In the design of Bridge Foundations, Well Foundations are preferred for major bridges over deep sandy rivers because
- AThey are cheaper than shallow foundations.
- BThey are only used for pedestrian bridges.
- CThey do not require any specialized machinery for installation.
- DThey can be sunk to great depths to reach a stable strata below the maximum scour level.Correct
Solution
Concept
Well Foundations
Formula
N/A
Step-by-step solution
1. Consider the advantages of well foundations in deep sandy riverbeds. 2. Recognize that well foundations can be sunk to large depths below maximum scour level to reach stable strata. 3. Select Option D as the correct choice.
Explanation
Well foundations can be dug deep into the riverbed to reach strong, stable soil or rock that lies far below the level where flowing water washes away the sand (scour level). This provides strong support and prevents the bridge from collapsing or shifting during heavy floods.
Shortcut
To easily remember why Well Foundations are used for major bridges over deep sandy rivers, use the memory rule "Well = Deep & Scour-proof": - Deep Sinking: Well foundations can be sunk to great depths through heavy sand. - Scour Protection: Reaches solid, stable strata well below the maximum scour level caused by river currents.
Common mistake
A common mistake is selecting Option A by assuming well foundations are chosen for low cost, whereas they actually involve high initial construction and sinking costs. Another common mistake is selecting Option C by assuming well sinking is a simple process, ignoring the heavy equipment, heavy cranes, and specialized sinking machinery required.
Correct answer: D) They can be sunk to great depths to reach a stable strata below the maximum scour level.