重塑粘性土的基质吸力与土水分及密度状态的关系

RELATION OF MATRIC SUCTION WITH MOISTURE STATE AND DENSITY STATE OF REMOLDED COHESIVE SOIL

非饱和土的基质吸力与其中水–气体系的温度、孔隙水的密度和孔隙气的相对湿度有关。测试了 23 组不同水分状态和密度状态的重塑非饱和粘性土三轴试验土样的温湿度,计算了相应的基质吸力。数据分析表明: 基质吸力与干密度的关系在不同的含水量段具有不同的特点;基质吸力与含水量呈强非线性关系;在土的水分状态和密度状态空间,基质吸力的分布为一变形的 W 型折曲面。该曲面左翼陡立上翘,位于低水分状态,表征强非饱和土,右翼水平伸展,位于高水分状态,表征弱非饱和土,中心部位是一个“Λ”型折面,位于中等水分状态,表征典型非饱和土。首次提出了孔隙充水结构的概念,藉以从孔隙结构和毛细凝结两方面来准确理解非饱和土的水气界面效应,从而利于认识和把握非饱和土中基质吸力的变化规律。

Matric suction is relevant with temperature of water-air system, density of pore-water, and relative humidity of pore-air of unsaturated soil. The values of temperature and relative humidity of 23 groups triaxal experimental specimens within different moisture states and density states of a kind of remolded unsaturated cohesive soil are measured through thermo-hygrometer, and then the associated matric suction are computed. Data analysis shows that relation between matric suction and density at different moisture states is of different characteristics. Relation between matric suction and water content is notably nonlinear. Distribution of matric suction looks like a transformed W-type flex surface in the moisture and density state space, in which the axial plan is parallel to the axis of dry density. Its left wing located in the low moisture state steeply raises and presents strong unsaturated soil, the right wing located in the high moisture state levelly stretches and presents weak unsaturated soil, the center part located in the middle moisture state is of a Λ type fold and presents typical unsaturated soil. Water-filling pore structure as a new concept has been offered, by which the water-air effect of unsaturated soil can be understood more accurately upon two aspects including pore structure and capillary condensation, so that the variation law of matric suction of unsaturated soil can be suitably recognized.