Type of Subsoil - EN 1998-1
The type of subsoil reflects the influence of local conditions on seismic loading. According to the EN 1998-1 standard we distinguish the following types: A - E, S1 and S2 with properties specified in table below.
Type of subsoil from seismic load point of view according to EN 1998-1:
Description of stratigraphic profile
NSPT [blows/30 cm]
Rock or other rock-like geological formation, including at most 5 m of weaker material at the surface.
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
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
Deposits of loose-to-medium cohesionless soil (with or without some soft cohesive layers), or of predominantly soft-to-firm cohesive soil.
A soil profile consisting of a surface alluvium layer with vs values of type C or D and thickness varying between about 5 m and 20 m, underlain by stiffer material with vs > 800 m/s.
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.
10 - 20
Deposits of liquefiable soils, of sensitive clays, or any other soil profile not included in types A - R or S1 d.
EN 1998-1: Design of structures for earthquake resistance - Part 1: General rules, seismic actions and rules for buildings, (2006).