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Propagation of Ground Vibrations Due to Explosives
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Propagation of Ground Vibrations Due to Explosives

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This is a slightly modified version of the powerpoint that I presented for the 2010 conference for the International Society of Explosives Engineers. If you would like a copy, please contact me.

This is a slightly modified version of the powerpoint that I presented for the 2010 conference for the International Society of Explosives Engineers. If you would like a copy, please contact me.

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  • The AXPRO Explosives Research Laboratory was established in 2007. As its focus was to collect research data and not the creation of a product, almost all of the charges are detonated at the surface. This meant that while the PPV model in the blasters handbook could be used, there was no real characteristic data on the vibrations since the model is usually used to predict the particle velocities emanating out from a borehole. So, until a real study could be performed and a model could be developed, the size limit for a charge at the test site was set at 20 lbs.
  • For anyone not familiar with the location of the Colorado school of Mines, it is located in Golden, CO just along the western edge of Denver in the foothills. The CSM explosives research laboratory is located in Idaho Springs which is about 45 minutes west of Denver along interstate 70.The test site itself is about .31 miles from the nearest inhabited building, which is right down the valley.The area around the site, and most importantly between the test site and the nearest inhabited building, is highly faulted and mostly granitic in nature.
  • For anyone not familiar with the location of the Colorado school of Mines, it is located in Golden, CO just along the western edge of Denver in the foothills. The CSM explosives research laboratory is located in Idaho Springs which is about 45 minutes west of Denver along interstate 70.The test site itself is about .31 miles from the nearest inhabited building, which is right down the valley.The area around the site, and most importantly between the test site and the nearest inhabited building, is highly faulted and mostly granitic in nature.
  • The test site lies just to the north of the town of Idaho Springs. It sits right above the Colorado School of Mines’ Edgar Experimental Mine which was acquired by the school in 1921.
  • The reason for the study is that, as you all know, keeping the neighbors happy is a very important issue in the explosives industry. Nothing can upset operations faster than complaints. So the close proximity of inhabited buildings in the area prompted this study to be performed. As a secondary concern, the adit to the main tunnel of the schools experimental mine also passes close by the test site down the valley a little ways and keeping individuals within different school organizations was important as well.
  • The study was undertaken with the desire to determine the radius that environmental effects from blasting were having on the area. We referred to this as the safety zone of environmental effects as far as “How much explosives could be safely initiated in the area without having adverse effects on the surrounding areas. The two areas of focus were air-blast and ground vibrations. The first phase—this study—was to find the parameters for completing the model from the blasters handbook on the prediction of PPVs.
  • The equation for the prediction of peak particle velocity is shown here from the ISEE blasters handbook. The peak particle velocity that we were actually interested was actually the peak vector sum of the velocities. At whatever point where the velocity reached the highest for any given axis, the magnitude of that velocity and the velocities along the other two axes was taken. H in this equation isa unitless site constant, equal to the y intercept of the line, when scale distance = 1. It is based on the rock properties of the area and takes into account how well particle velocities travel through a medium.R = distance/radius from the blast and for this study was kept in feet.Q = weight of charge which was recorded in poundsn= another site constant, equal to the slope of the trend line on a log-log scale which you will see laterZ = “Scale Distance” (feet/lb1/2) refers to a combination of distance from the blast and the charge weight. By combining this information into one unit, it makes it possible to plot the data as well as making comparisons between different charge weights easier.
  • This picture shows one of the seismographs that were used for our testing. All 7 instruments were the same model keeping consistency between testing.
  • Each monitor was set up, and turned on to continuously record up until the test. After each test they were checked to make sure that data was collected, and then set up to continuously record until the next blast. The software used to analyze the readings was Instantel’sBlastware v.10
  • This picture shows the road upon which the testing was done. The road leading into the test pit was chosen to be used for two reasons. First, it was the only straight shot from the test site that would allow for a scale distance of over 20 for a 2lb charge to be recorded horizontally without moving up or down slopes. Secondly, as the road was part of an old army installation at the site, it was of a mostly uniform material and very well compacted. This means that the transfer of velocities in this medium would be greater than the much more faulted area immediately adjacent to the test site, and would therefore produce provide higher readings. These higher readings would allow a more conservative model to be produced creating a buffer that would further decrease the risk of ANY damage in the area.
