Rock core recovery during subsurface investigation: in which boring/drilling method is a solid cylindrical core of rock formed inside the core barrel?

Introduction / Context:
Geotechnical investigations require representative samples of soil and rock. While many methods retrieve disturbed cuttings, core drilling specifically recovers relatively undisturbed cylindrical cores used for geomechanical testing and stratigraphic logging.

Given Data / Assumptions:

• Target material includes rock or very hard strata.
• Need for intact core for UCS, RQD, and petrographic studies.
• Equipment includes core barrel with diamond-set bit and drilling fluid circulation.

Concept / Approach:
Diamond core drilling uses a hollow, diamond-tipped bit to cut an annulus, leaving a solid core within the barrel. The core is broken at the bottom and retrieved. Auger boring is suitable for soils; it produces cuttings, not intact rock cores. Percussion drilling breaks material by repeated blows, yielding fragments. Wash boring erodes material with water jetting, again producing disturbed samples.

Step-by-Step Solution:
Identify method that yields a solid core: diamond core drilling.Exclude soil-only or destructive methods that do not preserve core continuity (auger, percussion, wash).

Verification / Alternative check:
Standard geotechnical texts discuss core barrels (single/double/triple tube) and RQD measurements only possible with core drilling.

Why Other Options Are Wrong:

• Auger, percussion, and wash borings mainly produce cuttings/spoil; core continuity is lost.

Common Pitfalls:

• Using non-coring methods in rock and expecting high-quality lab specimens.

Final Answer:
diamond core drilling