Practice Question: Lateral earth pressure on retaining wall

---

---

Solution

The active earth pressure coefficient is given by:

\[K_a=\frac{1-{\mathrm{sin} {\varphi' }}}{1+{\mathrm{sin} {\varphi' }}}\]

\[K_a=\frac{1-{\mathrm{sin} 30\ }}{1+{\mathrm{sin} 30\ }}=0.33\]

 

Active earth pressure resultant is given by:

\[R_a=\frac{1}{2}K_a\gamma H^2\]

\[R_a=\frac{1}{2}\times0.33\times 120\times {18}^2=6415.2\ {lb}/{ft}\]

---