Numerical Modelling of Lower Lias Rock Failures in the Coastal Cliffs of South Wales

by P. Davies, Bath Coll of Higher Education, Bath, United Kingdom,
A. T. Williams, Bath Coll of Higher Education, Bath, United Kingdom,
P. Bomboe, Bath Coll of Higher Education, Bath, United Kingdom,

Document Type: Proceeding Paper

Part of: Coastal Sediments


A model has been developed to evaluate slope failure in the interbedded limestone and mudstone Lower Lias series which outcrop for some 30 km in coastal South Wales. Computer simulation of the failure paths for steep cliff faces, with low bedding dip angles and steeply dipping joint sets running parallel and perpendicular to the cliff face, suggested several different scenarios. These include stepped failure, translation and toppling failure, for thick and thin strata in the presence/absence of cleft water. Failure risk is assessed using the overturning torque forces generated by the horizontal mass component and hydraulic forces induced by joint water pressures. The model assumes a rock prism delimited by the slope face, the failure surface and a tension zone descending along the joint set parallel to the cliff face. Various values were used to determine the critical distance of the tension zone from the cliff face controlling toppling torque force generation.

Subject Headings: Numerical models | Structural failures | Joints | Water pressure | Rocks | Failure analysis | Coastal environment | Cliffs | Wales | United Kingdom | Europe

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