黄土的构度及其与粒度、密度、湿度之间的关系

土的粒度、密度、湿度和构度是其固有的物质组成和状态特性指标,用来描述土的力学性质及其变化规律。土的构度是其结构性的定量描述指标,它不仅与土物质组成和存在状态的粒度、密度和湿度有关,而且与土骨架结构中土粒空间排列的组构和粒间联结特征有本质的联系。土骨架结构的土粒排列和粒间联结具有抵抗外荷作用的可稳性和遭受破坏的可变性,从比较黄土结构的可稳性和可变性出发,建立的构度指标实质上包括了原状黄土与其饱和条件下抗压强度比较确定的浸水灵敏度及原状黄土与重塑黄土抗压强度比较确定的扰动灵敏度。揭示黄土具有浸水灵敏度随含水率增大呈显著衰减的变化规律和不同含水率黄土的扰动灵敏度基本保持不变的特征。通过黄土构度随含水率和塑限差值的变化规律,构度随塑限、液限的变化规律,以及构度随液性指数的变化规律分析,揭示了构度与粒度、密度、湿度的之间的本质联系。通过黄土构度与液性指数、干密度和孔隙比表征的综合物理特征量之间的关系分析,揭示了干密度相近条件下黄土构度随综合物理特征量的单调变化规律。论证了黄土构度指标的可靠性与合理性。

Structural index of loess and its relation with granularity,density and humidity

The granularity, density, humidity and structure of soil are the natural indexes of its components and state behaviors, which can be used to describe its mechanical property and variation law. The structural index is a quantitative parameter of structure. It is related with the granularity, density and humidity of soil components and state behaviors and has an essential relationship with the fabric arranged with soil particles and the connection between soil particles. Both the fabric and connection have the steadiness to resist external loads as well as the variability under damage loads. The structural index is established from the steadiness and variability of loess structure in terms of the product of the ratio of intact to remolded sample unconfined compressive strengths (UCS) and the ratio of intact to saturated sample UCSs. It essentially covers water-immersion and load-disturbance sensitivities, and reveals their variation laws. By analyzing the relationships between the structural index and the difference between natural water content and plastic limit, liquid limit and liquidity index, the essential relations of the structural index with the granularity, density and humidity are revealed. In addition, a composite physical index in terms of liquid limit, dry density and void ratio is proposed to study its influence on the structural index. The results show the structural index of loess has a monotonic relation with the composite physical index under approximate dry densities. Thereby, the reliability and reasonableness of the structural index of loess are further verified.