Abstract

The Mam Tor landslide is a kilometre‐long feature in shales and sandstones. The initial slope failure occurred over 4000 years ago as a rotational landslide that developed into a large debris flow at its toe. A road built across it nearly 200 years ago, and now closed, provides graphic evidence of continued movement of the slide mass; this has now been monitored for eight years. Current mean annual movement is up to 0.25 m; this increases greatly when winter rainfalls exceed thresholds of both 210 mm/month and 750 mm in the preceding six months. The most rapid movement is now taking place in a central zone of slide blocks that rest on a steep slip surface located at or close to the buried ground surface just downslope of the initial failure toe. Both the main upper mass of landslide blocks and the debris toe move more slowly over basal shears at lower angles of dip. Deep drainage of the central part of the landslide would be the most effective means of stabilization, but may not totally eliminate movement.

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