改性黄土垂直方向毛细水上升作用研究

黄土中极易发生毛细水上升的现象,毛细水的上升作用会影响黄土的含水率、强度和土体的结构,造成土体稳定性下降,弱化黄土地基。石灰和水泥作为常用的改性材料被广泛应用于黄土改良。试验研究了黄土以及石灰、水泥不同配比下的改性黄土在毛细水上升作用50 d过程中的含水率变化,推算出毛细水在黄土和改性黄土中上升高度和速率,以及50 d后密度、干密度及无侧限抗压强度等参数的变化规律。评估了3%石灰改性土、5%石灰改性土和3%水泥改性土改善黄土中毛细水上升作用的可行性;并对三者的改性作用进行比较。试验结果表明:三种改性土都可以有效地减缓毛细水上升高度和速度(从黄土的160 cm最低降低到60 cm左右),提高强度(水泥土50 d后土水接触面处试件无侧限抗压强度为0.86 MPa,为同高度处黄土强度值的3倍)和密度。试验最后得出,石灰能够有效降低土体内的含水率,且随着含量的增加,吸水作用越明显,而水泥对于土体内部结构的改性作用更大,提升土体强度和遇水稳定性,阻碍毛细水上升作用显著。

Capillary Water Migration Effects of Modified Loess in Vertical Direction

The phenomenon of capillary water rising can be easily found in loess, thus affecting the moisture content, strength, and structure of the soil. Consequently, soil stability will be reduced and loess foundation weaken. This paper focuses on the behavior of capillary water rising and moisture content changing in loess and modified loess under different rates of lime and cement adding, in order to deduce height and velocity of capillary water as well as density, dry density and unconfined compressive strength after 50 days of capillary water rising. The study also estimates the feasibility of using lime and cement to resist influence of capillary water rising and makes comparison of the modifiers. In the test, loess was modified by three methods: 3% lime adding, 5% lime adding and 3% cement adding according to lime weight. Conclusion can be shown as follows: all of the three can effectively slow down height and velocity of capillary water (from 160 cm in loess to a low of merely approximately 60 cm), improve strength (after 50 days, unconfined compressive strength of cement modified loess at the soil-water interface was 0.86MPa, 3 times of that in loess sample) and density. What"s more, lime has the better impact on moisture content reducing while cement contributes more to soil inner structure improvement. Additionally, cement has greater effects to strength, water stability as well as capillary water rising obstacle in loess.