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:
Ground type | Description of stratigraphic profile | Parameters | ||
Vs, 30 | NSPT [blows/30 cm] | cu [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 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. | |||
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. |
Literature:
EN 1998-1: Design of structures for earthquake resistance - Part 1: General rules, seismic actions and rules for buildings, (2006).