The effect of cohesion on a soil is to A. reduce both the active earth pressure intensity and passive earth pressure intensity B. increase both the active earth pressure intensity and passive earth pressure intensity C. reduce the active earth pressure in-tensity but to increase the passive earth pressure intensity D. increase the active earth pressure in-tensity but to reduce the passive earth pressure intensity [GATE 99]

The correct answer is C.

Cohesion is a property of soil that resists the tendency of soil particles to slide past each other. It is caused by the attraction between the particles, which can be due to chemical bonds, electrostatic forces, or van der Waals forces.

The active earth pressure is the force exerted by a soil mass on a retaining wall or other structure when the soil is in a state of active failure. The passive earth pressure is the force exerted by a soil mass on a retaining wall or other structure when the soil is in a state of passive failure.

Cohesion increases the passive earth pressure and reduces the active earth pressure. This is because cohesion increases the resistance of the soil particles to sliding past each other, which makes it more difficult for the soil to move.

The following is a brief explanation of each option:

• Option A: This option is incorrect because cohesion increases the passive earth pressure.
• Option B: This option is incorrect because cohesion reduces the active earth pressure.
• Option C: This option is correct because cohesion increases the passive earth pressure and reduces the active earth pressure.
• Option D: This option is incorrect because cohesion reduces the active earth pressure.