Scholars' Mine Doctoral Dissertations Student Theses and Dissertations 1971 Statistical study of rock drilling by hypervelocity jets from explosive shaped charges John William Brown Follow this and additional works at: https://scholarsmine.mst.edu/doctoral_dissertations Part of the Mining Engineering Commons Department: Mining Engineering Recommended Citation Brown, John William, "Statistical study of rock drilling by hypervelocity jets from explosive shaped charges" (1971). Doctoral Dissertations. 1850. https://scholarsmine.mst.edu/doctoral_dissertations/1850 This thesis is brought to you by Scholars' Mine, a service of the Missouri S&T Library and Learning Resources. This work is protected by U. S. Copyright Law. Unauthorized use including reproduction for redistribution requires the permission of the copyright holder. For more information, please contact [email protected]. STATISTICAL STUDY OF ROCK DRILLING BY HYPERVELOCITY JETS FROM EXPLOSIVE SHAPED CHARGES by JOHN WILLIAM BROWN, 19 42- A DISSERTATION Presented to the Faculty of the Graduate School of the UNIVERSITY OF MISSOURI-ROLLA In Partial Fulfillment of the Requirements for the Degree DOCTOR OF PHILOSOPHY in T2608 164 pages MINING ENGINEERING c.l 1971 &~£~ £i?L;;~~ 202886 @ 1972 JOHM WILLIAM BROWN ALL RIGHI'S RESERVED iii STATISTICAL STUDY OF ROCK DRILLING BY HYPERVELOCITY JETS FROM EXPLOSIVE SHAPED CHARGES ABSTRACT 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. 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~ 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. iv 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. v ACKNOWLEDGMENTS The author wishes to gratefully acknowledge the assistance of Dr. George B. Clark--his thesis advisor and the director of the Rock Mechanics and Explosives Research Center--who suggested the project, obtained contracts to support the investigations, and directed the overall research program. He also wishes to thank the following: Drs. Charles J. Haas, Peter G. Hansen, Ronald R. Rollins, James J. Scott, and David A. Summers, who served on his doctoral committee; Mr. Upendra Parikh, who produced the microphotographs; Messrs. Bradford Hale and Clarence Rapier, who machined the shaped-charge components; and Miss Gini Miller, who typed the thesis. He is also grateful for the assistance of many staff members of the University. The author particularly wishes to mention with affection the inspira­ tion provided by his children, John, Russell, and Debra. The experimentation reported in this dissertation was conducted from November, 1967, to May, 1970. The author deeply appreciates the funding of contracts by the Department of Defense and by E. I. Du Pont de Nemours and Company, Inc. He also wishes to thank the Department of Mining, Petroleum, and Geological Engineering for fellowships during two semesters of this period, and the Denver Mining Research Center of the U. S. Department of the Interior, Bureau of Mines, for the use of an electronic calculator. Some of the results of this investigation were presented at the Twelfth Symposium on Rock Mechanics at the University of Missouri-Rolla in November, 1970 (Clark, Rollins, Brown, and Kalia, 1971). vi TABLE OF CONTENTS Page ABSTRACT .........................•................................. iii ACKNOWLEDGMENTS .............•........................•.............. · v LIST OF ILLUSTRATIONS .•••..••••..•.•...•......••..•.•..•.....•...•.•. x LIST OF TABLES ••.••••..•••..•.•.••••......•••••.•.•••.....•.•....• xiii 1 . INTRODUCTION •..•.•..•.••••..•...•.•...•..••...•••...••.•......••. 1 2 . REVIEW OF LITERATURE ••.....•.•.•.••••••......•.•••...•••.....•.• 10 I • THEORY OF JET FORMATION •••..•.•••••••...•••••...••...•..•• 10 I I • THEORY OF PENETRATION BY JET •...••••••..•••...•...•.•...•. 11 I I I . PHENOMENOLOGY ••.