掺砂水泥固化华南滨海软土的强度和干湿循环特性试验研究

Experimental Study on Strength and Dry-Wet Cycle Characteristics of Coastally Soft Soil in South China Cemented by Sand and Cement

为探索砂粒对水泥固化华南滨海软土强度和干湿循环特性的影响规律,制备了一系列不同掺砂量和掺砂粒径的水泥固化华南滨海软土试样,分别进行无侧限抗压强度试验和海水及淡水条件下的干湿循环试验,同时对加载完毕的试样进行扫描电镜(SEM)测试和X射线衍射(XRD)试验。试验结果表明:掺砂水泥土试样的第7,14,28天无侧限抗压强度随掺砂量的提高而增大,其第28天强度随掺砂粒径的减小而增大;掺砂水泥土试样经历两轮干湿循环后的强度损失率最大达61%,干湿循环导致的强度劣化特性随砂粒径的减小和掺砂量的增大而得到更好的改善,并且,掺砂水泥土试样在淡水条件下的抗干湿循环能力明显优于海水条件。SEM和XRD的测试结果表明:掺砂水泥固化华南滨海软土的作用主要表现在:1)模量替换作用(高模量的砂粒替换小模量的软土);2)砂粒-水泥土界面胶结作用;3)裂纹扩展阻隔作用。

To study the influence of sand on the strength and dry-wet cycle characteristics of cementedly coastal soft clay in South China,a series of cementedly coastal soft clay samples in South China with different contents and sizes of sand were prepared,and unconfined compression strength tests,dry-wet cycle tests,scanning electron microscopy tests and X-Ray diffraction tests were conducted in seawater and fresh water.The test results indicated that the unconfined compression strength of sand-mixed clay-cemented samples cured for 7,14,and 28 days increased with the increase of the sand content,and the strength cured for 28 days increased with the decrease of the size of sand particles;the maximum loss ratio of mass for sand-mixed clay-cemented samples was up to 61%.The properties of strength deterioration subjected to dry-wet cycles improved with the increase of the sand content and the decrease of the size of sand particles.Moreover,the resistant capability for dry-wet cycling of samples in the fresh water was obviously better than that in the seawater.The results by SEM and XRD tests showed that the reinforced mechanisms of sand-mixed cemented soft clay in South China mainly reflected the following:1)the modulus replacement effect(replacement of low modulus soft clay with the high modulus sand);2)the interfacial effect between sand and clay-cemented matrixes;and 3)the blocking and isolating effect for crack.