Question

The standard penetration resistance value obtained in a deep deposit of sand at a depth of 6.0 m was 28. The unit weight of sand is $18.0kN/m^3$. What is the corrected value of number of blows for overburden pressure?

• A. 60
• B. 57
• C. 59
• D. 55

Answer 1

The correct option is D 55

(d) The effect of overburden pressure on SPT value may be approximated by the equation

$N=n\times \left(\frac{350}{\sigma +70}\right)$

where $\sigma$ is effective overburden pressure in $kN/m^2$ not exceeding $280kN/m^2$

$But\sigma =\gamma H=18\times 6=108kN/m^2$

$\therefore N=28\times \left(\frac{350}{108+70}\right)=55$