Greathead shield
Quick Summary
The Greathead shield is an advancement in tunneling technology, primarily used for constructing tunnels in soft ground, especially under rivers or in water-logged soil. British civil engineer James Henry Greathead refined the tunneling shield, essentially creating its modern form.
Building upon earlier designs, Greathead's shield was circular in cross-section and could be pushed forward using screw jacks. As the shield advanced, the tunnel behind it was lined with cast-iron rings. Greathead also pioneered the use of compressed air in conjunction with his shield, which was crucial for preventing flooding in underwater tunnels. This combination of the shield, compressed air, and cast-iron lining became standard practice in tunnel construction.12
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