The Journal of Explosives Engineering - January/February 2015 - 16

Figure 10. Results after most of the blast mats were removed.

Figure 11. The cofferdam partly removed. One of the new, partly finished
piers can be seen in the background.

and protected, sections of used conveyor belting were draped
over the ends of the pier. Long pieces, 30 ft (9.2 m) were
used so that they covered the structure to within a few feet
of water level. Then six heavy rubber tire blasting mats were
placed over the pier. Each mat was 7 ft x 14 ft (2.2 m x 4.3 m)
and overlapped the belting. The lead in nonelectric shooting
line was looped down close to water level out of the way of
the heavy mats.
After work was stopped and project personnel were removed to a safe distance, the seismograph was in place under the railroad bridge and activated, the flagmen were in
place and traffic was stopped, nearby residents were notified,
and the video cameras were focused and running-the shot
was fired.

was only water surrounding the concrete mass, it seemed to
have moved better, allowing easier excavation. The powder
factors used seemed to be sufficient. The success of this project proves that given ample incentives, other similar debris
containment projects are possible.

The author would like to commend the professionalism of Archie
Johnson Inc.; The Sletten Construction Company; and Paul Cogley, PE MDT, whose combined efforts led to the success of this
part of the project.

References
International Society of Explosives Engineers, 1998. ISEE Blasters'
Handbook™, 17th Edition. Cleveland, Ohio.

Conclusions
The blast mat/belting cover on the concrete mass was sufficient to keep all the debris contained within the cofferdam.
The shot resulted in a terrific jolt against the sheet pile wall.
A few of the sheets in the cofferdam were stretched by the
explosives energy to the point that the vibratory puller was
needed when the cofferdam was removed. Removal of the debris with the clam bucket was difficult. But working blind with
that type of loading device is always slow. All the concrete
was broken to depth, but because the mass near the bottom
was confined by the packed gravel and river rock, there was
no room for the pieces to be displaced by the explosion. The
debris removal from subsequent shots on the remaining piers
was somewhat easier because the contractor put in more effort to remove the packed gravel prior to the shot. When there
16

Acknowledgments

International Society of Explosives Engineers, 2011. ISEE Blasters'
Handbook™, 18th Edition. Cleveland, Ohio.
Oriard, L. L. and Coulson, J.H., 1980. TVA's Criteria For Blasting
Effects on Concrete. American Society of Civil Engineers Specialty
Conference on Minimizing Detrimental Vibrations Portland, Oregon April, ASCE, New York.
Oriard, Lewis L., 1999. The Effects of Vibrations and Environmental Forces. ISEE. Cleveland, Ohio.
Revey, Gordon D. PE, 2006. Managing Rock Blasting in Urban
Environments. ASCE. New York.

The Journal of Explosives Engineering

January/February 2015

The Journal of Explosives Engineering - January/February 2015

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