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LA-11097-MS Los Alamos National Laboratory is operated by the University of California for the United States Department of Energy under contract W-7405-ENG-36. ControlledBlasting and Its Implications for the NNWSI Project Exploratory Shaft Los Alamos National Laboratory =(Do Ar1(HIM LosAlamos,NewMexico 87545 t An Affirmative Action/Equal Opportunity Employer Prepared by Nevada Nuclear Waste Storage Investigations (NNWSI) Project participants as part of the Civilian Radioactive Waste Management Program. The NNWSI Project is managed by the Waste Management Project Office of the US Department of Energy, Nevada Operations Office. NNWSI Project work is spon- sored by the Office of Geologic Repositories of the DOE Office of Civilian Radioactive Waste Management. i ,_.O. DISCLAIMER I This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any i warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness ofany information, apparatus, product, or process disclosed. or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product. process, or service by trade name. trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions ofauthors expressed herein do not necessarily state or reflect those ofthe United States I Government or any agency thereof. i LA-1 1097-MS UC-70 Issued: September 1987 Controlled Blasting and Its Implications for the NNWSI Project Exploratory Shaft Edward M. Van Eeckhout n5) Q g QELos Alamos National Laboratory ~Ln©J 6 Los Alamos,New Mexico 87545 CONTENTS Page LIST OF ILLUSTRATIONS . .... * * g vi LIST OF TABLES . .... .*.*.*.*.... viii ABSTRACT . 1 I. INTRODUCTION . .. .. g 1 II. SUMMARY . 3 III. RECOMMENDED SPECIFICATIONS FOR CONTROLLED BLASTING 4 IV. ROCK FRAGMENTATION FOR UNDERGROUND OPENINGS . 5 A. Charge Calculations and the Drilling Pattern 8 B. Controlled Blasting Techniques . * * fl 14 V. MONITORING TECHNIQUES . * * fl 26 REFERENCES 30 . * . 0 v LIST OF ILLUSTRATIONS Page 1. Stratigraphy of exploratory shaft (after Los Alamos National Laboratory 1984; Bentley 1984) . 2 2. Map of the Nevada Test Site and vicinity, showing Yucca Mountain and other sites (from Stock et al. 1985, p. 8692) . 3 3. Idealized schematic of fracturing induced by explosive detonation in a borehole (from Hoek and Brown 1980, p. 367) . 6 4. Various sections of a drift separated according to blast design (from Holmberg 1982, p. 182) . 9 5. Specific charge as a function of tunnel area (from Holmberg 1982, p. 1582) .... 9 6. Typical burn cuts used in underground mining (from E. I.duPont 1980, p. 251) . 10 7. A burn cut blast round (from E. I. duPont 1980, p. 249) . ..... ..... ..... 11 8. Typical fan or V-cuts used in underground mining (from Hoek and Brown 1980, pp. 368-369) . 11 9. A pyramid cut round in a circular shaft (from E. I.duPont 1980, p. 363) . 12 10. A typical drift round in medium-hard rock using a four- hole vertical V-cut with two-hole baby V-cut and millisecond-delay electric caps (from E. I. duPont 1980, p. 257) . 13 11. Theory of presplitting (from E. I. duPont 1980, p. 374) . 14 12. Plexiglass model of presplitting (from Langefors and Kihlstrom 1978, p. 298) .... * . 15 13. Presplitting example (spacing =0.7 ft., diameter = 1.25 in.) (from Langefors and Kihlstrom 1978, p. 299) . 15 14. Presplitting example illustrating drilling accuracy required (from Langefors and Kihlstrom 1978, p. 317) . 16 vi LIST OF ILLUSTRATIONS (cont) Page 15. Well-designed round where damage is limited by smooth blasting (from Holmberg 1982, p. 1586) . .., . 17 16. Recommended charge concentration and hole diameters for smooth blasting using two Swedish explosives (from Holmberg 1982, p. 1586) . 17 17. Smooth blasting in Swedish power station (from Langefors and Kihlstrom 1978, p. 319) . 18 18. Final contours formed by smooth blasting, Swedish power station (from Langefors and Kihlstrom 1978, p. 321). 19 19. Peak particle velocities at various distances from a borehole charge with different densities (from Hoek and Brown 1980, p. 372) . 22 20. Average disturbance depths for various controlled blasting techniques experienced in eight tests (from Worsey 1985, p. 1139) . .. 23 21. Example of acceleration registration and resulting particle velocity close to detonating charge (from Holmberg and Persson 1979, p. 282) . 28 22. Seismic profile equation for determining depth of disturbance using seismic refraction (from Worsey 1985, p. 1134) . 29 vii LIST OF TABLES Page I. SOME EXPLOSIVE WEIGHT STRENGTHS (after Holmberg 1982, p. 1581, and Holmberg 1983, p. 27). 7 II. EXPLOSIVE ROCK CONSTANTS FOR VARIOUS ROCK TYPES (from Holmberg 1983, p. 12) . 8 III. SOME RECOMMENDATIONS FOR SMOOTH BLASTING (from Hoek and Brown 1980, p. 374) . 19 IV. SOME RECOMMENDATIONS FOR PRESPLIT BLASTING (from Oriard 1982 p. 1592). 20 V. FURTHER RECOMMENDATIONS FOR SMOOTH BLASTING AND PRESPLITTING (from Langefors and Kihistrom 1978, p. 310) ........................ 