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digger-shield mole
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digger-shield mole

tunnel machine
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Quick Summary

The digger-shield mole is a type of tunneling machine that excavates earth with drag teeth and discharges muck onto a conveyor belt, operating within a protective shield. This machine features a hydraulic-powered digger arm that excavates ahead of the shield. The shield's protection can be extended forward using hydraulically operated poling plates, which act as retractable spiles.1

This type of machine has demonstrated impressive progress, with one instance in the Saugus-Castaic Tunnel near Los Angeles completing five miles of tunnel half a year ahead of schedule. Similar designs have also proven effective in compacted silt for sewer tunnels. Tunneling shields, in general, are machines designed for driving tunnels in soft ground, particularly under rivers or in water-bearing soil.12

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3 Britannica Sources
  1. tunnels and underground excavations - Soft-ground moles
  2. tunneling shield
  3. tunnels and underground excavations - Shield tunnels

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