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Tunnel Construction. Tunnels are dug in types of materials varying from soft clay to hard rock. The method of tunnel construction depends on such factors as the ground conditions, the ground water conditions, the length and diameter of the tunnel drive, the depth of the tunnel, the logistics of supporting the tunnel excavation, the final use and shape of the tunnel and appropriate risk management.
The risk of cave-in increases from surcharge load, which is any weight placed outside the trench near its edge. These loads include the spoil pile (soil excavated from the trench) or heavy equipment. These add extra stress to the walls of the trench. Inability to escape the trench because of steep and unstable walls, which may be difficult to ...
Various geotechnical engineering methods can be used for ground improvement, including reinforcement geosynthetics such as geocells and geogrids, which disperse loads over a larger area, increasing the soil's load-bearing capacity. Through these methods, geotechnical engineers can reduce direct and long-term costs. [12]
Over time a 525 m (0.326 mi) section of the deep cutting has been converted back into tunnel due to sections having buildings built over. Box Tunnel in England, which opened in 1841, was the longest railway tunnel in the world at the time of construction. It was dug by hand, and has a length of 2.9 km (1.8 mi).
Excavation may be classified by type of material: [1]: 13.1 Topsoil excavation; Earth excavation; Rock excavation; Muck excavation – this usually contains excess water and unsuitable soil; Unclassified excavation – this is any combination of material types; Excavation may be classified by the purpose: [1]: 13.1, 13.2
A pile or piling is a vertical structural element of a deep foundation, driven or drilled deep into the ground at the building site. A deep foundation is a type of foundation that transfers building loads to the earth farther down from the surface than a shallow foundation does to a subsurface layer or a range of depths.
It is typical for progress (the "sinking rate") in the sinking phase (that is excavation, ground support and lining) of a shaft project to follow a learning curve as the project team repeats the same series of activities over and over in what is called "the sinking cycle", eventually approaching the theoretical maximum rate for that sinking set ...
Formwork for beams takes the form of a box that is supported and propped in the correct position and level. The removal time for the formwork will vary with air temperature, humidity and consequent curing rate. Typical striking times are as follows (using air temperature of 7-16 °C): Form work. Beam sides: 9–12 hours. Beam soffits: 8–14 days.