20 VI. TYPICAL PUBLISHED VALUES FOR THE CONSTANTS k, a, AND , (from Hoek and Brown 1980, p. 379) . 23 VII. CASE HISTORIES OF BLAST DAMAGE MEASURED IN TUNNELS (after Kelsall 1986). 24 viii CONTROLLED BLASTING AND ITS IMPLICATIONS FOR THE NNWSI PROJECT EXPLORATORY SHAFT by Edward M. Van Eeckhout ABSTRACT This report reviews controlled blasting techniques for shaft sinking. Presplitting and smooth blasting are the techniques of principal interest. Smooth blasting is preferred for the Nevada Nuclear Waste Storage In- vestigations exploratory shaft. Shaft damage can be monitored visually or by peak velocity measurements and refractive techniques. Damage into the rock should be limited to 3 ft. I. INTRODUCTION This report reviews controlled blasting techniques that are appropriate for shaft-sinking operations at Yucca Mountain, Nevada, a potential repository for high-level -nuclear waste. These studies are being coordinated under the Nevada Nuclear Waste Storage Investigations (NNWSI) Project managed by the Waste Management Project Office of the US Department of Energy. The principal concern is the extent of overbreak damage to the in-situ rock mass, particularly that affecting permeability surrounding the shaft, and ways of quantifying that damage. Specific questions to be addressed are: 1. How extensive is the damage from various controlled blasting techniques--which is the best? 2. What monitoring techniques might be used for quality assurance? 3. How tight should the specifications be for damage control? 1 The proposed depth of the NNWSI shaft is 1480 ft in Yucca Mountain in Nevada (see Fig. 1 for the conceptual drawing). The stratigraphic rock sequence is also shown in Fig. 1. The shaft will have a diameter of 12 ft and will be concrete lined. Figure 2 is a map of the Nevada Test Site and shows Yucca Mountain. ELEVATION DEPTH (FEET) (FEET) Alluvium _ _ _ I , TIVA CANYON 4100. MENDER YUCCA MOUNTAIN' -Z00 MENDER Imoe-wolded vilrcfull Welded devieifi~eg tuft 3700. * 400 t_ -'.520' * aoo TOPOPAH SPRING Welded devirtfied MEMBECR fitlhopt Ielulf 3300-' * 000 Me ouDtitl (p.e@ction) =_= = 1000 = = s = = =- == = 3100- t "s' -tW--t 2o0 Moevolae/dthsttly welded. 1200 Dattially veiric tuft BrekeutI !Welded vibophyric lult ParliaIly welded, vilifc ZJ00- -1400 Iad/or leolitiled full st-, t§-81480rr 8rceake" CALICO HILLS -lS00 EXPLORATORY SHAFT TUFF 40500- (Test loolityjtdiaensioes hot lesoIle) Static wait? level -1800 300 CRATER FLAT 2 .j TUFF ,r/0 0.J STRATIGRAPmY Of TEST WELL USW 6-4 Fig. 1. Stratigraphy of exploratory shaft (after Los Alamos National Laboratory 1984; Bentley 1984). 2 I t S NEVADA YUCCA g TEST MTN + SITE -3rot X\OTER G f BARE MTN FLAT 0 10 20 ^ ---' *KM I IM6O Fig. 2. Map of the Nevada Test Site and vicinity, showing Yucca Mountain and other sites (from Stock et al. 1985, p. 8692). II. SUMMARY We review two common controlled blasting techniques used for driving underground openings, smooth wall and presplitting. For this application smooth-wall blasting is preferred, given the fact that two separate blasts are required for presplitting. Presplitting would require considerable time and coordination during a shaft-sinking operation, but it does appear to yield less damage than smooth-wall blasting. Because there is no all-encompassing formula that can be used through- out an entire shaft-sinking operation for all rock types, we recommend that certain leeway should be given to the blasting contractor in the shaft- sinking specifications. However, clear quality control checks should be provided on peak particle velocity (maximum of 2.75 in./s or 700 mm/s) in rock and on depth of rock breakage (a value of 3 ft or 1 m is clearly achievable). 3 Peak particle velocity is the most monitored characteristic of a blast. Velocity monitors can be installed on the surface, in the shaft, and in vertical boreholes near the shaft if necessary. A threshold of 2.75 in./s or 700 mm/s has oftentimes been used to mark the onset of rock damage. This threshold is much larger than that cited in WIPP specifica- tions for concrete damage (5 in./s) (Cottle 1985). If 5 in./s is used, in situ rock damage should be minimized. Actual rock breakage can be monitored by borescopes or seismic refraction techniques. The former requires extra boreholes, whereas the latter can be done along the shaft perimeter. Seismic refraction appears to be a good way to monitor and measure the depth of rock breakage. III. RECOMMENDED SPECIFICATIONS FOR CONTROLLED BLASTING The following is recommended: 1. Smooth-wall blasting is the preferred controlled blasting technique for shaft sinking. 2. Because rock damage can be limited to less than 3 ft by controlled blasting techniques, a tolerance of 3 ft of damage is recommended (to be checked by refractive techniques).

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