STUDIES ON HYDRAULIC PROPERTIES OF SOILS FOR DESIGN OF LEVEES

Abstract

The seepage erosion phenomenon, occurring through and below water retaining structures (Levees, dams) has been studied for decades. The seepage erosion mechanism in form of heave, piping and internal erosion is complicated and an adequate fundamental description has not yet been presented. Normally applied design criteria, in general are based on statistical methods. Another approach is to find a suitable criterion by laboratory testing on a model. The present study is aimed to study the various aspects of seepage erosion (Failure) in the form of heave, piping and internal erosion on different types of soils. This may help in predicting the mechanism of seepage erosion of the soil and provide necessary data, to a Geotechnical Engineer to account for in the design of earthen dams or levees. A well planned seepage failure test programme, to study the influence of various parameters as flow conditions, relative density and overburden pressure has been carried out on fine and medium sand. A piping test has been carried out to study the effect of density on internal stability on sandy gravels. Soil security test has also been conducted on clays soil to study the characteristic failure time and mode of failure. A new pinhole test for identifying dispersive soils has also been carried out on two different types of soil. The influence of compaction water content on erodibility have been investigated. Based on these study, it is observed from the seepage failure test that sand column collapses in quite different ways according to the flow conditions. The piping tests indicates that piping of fine particles occur at hydraulic gradient one fifth to half of the theoretical hydraulic gradient. The result of pinhole test indicates that the variation of compaction water content has no significant effect on the erodibility characteristic of soil.