Chicago : Engineering and Contracting Pub. Co. · leaf 80
firing, and clearingaway was then done by 22 men in from 3 to 4 hr. The charge per hole averaged 1.75 lb., and after firing, a strong current of com-pressed air was directed over the face of theexcavation. Four sets of holes were, underfavorable circumstances, drilled in 24 hr.,which rendered… … Fig. 2—Drill Shaft in Position to be Jacked.
Buildings
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