兰州大学机构库 >土木工程与力学学院
改性黄土中毛细水上升作用研究
Alternative TitleMoisture Migration Effects of Modified Loess in Vertical Direction
王圣麟
Thesis Advisor谌文武
2015-05-23
Degree Grantor兰州大学
Place of Conferral兰州
Degree Name硕士
Keyword改性黄土 毛细水 密度 无侧限抗压强度 易溶盐试验 微观结构
Abstract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、易溶盐含量和土体的微观结构,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。本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天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天后密度、干密度、无侧限抗压强度、易溶盐种类及含量、比表面积SSA、离子交换能力CEC和微观结构等参数的变化规律。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160cm最低降低到60cm左右),提高强度(水泥土50天后土水接触面处试件无侧限抗压强度为0.86MPa,为同高度处黄土强度值的3倍),抑制土体中易溶盐离子的迁移。同时,改性剂还产生大量水化产物填补细小孔隙,减少大孔隙,并包裹和连接黄土颗粒,在毛细水作用下仍保持了原有的镶嵌空间网状结构和面接触方式,并在黄土内形成相对稳定的空间结构,增加改性土的强度,阻碍毛细水的继续上升。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。
Other AbstractThe phenomenon of capillary water rising can be easily found in loess, thus affecting the moisture content, strength, soluble salt content, and microstructure 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, unconfined compressive strength, content and category of soluble salt, specific surface area (SSA), cation exchange capacity (CEC) and microstructure 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), restrain migration of soluble salt in sample. Meanwhile, lime and cement create a large amount of hydration products which fill the tiny voids, parcel and connect loess particles into bigger ones. Under the effects of capillary water rising, soil particles can maintain face-to-face contact pattern and soil still have net structure, what's more, the hydration gel prevent capillary water from continuous rising. Last but not least, 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.
URL查看原文
Language中文
Document Type学位论文
Identifierhttps://ir.lzu.edu.cn/handle/262010/226497
Collection土木工程与力学学院
Recommended Citation
GB/T 7714
王圣麟. 改性黄土中毛细水上升作用研究[D]. 兰州. 兰州大学,2015.
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