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Geometrical simulation studies of coastal cliff failures in liassic strata, South Wales, U.K.
Author(s) -
Williams A. T.,
Davies P.,
Bomboe P.
Publication year - 1993
Publication title -
earth surface processes and landforms
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.294
H-Index - 127
eISSN - 1096-9837
pISSN - 0197-9337
DOI - 10.1002/esp.3290180805
Subject(s) - cliff , geology , geomorphology , landslide , thrust , infill , weathering , rockfall , series (stratigraphy) , tension (geology) , geotechnical engineering , paleontology , ecology , physics , classical mechanics , biology , thermodynamics , moment (physics)
Three numerical models of cliff failure have been developed, based on analyses of rockfalls along the 22 km Liassic coastline of the Glamorgan Heritage Coast, U.K. Detailed field investigation of the bucklandi (limestone dominated) and angulata (mudstone dominated) Lias series at four locations confirm the veracity of the models. Translation failure was correctly predicted at the mainly limestone buttressed cliff sites in the bucklandi and at locations where the angulata series formed a high proportion of the cliff mass. Toppling was predicted for vertical and overhanging cliffs with basal undercutting. The factor of safety reduces as the ratio of undercutting depth ( d ) to tension fracture distance ( D ) from the cliff face increases. Instability can be triggered by thrust forces generated by wave/tide impact, freeze/thaw and expansion/contraction associated with clay infill. Thrust forces can be modest, ranging from 1·7 to 2·7 MN m 2 , but can exceed the cross‐joint strength as weathering proceeds.