FRACTURE CONTROL IN TUNNEL BLASTING

This paper describes a procedure for achieving control of the fracture plane in construction blasting. The conventional drill-and-blast technique is modified in three ways. First, side notches that extend the length of the borehole are used to control the initiation site for the cracks that produce the fracture plane. Second, the pressure in the borehole is maintained between specified limits by using light and cushioned charges. Third, stemming length is increased to avoid venting that could produce premature arrest of the crack that produces the controlled fracture plane. The procedures suggested have been validated by using fracture mechanics computations, two-dimensional experiments in rock and polymeric models, and field tests in large rock boulders. Fracture control in tunnel blasting can reduce the time and equipment required to make the opening cut while increasing the size and improving the quality of the cut. Fracture control can also reduce the cost of contouring the walls and roof of a tunnel and at the same time improve tolerances and reduce structural damage to the remaining rock. /Author/

Media Info

  • Media Type: Print
  • Features: Figures; Photos; References; Tables;
  • Pagination: pp 8-14
  • Monograph Title: Tunneling and underground structures
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00196623
  • Record Type: Publication
  • ISBN: 0309028299
  • Files: TRIS, TRB
  • Created Date: Aug 28 1979 12:00AM