Question

Consider the following statement
1. The ultimate bearing capacity of a footing on sand increase.
2. The settlement of the footing on sand increases with increase in its width.
Which of the above statements are correct?

• A. 1 only
• B. Both 1 and 2
• C. 2 only
• D. Neither 1 nor 2

Answer 1

The correct option is B Both 1 and 2

Following equation is used from Plate load test data for sands.

$q_f=q_p\frac{B_f}{B}$

Settlement of footing $\left(S_f\right)$ on sand increases with increase in its width $\left(B_f\right)$, can be explained as

$\frac{S_{f_1}}{S_p}={\left[\frac{B_{f_1}(B_p+0.3)}{B_p(B_{f_1}+0.3)}\right]}^2\left(for{1}^{st}footing\right)$

$\frac{S_{f_2}}{S_p}={\left[\frac{B_{f_1}(B_p+0.3)}{B_p(B_{f_2}+0.3)}\right]}^2\left(for{2}^{nd}footing\right)$

$\therefore \frac{S_{f_1}}{S_{f_2}}={\left[\frac{B_{f_1}(B_{f_2}+0.3)}{B_{f_2}(B_{f_1}+0.3)}\right]}^2={\left(\frac{1+\frac{0.3}{B_{f_2}}}{1+\frac{0.3}{B_{f_1}}}\right)}^2$

$If{B}_{f_2}>B_{f_1};\frac{S_{f_1}}{S_{f_2}}<1$

$\therefore S_{f_2}>S_{f_1}$

Hence settlement increases.