Introduction to Earth Pressure, Soil Mechanics | Soil Mechanics Notes- Agricultural Engineering PDF Download

Introduction

The soil that is retained by various structures like retaining walls, sheet piles (as shown in Figure 25.1) exerts a force on those structures. This force is called the earth pressure and the material that is retained by the structures is referred as backfill. Based on the wall movement, the earth pressure is classified as:

(i) Earth pressure at rest

(ii) Active earth pressure

(iii) Passive earth pressure

In case of a rigid and unyielding retaining wall, soil mass is in rest condition and no deformation or displacement is occurred in the wall. The earth pressure under this condition is called earth pressure at rest. If a retaining wall rotates about its toe and moving way from the backfill (as shown in Figure 25.2), the soil mass expends which causes reduction of the earth pressure on the wall. The earth pressure under this condition is called active earth pressure. On the other hand if a retaining wall moves towards the backfill (as shown in Figure 25.2), the soil is compressed and the earth pressure on the wall increases. The earth pressure under this condition is called passive earth pressure. Thus, the passive earth pressure is more than the earth pressure at rest and the earth pressure at rest is more than the active earth pressure.

Fig. 25.1. Earth pressure acting on structure like (a) retaining wall (b) sheet Pile.

Fig. 25.2. Active and Passive earth pressure.