脱湿路径下重塑膨胀土的体变修正与土水特征

Volume change correction and soil-water characteristics of remodeling expansive soil under dehydration path

采用南水北调中线工程河南南阳试验段重塑中膨胀土为试验土样,完成了5种不同初始干密度试样的脱湿试验和平行收缩试验,推导给出了更为合理的体积修正公式。试验结果表明,膨胀土脱湿路径下的体积收缩对其土水特征曲线(SWCC)影响较大,同一基质吸力状态下,体积修正后的试样饱和度/体积含水率明显高于修正前的饱和度/体积含水率,在吸力越高的区域,差别越明显。以Fredlund-Xing模型和试验结果为基础,建立了能考虑膨胀土体积变化的SWCC模型,并结合前人的试验成果深入分析了初始孔隙比对模型参数的影响规律。最后探讨了反映含水率-吸力-孔隙比关系的土水特征曲面的特性,考虑膨胀土试样体变修正时,孔隙比与含水率之间的函数关系为一个三次多项式,而不是线性关系。

A set of dehydration tests and shrinkage tests of the specimens with five different initial dry densities are conducted to investigate the effects of volume change on soil-water characteristics of remodeling expansive soil from the field test section in Nanyang, where the Middle Route of the South-to-North Water Diversion project of China passes. A more reasonable formula for volume change correction is derived. The test results indicate that the volume change of expansive soil specimens has significant influence on the soil-water characteristic curve （SWCC） under dehydration path. For the same matric suction, the saturation degree/volumetric water content of the specimens after volume change correction is greater than that before volume change correction, while the difference between them is more distinct in the high suction section. Based on the Fredlund-Xing model and the test results, a SWCC model, which can take the volume change of specimens during dehydration process into account, is developed, and the effect laws of the initial void ratio of the specimens on the parameters of the SWCC model are discussed. Moreover, the behavior of spatial curved surface showing the relationship among water content, suction and void radio is investigated. Considering the volume change of the specimens during dehydration process, the functional relationship between the void ratio and the water content is a cubic polynomial, not linear relation.