Inclined Back and Backfill

Q. Which of the following assumption(s) is/are 'INCORRECT' regarding Rankine's earth pressure theory?

1. The soil is dry and cohesionless

2. The back of retaining wall is rough and vertical

3. The ground surface is plane which may be horizontal or inclined

1. 1 and 2
2. 2 only
3. 2 and 3
4. 3 only

Q. A retaining wall of height H with smooth vertical backface supports a backfill inclined at angle $\beta$ with the horizontal. The backfill consists of cohesionless soil having angle on internal friction $\varphi$. If the active lateral thrust acting on the wall is $P_a$ which one of the following statements is TURE?

1. $P_a$ acts at a height H/3 from the base of the wall and at an angle $\beta$ with the horizontal
2. $P_a$ acts at a height H/2 from the base of the wall and at an angle $\varphi$ with the horizontal
3. $P_a$ acts at a height H/2 from the base of the wall and at an angle $\beta$ with the horizontal
4. $P_a$ acts at a height H/3 from the base of the wall and at an angle $\varphi$ with the horizontal