SLOPE FAILURE TYPES:

Translational slide

traslational

SLOPE FAILURE NAME:

Translational slide

DEFINITION:

Consists of a non – circular failure which involves motion on a near – planar slip surface (DIKAU et al., 1996).

MAIN CHARACTERISTICS:

The movement appears to be largely controlled by surfaces of weakness (faults, bedding lines...). In case of the Giant’s Causeway almost all translational slides occur along the line between the substratum and superficial debris or soils. They therefore tend to be shallow and mainly affect thin material (clays, silts and sand) with some coarser stones. If the slope is not too steep debris remains near the scar, and do not lose its previous shape. In the case of steep and long slopes debris can break up, gain speed and turn into a complex failure.

CAUSES:

High moisture content (local possitive pore water pressure) is the main factor, usually associated with prolonged rainfall. Such rainfall also activates the subterranean percolation of water, mainly along the contact between the substratum and debris, usually focused on ‘percolines’. Finally natural or human induced undercutting can dramatically reduce debris’ strength and encourage failure.

AREAS PRONE TO FAILURE:

Highly weathered areas, incluiding palaeosoils, or till covered areas, tend to develop thicker debris mantles and soils. These are the most likely areas for this kind of failure.

OCCURRENCE:

During or after frequent and / or continuous rainfall events.

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