WorldWide Drilling Resource

Ten Tips for Blasting Seismographs Adapted from Information by the International Society of Explosives Engineers and Society of Explosives Engineers, Inc. A blasting seismograph is a special instrument used to measure and record ground and air vibrations from a blast. It has two sensors: a geophone (for monitoring ground waves) and a microphone (for monitoring air waves). The geophone meas- ures ground motion in 3D, while the microphone measures air overpressure (additional pressure generated by a blast). Accuracy of the recordings is essential. Here are ten tips for deploying blasting seismographs in the field: 1. Take time to read the instruction manual so you understand how to operate the instrument before monitoring a blast. 2. Seismographs should be calibrated annually. 3. Keep proper blasting seismograph records including the user’s name, date, time, place, and other important data in the user’s log. 4. Document the location of the seismograph, including the name of the structure and where it was placed on the property relative to the structure. Any person should be able to locate and identify the exact monitoring location at a future date. 5. Know and record the distance to the blast. The horizontal distance from the seismograph to the blast should be known to at least two significant digits. For example, a blast within 1000 feet would be measured to the nearest tens of feet and a blast within 10,000 feet would be measured to the nearest hundreds of feet. Where elevation changes exceed 2.5 horizontal:1 ver- tical, slant distances or true distance should be used. 6. Record the full time history waveform. Summary or single peak value recording options on seismographs should not be used for monitoring blast-generated vibrations. Operating modes reporting peak velocities over a specified time interval are not recommended when recording blast-induced vibrations. 7. The sampling rate should be set to record the entire blast event in enough detail to accurately reproduce the vibration trace. Typically, the sample rate should be at least 1000 samples per second. 8. Know the data processing time of the seismograph. Some units take up to five minutes to process and print data. If another blast occurs within this time, the second blast may be missed. 9. Ensure the memory capacity of the seismograph is enough to store the event. The full waveform should be saved for future reference in either dig- ital or analog form. 10. Allow ample time for proper setup of the seismograph. Many errors occur when seismographs are set up in a hurry. From the time the user arrives at the monitoring location until the blast, can take more than 15 minutes. The complete Field Practice Guidelines for Blasting Seismographs 2020 is available online at: www.isee.org EXB 38 NOVEMBER 2020 WorldWide Drilling Resource ® Foremost is excited to announce the DR-40SHD Dual Rotary drill has been added to their product lineup. It is Foremost’s first fully electric drill, which is controlled remotely using a mobile console for operator safety. The DR-40SHD features a new 40-inch lower drive with increased capacity (close to twice the torque of the current DR-40), and an improved chucking system. Utilizing a flexible setup to drill anywhere from vertical to horizontal angles, the DR-40SHD can be used in a wide variety of applications, including desali- nation projects and deep hole water wells. Foremost Industries is a Valued WWDR Advertiser.

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