Bulletin of the Geological Society of Malaysia, Volume 67, June 2019, pp. 113-118

Efficiency analysis of seepage of Baz Ali small dam, Kurram Agency using clay blanket and cut-off wall with sand filter

Arshad Ullah^1,*, Azman Kassim¹, Ishtiaq Alam², Muhammad Junaid¹, Izwan Shah Ahmad¹

1Department of Geotechnics and Transportation, School of Civil Engineering,
Universiti Teknologi Malaysia, 81310 Skudai, Johor Bahru, Malaysia
2Ministry of Planning, Development and Reform, Government of Pakistan, Pakistan
*Corresponding author email address: engrarshadswati@yahoo.com

Abstract: Seepage always eventuates through the foundation of all dams. The flow of water through the dam body generate seepage forces and endanger the dam stability due to piping. Controlling seepage after construction is quite difficult and an expensive job, hence proper practices should be adopted for seepage remediation in the designing stage. In order to investigate the more effective techniques among downstream (D/S) sand filter with upstream (U/S) clay blanket and cut-off wall, the Baz Ali small dam was analyzed using finite element approach SEEP/W 2D. The seepage behaviour through the dam was intuited by employing 1 m thick clay blankets on the upstream side with extending lengths of 50 m, 100 m, 150 m, 200 m, 250 m and 300 m. Furthermore, 5 m, 7.5 m and 10 m deep cut-off walls having 0.5 m and 1 m thickness were embedded for seepage mitigation. The seepage values obtained from SEEP/W 2D models were compared with each other. The SEEP/W 2D results and cost analysis show that clay blanket is more effective and an economical technique than a cut-off wall for tackling seepage issue. Hence, an upstream blanket of 100 m length is more efficient to diminish the seepage up to 58.65% in contrast to the base case without the remedial system.

Keywords: Seepage, D/S sand filter, U/S clay blankets, cost analysis

DOI : https://doi.org/10.7186/bgsm67201914