NEW METHODS FOR CALCULATING EXPLOSIVES CHARGES

THE RAPID DEVELOPMENT OF BLASTING TECHNIQUES AND THE INTRODUCTION OF SHORT-DELAY BLASTING HAVE MADE IT POSSIBLE TO OPERATE WITH AN ENTIRELY DIFFERENT AMOUNT OF CHARGE. BLASTING CAN BE CARRIED OUT AT PLACES WHERE MORE EXTENSIVE OPERATIONS PREVIOUSLY WERE OUT OF THE QUESTION BECAUSE OF THROW AND GROUND VIBRATIONS. IN CONSEQUENCE, THE DEMANDS FOR ACCURATE METHODS IN CALCULATING THE SIZE OF CHARGES AND THEIR DISTRIBUTION IN THE DRILL-HOLES HAVE BECOME MORE RIGOROUS. A BETTER UNDERSTANDING OF THE EFFECTS OF SUCH FACTORS AS DIAMETER OF THE HOLE, DEGREE OF TAMPING, HEIGHT OF THE CHARGE, ETC., UPON THE RESULT IS ALSO NECESSARY. TAKING THE BREAKING MECHANISM AS A STARTING POINT, THE FOLLOWING IS A GENERAL ORIENTATION FOR DETERMINING THE FACTORS WHICH INFLUENCE EXPLOSIVE EFFECT IN ROCK BLASTING. THE BREAKING PROCESS IN THE BLASTING ROCK TAKES PLACE IN TWO STAGES PRODUCING A SYSTEM OF RADIAL CRACKS AROUND THE DRILL HOLE. THESE PRIMARY CRACKS ARE IMPORTANT IN THAT THEY ENABLE ENERGY TO BE UTILIZED IN THE RIGHT DIRECTIONS. A MORE POWERFUL CHARGE IS USED AT THE BOTTOM OF THE HOLE. SMALLEST CHARGE REQUIRED FOR LOOSENING THE ROCK PRESUPPOSES A CONCENTRATION BOTTOM CHARGE AND AN EVENLY DIVIDED PIPE CHARGE. THE BOTTOM CHARGE IS THEN SUFFICIENT FOR THE LOOSENING ACTION UP TO A HEIGHT V, THE BURDEN. EACH PIPE AND BOTTOM CHARGE IS DETERMINED IN TWO PARTS: ONE BEING PROPORTIONAL TO THE VOLUME AND THE OTHER PROPORTIONED TO THE TEARING AREA. THESE ARE DEPENDENT ON THE ROCK, WHICH CANNOT BE CHARACTERIZED BY ONE CONSTANT ONLY, BUT BY SEVERAL AND THESE DIFFER FOR THE BOTTOM AND THE PIPE. THE DIFFERENCE IS SO IMPORTANT THAT THE CHARGE PER CUBIC YARD IS 2.5 TIMES GREATER IN THE BOTTOM THAN IN THE PIPE. SHORT-DELAY- BLASTING HAS MADE IT POSSIBLE TO INCREASE FRAGMENTATION WITHOUT INCREASING THROW BY VARING THE BOTTOM AND PIPE CHARGES.

• Supplemental Notes:
  • Vol 26, No 7, PP 34-40, 3 FIG, 4 REF
• Authors:
  • Langefors, U
• Publication Date: 1956-7

Media Info

• Serial:
  • Highway Research Abstracts
  • Publisher: Highway Research Board (HRB)

Subject/Index Terms

• TRT Terms: Calculation; Depth; Explosives; Strength of materials
• Uncontrolled Terms: Computation
• Old TRIS Terms: Explosive charges
• Subject Areas: Construction; Highways;

Filing Info

• Accession Number: 00215491
• Record Type: Publication
• Files: TRIS, TRB
• Created Date: May 29 1972 12:00AM