基于应变能密度映射的黄土结构性参数研究

Study on structural parameter of loess based on the mapping of the strain energy density

岩土体结构的破坏是由于施加能量超过变形能阈值所造成,基于能量的结构性参数更有利于反映结构性的本质特征。对不同含水状态,不同干密度的延安桃花山原状与压实重塑黄土进行了侧限压缩试验,发现孔隙比e与竖向压力P在ln(1+e)-lg P双对数坐标系内有良好的分段线性关系。在此基础上,基于应变能密度理论,推导提出了侧限压缩条件下的结构性参数映射能,并将该参数推广至复杂加载条件。进一步通过多个区域内,原状与重塑,不同含水率,不同干密度,不同埋深深度,不同粒度土体的侧限压缩试验结果,以及不同含水率土体的等向压缩试验结果,对提出结构性参数的合理性进行了验证。结果表明提出的结构性参数映射能物理意义明确,且能准确地定量表征不同状态,不同试验条件下土体的结构性。

The destruction of natural soils occurs when the external loading energy is greater than the limit deformation energy of the soils,thus,a structure parameter in terms of the deformation energy is more suitable to describe the essential characteristic of soil structure. The confined compression tests were conducted on compacted remolded and undisturbed loess samples with various water contents and dry densities from the Taohua Hill,Yan’an city. Test results suggest that there is an obvious piecewise linear relationship between the void ratio e and the vertical pressure P in ln(1+e)-lg P bi-logarithmic coordinate system. Based on this,a structure parameter in terms of the mapping energy was derived according to the strain energy density theory,and further extended into complex loading conditions. Moreover,the verification of the proposed parameter was carried out based on the oedometer tests on remolded and undisturbed soils with different water contents,dry densities,burial depths and particle size distributions,as well as the isotropic compression tests with various water contents. The results show that the proposed parameter has a clearly physical meaning and is able to represent the soil structure quantitatively and accurately under diverse experimental conditions.