Practice Question: Rankine Active Pressure on Cantilever Wall

---

---

Solution

Answer: D) 2.3 k/ft

Total Height of Wall:
\[H=8\ ft+2.5\ ft=10.5\ ft\]
Effective Friction Angle:
\[\phi=29°\]
Unit Weight of Soil:
\[\gamma=120\ pcf\]
Rankine Active Earth Coefficient:
\[K_a=\tan^2{\left(45-\frac{\phi}{2}\right)}\]
\[K_a=tan^2(45°-29°/2)=0.35\]
Active Earth Pressure Resultant:
\[P_a=\frac{K_a\ \gamma{\ H}^2}{2}\]
\[P_a=\frac{(0.35)\ (120\ pcf){(10.5\ ft)}^2}{2}=2315.25\ lb/ft\]

\[P_a=2.3\ k/ft\]
 

---