Statistical study of rock drilling by hypervelocity jets from explosive shaped charges

<p>"The drilling effect in rock of hypervelocity jets from explosive shaped charges was investigated experimentally to supplement a rapid excavation concept. The effects of the design factors of the charge and the mechanical properties of eight rock types were studied. Experiments were both designed and analyzed upon statistical principles. A full factorial experimental design was used for each of seven rock types. An analysis of variance and the k-ratio least significant-difference test were applied to the results.</p> <p>The optimum design of shaped charges for drilling was found to be independent of rock type and rock properties. For composition C-4 charges having cast iron liners, the optimum design for depth of penetration includes a standoff distance equal to 1 1/4 times the charge diameter, a liner wall thickness of 0.030 times the diameter, and a liner apex angle of 45 degrees. The penetration depth is directly proportional to the size of the charge, and increases significantly with length/diameter ratio of the charge. Drilled depth does not vary significantly between cylindrical and cylindro-conical shaped charges, nor between cast iron and Armco iron liners. Composition C-4 explosive produces significantly greater drilled depths than does 100 percent blasting gelatin, which in turn is obviously better than 67 percent dynamite.</p> <p>The penetration process in rock is partially hydrodynamic but not completely so. The hydrodynamic theory does not agree well with the experimentally-determined relationship of the depth, diameter, and volume of penetration to scaled values of the jet/rock density ratio. The complementary effects of additional rock properties must be included to produce agreement between theory and experiment. Those additional properties which are most probably related causally to penetration are compressive strength, porosity, hardness, drillability, and modulus of elasticity. The phenomenology of penetration in high-strength rock is consistently different from low- and medium-strength rock in terms of penetration depth, hole taper, the presence of spalled craters, delayed spallation, microseismic activity, and partial filling of the hole and plating of its walls by liner material"--Abstract, pages iii-iv.</p>

Name thesis:degree_name

Ph. D. in Mining Engineering

Grantor

University of Missouri--Rolla

Year dc:date.available

2016

Author dc:creator

• Brown, John William

• Mining Engineering

Repository record dc:identifier

https://scholarsmine.mst.edu/doctoral_dissertations/1850

OAI identifier oai:identifier

oai:scholarsmine.mst.edu:doctoral_dissertations-2852