RELIEF WELLS AS A SEEPAGE CONTROL MEASURE FOR DAMS AND LEVEES

Abstract

seepage through ombankinonts and their foundations create a number of problems. Uncontrolled sub-stratum pressure or under seepage may cause piping, progressive . of subsurface or '..k~avin of the top stratum. It may aid directly or indirectly in the failure of the structure itself. In order to have a controlled release of uplift pressures and undorsoopago, thoro are diff- oront typos of seepage control measures among them relief walls are also one, In spite of some disadva- ntagos and limitations of relief wells, they are best ti suited for the structures founded on deep stratified pervious foundations. This work aims at bringing out salient features of design, construction and maintenance of relief wells. Fundamentally for a good design, it is necessary to ost-imato the basic data as accurately as possible. Defini-tions and estimation of the basic data is therefore explained in brief before doalirg with actual design of relief wells in chapter II. In design it is necessary to got rosonaUy accurate results quickly computod rather than more elaborate mathematically exact solu- tions. Also design data has to be appliod properly to represent realistic field conditions , this t dup,11 ds on engineering judgomont. With this viowg simple design procedures are oxp Lined for design of relief wells.. For officiont functioning of relief wells, it is necessary that they should be constructed and maintained as par the standards sot for the roliof wells. These are explained in Chapter III • Every dam site has got its own goologjrcal and topographical features in addition to design pr obloms. To design a proper relief wells system the designer has to study the behaviour of relief wells on roxistirggpro jocts. Such study will yield more valuable guidance and it may help the D%signor to solve the problems unterud easily. In view of this, detailed discussion of some existing relief wells installations on z s y.tng projects has boon made in Chaptor IV. Commort shave been given at the end of each project based on writer's understanding of the problems and its solution. In conclusion if properly designed constructed and maintained relief walls offer a very 7ood solution for seepage control for structures founded on deep pervious foundations. Relief walls have proved to be successful for many dams both in India and other countries. It is hoped that this work will provide useful information for design, construction and maintenance of relief wells.