Which of the following methods of quarrying is suitable for costly, soft and stratified rocks such as sandstone, limestone, laterite, marble and slate?
- AExcavating
- BWedgingCorrect
- CHeating
- DBlasting
Solution
Concept
Wedging is used for costly, soft and stratified rocks because the stone splits along natural layers with little waste.
Step-by-step solution
1. List the quarrying methods: excavating (digging), heating, wedging and blasting. 2. Excavating is for very soft rocks or stones buried in earth. 3. Heating is for small, thin surface layers of rock. 4. Blasting is for hard, compact rocks like granite and basalt. 5. Wedging splits soft, layered rocks (sandstone, limestone, laterite, marble, slate) along bedding planes without wasting costly stone. 6. So the answer is (B) Wedging.
Explanation
In wedging, holes are made along the natural layers of the rock and steel wedges are driven in to split it. This gives large, clean blocks with very little waste. So it suits costly, soft and stratified rocks like marble and slate.
Why the other options are wrong
A: Excavating is only for very soft rocks or stones under earth. C: Heating is used only for thin surface layers and gives small pieces. D: Blasting breaks rock into irregular pieces and wastes costly stone; it is used for hard rocks.
Shortcut
Stratified (layered) + costly stone = Wedging; hard rock = Blasting.
Common mistake
Choosing blasting because it is the most common method, but it wastes costly stone.
Correct answer: B) Wedging