紫红色砒砂岩冻融循环下变形特性及微观结构试验研究

发布时间：2017-12-31 11:20

本文关键词：紫红色砒砂岩冻融循环下变形特性及微观结构试验研究　出处：《内蒙古农业大学》2017年硕士论文　论文类型：学位论文

【摘要】：砒砂岩区的产沙量是以非径流的冻融风化侵蚀为主形成的,冻融循环作为一种温度变化的具体形式,可以被理解为一种特殊的强风化作用。本文以内蒙古自治区鄂尔多斯准格尔旗紫红色砒砂岩作为研究对象,通过三温冻融、超景深、压汞试验,研究并分析了冻融次数、含水率对原状砒砂岩变形特性的影响以及反复冻融后砒砂岩微观结构的变化规律。研究结果表明:砒砂岩每一个冻融周期的完成大体都经历迅速降温、恒温冻结、迅速升温、恒温融化和继续升温5个阶段。冻融循环过程可以很清晰反应砒砂岩在冻结和融化中固相、液相相互转化时其内部热量的变化,以及砒砂岩冻结、融化过程的体积变化。在冻结过程中冻胀量随时间增大遵循对数函数规律增加;当含水率大于10.27%时,发生冻胀明显,试样冻胀量会随冻融次数增加而增大;当含水率为11.53%及以上时,冻融循环大于6次,冻胀率趋于平缓。在融化过程中,含水率在12%到13%之间存在一个阈值,小于该阈值时,融沉系数随着含水率的增大而增长,当土体含水率达到该阈值含水率,融沉系数随着冻融次数的增加而趋于平缓,含水率是引起冻融总变形的主要影响因素。含水率小的原状砒砂岩反复冻融后发生压缩变形,含水率大的发生隆起变形,但最终的融沉都会趋于稳定。含水率越大,反复冻融对砒砂岩内部的微观结构影响越大,含水率小冻融对砒砂岩微观结构影响浅。当含水率为8.56%时,孔深相对高差50%在450 um以内;当含水率为13.7%时,砒砂岩的冻融孔深达到最大值,高差相差达610um,所占面积达41.5%。
[Abstract]:The sediment yield in the soft rock area is mainly formed by non-runoff freeze-thawing weathering erosion. The freeze-thaw cycle is a specific form of temperature change. It can be understood as a special kind of strong weathering. This paper takes the fuchsia soft rock of Zhungeer Banner of Inner Mongolia Autonomous region as the research object, through three temperature freezing and thawing, the depth of field, mercury injection test. The freeze-thaw times were studied and analyzed. The effect of water content on the deformation characteristics of undisturbed Pisha sandstone and the variation of microstructure of Pisha sandstone after repeated freezing and thawing. The results show that the completion of each freezing and thawing cycle of arsenopyst has generally experienced rapid cooling down. The freeze-thaw cycle process can clearly reflect the change of internal heat of Pisha sandstone during freezing and melting solid phase and liquid phase conversion. And the volume change of the freezing and thawing process of arsenopyst. During the freezing process, the frost heave increases with time and follows the law of logarithmic function. When the moisture content is greater than 10.27, the frost heave is obvious, and the frost heave will increase with the increase of freeze-thaw times. When the moisture content is 11.53% or above, the freeze-thaw cycle is more than 6 times, and the frost heaving rate tends to be gentle. In the melting process, there exists a threshold between 12% and 13%, which is less than this threshold. The thawing coefficient increases with the increase of moisture content. When the soil moisture content reaches the threshold moisture content, the thawing coefficient tends to smooth with the increase of freezing and thawing times. Water content is the main factor that causes the total deformation of freeze-thaw. The undisturbed arsenic sandstone with low moisture content occurs compression deformation and uplift deformation after repeated freezing and thawing. However, the final thawing will tend to be stable. The larger the moisture content, the greater the impact of repeated freezing and thawing on the microstructure of arsenite, and the smaller the water content is, the more shallow the impact is on the microstructure of Pisha sandstone, when the moisture content is 8.56. The relative height difference of pore depth is within 450um; When the water content is 13.7, the depth of frozen-thawed pores reaches the maximum, the difference of height reaches 610umand the area occupied is 41.5.
【学位授予单位】：内蒙古农业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU45

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