昆明呈贡石灰岩上覆红黏土干缩裂隙的温度效应
投稿时间:2021-04-11  修订日期:2023-04-11  点此下载全文
引用本文:何岱洵.昆明呈贡石灰岩上覆红黏土干缩裂隙的温度效应[J].地质与勘探,2023,59(5):1083-1092
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作者单位E-mail
何岱洵 昆明理工大学建筑工程学院云南昆明 zhangjiaming@kust.edu.cn 
基金项目:国家自然科学基金青年科学基金项目“强降雨条件下植被发育斜坡非饱和带土体大孔隙流试验研究”(编号:41807258)和国家自然科学基金重点项目“非冰川型高山远程粘性泥石流的形成-运移机理及其灾害效应”(编号:41931294)联合资助
中文摘要:温度是影响土体干缩开裂的重要外部环境因素之一。为研究温度对红黏土干缩裂隙的影响,以昆明呈贡石灰岩上覆红黏土为对象,经风干、碾碎和筛分后,选取2 mm以下的细颗粒,用正方形钢化玻璃容器制备9个厚度为10 mm的饱和泥浆样,分成3组,每组3个平行样,利用控温烘箱分别进行30℃、50℃和70℃的干燥试验,试验过程中定时称重试样和对土样表面进行拍照,然后用PCAS软件对照片进行图像处理。结果表明:红黏土的蒸发过程可分为3个阶段,干缩裂隙的形成和发展可分为5个阶段;温度升高,干燥完成时间减短,常速率阶段的蒸发速率和蒸发量增大,最终含水率降低;初始临界含水率随温度升高而增大;随着土体含水率持续减小,表面裂隙率先缓慢增加,然后快速增大,最后趋于稳定;温度升高,裂隙交点数、裂隙条数、裂隙总长度和土块数减少,裂隙平均长度、裂隙平均宽度、表面裂隙率、土块平均面积、土块最大面积、干缩厚度和干密度增大。温度显著影响红黏土的水分蒸发过程,干缩裂隙的形成和发展,以及表面裂隙结构和形态。
中文关键词:红黏土 温度 干燥试验 蒸发 干缩裂隙 表面裂隙 呈贡 昆明
 
Temperature-dependent behaviors of desiccation cracks in red clay overlying carbonate rocks in the Chenggong area of Kunming City
Abstract:Temperature is a significant external environmental factor impacting the drying shrinkage and cracking of clayey soil. To explore the impact of temperature on the drying shrinkage and cracking of red clay, this work performed laboratory desiccation tests on the red clay from the Chenggong area of Kunming City. The red clay, once collected, underwent air-drying, crushing, and 2 mm sieving procedures within the laboratory. By utilizing nine square tempered glass containers, nine slurry specimens, initially saturated and 10 mm thick, were prepared. The specimens were categorized into three groups, with each group composed of three parallel samples. The grouped specimens were subjected to oven drying at three distinct temperatures of 30℃, 50℃, and 70℃. During the entire drying period, close monitoring of the specimens' weight and surface cracks occurred. The PCAS software enabled a quantitative analysis and description of the structures and geometric characteristics of the surface cracks. Results indicate that the moisture evaporation process in red clay can be classified into three stages, and the formation and development of shrinkage cracks span five stages. A rise in temperature results in a decrease in the drying time necessary to reach the final moisture content. In the constant rate stage, both the evaporation rate and capacity see an increase as temperature escalates. As temperature ascends, the final water content experiences a decrease. As temperature rises, the initial critical water content at the onset of cracking also shows an upsurge. As the soil moisture content continuously diminishes, the surface crack ratio initially escalates slowly, then swiftly, before eventually stabilizing. Rising temperatures contribute to a decrease in the intersections within the crack network, the number of crack segments, the total length of cracks, and the number of aggregates. Conversely, an increase is noted in the average crack length, average crack width, surface crack ratio, average aggregate area, maximum aggregate area, final specimen thickness, and dry aggregate density. It is inferred that temperature significantly influences the process of water evaporation, the formation and progression of shrinkage cracks, as well as the structure and morphology of red clay surface cracks.
keywords:red clay, temperature, desiccation test, evaporation, desiccation crack, surface crack, Chenggong area, Kunming City
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