 0.7 %.In addition,the permeability coefficient of the lime-treated and untreated expansive soil all decrease with increasing dry density.This relation can be represented by the power function as well.The permeability coefficient of the lime-treated soil is larger than that of the untreated expansive soil under the same compactness;however,for the approximate dry density,the difference of the permeability coefficient between the two types of soil is not large.