Abstract: The backfilling of an existing excavated foundation pit was required to address the safety concern since the design life of an exposed deep excavation was exceeded. This paper presents a case history of back filling of a fully excavated foundation pit with exposure of six (6) years. The observed distresses of this deep excavation were cracks behind the supporting structure; spalling of shotcrete covering the soldier piles; localized shallow failures on back slopes behind the reinforced concrete waler beams; rusted anchor and anchor plates and overgrown vegetation at the bottom of excavation. Since there were no anticipated further construction activities for this project, it was decided to backfill the excavated area using rakers and soil berms to provide back pressure. During the backfilling operation, the deformations of the existing supporting structure were monitored, and the monitoring results suggested that the method used in the backfilling was effective and the construction was safe.

Key words: Soil improvement for the Deep Excavation, Backfilling Backpressure