摘要:
为了研究浅层膨胀土的细观结构在湿干循环过程中的演化规律,研制了可以进行CT扫描的CT-固结仪。在不同压力作用下对南阳膨胀土的原状样及其重塑土样进行多组多次湿干循环试验,并对每次烘干和增湿稳定后的试样进行CT扫描,跟踪观察湿干循环过程中试样的细观结构变化。结果表明:在湿干循环中,土样的膨胀量和收缩量都比较大,经历三次湿干循环之后,相同饱和度下土样体积基本不再变化;增湿和干燥都能使原状膨胀土及其重塑土的结构损伤,第一次烘干之后,土样即产生明显裂隙;随着湿干循环次数的增加,土样裂隙继续开展,土样结构损伤发生累积;上部荷载对裂隙开展有一定抑制作用,并影响裂隙的发育和裂隙网络的形状;原状膨胀土的裂隙围绕第一次形成的主裂隙发育,而重塑膨胀土的裂隙呈龟背状或辐射状;原状膨胀土及其重塑土在湿态(饱和度Sr=85%)时的CT数ME值均较干态(饱和度Sr=25%)时的ME值大;湿态和干态的ME值均随湿干循环次数呈近似线性变化,前者的坡度比较平缓,后者则较陡;基于CT数据定义了膨胀土的细观结构参数,提出定量描述湿干循环过程中膨胀土细观结构参数与试样饱和度、湿干循环次数及所受荷载的数学表达式,预测结果与试验资料比较接近。
Abstract:
In order to study the meso-structural evolution of expansive soil during wetting-drying cycles, the CT-consolidation apparatus was developed; A number of tests of wetting-drying cycles were carried out for intact and remolded expansive soil under loading condition, and CT scanning was taken on samples after each wetting and drying finished.The research results indicate that during wetting-drying cycles the amount of shrinkage and swell of samples are large. After three times of wetting-drying cycles, the volume of soil samples under the same saturation is no longer changed. Both wetting and drying can induce the structural damage of expansive soil samples. After first drying, cracks generate on expansive soil samples obviously. Along with the experiment, cracks continue to expand, soil damage accumulate. The upper load has some inhibitory effect on the crack development and influences the development of the crack and the shape of the crack-network. The crack of undisturbed expansive soil is developed around the first formation of main crack while remolded expansive soils crack is a turtleback. The CT data ME of samples are bigger in saturation of 85% than in saturation of 25%. TheCT data ME of samples in both wet and dry states are all approximately linear with the number of wetting-drying cycles and the slope of the former is relatively flat, while the latter is steeper. Meso-structural evolution parameters are defined, and the relationship between meso-structural evolution parameters and saturation, wetting-drying cycle times is proposed, the predicted results are close to the experimental data.
百度学术
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