Role of the borehole pressure in blasting: the formation of cracks

Thesis/Dissertation · Fri Jan 01 04:00:00 EST 1971

OSTI ID:5452054

Porter, D D

An investigation into the generation of cracks in rocks around a statically pressurized hole is made. The sustained stress around a borehole is defined and reference is made to field measurements where it is observed. The case of a single-hole bench blast was reduced to a plate model which is considered both theoretically and experimentally. Based on the principal of least work, it is hypothesized that any crack in the plate will assume the shape of a maximum principal stress trajectory. Critical experiments designed to test such aspects as the effects of controlled crack origin, and permanently changed trajectories, confirm this hypothesis. While it is shown theoretically that a preferred point of origin for a crack exists, material flaws dominated, and randomly oriented cracks resulted. Cracks which originated at a notch on the hole wall reproducibly follow the same curves. High-framing-rate photography revealed that cracks originate at the hole, that several cracks form simultaneously, and that the hole pressurizing medium does not enter the running cracks.

• OSTI ID: 5452054
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
020300* -- Petroleum-- Drilling & Production
03 NATURAL GAS
030300 -- Natural Gas-- Drilling
Production
& Processing
BOREHOLES
CAVITIES
COMMINUTION
CRACKS
DEFECTS
DESIGN
ENGINEERING
ENHANCED RECOVERY
FAILURES
FIELD TESTS
FRACTURE PROPERTIES
FRACTURING
HYPOTHESIS
IMAGES
MATERIALS TESTING
MECHANICAL PROPERTIES
MECHANICS
NATURAL GAS WELLS
OIL WELLS
PLATES
PRESSURIZING
RANDOMNESS
RECOVERY
RESERVOIR ENGINEERING
RESERVOIR PRESSURE
ROCK MECHANICS
SHAPE
STIMULATION
STRESS INTENSITY FACTORS
STRESSES
TESTING
TRAJECTORIES
WALLS
WELL COMPLETION
WELL STIMULATION
WELLS