Which one of the following is an advantage when geotextiles is used in road works?
- APrior stripping of the natural soil
- BEconomy of aggregateCorrect
- CIncrease of different settlings
- DSlower consolidation of fills
Solution
Concept
A geotextile separates the subgrade from the aggregate and reinforces the base, so less aggregate is needed and it is not lost into soft soil.
Step-by-step solution
1. Recall the functions of a geotextile in roads: separation, filtration, drainage and reinforcement. 2. Separation stops aggregate from sinking into the soft subgrade, so less aggregate is wasted. 3. Reinforcement allows a thinner aggregate layer. 4. So the advantage is economy of aggregate, option B.
Explanation
A geotextile laid on the subgrade keeps the aggregate and the soil apart. Aggregate does not get pushed into the soft soil, and the layer can be thinner. This saves aggregate and cost.
Why the other options are wrong
A: A geotextile avoids the need for stripping the natural soil. Stripping is extra work, not an advantage. C: A geotextile reduces differential settlement. It does not increase it. D: Drainage through the geotextile makes consolidation of fills faster, not slower.
Shortcut
Options A, C and D describe bad effects. Only B is a benefit.
Common mistake
Thinking that stripping of the soil is an advantage. In fact, a geotextile reduces the need for stripping.
Correct answer: B) Economy of aggregate