Nepal Subsoil

Site Subsoil Category

The site shall be classified into one of the following site subsoil categories.

Type I Rock or Stiff Soil Sites.

Sites with bedrock, including weathered rock with an unconfined compression strength greater than 500 kPa, overlain by less than 20 m of :

(a) very stiff cohesive material with an unconfined compression strength greater than 100 kPa, or
(b) very dense cohesion less material with N > 30, where N is the standard penetration (SPT) value.

Such sites will typically have a low amplitude natural period of less than 0.2 s.

Type II Medium Soil Sites

Sites not described as either Type I or Type III

Type III Soft Soil Sites

Sites where the depth of soil or a particular type exceeds the following values :

a) Cohesive Soils

Cohesive Soil Classification	Representative undrained shear strength (kPa)	Minimum Depth of Soil (m)
Soft	12.5-25	20
Firm	25-50	25
Stiff	50-100	40
Very Stiff	100- 200	60

contd.../

b) Cohesion less Soils

Cohesive Soil Classification	Representative SPTY(N)	Minimum Depth of Soil (m)
Loose	4 - 10	40
Medium Dense	10 - 30	45
Dense	30 - 50	55
Very Dense	> 50	60
Gravels	> 30	100

Such sites will typically have a low amplitude natural period greater than 0.6 s.