初始干密度对不同材料改良膨胀土的抗剪指标影响

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

本研究对宜昌市小溪塔至鸦鹊岭一级公路改建项目K25+000段的膨胀土,分别采用风化砂、水泥、石灰、粉煤灰进行改良.通过室内直接剪切试验,对比分析了初始干密度对不同材料改良膨胀土抗剪强度指标的影响.试验研究得出,不同初始干密度、不同改良材料及不同的掺入量对改良膨胀土的抗剪强度指标有着显著的影响,在膨胀土中掺入风化砂、水泥、石灰和粉煤灰均能有效提高膨胀土的黏内摩擦角和抗剪强度,除风化砂改良后小幅降低了黏聚力外,其余3种材料均能有效提高膨胀土的黏聚力.对于黏聚力和抗剪强度,掺入水泥和石灰提高的幅度明显大于掺入风化砂和粉煤灰;对于内摩擦角,掺入水泥、石灰、粉煤灰和风化砂提高的幅度相差并不是太大.从抗剪强度指标来评价改良效果,则由好到差依次为水泥、石灰、粉煤灰、风化砂.随着初始干密度的增加,4种不同材料改良的膨胀土的抗剪强度指标变化趋势基本一致,即黏聚力和抗剪强度值随着初始干密度的增加而增大,内摩擦角随着初始干密度的增加,先增大后减小再增大,总体有增大趋势.

In this paper, direct on expansive soil of K25 ＋ 000 section of Xiaoxita to Yaqueling high- way rebuilding project, respectively adopt weathered sand, cement, lime, fly ash to improve expansive soil. ent dry Through indoor direct shear test, comparison and analysis of the initial dry density effects on differ- material modified index of shear strength of expansive soil. It is concluded that, with different initial 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.