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,测试黄土在无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 construc-tion projects are proposed in regions with seasonally frozen ground and collapsible loess in west-ern 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 freez-ing-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 indi-cate 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.How-ever,there is a reduced coefficient of collapsibility;the freeze-thaw action weakens loess collaps-ibility.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 temper-ature is decreased but moisture content remains unchanged.