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

结合饱和流和非饱和流的数值渗流分析可以精确预测堤坝内的水运动。这种方法可以很容易地处理渗流面和遭受降雨、渗透和蒸发的地表等边界面。分析中使用的有限元网格在瞬态流动和数值迭代期间保持不变。使用相同的网格进行应力分析，可以直接评估渗流力和浮力对堤坝应力和稳定性的影响。研究重点是开发1.非饱和土水分特性的有效测量方法，2.渗流和应力分析的数值方案。课题1设计并建立了一种采用小型压力传感器和无线电同位素法的测量装置。室内实验表明该装置提供了可靠的数据。参考已发表的数据，讨论了基于lrmay型方程的不饱和电导率建模。在第二个主题中，开发了一种基于有效应力概念的有限元方法，用于大坝的渗流、应力和稳定性分析。该程序用于评估土坝在蓄水和水位下降期间的稳定性。数值结果表明，稳定性受到坝内主应力变化的强烈影响，并且这种变化的方式受蓄水和水位下降期间发生的体力分布的控制。

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.