Q1: According to Coulomb's wedge theory, the active earth pressure slides the wedge

ANS:A - down and outwards on a slip surface

Option A is the right answer.

In active state, wedge moves outwards and down.

In passive state, wedge moves inwards and up. Pressure at rest:

When the wall is at rest and the material is in its natural state then the pressure applied by material is known as Earth Pressure at Rest. It is represented by Po.

Active earth pressure:

When the wall moves away from the backfill, there is a decrease in the pressure on the wall and this decrease continues untill a minimum value is reaceh after which their is no reduction in the pressre and the value will become constant. This kind of pressure is known as active earth pressure.

Passive earth pressure:

When the wall moves towards the backfill, there is an increase in the pressure on the wall and this increase continues untill a maximum value is reaceh after which their is no increase in the pressre and the value will become constant. This kind of pressure is known as passive earth pressure. Active earth pressure means soil is left from the retaining wall and passive earth pressure is soil tends to move towards the retaining wall.