  • The minimate monitors were set up in the arrangement shown here for the first two charges, a 20 gram booster (for validation purposes and a 2lb charge. The blast point is shown in red and the monitors were spaced out in a straight line away from blast in increments of scale distances of 10 for a 2 lb charge. For the third charge, 2lbs were again used, but stations 1-5 were moved behind station 7 for a representation of scale distances for 60-120, once again in increments 10 and again for 2 lbs.
  • This picture is from the first blast during which the monitors were between scale distances of 10 and 70. The large arrow shows the location of the blast in relation to the line of monitors.
  • These two pictures show the monitors being prepared for the second blast at which time they were moved back to between scale distances of 60 and 120 for the 2 lb charge.
  • The two pound charge was made up of 4 sticks of dynamite, with a velocity of about 6000 m/s were used in a horizontal configuration. The sticks were angled towards the blast along the wall of a hole that was dug the morning of testing. This arrangement was used so that the most energy would be directed towards the monitoring stations producing a strong signature and also so that the test would be easily repeatable
  • Since everyone likes pictures of blasts, we have a couple of pictures of the 2 lb charges going off. The first 2 lb test is on the left, and the second is on the right.
  • The picture on the left shows the crater that was created by the 20 gram booster in the very first test. The picture on the right shows the rock being dug away to get to the road base to set up for the third blast. This was done to provide good coupling with the well compacted material and not just setting the monitor on the loose rock road.
  • This table illustrates the different scale distances that were used for a 2 lb charge. We chose to start at a scale distance of ten after speaking to an industry professional who recommended nothing less than that. He said that based on the specific gravity of the monitor, anything less than ten would cause the monitor to become uncoupled and the readings would be inaccurate. The horizontal scale distances to different structures in the area are also included, most importantly the distance to the nearest inhabited building.
  • The data shown here is a graph of the PPV vs horizontal scale distance. A power trendline was fit to the data which compareddata was graphed as PPV (vertical axis) vs scale distance (horiz. Axis). A Power trendline was used to fit the data which compared well to the accepted model in which the ppv drops off drastically over a short distance and then flattens out.
  • By using the same data in a log-log scale, we can see a straight attenuation line. The slope of this line gives us our site constant n.
  • Coming back to the PPV equation we can put in the newfound constants based on testing. The n was given by the slope of the log-log line of data, and the 305.21 was found based on inputting different known PPV values for a given scale distance and then solving for the H-factor.
  • By using the new site constants that were found, a graph can easily be made showing the effects of different charges allowable for different distances that within 2, 1, and ½ inch/secThe vertical lines on the graph represent the horizontal distance to different important structures in the area, the most important being the nearest inhabited building. Here we can see that to keep the PPV under ½ inch/sec, a charge of about 12 lbs could be shot, for 1 in/sec– 50 lbs and 2 in/sec 225 lbs.
  • This graphic shows an overlay of radii at which 1.0 in/sec peak particle velocities are present for different size charges. The numbers present here were determined to be very conservative numbers based on our test setup as we have never had a PPV of 1.0 in/sec at the first office which according to the results should be present at a charge as small as 7.3 lbs. of the test setup.Note that based on previous testing, we have never had a ppv of over 1.0 in/sec at our test site’s office.LABEL LARGE SIZE THAT THIS IS 1.0 in/sec
  • The continuation of the first study involved testing to see what the effects of elevation on PPV were.This is highly useful information for two reasons. The first reason is that the Explosive Research Laboratory is on the side of a mountain above inhabited buildings.The second is that no well published articles have been done and so the effects are relatively unknown
  • As we can see, elevation can affect the peak particle velocity from 2 to 3 times as much even over as short of a distance as this test which was about 56 ft.
  • More elevation studies are going to be done in the same manner as the first set of tests. The goal of the next testing will be to determine at what point does the vertical ground displacement begin to subside. At the current ranges that have been tested, there is there is not statistically significant differences between the blast and a Scale distance of thirty and between a scale distance of 30 and 40.The air blast testing will be done using our new data asquisition system through the use of pressure (CHECK NAME) pressure guages (TRANSDUCERS?)Measurements
  • This is our new data acquisition system showing our pressure transducers. It also allows us to measure up to 8 channels of velocity of detonation.No vertical titling
  • POST PRESENTATION NOTES:One gentlemen interested in the Data acquisition system. He had not seen it before and found it intriguing.Another gentlemen suggested getting in contact with geophysics. “Single shot monitors are just toys”. They can record nine readings at once with some of their machines.

