含砂黏土蒸发开裂特性试验研究

Experimental Study on the Evaporation Cracking Characteristics of Sandy Clay

摘要:

为明确含砂条件对黏土蒸发开裂的影响规律,通过室内试验模拟干旱环境,使黏土试样发育干缩裂隙;通过数字图像处理技术对形成的裂隙进行定量分析,基于裂隙发育的阶段性形态特征,建立土体干缩裂隙分级命名体系,探究不同温度(40~60 ℃)、不同掺砂率(0%~30%)以及不同掺砂粒径(0.0~2.0 mm)对黏土干缩开裂的影响规律。试验结果表明:(1)含砂黏土干缩裂隙的发育可以分为三个阶段:形成阶段、发育阶段和稳定阶段。砂粒通过降低黏土的水分蒸发速率,减小了黏土表面应力场的变化幅度,延缓黏土裂隙的形成和发育;由于砂粒持水能力弱于黏土,裂隙容易在砂粒和黏土之间形成。(2)黏土基质中掺入砂粒可显著抑制裂隙发育,且随着含砂率的提高,其抑制效果逐渐增强;随着砂粒粒径的增大,砂粒对黏土发育裂隙的抑制作用呈现先增强后减弱的趋势,在试验条件下存在最优粒径范围(0.5~1.0 mm);砂粒的阻裂效应随温度升高而增强。

Abstract:

To clarify the influence of sand incorporation on the evaporation cracking behavior of clayey soils, indoor experiments were conducted to simulate arid environments to induce the development of desiccation cracks in clay samples. Quantitative analysis of the formed cracks was performed using digi-tal image processing techniques. Based on the staged morphological characteristics of crack evolution, a classification nomenclature system for soil desiccation cracks was established. The present study investigated the effects of temperature (40 to 60 ℃), sand content (0% to 30%), and sand particle size (0 to 2.0 mm) on clay desiccation cracks. The experimental results demonstrate that: (1) Desiccation crack development in sandy clay progresses through three distinct stages: formation, development, and stabilization. Sand particles reduce the rate of moisture evaporation in clay, thereby diminishing fluctuations in the surface stress field and decelerating the crack initiation and development. Sand particles exhibit inferior water-holding capacity compared to clay particles, leading to the preferential formation of cracks at the interfaces between sand particles and clay particles. (2) Incorporating sand into the clay matrix significantly suppresses crack development, with this effect strengthening as the sand content increases. The crack-suppressing efficacy of sand particles exhibits a first increasing then decreasing trend as the particle size increases, with an optimal particle size range (0.5 to 1.0 mm) determined under the experimental conditions. Furthermore, the crack-suppressing effect of sand particles amplifies with rising temperatures.