干湿循环下红土模型坝坡劣化特性研究

发布时间：2018-04-29 02:08

本文选题：红土坝坡模型试验 + 干湿循环作用　；参考：《昆明理工大学》2017年硕士论文

【摘要】：本文以云南红土为研究对象,结合云南极端干旱和雨季频繁交替的干湿作用及这种干湿作用对云南红土型坝坡的影响,提出开展“干湿循环下红土模型坝坡劣化特性研究”这一课题。以室内红土坝坡模型试验为基础,以库水位升降作为干湿循环控制条件,结合宏微观试验方法,研究干湿循环过程中红土模型坝坡的坡面劣化特性、土水压力变化特性、抗剪强度特性、压缩特性及其对应的微结构特性,分析了红土模型坝坡劣化特性规律。该研究年成果对于实际红土型病险大坝的病害防治具有重要意义。干湿循环下红土模型坝坡试验表明:增湿过程中土压力减小,孔隙水压力增大,脱湿过程中,土压力增大,孔隙水压力减小。随干湿循环次数增大,坝坡高程较低时红土体的土压力呈减小稳定趋势,高程较大时土压力呈增大稳定趋势。随干湿循环次数增大,坝坡红土体的孔隙水压力呈增大趋势。库水位升降的干湿循环过程中,水分反复迁入迁出引起的吸水膨胀、失水收缩的加深加剧,红土坝坡呈现出坡顶开裂、大块体剥落、坡脚颗粒堆积的上凹下凸的坡面轮廓线变化特征,改变了坝坡红土体的坡面轮廓线形状,出现坝坡劣化特性。干湿循环下坝坡红土宏观特性试验表明:干湿循环前后,坝坡红土粘粒百分含量降低,含水率先增大后减小,干密度减小,抗剪强度降低,压缩性能增大。随坝坡高程增大,粘粒百分含量降低,含水率降低,干密度减小,抗剪强度降低,压缩性能增大。随干密度增大,抗剪强度、压缩性能增大。干湿循环下坝坡红土微结构特性试验表明:干湿循环次数的影响下,随干湿循环次数增加,模型坝坡逐渐劣化,大团粒结构减少,细颗粒增多,土体变得松散,孔隙率、分维数、颗粒个数增大,坝坡高程的影响下,坝坡高程越大,土体就越松散,劣化较为严重,孔隙率、分维数、颗粒个数越大,干密度的影响下,干密度越大,土体越密实,劣化程度较轻,孔隙率、分维数、颗粒个数越小。干湿循环下模型坝坡逐渐劣化,坝坡土体的宏微观特性存在一定对应关系。干湿循环过程中,水分对坝坡土体有软化、化学溶解等作用,水化膜增大变薄,坝坡裂缝逐渐变大以及胶结作用减弱,使坝坡强度等特性降低,对坝坡抵抗库水位干湿循环、恶劣降雨干湿环境、风暴以及冻融环境不利,提供一定的工程参考意义。
[Abstract]:In this paper, Yunnan laterite is taken as the research object, combined with the dry and wet action of extreme drought and frequent alternate rainy season and the influence of this kind of dry and wet action on the red soil dam slope in Yunnan. The subject of "study on deterioration characteristics of Red soil Model Dam Slope under dry and Wet cycle" is put forward. On the basis of indoor red earth dam slope model test, taking the rise and fall of reservoir water level as the control condition of dry and wet circulation, combined with macro and micro test method, the slope deterioration characteristics and soil water pressure variation characteristics of red earth model dam slope during dry-wet cycle are studied. The characteristics of shear strength, compression and its corresponding microstructure are analyzed, and the degradation characteristics of laterite model dam slope are analyzed. The results of this study are of great significance to the prevention and treatment of actual red earth dam. The results of dam slope test of laterite model under dry and wet cycles show that the soil pressure decreases, pore water pressure increases during humidification, and pore water pressure decreases during dehumidification. With the increase of dry-wet cycle times, the earth pressure of laterite decreases when the height of dam slope is low, and increases with the increase of height. With the increase of dry and wet cycles, the pore water pressure of red soil on dam slope increases. During the dry-wet cycle of water level rise and fall, the water absorption and expansion caused by water moving in and out repeatedly, the deepening of the shrinkage of water loss, the cracking of the slope of the red earth dam, the spalling of the large block, The shape of slope profile of red earth body on the slope of the slope is changed and the deterioration of the slope occurs because of the variation characteristics of the contour line of the slope in the upper concave and the lower convex of the grain accumulation at the foot of the slope. The macroscopical characteristic test of red soil on dam slope under dry and wet circulation shows that before and after dry and wet cycling, the clay content of red soil in dam slope decreases, the moisture content increases first and then decreases, the dry density decreases, the shear strength decreases and the compressibility energy increases. With the increase of the height of the dam slope, the percentage content of clay particles decreases, the moisture content decreases, the dry density decreases, the shear strength decreases and the compressibility energy increases. With the increase of dry density, shear strength and compressibility increase. The experimental results of microstructural characteristics of red soil on dam slope under dry and wet cycles show that with the increase of dry-wet cycle times, the dam slope of the model gradually deteriorates, the large aggregate structure decreases, the fine particles increase, and the soil becomes loose and porosity. Under the influence of the increase of fractal dimension, the number of particles and the height of dam slope, the larger the height of dam slope, the looser the soil, the worse the deterioration, the larger the porosity, fractal dimension, the number of particles, and the more dry density, the larger the dry density, the more dense the soil. The degree of deterioration is lighter, the porosity, fractal dimension and the number of particles are smaller. Under the dry and wet cycle, the model dam slope is gradually deteriorating, and the macro and micro characteristics of the dam slope soil have a certain corresponding relationship. In the process of dry-wet circulation, water has the functions of softening and chemical dissolution of dam slope soil, increasing and thinning of hydration film, increasing cracks of dam slope and weakening of cementation, which makes the strength of dam slope lower, and resists the dry and wet circulation of reservoir water level to dam slope. Severe rainfall dry and wet environment, storm and freezing and thawing environment are unfavorable, which provides certain engineering reference significance.
【学位授予单位】：昆明理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TV223

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