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Ground type

Description of stratigraphic profile

Parameters

V_{s, 30}

N_SPT [blows/30 cm]

c_u [kPa]

A

Rock or other rock-like geological formation, including at most 5 m of weaker material at the surface.

> 800

-

-

B

Deposits of very dense sand, gravel, or very stiff clay, at least several tens of meters in thickness, characterised by a gradual increase of mechanical properties with depth.

360 - 800

> 50

> 250

C

Deep deposit of dense or medium-dense sand, gravel or stiff clay with thickness from several to many hundreds of meters.

180 - 360

15 - 50

70 - 250

D

Deposits of loose-to-medium cohesionless soil (with or without some soft cohesive layers), or of predominantly soft-to-firm cohesive soil.

< 180

< 15

< 70

E

A soil profile consisting of a surface alluvium layer with v_s values of type C or D and thickness varying between about 5 m and 20 m, underlain by stiffer material with v_s > 800 m/s.

S₁

Deposits consisting, or containing a layer at least 10 m thick, of soft clays/silts with a high plasticity index (PI > 40) and high water content.

< 100

(indicative)

-

10 - 20

S₂

Deposits of liquefiable soils, of sensitive clays, or any other soil profile not included in types A - R or S₁ d.