Question

A plate load test was conducted using 30cm diameter plate on a subgrade during monsoon which is soaked . The load settlement curve was drawn and the following are the salient points on the curve. The modulus of subgrade reaction for standard plate in kg/cm${}^3$ is
$\begin{array}{ccccccccc}\text{Mean}& 0& 0.24& 0.5& 0.78& 1.0& 1.25& 1.5& 1.75\\ \text{settlement in}& & & & & & & & \\ \text{mm}& & & & & & & & \\ \text{Load in kg}& 0& 450& 890& 1150& 1350& 1430& 1580& 1650\end{array}$

• A. 16.18
• B. 7.66
• C. 17.87
• D. 6.93

Answer 1

The correct option is D 6.93

Modulus of subgrade reaction is calculated for the pressure caused because of the load corresponding to a settlement of 1.25 mm
=1430 kg
Pressure =$p=\frac{1430}{\pi {15}^2}=2.023\frac{kg}{c{m}^2}$
$K_1=\frac{2.023}{0.125}=16.18\frac{kg}{c{m}^2}$
Standard plate diameter = 70cm
Modulus of subgrade reaction corresponding to standard plate size
$=\frac{k_1{a}_1}{a}=\frac{16.18\times 30}{70}=\frac{6.93kg}{c{m}^3}$