Passive Pressure I

Q. Why are weep holes provided at the back of retaining walls?

1. To reduce the active earth pressure on the walls.
2. To reduce the build-up of hydrostatic pressure.
3. To provide better compaction.
4. To increase the passive earth pressure.

Q. The inclination of failure plane behind a vertical wall filled with cohesionless soil $(\varphi ={36}^0)$ in passive earth case from vertical is

1. ${27}^0$
2. ${36}^0$
3. ${45}^0$
4. ${63}^0$

Q. A retaining wall with vertical back retains a cohesionless dry backfill at an inclination of $\beta$ with the horizontal. The backfill has an angle of internal friction $\varphi ,$ unit weigth $\gamma$ and height of the wall is $H.$ The passive earth pressure on the wall is given by (where $P_p$= Total passive earth pressure)

1. $P_p=\frac{1}{2}\gamma H^2\cos \beta \left[\frac{\cos \beta -\sqrt{{\cos }^2\beta -{\cos }^2\beta }}{\cos \beta +\sqrt{{\cos }^2\beta -{\cos }^2\beta }}\right]$
2. $P_p=\frac{1}{2}\gamma H^2\cos \beta \left[\frac{\cos \beta -\sqrt{{\cos }^2\beta +{\cos }^2\beta }}{\cos \beta +\sqrt{{\cos }^2\beta +{\cos }^2\beta }}\right]$
3. $P_p=\frac{1}{2}\gamma H^2\cos \beta \left[\frac{\cos \beta +\sqrt{{\cos }^2\beta -{\cos }^2\varphi }}{\cos \beta -\sqrt{{\cos }^2\beta -{\cos }^2\varphi }}\right]$
4. $P_p=\frac{1}{2}\gamma H^2\cos \beta \left[\frac{\cos \beta +\sqrt{{\cos }^2\beta +{\cos }^2\varphi }}{\cos \beta -\sqrt{{\cos }^2\beta +{\cos }^2\varphi }}\right]$

Q. Statement (I): For a cantilever retaining wall. Rankine's theory of earth pressure may be used.
Statement (II): For a retaining wall with smooth vertical back, Rankine's theory is appropriate.

1. Both Statement (I) and Statement (II) are individually true and Statement (II) is the correct explanation of Statement (I).
2. Both Statement (I) and Statement (II) are individually true and Statement (II) is not the correct explanation of Statement (I).
3. Statement (I) is true but Statement (II) is false.
4. Statement (I) is false but Statement (II) is true.