THE PERFORMANCE OF A SINGLE ROW OF SPACED BORED PILES TO STABILISE A GAULT CLAY SLOPE ON THE M25

Following extensive TRL research on the topic, a single row of bored piles spaced at intervals was selected by the HA Maintaining Agent for the remediation of a failed cutting slope on the A12 Colchester Bypass. This London Clay slope has had a history of failures and been previously reinstated, but failed again by deep-seated slippage in the underlying clay. A more permanent structural solution was therefore sought by using the piling technique to stabilise the slope. The performance of the slope and piles was monitored both during construction and over the first two years in service. Instrumentation was installed to monitor the subsurface lateral movements of the ground and piles, the distribution of bending moment in the piles, and the pore water pressure regime in the remediated slope. This report describes the instrumentation and interprets the monitoring data. The implications of the findings are discussed with a view of improving the design guidance for future construction of a similar type. (A)