混掺粉土与水泥改良风积沙堤坝性能试验研究

Experimental Study on Performance of Aeolian Sand Dike Improved by Cement and Silt

风积沙堤坝结构在地震荷载作用下易发生液化破坏。为有效提高堤坝抗震性,开展了掺入适量水泥与粉土改良筑堤风积沙的相关性能试验,并仿真分析了边坡抗震稳定性。研究表明,单掺5%水泥可有效提高风积沙最大干密度、粘聚力,但保证压实度时难以充分发挥水泥粘结作用,且风积沙颗粒表面光滑,胶凝-沙粒联结体形成骨架对内摩擦角影响相对较小;单掺5%水泥基础上掺入粉土可进一步提高风积沙最大干密度,且粉土掺量为10%时风积沙改良效果最好,边坡抗震稳定安全系数最大;掺粉土至15%~20%时内摩擦角提高,但粘聚力下降。说明适量粉土掺入后颗粒吸水性增强,改善了水泥胶凝和沙土粘结性能,而过量粉土掺入,粉土吸附水分超量进而制约了水泥水化联结效应,导致混合土体粘聚力下降;基于5%水泥掺量下的粉土掺量不超过15%,可显著改善整体级配、降低孔隙比、增大风积沙内摩擦角。

The structure of aeolian sand dike is prone to liquidize and damage under earthquake load.In order to effectively improve the physical and mechanical properties of dike,this paper carried out the relevant performance test of aeolian sand dike mixed with appropriate amount of cement and silt,and simulated to analyze the seismic stability performance of the slope.The results show that the maximum dry density and cohesion of aeolian sand can be effectively improved by adding 5%cement,but it is difficult to give full play to the cement bonding effect while ensuring the compactness.Moreover,the aeolian sand particles have smooth surface so the skeleton formed by the cementitious sand particles has relatively small impact on the internal friction angle.The maximum dry density of aeolian sand can be further improved by adding silt on the basis of 5%cement,and the improvement effect of aeolian sand is the best when the content of silt is10%.Meanwhile the anti-seismic stability safety factor of slope is the largest.The friction angle increases and cohesion decreases when silt content reaches 15%-20%.It shows that mixing proper amount of silt reducing water cement ratio is conducive to exert cement bonding;While add excessive silt,in view of the specific surface area of silt is larger than the aeolian sand,the excessive amount of water absorbed by silt will restrict the hydration bonding effect of cement,which will lead to the decrease of cohesive force of mixed soil.Based on 5%cement content,silt content less than 15%can significantly improve the overall gradation,reduce the void ratio and increase the internal friction angle of aeolian sand.