TGB f TRANSPORT y 3 2 0 0 • M58 Si 141973 r REVIEW OF EFFECTS OF HYPERVELOCIT JETS AND PROJECTILES ON ROCK June 1968 FINAL REPORT George B. Clark y John W. Brown , Charles J. Haas Clifford D. Muir for OFFICE OF HIGH SPEED GROUND TRANSPORTATION U.S. DEPARTMENT OF TRANSPORTATION WASHINGTON D.C. 20591 CONTRACT NO. DC7-35511 Rock Mechanics & Explosives Research Center UNIVERSITY OF MISSOURI - ROLLA Rolla, Missouri 65401 09-Materials Science DEPARTMENT OF TRANSPORT TmoN • tAs t REVIEW OF EFFECTS OF HYPERVELOCITY JU II141973 JETS AND PROJECTILES ON ROCK: .jr I - l h h j* . 11' June 1968 FINAL REPORT by George B. Clark Charles J. Haas John W. Brown Clifford D. Muir for OFFICE OF HIGH SPEED GROUND TRANSPORTATION U .S . DEPARTMENT OF TRANSPORTATION WASHINGTON, D .C. 2 0591 CONTRACT NO. DC7-355 11 M ', S S t n * <r>, Uvi>v ^ c S ' i y * Rock Mechanics & Explosives Research Center. ,1 UNIVERSITY OF MISSOURI-ROLLA Rolla, Missouri 65401 TABLE OF CONTENTS Chapter Page I Introduction 1 G eneral 1 Objective 1 H istory 2 Report Organization 4 II Equations of State 6 Shock Waves 8 III W ater Jets 15 Jet Stability-Theory 15 Summary 2 6 Jet Stability-Experimentation 2 6 Pulsed Jets-Theory and Experiment 44 N ozzles 45 Summary-Nozzles 5 7 Compressors 5 7 Water Jet Production 60 Fluid Jet Augmentation 81 High Pressure Freezing of Water 87 Calculation of Shock Front Parameters 88 Extrapolation of p-V-T Data 91 Discussion 98 IV Water Jet Impact on Rock 102 V Projectile Acceleration and Impact 142 Introduction 142 Limitations-High Velocity Guns 142 Cratering and Penetration Theories 150 Thermal Penetration 15 8 Explosive Analogy 15 8 Empirical Relations 159 Penetration-General 159 Impact Experiments-Metals 162 Impact Data-Metal Targets 171 Dimensional Analysis 184 Impact Experiments-Rock 192 Comminution 207 i i TABLE OF CONTENTS Chapter Page VI Explosive Shaped Charges and Cumulation 2 09 Design of Shaped Charges with Conical Liners 218 Jet Penetration of Rock 22 1 Energy Partitioning 231 Cumulation-Tubular Booster 2 34 Miscellaneous 238 VII Pressure Vessels 242 Introduction 242 Dynamic Pressure Vessels 242 Static Pressure Vessels 246 Material Considerations 2 78 VIII Conclusions and Recommendations 2 86 G en eral 2 86 Equations of State 2 87 Water Jets 2 88 Water Jet Impact 2 89 . Hypervelocity Projectiles 292 Pressure Vessels 294 Shaped Charges and Cumulation 296 Discussion 297 Summary-Status of Research and Development 300 Recommendations 305 A ppendices A Theory of Single Stage Light Gas Guns 307 Projectile Velocity 307 Velocity-Constant Base Pressure 307 Pressure Disturbances 308 Characteristic Theory 3 14 Simple Wave Region-Constant Diameter 314 Numerical Calculations 319 First Reflected Wave 324 Projectile Path-Post-Reflection 326 Isentropic Expansion-Constant Diameter 327 Infinite Chamber 32 8 Acoustic Inertia-Infinite Chamber 329 Ideal Gas 329 Projectile Equations 333 Finite Length Chamber 335 Chambered Gun 3 42 Back Pressure of Gas in Barrel 347 Heating Propellant Gas 350 iii TABLE OF CONTENTS Appendices Page B Pressure Vessels 351 B-I Stress Analysis 351 Thin-Walled Vessels, Elastic Analysis 351 Thick-Walled Vessels , Elastic Analysis 351 Autofrettage-Theoretical Analysis 355 B-II Tabulation of Material Properties 361 C Shock Waves-Water Cannon 3 83 P iston -W ater Im pact 3 83 Piston-Water Impact with Air 393 References 413 iv CHAPTER I INTRODUCTION G eneral s Although many advances have been made in tunnel excavation in rock in the past few decades, improvements have been built around established practices of drilling, blasting, loading and haulage of broken rock. Loading and haulage, as well as drilling and blasting have been improved until little feasible increase in efficiency or time saving appears possible. New and faster methods of tunneling are necessary if planned highspeed ground trans­ portation is to become a reality. One of the current disadvantages of conventional explosive excava­ tion systems is that they are cyclic in nature, involving individual opera­ tions which cannot be performed simultaneously. Some factors which cause delays include: (1) The method does not permit simultaneous and continuous breakage, loading and haulage; (2) There is a delay to clear out gases from explosives; (3) Turnaround time is required in moving drilling equipment; (4) There are delays in track haulage due to moving in empties; (5) Other d e la y s . O b je ctiv e Several approaches have been made to solve the basic and engineer­ ing problems of devising new rapid tunnel excavation system s. Tunnel bor­ ing machines have been developed which will excavate tunnels of circular cross-section at rapid rates in soft rock such as shale. Conventional drilling, 1 2 blasting and loading methods have been improved by ingenious m echanization. Low velocity jets are in use for rapid mining of soft materials such as bitumi- nous coal. However, each^of these