Engineering behaviors of weak expansive soil and its treatment measures for roadbed filling

Compacting properties,swelling-shrinkage behavior and mechanical behavior of compacted sample for weak expansive soils in Xiang-Jing Expressway of Hubei Province are investigated.It is discovered that the engineering behavior of weak expansive soils is controlled by the coupled action of water content and degree of compaction,while the swelling-shrinkage behavior is inherent property of weak expansive soils and its value depends on the initial water content and dry density;the optimum moisture content and maximum dry density of expansive soils depends on tamping effort,bigger tamping effort;bigger the maximum dry density,and smaller the optimum moisture content correspondingly;the variation of California bearing ratio(CBR)of the expansive soils with water content is similar to the compaction curve.However,the water content of soil corresponding the maximum CBR is higher than the optimum water content.In the construction of expansive soil embankment,the influence of total swell-shrink ratio should be considered besides the degree of compaction and CBR value;and it is helpful to understand the engineering properties of expansive soils.At last,the structural shape of weak expansive soil embankment and the standard of controlling compaction of weak expansive soil for constructing embankment are suggested.