某水利工程泥化夹层的形成及变化趋势的研究

在我国大规模的水利水电工程建设中,遇到了各种各样的工程地质问题,其中软弱夹层问题,便是经常碰到的重大技术课题之一。由于软弱夹层的影响给工程造成许多危害:被迫停工,增加投资,改变设计方案,延长施工周期,降低设计标准使用。在国外不少工程由于没有进行深入的工程地质勘察和研究,潜伏的软弱夹层的危害,曾导致发生了数十起的垮坝事件。如美国圣佛兰西重力坝、奥斯丁重力坝、德克萨斯重力圬工坝、俄亥俄河26号坝、印度的提格拉坝等的失事,以及意大利瓦依昂坝水库的巨大滑坡。

OCCURRENCE OF ARGILLITIZATION INTERBEDS AND THE TREND OF ITS CHANGES IN A CERTAIN CONSTRUCTION PROJECT

One of the important technical topics for hydroelectric and water conservancy constructions is the engineering geology problem involving the presence of incompetent interbeds in construction-sites, which usually brings about great damage to engineering projects. This paper deals with the structural features of argillitization interbeds in clay-rocks present in a certain hydroelectric construction, and the results obtained in mineralogical, physico-chemical and hydro-physical investigation of clay minerals. Our study on, the occurrence of argillitization interbeds includes both field observations and laboratory work involving the use of polarizing microscope as well as scan electron microscope. On the basis of these studies the present paper presents the changing trend of the argillitization interbeds under the long-term action of seepage pressure water since the impounding of the reservoir. It is imperative to know whether the clay-rock involved would be argillited under the long-term action of seepage pressure water and whether the argillitization clay-rock would be further worsened under the same conditions. These are in fact connected with engineering geology prediction for the argillitization of clay-rock.The research-results show that the argillitization interbeds are derived from the primary clay-rock interbeds. Thai is to say, argillitization interbeds have resulted from the change in composition, behaviour and physico-chemical nature of clay-rock under the action of tectonic stress and long-term effect of ground water, which have produced interformational dislocations during the structural change of clay-rock, and subsequent geologic process. Moreover, the present writers point out that the argillitization clay-rock depends not on the type of clay minerals and the degree of their activity but on whether the rock structure, especially the intergranular bond has suffered destruction. Apparently, the different destruction products, the behaviour of argillitization materials and the degree of argillitization are associated to a great extent with the various types of clay minerals.