NTS STUDY

🏗️ Methods of Quarrying Stones: Tools and Techniques

Quarrying is the process of extracting high-quality stones from natural solid rock formations. Unlike mining, which deals with minerals like coal or gems, Quarrying specifically refers to extracting building stones exposed to the surface.

As a civil engineer, understanding the method of extraction is vital because it determines the shape, strength, and final use of the stone.

1. Excavation using Hand Tools

This is the traditional method, best suited for soft stones or when specific block shapes are needed for masonry.

• Digging & Cutting: Used for soft stones like Laterite. Tools used include pickaxes, shovels, and chisels.

• Heating: Fire is used to heat the rock surface. The differential expansion causes the upper layer to separate from the lower one.

• Wedging: Used when natural cracks are present. Steel wedges are driven into cracks to split the rock. If cracks are absent, holes (10cm dia) are drilled, and conical steel plugs (feathers) are driven in to create a split. This works excellently for Marble, Limestone, and Sandstone.

2. Quarrying by Channeling Machines

This modern method is used for large-scale extraction of solid rocks like Granite. It requires at least one face of the rock to be exposed.

• Process: The machine (powered by electricity or compressed air) cuts deep channels (up to 240-370 cm depth).

• Horizontal Splitting: Once vertical channels are cut, horizontal holes are drilled at the bottom. Wedges are then driven in to lift the massive block.

• Use: Ideal for producing large slabs for flooring or export.

3. Quarrying by Blasting

This is the most common method for producing Stone Aggregates (Gitti) for roads and railways. It shatters the rock into irregular pieces.

Materials Used in Blasting:

• Gunpowder: A mixture of charcoal, saltpetre, and sulfur. It produces larger blocks and is ignited using a Cotton Fuse Wire (burn rate: 1cm/sec). It cannot be used underwater.

• Dynamite: A high-velocity chemical explosive used for shattering rocks into small pieces (aggregates).

• Detonators: Small copper cylinders containing mercury fulminate. They are used to trigger the main dynamite explosion, often via electric circuits for precise timing (essential for tunnels or demolitions).

📊 Comparison: Gunpowder vs. Dynamite