Question

Refusal of standard penetration test occurs when the sampler penetrates ________

(a) less than 2.5cm under 50 blows

(b) less than 2.5cm under 20 blows

(c) less than 2.5cm under 10 blows

(d) less than 2.5cm under 5 blows

I got this question in a job interview.

I'd like to ask this question from Geophysical Methods topic in division Stabilisation of Soils, Site Investigation and Sub – Soil Exploration of Geotechnical Engineering II

Answer 1

Right answer is (a) less than 2.5cm under 50 blows

The explanation is: In standard penetration test, the refusal has is said to have been reached when the sampler penetrates less than 2.5cm under 50 blows. In very fine, silty, saturated sand, an apparent increase in resistance occurs.