陈爱军, 陈俊桦, 程峰, 吴迪. 湖南邵阳地区高液限红黏土干缩裂隙演化过程的量化分析[J]. 农业工程学报, 2021, 37(20): 146-153. DOI: 10.11975/j.issn.1002-6819.2021.20.016
    引用本文: 陈爱军, 陈俊桦, 程峰, 吴迪. 湖南邵阳地区高液限红黏土干缩裂隙演化过程的量化分析[J]. 农业工程学报, 2021, 37(20): 146-153. DOI: 10.11975/j.issn.1002-6819.2021.20.016
    Chen Aijun, Chen Junhua, Cheng Feng, Wu De. Quantitative analysis of the evolution process of high liquid limit laterite shrinkage fracture in Shaoyang areas of Hunan Province of China[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2021, 37(20): 146-153. DOI: 10.11975/j.issn.1002-6819.2021.20.016
    Citation: Chen Aijun, Chen Junhua, Cheng Feng, Wu De. Quantitative analysis of the evolution process of high liquid limit laterite shrinkage fracture in Shaoyang areas of Hunan Province of China[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2021, 37(20): 146-153. DOI: 10.11975/j.issn.1002-6819.2021.20.016

    湖南邵阳地区高液限红黏土干缩裂隙演化过程的量化分析

    Quantitative analysis of the evolution process of high liquid limit laterite shrinkage fracture in Shaoyang areas of Hunan Province of China

    • 摘要: 红黏土对环境湿度变化非常敏感,在干燥环境中极易开裂,纵横交错的裂缝网络损害了土壤结构的完整性,很容易诱发红黏土边坡失稳和崩塌,导致农田水利设施的破坏,甚至加剧整个生态环境的水旱灾害。为探究红黏土裂隙的演化规律,该研究采用自制试验装置和三维应变测量系统开展了自然湿热条件下的红黏土泥浆样干燥试验,通过采集土体水分和土表位移、应变和裂隙的变化,定量分析脱湿过程中土体表面裂隙形态和应变场的演变特征,并进一步探讨水分变化对裂隙形态和应变场的影响。结果表明:1)土样表面干缩裂隙的演化一共经历了6个阶段,后阶段裂隙分割前阶段裂隙围成的区域,且不同阶段裂隙的交叉角接近90o;2)裂隙产生初始,裂隙尖端处拉应变约为0.5%,土表面大部分区域处于受拉状态;随着裂隙进一步发展,裂隙周边土体逐渐由拉应变状态向压应变状态转变;当所有裂隙发育完成,裂隙周边土体处于压应变状态;3)裂隙演化阶段与界限含水率有关,当泥浆土样的含水率接近液限时(67.7%),土体表面裂隙开始发育,裂隙迅速张开和延伸;当土的含水率达到塑限时(28.3%),裂隙发展的速率逐渐变缓;当含水率小于缩限时(18.8%),裂隙变化已经很小,裂隙发育接近完成;4)在裂隙演化过程中,早期裂隙的发展持续时间和裂隙宽度均超过后期裂隙;土表不同位置的位移和应变均不相同,土块中心竖向收缩大于边缘竖向收缩,而土块中心位移及应变均小于土块边缘,研究可为红黏土开裂引发的工程地质灾害的预防及治理提供参考。

       

      Abstract: Abstract: Laterite is a special type of soil in tropical and subtropical humid areas. It is evolved from carbonate rocks to physical, chemical, and biological weathering, as well as laterization with the color of brown-red, maroon and yellowish-brown. Furthermore, laterite is very likely to crack in a dry environment, due to its sensitivity to ambient humidity. The resulting dry shrinkage cracks have posed a great threat to the strength and stability of the soil. Therefore, there is a commonly-hidden danger of collapse from the shrinkage cracking of laterite in slope projects. Most cracking of cohesive soil comes from the evaporation of water in the soil. Boundary constraints and uneven shrinkage can result in the formation and development of a stress-strain field in the soil. Once the tensile exceeds the maximum tensile strength of the soil, the cracks gradually occur and continue to develop during evolution. In this study, a quantitative analysis was performed on the dry shrinkage cracking of red clay in high liquid-limit laterite in Shaoyang area of Hunan Province in China. A drying test was also conducted to explore the evolution and formation mechanism of cracks in the laterite using slurry samples under natural hot-humid conditions. A three-dimensional strain measurement system was adopted to collect the moisture, displacement, strain, and crack of the soil. Then, a quantitative description was made on the evolution characteristics of crack morphology and strain field during dehumidification, thereby investigating the influence of water content on fracture morphology and strain field. The results show that: 1) Six stages were found in the evolution of dry shrinkage cracks on the surface of the soil sample. The cracks were formed in the later stages with the cracking surroundings from the previous stages. Specifically, the intersection angle of fractures was close to 90o in different stages. 2) Most soil was in the tensile state with a nearly 0.5% strain at the crack tip during the initial stage of crack development. The soil around the cracks gradually evolved into a compressive state, as the crack developed. Once all the cracks developed, the soil around the crack was totally in a compressive state. 3) The evolution of cracks was closely related to the limited water content. Specifically, the cracks on the soil surface began to rapidly develop, widen and extend, when the soil water content approached the liquid limit of 67.7%. The developing rate of crack began to slow down when the soil water content reached the plastic limit of 28.3%. Once the soil water content was less than the plastic limit of 18.8%, there was no obvious change of fracture, indicating that the fracture development was nearly completed. 4) The cracking time and width of early fracture exceeded those of later fracture in the process of fracture evolution. The displacement and strain varied at the different parts of the soil surface. The vertical shrinkage at the center of the soil block was greater than that at the edge, but the displacement and strain at the center of the soil block were much less than that at the edge. The finding can offer a great engineering reference to prevent geological diseases or environmental disasters in laterite areas.

       

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