Fluorescent Dye Tracer Tests for Seepage Detection in Earthen Dams

Seepage and its control measures are important aspects during the design and construction stages of earthen dams. Despite the fact that all dams are designed to lose some water through seepage, it is always a matter of concern when water finds its way out through a weak area in the dam or works its way through the foundation or abutment, as it can pose a threat to dam safety. This seepage problem will lead to instability of embankments causing sloughing of slopes due to the rising pore water pressure and internal erosion which may further cause piping of embankments. Generally, the seepage analysis is carried out in earthen dams to analyse the phreatic line, the pore pressure within the dam or its foundation, the exit gradient at the downstream face of the dam and the amount of seepage flow that may pass through the dam’s cross sections. Excessive seepage in earthen dams could ultimately lead to its failure. Dam seepage detection often requires integrated use of different techniques. Among these, dye tracer techniques are often always necessary as they are an economic and proven tool providing a detailed perspective into dam seepage investigations. These non-destructive tracer tests facilitate in identifying seepage zone and probable path both qualitatively and quantitatively. The main objective of this paper is to highlight the significance of dye tracer techniques for identifying the seepage in earthen dams along with some important case studies carried out by CWPRS in Kota Barrage, Rajasthan; Rockfill Dam at Sardar Sarovar project, Gujarat; and Salaulim Dam, Goa. The application of these tracer techniques was useful in pinpointing the seepage prone zones, and suitable cost-effective remedial measures were recommended to mitigate the seepage.