Case Study: Challenges of Earthen Cofferdam in Deep Excavations for Waterfront Structures-Video

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Venkat Ramana Pamu presents a case study on an earthen cofferdam built for an intake well near Mukhane Dam in Maharashtra. The design assumed clayey sand fill, but nearby conditions forced the team to use black cotton clay. The embankment was built across two seasons, submerged during monsoon, then raised over the softened submerged section. After rapid dewatering, part of the downstream slope slid.<br /><br />The analysis identified changed fill material, a weak interface between old and new embankment, and excess pore-water pressure from sudden drawdown as key causes. The team stopped pumping, widened and compacted the embankment, removed unstable soil, then resumed dewatering after river levels fell. The intake well was completed successfully.<br /><br />Key lessons include checking local fill availability during design, completing cofferdams in one season where possible, carefully managing dewatering in clayey embankments, and considering an upstream HDPE sheet to reduce seepage.

Keywords

earthen cofferdam

black cotton clay

rapid dewatering

embankment slope failure

intake well construction