Secant Pile Wall for Cut off at Sundilla Barrage-Paper

Paper

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The paper describes the use of a secant pile wall as a seepage cut-off beneath Sundilla Barrage in Telangana, India—a novel application of a system more commonly used to retain soil in basements and excavations.<br /><br />A barrage creates a difference in water levels upstream and downstream, driving seepage through the foundation. If this flow carries soil particles downstream, piping can develop and threaten the structure. Cut-off walls lengthen the seepage path and reduce the hydraulic gradient; vertical cut-offs are considered more effective than increasing the horizontal path alone.<br /><br />At Sundilla, two cut-off walls were installed, one at each end of the barrage’s 89 m-wide base. The barrage is 1,344 m long, with a high flood level 13.63 m above its crest. Its design discharge is 57,000 cubic metres per second, and the estimated scour depth is 19.43 m.<br /><br />The wall consists of overlapping piles installed in sequence. Alternate piles are plain-concrete “soft” piles, installed first; reinforced piles are then bored partly through the adjacent plain piles and concreted around reinforcement cages. The reinforced piles provide the principal structural resistance, while the plain piles contribute to the continuous wall. At Sundilla, reinforced piles used M30 concrete and plain piles used M20. Guide walls helped ensure alignment and verticality.<br /><br />Secant pile walls can be installed with conventional piling equipment, avoiding some of the heavy equipment required for diaphragm walls. Construction of the Sundilla cut-off walls was complete while the barrage superstructure was still in progress. The paper focuses on construction and identifies this project as a distinctive use of secant piles for barrage seepage control.

Keywords

secant pile wall

seepage cut-off

barrage foundation

piping prevention

cut-off wall

Sundilla Barrage

Telangana India

seepage control

overlapping piles

hydraulic gradient