Evaluation of Slope Stability Failure on Reclamation Bund

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The paper examines two slope failures in an 11 km perimeter bund built for a container terminal reclaimed from the sea on the western coast of India. The site is underlain by very soft to soft marine clay, up to about 24 m thick. Because the clay is prone to settlement and failure under heavy loading, the project used prefabricated vertical drains, preload, staged construction and geotextile reinforcement.<br /><br />Slope stability was assessed using Slope/W and the Morgenstern–Price method. Construction was planned in stages, with pauses intended to allow excess pore pressure to dissipate and the clay’s shear strength to increase. Settlement, pore pressure and lateral movement were monitored, and field investigations—including vane shear tests and additional boreholes—were used to check soil strength.<br /><br />The first failure occurred after surcharge placement beside a temporary perimeter bund that had not been included in the original design. Probable contributing factors were excavation near the embankment toe, inadequate berm width and insufficient pauses between filling stages. The response was to identify and design temporary bunds, provide adequate berms, limit filling to 0.5 m per day, and verify strength gains before proceeding with each stage.<br /><br />The second failure occurred during final-stage surcharge placement. Investigation showed that the clay’s achieved shear strength was below the value assumed in design; additional strength testing had not been completed before advancing. The design was revised using measured strength, intermediate pauses were extended, and the final surcharge elevation was reduced by 750 mm.<br /><br />The cases demonstrate the importance of accounting for temporary works and actual ground conditions, controlling surcharge placement, and confirming strength gain before each construction stage.

Keywords

slope failure

marine clay

perimeter bund

prefabricated vertical drains

preload surcharge

staged construction

Morgenstern-Price

slope stability

geotextile reinforcement

settlement monitoring