论文部分内容阅读
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S_r=85%)时的CT数M_E值均较干态(饱和度S_r=25%)时的M_E值大;湿态和干态的M_E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。
In order to study the evolution law of the mesostructures of shallow expansive soils during the wet-dry cycle, CT-CT was developed. Under different pressures, the original samples of Nanyang expansive soils and their remolded soil samples were subjected to multiple wet-dry cycles, and CT scanning was performed on the samples after each drying and humidification. Microstructure change of specimen during cycling. The results show that in the wet-dry cycle, the expansion and shrinkage of soil samples are relatively large. After three times of wet-dry cycles, the volume of soil samples under the same saturation basically does not change any more. Both humidification and drying can make original expansive soil And its remolded soil structure damage, after the first drying, soil samples that have significant cracks; with the number of wet and dry cycles, soil samples continue to carry out cracks, soil structure damage accumulation; upper load on the crack development Which will affect the development of fractures and the shape of the fractured network. The fractures of undisturbed expansive soils are developed around the first major fractures formed, whereas the fractures of remolded expansive soils are turtle-shaped or radial. The undisturbed expansive soils and The values of M_E of the remolded soils in the wet state (S_r = 85% saturation) were all higher than those in the dry state (saturation S_r = 25%). The values of M_E in the wet and dry The number of dry cycles showed an approximate linear change, the slope of the former was relatively gentle, while the latter was steeper. Based on the CT data, the mesostructural parameters of expansive soils were defined, and the quantitative description of microscopic structure parameters of expansive soils and samples Saturation, wet-dry cycles and the load of the mathematical table Style, predictions and experimental data closer.