Question

With a vertical point load on the surface when considering the vertical plane passing through the load, the stress gets reduced by 52.3% at a depth of

• A. 0.25 of unit length
• B. 0.5 of unit length
• C. 0.75 of unit length
• D. 1 of unit length

Answer 1

The correct option is D 1 of unit length

For the vertical plane passing through the load, the vertical stress is
${\sigma }_z=0.4775\frac{Q}{z^2}$
$\begin{array}{ccc}\text{z (unitlength)}& {\sigma }_z& \text{\% reduction}\\ 0.25& 7.64Q& \text{more than Q}\\ 0.5& 1.91Q& \text{more than Q}\\ 0.75& 0.84Q& \text{16\% reduction}\\ 1.0& 0.4775Q& \text{52.25\% reduction}\end{array}$