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Discussion |
Department of Building and Civil Engineering, Liverpool Polytechnic
The recent landslipping in the Lyme Regis area has, as Mr Conway indicates, related to reactivation of reconstituted and ‘brecciated’ Lias (Lias Head) and Upper Greensand (Cretaceous Head) (Conway, this issue). This is exemplified by the current slippage of East Cliff, and that adjacent to Cobb Road in March 1977. However, not all the movements in the area are of this type, and I would like to present a short case study of a different kind of slip and to comment on the present situation at that site.
On 12 February 1962, the area of Lyme Regis now occupied by Lister Gardens, near the Cobb, slipped, severely damaging a number of properties including Cliff Cottage and Cliff House (Fig. 1). Regrading of the slope had been under-taken with a view to developing the site (Anon. 1962) and may have led to local oversteepening of the slope. Movement took place a few days after the completion of regrading work, with a large tension crack and subsequently a back scar developing in the slope (Fig. 2). A length of slope (almost 200 m) parallel to Marine Parade was affected.
A programme of remedial works was carried out, consisting of drainage and regrading of the slipped area of the slope, the construction of a large retaining structure at the toe (which now houses a parade of shops and part of the promenade), and a small retaining wall at the head of the slipped area. The regraded
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