Propagation of Ground Vibrations Due to Explosives Presentation Transcript

  • 1. Environmental Concerns at Colorado School of Mines Explosive Research Laboratory
    Presented by:
    Nicholas Matthews, AXPRO Group
    Mining Engineering Undergraduate at Colorado School of Minesnmatthew@mines.edu
    Presented to:
    MNGN 407
    Saturday February 20, 2010
  • 2. Special Thanks
    To Colin Matheson, of Matheson Mining Consultants, for his generous support, and also to Damian Murphy of Oldcastle Materials.
  • 3. CSM Explosives Research Laboratory
    Established in 2007
    Predominantly Surface Blasts
    Initial Limit Set at a 20 lb limit
  • 4. Location
  • 5. Location
  • 6. Location
  • 7. Reason for Study
    Inhabited buildings in the area
    CSM Edgar Mine
  • 8. Safety Zone of Environmental Effects
    Air Blast
    Decibels
    Ground Vibrations
    PPV
    frequency
  • 9. Prediction of PPV
    Equations
    Legend
    PPV = peak particle velocity
    H = a unit-less site constant,
    R = radius
    Q = charge weight
    n= site constant, equal to the slope of the log-log trend line
    Z = Scale Distance
  • 10. Instrumentation
  • 11. Instrumentation
    Range: up to 10 in/s (254 mm/s)
    Accuracy: +/- 5% or .02 in/sec (0.5 mm/sec)
    Frequency Range: 2 to 250 Hz
    Settings used:
    Continuous Record
    .125 mm/s (.005 in/sec) trigger
  • 12. Experimental Setups to Determine Site Specific Parameters
  • 13. Experimental Setups to Determine Site Specific Parameters
    Station: 1 2 3 4 5 6 7
    ScaleDist:
    1020 30 405060 70
    *Each represents one blasting monitor (geophone +/- microphone)
  • 14. Experimental Setups to Determine Site Specific Parameters
    60
    10
    50
    30
    40
    20
  • 15. Experimental Setups to Determine Site Specific Parameters
  • 16. Experimental Setups to Determine Site Specific Parameters
    Towards Seismographs
    Towards Seismographs
  • 17. Experimental Setups to Determine Site Specific Parameters
  • 18. Experimental Setups to Determine Site Specific Parameters
    Post Blast Crater—20 g Booster
  • 19.
  • 20.
  • 21.
  • 22. Site Constants
    n = -1.04
    H= 305.21
    Z = Scale Distance
    PPV = 305.21*Z-1.04
  • 23. Research Office
  • 24. 1.0 in/sec
  • 25. Elevation Studies
    Effect on PPV
    How much PPV is affected
    Range of effects from elevation change
  • 26. Elevation Scale Distances
    60.43
    45.05
    21.26
    15.19
    19.7°
    20.6°
    56.57
    42.42
    30
    40
  • 27. 30
    40
  • 28. 30=
    ~10.65
    ~12.25
    Monitor Scale Distances:
    40=
    ~15.7
    ~14.3
    ~15.0
    ~6.83
    ~2.5
    Average PPVs at Seismographs
  • 29. Horizontal Vs. Elev.
  • 30. Conclusions
    Elevation Can drastically affect PPV
    Below vs. Above
  • 31. Further Testing
    More Studies at Elevation
    More accurate air blast readings to complete model
    Using new pressure gauges and data acquisition system
  • 32. Further Testing
  • 33. QUESTIONS?
    Thank you for listening.
  • 34. References
    Attewell, 1964 P.B. Attewell, Recording and interpretation of shock effects in rock, Min. Miner. Eng. 1 (1964), pp. 21–28 (USA). (Attewell)
    Davies et al., 1964 B. Davies, I.W. Farmer and P.B. Attewell, Ground vibration from shallow sub-surface blast, The Engineer 217 (1964), pp. 553–559 (London, UK). (Davies)
    Daemen, 1983 Daemen, J.J.K., 1983. Ground and air vibrations caused by surface blasting. USBM report prepared by Department of Mining and Geological Engineering, University of Arizona, Tucson, AZ 85721, USA. (Daemen)
    E.I. du Pont de Nemours & Company. 1900s. Blaster's handbook. Wilmington, Del: E.I. du Pont de Nemours, pp 591-622. (du Pont).
    Google. "Edgar Mine--Idaho Springs, CO." 39° 44' 49.53" N and 105° 31' 30.98" W  Google Earth. November 5, 2004. October 3, 2009. (Google)
    Instantel. "Event Report". Blastware 10.02, Xmark Corporation.  2009. October 8, 2009. (Instantel)
    Khandelwal and Singh, 2007 M. Khandelwal and T. Singh, Evaluation of blast-induced ground vibration predictors, Soil Dynamics and Earthquake Engineering 27 (2007), pp. 116–125. (Khandelwal)
    Moris, 1950 Moris, G., 1950. Vibration due to blasting and their effects on building structure. The Engineer 394–395 (London). (Moris)
    R. Nateghi, M. Kiany, O. Gholipouri, Control negative effects of blasting waves on concrete of the structures by analyzing of parameters of ground vibration, Tunnelling and Underground Space Technology, Volume 24, Issue 6, November 2009 (Nateghi)
    Olofsson, 1998 S. Olofsson, Applied Explosive Technology for Construction and Mining, Publisher APPLEX (1998). (Olofsson)
    Pal Roy, 2005 P. Pal Roy, Rock Blasting Effects and Operations, Balkema Publisher (2005). (Pal Roy)
    United States, and D. E. Siskind. 1980. Structure response and damage produced by ground vibration from surface mine blasting. [Washington, D.C.]: U.S. Dept. of the Interior, Bureau of Mines. (Siskind)
    Sivarajan et al., 2007 V. Sivarajan, K.L.D.S. Kumara, H.M.S.D. Hearath and N.W.P. Nanayakare, Ground vibration and air blast overpressure assessment using scaled distance, Proceedings of ERE (2007), pp. 33–36. (Sivarajan)