JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech II Year DRILLING AND BLASTING Previous Question Paper (February - 2024 - R18)

Exploratory drilling is a critical phase in geological investigation and resource evaluation. Its primary purposes include:

• Resource Estimation: To determine the spatial extent, thickness, grade, and quality of mineral deposits or hydrocarbon reservoirs, allowing for precise calculation of reserves.
• Geological Characterization: To obtain core samples for detailed lithological, structural, and stratigraphic analysis, which helps in understanding the rock mass quality and geological features of the subsurface.
• Feasibility Studies: To gather essential data required for designing mine layouts, selecting appropriate mining methods, and assessing the economic viability of a project.
• Geotechnical Assessment: To evaluate the physical and mechanical properties of rock formations, which is vital for slope stability analysis, underground support design, and foundation engineering.
• Hydrogeological Mapping: To identify groundwater levels, flow patterns, and potential water-bearing zones that may impact future drilling and blasting operations.

The diamond drilling method is a core-sampling technique that utilizes a rotary drill equipped with a diamond-impregnated bit to cut through rock formations. The fundamental principles are as follows:

• Rotary Action: The drill string, consisting of a series of hollow rods, is rotated at high speeds by a power head. This rotation provides the necessary mechanical energy for the bit to penetrate the rock.
• Abrasion and Grinding: Unlike percussion drilling which uses impact, diamond drilling relies on abrasion. The industrial-grade diamonds embedded in the matrix of the bit act as cutting edges that grind away the rock in a circular path.
• Core Recovery: The bit is designed as an annular (ring-shaped) cutter. As it advances, it leaves a cylindrical column of rock, known as the core, intact inside the inner tube of the core barrel.
• Circulation System: A drilling fluid (usually water or a specialized mud) is pumped down through the drill rods to the bit face. This fluid serves three critical functions: it cools the diamond bit, lubricates the cutting process, and flushes the rock cuttings (sludge) up to the surface through the annulus between the drill rods and the borehole wall.

This technique is primarily employed in mineral exploration and geotechnical investigations where high-quality, continuous core samples are required for geological analysis.