Stabilisation of Stanton Lees landslip using pile retaining wall solution

Abstract

A landslip in the village of Stanton Lees, Derbyshire, UK, was reported in November 2000 following a period of torrential rainfall. The slip resulted in the gradual and progressive down-slope movement of a relatively steeply sloping embankment that had supported an existing gabion retaining wall and a minor road which was subsequently closed to vehicular traffic. This paper describes the site, an interpretation of the ground conditions, onsite monitoring data and the design and construction of the remedial works necessary to return the road to serviceability. The landslip occurred due to the superficial deposits moving over the weathered bedrock under conditions of elevated groundwater following a period of heavy rainfall. Autumn 2000 was the wettest season since local records began in 1870. A stability analysis indicated that the embankment slope was at limiting equilibrium and was particularly sensitive to relatively minor fluctuations in the groundwater levels. The remedial works involved replacing the existing gabion wall with a cantilevered, 600-mm diameter, bored pile retaining wall that comprised two rows of piles, staggered in plan arrangement, and located along the southern verge of the road.