干湿循环效应对风化砂改良膨胀土膨胀力影响的研究

Study of the Wet and Dry Cycle Effect on the Expansive Force of Improved Weathered Sand Expansive Soil

本文将0、10％、20％、30％、40％、50％的风化砂掺入膨胀土中，分别进行0、1、2、3、4、5次干湿循环，对干湿循环之后的试样进行膨胀力测试；研究了不同掺量风化砂改良膨胀土膨胀力的大小及增长时程随着干湿循环次数的变化规律，分析了干湿循环作用一定次数后，风化砂掺量对试样表面的剥落程度及裂隙发育的影响。实验结果表明：干湿循环效应对风化砂改良膨胀土的膨胀力影响较为显著，且膨胀力与干湿循环次数间的关系可以用三次方函数很好地进行描述；在风化砂掺量一定时，经过2～3次干湿循环时膨胀力降低幅度最大，且随着风化砂掺量的增加，这一降低幅度在逐渐减少，干湿循环4～5后膨胀力趋于稳定；当风化砂掺量相同时，随着干湿循环次数的增加，膨胀力达到稳定所需要的时间逐渐减少，而膨胀力的增长速度先增大后减小；干湿循环5次后，试样表面的裂隙发育已基本达到稳定，裂隙数量随着风化砂掺量的增加而逐渐减少；当风化砂掺量为30％时，试样周边基本上不存在剥落现象。

Expansive soil mixtures containing respective 0, 10%, 20%, 30%, 40%, 50% weathered sand were prepared first. After respective 0, 1, 2, 3, 4, 5 times of wet and dry cycle, expansive force test of above specimens was carried out. The relation between expansive force of improved expansive soil and the content of weathered sand and the variation of growth schedule along with wet and dry cycle times were experimentally investigated. The influence of weathered sand content on spalling degree and fracture development on sample＇s surface were analyzed. Experimental results indicate that the wet and dry cycle effect significantly influences on the expansive force of improved weathered sand expansive soil. The relationship between expansive force and wet and dry cycle times can be well described by a third power function. Keeping the content of weathered sand unchanged, after 2-3 times of wet and dry cycle, the reduction of expansion force is maximum. With the increase of weathered sand,the reduction is gradually reduced; the expansion force is stable after 4-5 times of wet and dry cycle. For the same content of weathered sand, with the increase of wet and dry cycle times, the time to reach expansion force stability is gradually reduced. The growth rate of expansion force first increases then decreases. After 5 times of wet and dry cycle, the fracture development on specimen＇s surface is basically stable. The fracture amount gradually reduces along with the increase of weathered sand content. When the content of weathered sand reaches 30%, there is substantially no spalling surrounding the specimens.