Assessing the suitability of filter materials

摘要

The water sepping through the dam and foundation will be drained off, if the shells or outer core on the upstream and downsream sides are highly pervious. Exit gradients are of primary concern since these can cause internal erosion and piping. when the shells are not adequately pervious, different types of drainage arrangements are provided. The drainage blanket must be pervious enough to drain off effectively and its desing should fulfill all the filter criteria as suggested by Karl Terzaghi. The two principal requirements for a satisfactory filter are that it must be pervious than the protected soil (core material) in order to act as a drain and that it must be fine enough to prevent particles of the soil to be prevented from migration into its voids. central Soil and Materials Researdch Station has been involved in many river valley projects to analyse the suitability of filter materials with the base materials. This paper presents in brief the current practice of filter deisng criteria and the suitability of filter materials proposed. used in respect of three hydraulic structures, viz. Pancheshwar-Multipurpose project, UP/Nepal, Sankosh Multipurpose project, Bhutan and Sawan Bhadon Dam project, Rajasthan, India.