Rock types

General lithology

Susceptibility

Representative groups

Rock of any type, sedimentary or crystalline

Rigid soils with a thickness of less than 60 m to the rocky base, as long as the upper strata are composed of stable deposits of sand, gravel or hard clay

Impervious limestones, basalts, andesites, low degree of weathering, little fracturing, rocks with high resistance to shear, low groundwater level.

Very high

(0.76 - 1)

Basalts, diabases, gabbro

Andesite, diorite, porphyry, granites

Serpentinite, riodacite, rhyolite, marbles, compact limestones

Stable deposits of non-cohesive soils or hard clays when their depth to the rocky base exceeds 60 m and the upper strata are composed of sands, gravels or hard clays

High degree of weathering of the above mentioned rocks and massive clastic sedimentary rocks, low resistance to shear, shear fracture.

high

(0.51 - 0.75)

Permeable limestones,

Schists, clastic metamorphites, fissured igneous

Gaps and compact conglomerates, cohesive sandstones

Deposits of soft or medium clays and sands with thicknesses of 10 m or more with or without the presence of intermediate layers of sand or other non-cohesive soils

Poorly consolidated rocks or soils, considerable weathering of sedimentary, intrusive and volcanic rocks, fluctuations in the water table.

Moderate

(0.26 - 0.5)

Vulcanogenic-sedimentary rocks

Compact clays

Massive clayey rocks with jointing, jointed conglomerates with medium cohesion

Clay and soft sand deposits with thicknesses greater than 12 m

Quaternary unconsolidated soils, clay fill, unconsolidated pyroclastic and fluvio-lacustrine soils, surface water tables.

Come down

(0 - 0.25)

Marls, silts, sandstones

Sandy clay soils,

Marsh, fluvial-lacustrine, alluvial deposits