•..•.•.••.•••.•...•.••..•...•..•.•.•..••.• 14 A. Metals •....•.••.••••..••..•.•.•.•..•............•.•. 14 B . Rock ••.••••.•....•••..••..••••.•....••....•.....•..• 18 IV. INFLUENCE OF TARGET PROPERTIES ON PENETRATION ••.•.....••.. 20 A • Me t a 1 s . ........ 2 0 B. Rock •••..•..•••..••.••...••••.••.•...••.••.•...••... 21 V. DESIGN FACTORS OF THE SHAPED CHARGE .....•••.••.•••.....•.• 21 A • Me t a 1 s . • • . • • . • • • . • • . • . • . • . • . • . • . • . • . 2 1 B • Rock •••.•.•..•.•............•.....•....•.......•.... 2 6 3. DESIGN OF INVESTIGATION .....•.••......•.•...••..•.•••......••••. 28 I. EXPERIMENTAL DESIGN ....••...••..........••........•......• 28 A. Preliminary experiments •••..•••.•...•.•...•...•••... 28 B. Factorial experiments on standoff, liner angle, and liner thickness ....•.•••.•.•.•..•......••.....•. 29 C. Other design factors •...•••••.••.....•••.•......•.•• 32 II. PROCEDURE •.•.••••....•.•..•••••..•..•.•.•..•••••.••.•...•• 32 A. Construction of shaped charges •.••••••..••••.••.•••• 32 vii B. Shaped-charge drilling experiments ................. 34 C. Mechanical properties of rock ...................... 35 III. STATISTICAL ANALYSIS ..................................... 35 4. RESULTS ......................................................... 38 I. DRILLED DEPTH VERSUS STANDOFF, LINER ANGLE, AND LINER THICKNESS FROM FACTORIAL EXPERIMENTS ON SEVEN ROCK TYPES ........•................................ 38 A. Means for all rock types ........................... 59 B. Pooled data for seven rock types ................... 60 C. Missouri granite ................................... 60 D. Jefferson City dolomite ............................ 60 E. Bedford limestone .................................. 61 F . Berea sands tone .................................... 61 G. Kitledge granite ................................... 62 H. Jasper quartzite ................................... 62 I. Buena gabbro ....................................... 62 J. St. Peter sandstone ................................ 63 II. DRILLED DIAMETER AND VOLUME VERSUS STANDOFF, LINER ANGLE, AND LINER THICKNESS FROM FACTORIAL EXPERIMENTS ON SEVEN ROCK TYPES .......................... 63 III. DRILLED DEPTH, DIAMETER, AND VOLUME VERSUS OTHER DESIGN FACTORS ..................................... 6 3 A. Charge size ........................................ 63 B. Charge shape . ........ 6 9 c. Charge length ...................................... 71 D. Type of explosive .................................. 71 E. Type of liner metal ................................ 71 IV. DRILLED DEPTH, DIAMETER, AND VOLUME VERSUS ROCK PROPERTIES .......................................... 7 2 V . PHENOMENOLOGY ...•......•................................. 8 5 viii 5 . DISCUSS ION ....•................................................ 91 I. DRILLED DEPTH VERSUS STANDOFF, LINER ANGLE, AND LINER THICKNESS FROM FACTORIAL EXPERIMENTS ON SEVEN ROCK TYPES ......................................... 91 II. DRILLED DEPTH, DIAMETER, AND VOLUME VERSUS OTHER DESIGN FACTORS ..................................... 9 3 III. DRILLED DEPTH, DIAMETER, AND VOLUME VERSUS ROCK PROPERTIES •..........•.......................•...... 9 5 IV. PHENOMENOLOGY .........•.................................. 96 V. SHAPED-CHARGE MATERIALS .....•........................... 100 VI. ENVIRONMENTAL, HEALTH, AND SAFETY HAZARDS .............•. 101 6. SUMMARY AND CONCLUSIONS ..•.............................•...... 104 I . SUMMARY •................................................ 104 II. CONCLUSIONS ...........•.•............................... 104 III. RECOMMENDED FURTHER RESEARCH ............................ 107 SELECTED BIBLIOGRAPHY ...............•....•.........•...•.......... 110 VITA .............................................................