Page 473 - Moving the Earth_ The Workbook of Excavation
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BLASTING AND TUNNELING
BLASTING AND TUNNELING 9.73
FIGURE 9.63 Installation of headed and slotted bolts.
The soft ground technique is to follow the heading closely, with some resulting interference
between operations. Perhaps the most serious is maintaining a track for muck cars through the
pouring operation, and across the freshly laid invert (floor). Steel beam bridges may be used to
carry the track in this section.
1
The invert may be laid about 1 ⁄ 2 inches low, protected with planking, and brought up to grade
with a top dressing of thin concrete as a finishing operation after the tunnel is complete.