methods appears to be reaching an eco­ nomic or technical limit of improvement. New methods are being continuously sought, which will not have some of the disadvantages of the above systems, and which will radically increase the rates of tunnel excavation. Attention has turned to the use of hyperveloc­ ity impact as a means of cutting and breaking rock, as well as the use of lasers, electric current, explosive drilling, high frequency vibration, etc. Many of these techniques are currently under investigation. The information in this report was assembled and analyzed to give a state of the art summary of hypervelocity techniques which show promise for use in cutting and breaking rock. These include the use of water jets, me­ tallic jets and hypervelocity projectiles. H istory Investigation of water jets has been carried on extensively in the USSR for well over a decade. Low velocity jets are used successfully to mine coal, and high velocity capillary jets have been employed to cut and break rocks under laboratory conditions. Velocity ranges for breaking and cutting are dependent upon rock properties, while pulsed jets appear to break some rocks more easily than continuous jets. Spectacular results have been re­ ported for breakage of some rocks. Several agencies in the USSR have re­ ported results. Compressors, pressure multipliers, gas explosion chambers . 3 and water cannons have been used to generate jets. Jet properties, including continuity, unit pressure, total pressure, and stability have been measured by various means. Results appear to agree with theory, although the latter has been established only for low velocity flow,. Speed of traversing and frequency of pulsed jets are items of basic in­ te re s t. Investigations have also been carried out in Britain,-but this work was limited to somewhat softer rock and lower velocities. Interesting discover­ ies have been made concerning the continuity of jets, i.e . , the core is more continuous than previously believed. Lower limits of velocity for rock cut­ ting were found for the rock investigated. Shaped charge jets were discovered in 1888 by Charles Munroe, and have long been known as the Munroe effect in the United States and England. Early shaped charges were unlined and produced only indentations. With the emphasis on armor in World War II there was a need to de­ velop anti-tank weapons. The "Bazooka," employing lined shaped charge projectiles, proved very effective for armor penetration. A great deal of re­ search has been done with them, primarily for military applications . They have found industrial application in tapping iron furnaces and perforating oil well casings. Attempts to use them for mining or excavating rock in the late 1940's failed, largely because of the cost of their use. Hypervelocity projectile studies developed mainly because of the in­ terest in the impact of meteorites on metals and rocks. One concern has been with the effect of particle impact on aluminum space vehicles. A second area 4 of interest is the effect of meteorite impact on rock on the moon. The phe­ nomena of impact on rock and metal are similar in many respects, although craters in rock are larger because of the brittleness and low tensile strength of rock. Most projectiles are accelerated by means of the light gas gun which was developed at the New Mexico School of Mines in the 1950's. Report Organization The use of hypervelocity agents for excavation purposes has been un­ der investigation for only a relatively short time, and research results are somewhat fragmeptary. Hence, in most cases the investigations are described by the author under the appropriate subject. Summaries and analyses have been made where possible. If hypervelocity systems can be successfully employed to perform si­ multaneous "drilling and blasting," no other large scale drilling equipment may be required. Drilling and turnaround time for drills could be eliminated. For practical applications at a working face a cross-face conveyor is visu­ alized, which would feed a larger conveyor leading away from the face. Ide­ ally, sequences should be arranged so that the broken material will be loaded on the cross conveyor by the excavating process. With proper design of a loading-hauling system (conveyors) at the face, mucking and haulage would proceed simultaneously. Such methods should be applicable to all types of rock, strong and weak, wet or dry, and largely independent of the composi­ tion and structure of the rock. Other proposed systems do not enjoy this advantage. Flame jet pierc­ ing is markedly dependent on the quartz content and composition of the rock. 5 Boring methods of tunneling are only applicable to soft rocks. Laser and chemical methods are sensitive to rock composition and structure and prob­ ably will only supplement primary excavation methods if they are technically and economically applicable.