Problems of seepage/leakage in earth and masonry dams - Few case studies

After the independence, large number of masonry cum earth dams have been constructed in the country and in Gujarat State as well as,. being labour intensive and economically acceptable the composite dam construction has been widely adopted. These darns are in operation for last 30 to 40 years. In these dams, it has always been hard to achieve sufficient impermeability, even though certain preventive measures were taken as a part of original construction. Records of seepage through the body of darn as well as through the foundation for most of the dams are now available for analysis. Of late, few dams have posed the problems of excessive leakage through foundation and the body of dam. darn. Most of the post construction problems have occurred because of unsatisfactory performance of (i) joints within the body of the dam (ii) junction and/or (iii) foundation, resulting in seepage/leakage through these weak features. Seepage/leakage have sometimes been found coupled with appearance of surface cracks causing damages to masonry of different components of dam leading to major problems of sudden and excessive leakage. The junction between earth darn and masonry dam components such as abutment, foundation etc. is the vulnerable link. They are major sources for distress and damage to wrapround and piping along the interface. The main causes are (a) different stress-strain characteristics of adjoining materials and (b) practical difficulties iii achieving cll siren quality standards of workmanship at the junctions. The quality of workmanship is an important aspect for obtaining the required imperviousness of the dam body. It has been noticed that junction problems are more pronounced in minor and medium height projects than in major projects. Detection of actual cause and path of seepage and its remedial measures are found very difficult, time consuming, expensive and less effective if not properly treated.