Initial dry density on the shear effect of different material improved expansive soil

In this paper,direct on expansive soil of K25 +000 section of Xiaoxita to Yaqueling highway rebuilding project,respectively adopt weathered sand,cement,lime,fly ash to improve expansive soil. Through indoor direct shear test,comparison and analysis of the initial dry density effects on different material modified index of shear strength of expansive soil. It is concluded that,with different initial dry density,different modified material and different mixing amount have significant effects on shear strength of improved expansive soil. The incorporation of weathered sand,cement,lime and fly ash can effectively increase the expansive soil internal friction angle and shear strength,In addition to weathered sand slightly decreased cohesion force,the other 3 kinds of materials can effectively improve the cohesion force..,For the cohesive strength and shear strength,cement and lime improved more greatly than the incorporation of weathered sand and fly ash; For the inner friction angle,cement,lime,fly ash and weathered sand increase amplitude is not too large. From the shear strength index to evaluate the effect of improvement,the order from good to bad is cement,lime,fly ash,weathered sand. With the increase of initial dry density,four kinds of different materials of improved expansive soil shear strength indexes of almost the same change trend,namely the cohesive force and the shear strength values increased with the increase of initial dry density increased,internal friction Angle increased with the increase of initial dry density,decrease then increase first,overall had a tendency to increase.