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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 study, the expansive soil in section K25 + 000 of Xiaoxi Tower to Yaqueling Class I Highway of Yichang was modified by weathered sand, cement, lime and fly ash, respectively. Through direct indoor shearing test, Initial dry density on the shear strength index of expansive soil with different materials.Experimental study shows that different initial dry density, different modified materials and different dosage have a significant impact on the shear strength index of modified expansive soil, In the expansive soil, weathered sand, cement, lime and fly ash can all effectively increase the viscous internal friction angle and the shear strength of the expansive soil. Except for the slightly weakened cohesion, the other three kinds of materials Effectively improve the cohesion of expansive soil.For the cohesion and shear strength, the increase of cement and lime incorporation was obviously higher than that of the mixture of weathered sand and fly ash; for the internal friction angle, cement, lime and pulverized coal Ash and weathered sand to enhance the difference between the extent is not too big.Considering the shear strength index to evaluate the improvement effect, from good to bad followed by cement, lime, fly ash, weathering sand.With the initial dry density increases, 4 Different kinds of materials The change trend of shear strength index of the expansive soils is basically the same, that is, the cohesion and the shear strength increase with the increase of the initial dry density. The internal friction angle increases first with the increase of the initial dry density Reduce and then increase, there is an overall trend of increase.