Review and Analysis of Blasting and Vibrations at Bankhead Lock.
ARMY ENGINEER WATERWAYS EXPERIMENT STATION VICKSBURG MISS
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The U.S. Army Corps of Engineers recently replaced the old Bankhead Lock on the Black Warrior River, Alabama, with a larger lock. The new lock required an approach canal excavated by the removal of more than 5 million cu yd of rock. Preliminary test shots and an exploratory excavation contract of 0.35 million cu yd established blasting and monitoring techniques that assured that vibration and settlement of the old lock would not be excessive. Shots were monitored with particle velocity pickups on and adjacent to the lock. A relationship between peak particle velocity and scaled distance was checked on the basis of these data after normalization for structure behavior, coupling, and transmissivity. Recommendations from the test shot program were used in specifications for the exploratory excavation contract. The exploratory excavation, with about 50 presplit and production shots, served as a second testing program for refining the previous observations and conclusions, according to various blasthold arrays and time delays. A principal product of this work was a refined criterion for no-damage to be used in the main excavation contract. The experience gained in preliminary work allowed for more realistic and lower unit-price bids on the main contract. During the main contract, involving the excavation of 5 million cu yd of rock, about 1000 shots were fired on nine working levels. Analyses of data generated on this project revealed the effects of three factors delay, confinement, and to a lesser degree, explosive type. A log normal distribution of peak particle velocities was indicated by analyses of data from large groups of presplit and production shots.
- Hydrology, Limnology and Potamology
- Civil Engineering