崩解性砂岩-水泥改良膨胀土物理力学特征及微观机理研究

Study on physical and mechanical properties and micro-mechanism of modified expansive soil with disintegrated sandstone-cement

基于引江济淮工程特有的地质条件,采用常规物理力学试验及扫描电镜试验,开展渠道下层崩解性砂岩弃料及水泥改良渠道上层膨胀土的改良效果及改良机理研究。结果表明,膨胀土中掺入砂岩与水泥后,土体最大干密度与抗剪强度增大,最优含水率减小,击实曲线曲率半径增大,土体胀缩特性被有效抑制,呈现出非膨胀特性。砂岩掺入能有效改善膨胀土颗粒级配,增加土体密实度,减小土体孔隙比,其对土体击实特征的影响更为显著。水泥掺入后,水泥水化反应使土中强亲水性黏粒被侵蚀,土体微观结构被改变,胀缩性及水敏感性降低;水泥水化产物具有强吸附性,相互之间连接紧密,能有效增强土体的整体性,因此,水泥掺入对膨胀土胀缩特性及抗剪强度影响更为显著。同时掺入崩解性砂岩与水泥,膨胀土改良效果最佳。

Based on the unique geological conditions of the project of diverting water from the Yangtze River to the Huaihe River,conventional physical and mechanical tests and scanning electron microscopy tests are used to carry out research on the improvement effect and mechanism of the cement and disintegrated sandstone waste in the lower layer of the channel to improve the expansive soil in the upper layer of the channel.The test results show that the addition of sandstone and cement can increase the maximum dry density and shear strength,decrease the optimal water content,increase the radius of curvature of the compaction curve,restrain the expansion and contraction characteristics of expansive soil,and make the modified soil shows non-expansive characteristics.The addition of sandstone can effectively improve the grain gradation,increase the compactness and reduce the porosity ratio of expansive soil,which has a more significant effect on the compaction characteristics of soil.After the cement is mixed,the cement hydration reaction causes the strong hydrophilic clay particles to be eroded in the soil,the soil microstructure is changed,and the expansion and shrinkage and water sensitivity are reduced.Cement hydration products have strong adsorp-tion,which can effectively enhance the integrity of soil.Therefore,cement incorporation has a more significant effect on the swelling and shrinkage properties and strength of soil.When the expansive soil is mixed with disintegrated sandstone and cement at the same time,the improvement effect is best.