Measurement and estimation of unsaturated moisture properties of compacted soils and its application to analyses of embankment dams.

结合饱和和非饱和渗流的数值渗流分析可以准确预测堤防内的水流运动。这种方法易于处理渗水面和受降雨、入渗和蒸发影响的地表等边界面。分析中使用的有限元网格在瞬态流动和数值迭代过程中保持不变。采用相同的网格进行应力分析，可以直接评价渗流力和浮力对堤坝应力和稳定性的影响。研究的重点是发展1。一种测量非饱和土水分特性的有效方法；渗流和应力分析的数值格式。课题1设计并制作了小型压力传感器和放射性同位素法测量装置。实验结果表明，该装置数据可靠。参考已发表的数据，讨论了基于lrmay型方程的不饱和电导率模型。在课题二中，基于有效应力的概念，提出了大坝渗流、应力和稳定性分析的有限元方法。将该方法应用于某土坝蓄水和降压过程的稳定性评价。结果表明，坝体稳定性受坝体内主应力变化的强烈影响，而主应力变化的方式又受蓄水和落水过程中坝体力分布的支配。

A numerical seepage analysis which integrates both saturated and unsaturated flows can precisely predict water movement within embankment dams. The treatment of boundary surfaces such as seepage face and ground surfaces subjected to rainfall, infiltration and evaporation is easy with this approach. The finite element mesh used in the analysis remains invariant during transient flow and numerical iterations. Using the same mesh for stress analysis, it is possible to evaluate directly the effects of seepage forces and buoyancy on stresses and stability of embankment dams.Subjects focused in RESEARCH are to develop1.an efficient method for measuring moisture properties of unsaturated soils, and2.a numerical scheme for seepage and stress analysis.A measuring equipment using small-sized pressure transducers and Radio lsotope method is designed and set up in Subject 1. Laboratory experiments show that the equipment gives reliable data. Referring to published data, modeling of unsaturated conductivity based on lrmay-type equation is discussed. In the 2nd subject, a finite element method based on the concept of effective stress is developed for seepage, stress and stability analysis of dams. The procedure is applied to evaluate stability of an earthdam during reservoiring and drawdown. Numerical results show that the stability is strongly influenced by the change of principal stresses within the dam, and that the manner of this change is governed by the distribution of body force which occurs during reservoiring and drawdown.