2010 Construction and Material Specifications - Ohio Department of ...

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208.10
S. Use the same diameter and drilled in the same plane and to the same
tolerance as the presplit holes when using unloaded and unstemmed guide holes
between presplit holes.
T. Detonate the presplit line before detonating any production holes, except
when the closest horizontal distance between the production line and presplit line
is greater than 50 feet (16 m).
208.10 Cushion (Trim) Blasting. If the horizontal distance from the cut face
to the existing rock face is less than 15 feet (4.5 m), the Contractor may use
cushion blasting instead of presplitting. Perform cushion blasting according to
208.09, except as follows:
A. Detonate along the cut face after the detonation of all production holes.
B. Between the trim line and the nearest production row, use a difference in
delay time of 25 to 75 milliseconds.
208.11 Sliver Cuts. For sliver cuts, pioneering the top of cuts and preparing a
working platform to begin the controlled blasting and drilling operations may
require unusual working methods and use of equipment. Use angle drilled holes or
fan drilled holes during the initial pioneering operations to obtain the desired rock
face. Apply the hole diameter requirements for controlled blasting for pioneering
work. Do not exceed a hole spacing of 36 inches (900 mm).
208.12 Blaster. Use an experienced blaster in charge of all blasting
operations. Use a blaster with at least 5 years of proven experience in heavy
construction or highway rock blasting and with a sufficient amount of proven
experience of the type of highway rock blasting required by the Contract.
Before or at the preconstruction conference, submit a resume of the credentials
of the proposed blaster. Include in the resume a list of at least five heavy
construction or highway rock blasting projects on which the blaster was
responsibly in charge of the rock blasting. List a description of the projects, with
details of the blasting operations. List the names and telephone numbers of project
owners with sufficient knowledge of the projects to verify the submitted
information. Obtain approval of the blaster before beginning any drilling and
blasting work. Allow 30 days for the review of this documentation. The blaster
shall perform the following:
A. Control the ground vibrations by the use of properly designed delay
sequences and by using allowable charge weights per delay.
B. Base the allowable charge weights per delay on vibration levels that will not
cause damage.
C. Establish the allowable charge weights per delay by carrying out trial blasts
and measuring the vibration levels.
D. Independently measure the vibrations and airblast at the closest structure
using the criteria and limits set in 208.15 and 208.16. Ensure that only trained and
certified personnel set up the seismographs.