庆阳黄土冻融环境下的特性研究
Characteristics of Qingyang Loess under Freeze-thaw Cycle

为了解冻融作用对黄土湿陷性的作用效果,以Q3黄土为研究对象,采用增(减)湿法配制不同含水量黄土试样,测试黄土在补水条件下受温度影响的冻融变形、压缩变形和湿陷变形;对原状黄土进行颗粒分析及基本物理力学参数试验。分析表明:(1)黄土是否产生冻胀取决于其含水量是否超过"临界冻胀含水量"。(2)冻融黄土与原状黄土相比压缩变形量较大,把部分浸水湿陷变形转化为压缩变形,冻融作用使黄土的湿陷性弱化。(3)冷冻黄土在相同温度下,含水量越大,湿陷系数越小;在同一含水量下,冻结温度愈低湿陷系数愈小。
With the development of One Belt and One Road, a number of key national construction projects are proposed in regions with seasonally frozen ground and collapsible loess in western China. Researchers have determined engineering problems associated with freeze-thaw and the collapse of loess, and based on previous studies this study aims to determine the rules of change pertaining to loess collapsibility after the effects of freeze-thaw. Therefore, Q3 loess samples with different moisture contents are prepared using a moistening or demoistening method. After freezing-thawing at different test temperatures, and with no water supply, tests are conducted on frost-heave and thawing deformation, compression deformation, and the collapsible deformation of loess. Particle and physo-mechanical parameters of natural loess are also analyzed. Results indicate the following: firstly, when the moisture content is greater than the critical value, frost heave deformation is generated in loess in a freezing environment. Secondly, compared to pre-freezing samples, there is a greater compression deformation of post-thaw loess samples. However, there is a reduced coefficient of collapsibility; the freeze-thaw action weakens loess collapsibility. Thirdly, when using the same test temperature, the coefficient of collapsibility of frozen loess decreases with an increase in the moisture content, and also decreases when the test temperature is decreased but moisture content remains unchanged.