7.1. Compaction increases density and decreases void ratio.

Try these first

1. 1.

   What happens to the voids in a soil mass when it is compacted?

   Hint

   Think about what happens when you press a sponge.

2. 2.

   Which has higher shear strength, dry of optimum or wet of optimum soil?

   Hint

   Remember the effects of moisture on soil structure.

3. 3.

   What is the primary effect of soil compaction?

   • Increase void ratio
   • Decrease void ratio
   • No effect on void ratio

   Hint

   Consider what happens when soil is compacted.

4. 4.

   True or False: Soil compacted wet of optimum always displays higher shear strength.

   • True
   • False

   Hint

   Think about how water affects soil particles.

5. 5.

   Given a soil type with a starting void ratio of 0.8, calculate the new void ratio after compaction that doubles the soil density, assuming no change in volume.

   Hint

   Consider the formula density = mass/volume and how void ratio relates to the volume of solids and voids.

6. 6.

   Evaluate how changing the moisture content during compaction of a clayey soil impacts its long-term consolidation settlement.

   Hint

   Think about how the state of water affects clay particle arrangements.