干湿循环下云南红土的裂缝发展研究

发布时间：2018-02-16 01:04

本文关键词： 云南红土干湿循环水分迁移特性含水率-干密度-温度影响裂缝发展特性微结构特性裂缝发展机理　出处：《昆明理工大学》2017年硕士论文　论文类型：学位论文

【摘要】：本文以极端气候对云南红土的影响为研究背景,以云南红土为研究对象,提出了“干湿循环下云南红土的裂缝发展研究”的课题。考虑初始含水率、初始干密度、试验温度和干湿循环次数等因素的影响,通过垂直土柱迁移试验、干湿循环试验和微结构试验结合图像处理方法,研究不同影响因素下干湿循环红土的水分迁移特性、裂缝发展特性、微结构特性及裂缝发展机理。该研究成果对于有效防治云南红土地区的裂缝问题具有重要的参考价值。干湿循环下红土中的水分迁移特性表明:增湿条件下,红土中的水分迁入量随初始干密度和初始含水率的增大而减小;脱湿条件下,红土中的水分迁出量随初始干密度的增大而减小,随初始含水率的增大保持不变;干湿循环条件下,红土中表层含水率降低、内部含水率升高,干密度减小。干湿循环下含水率对红土裂缝发展的影响表明:增湿过程中,红土样产生裂缝,初始含水率越高的红土样越早产生裂缝;脱湿过程中,初始含水率越大的红土样裂缝越显著;裂缝数量、长度和面积与初始含水率正相关;裂缝宽度存在峰值,随初始含水率的增加先增大后减小。干湿循环下干密度对红土裂缝发展的影响表明:增湿过程中,红土样产生裂缝,初始干密度越高的红土样越早产生裂缝;脱湿过程中,初始干密度越大的红土样裂缝越显著;干湿循环中,裂缝数量、长度和面积随初始干密度的增大而增大,随初始干密度的增大裂缝宽度先增大后减小;初始干密度越大的红土样膨胀稳定时间越长。干湿循环下温度对红土裂缝发展的影响表明:温度越高的红土样产生裂缝的循环次数越少;试验温度低时无裂缝产生,随试验温度的升高红土样在增湿中产生裂缝,温度进一步升高时,红土样在脱湿中开裂;裂缝数量、长度和面积与温度正相关,裂缝均宽在增湿中与温度正相关,脱湿中先增大后减小;在干湿循环中裂缝特征参数波动上升。干湿循环下红土的微结构特性表明:干湿循环前红土样颗粒连接方式为片架结构与片堆结构同时存在,干湿循环后红土样的颗粒连接方式由片架结构向片堆结构转变;随初始含水率、初始干密度和温度的升高土颗粒的片架结构减少,片堆结构增加;干湿循环后红土样的孔隙比增大、颗粒数增加、圆形度降低,分维数和定向度的变化与初始干密度和初始含水率有关。干湿循环下红土裂缝的发展机理:干湿循环对红土裂缝的作用机理可以从双电层理论、土壤胶体理论、膨胀力、水分子动能四个作用来解释,其综合作用导致了红土样的开裂现象;含水率升高、干密度增大和温度上升放大了干湿循环对红土的劣化作用,使裂缝发展周期缩短;根据裂缝的发展过程,可以将裂缝发展分为裂缝孕育期、裂缝产生和扩展期、裂缝稳定期3个阶段。
[Abstract]:The impact of extreme weather on Yunnan clay as the research background, taking Yunnan clay as the research object, put forward the "research" the development of cracks of Yunnan red clay under cyclic wetting drying problem. Considering the initial water content, initial dry density, the influence factors of test temperature and wetting cycles, the vertical soil column migration test, image processing method combining the dry wet cycle test and microstructure test, effects of different factors on the migration characteristics under cyclic wetting and drying red water, the characteristics and development of cracks, micro structure characteristics and development mechanism of crack. The crack problem of the research results for the effective prevention and treatment of red soil in Yunnan region has an important reference value. The result showed that water migration characteristics of wet dry cycles in laterite the wet conditions, the water in the clay migration with initial dry density and initial water content decreased; desorption conditions, soil moisture in red The migration quantity density increases with the decrease of the initial dry, with initial water content increased unchanged; cyclic wet dry conditions, surface water reducing rate in laterite, the internal moisture content increased, dry density decreases. Under cyclic wetting drying effect of moisture content on the clay crack development showed that the humidification process of cracks in clay. The higher the initial moisture content of the clay samples early cracks; dehydration process, initial moisture content of clay samples larger cracks significantly; fracture number, length and area and initial water content are positively correlated; the crack width has a peak value, the first increase with the initial water content and then decreases. Under the cycle of dry and wet dry effect of density on clay crack development showed that the humidification process of cracks in clay samples, initial dry density and higher clay like the earlier cracks; during the drying process, the initial dry density is large crack like laterite is significant; dry wet cycle In the fracture number, length and area density increases with the increase of the initial dry density, the crack width increases first and then decreases with initial dry; the initial dry density is large laterite. The longer the steady expansion of samples showed that the effect of temperature on clay under cyclic wetting drying crack development cycles: the higher the temperature of the clay samples cracks less; no cracks test at low temperature, cracks in the wet clay samples with elevated temperature, temperature rises further, like in laterite dewetting cracking; crack number, length and area was positively correlated with temperature, cracks are wide in humidity and temperature are related, dehydration in the first increases and then decreases; in the dry wet cycle in the crack characteristic parameters of wave rise. Results show that the micro structure characteristics of clay under cyclic wetting drying: wet and dry cycle before clay like particles connection structure frame and sheet pile structure exist at the same time, dry After the red wet cycle like particles connection from the frame structure to stack structure transition; with the initial water content, reduce the rack structure of the initial dry soil increased particle density and temperature, stack structure increased; after dry wet cycles like laterite void ratio increases, the increase in the number of particles, the round of changes with the fractal dimension and the orientation of the initial dry density and initial water content. The development mechanism of clay crack under cyclic wetting drying mechanism of dry wet circulation on the clay cracks from the double layer theory, soil colloid theory, expansion force, water molecular kinetic energy four to explain the role, the comprehensive effect leads to the cracking phenomenon of laterite the sample; the increase of water content, dry density increase and temperature rise amplifies the deterioration effect of dry wet circulation on the clay, the crack development cycle shortened; according to the development process of the cracks, cracks can be divided into the incubation period of crack development, crack The formation and expansion period of the seams, the 3 stages of the fracture stabilization period.

【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】：TU43

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