What will be the correct range of the standard penetration number (N) for a soil having unconfined shear strength in the range of 100 kN/m² to 200 KN/m² and its consistency said to be stiff?

Question

Question

This question was previously asked in

PGCIL DT Civil 5 May 2023 Official Paper

Answer 1

Explanation:

Standard penetration test gives an idea about the unconfined compressive strength of clayey soil.

N values	Unconfined Compressive Strength (kN/m²)	Consistency
< 2	<25	Very Soft
2 - 4	25 -50	Soft
4 - 8	50 - 100	Medium
8 - 16	100 - 200	Stiff
16 - 32	200 - 400	Very Stiff
> 32	> 400	Hard

Additional InformationStandard Penetration Test (SPT):

It is specially used for cohesionless soils. It is used to determine the relative density and the angle of shearing resistance of cohesionless soils.
It can also be used to determine the unconfined compressive strength of cohesive soils.
The standard penetration number is equal to the number of blows required for 300 mm of penetration beyond a seating drive of 150 mm.
lf the number of blows for 150 mm drive exceeds 50. it is taken as refusal and the test is discontinued.
Hence the standard penetration test is useful to measure the angle of shearing resistance of cohesionless soils, i.e Shear strength of sands.