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Size

Size is an important distinction in pipe jacking and microtunnelling because, when there is no possibility for access to the tunnel face, there is no possibility to change cutterheads or remove obstacles ahead of the face without sinking a shaft from the surface. Also, in larger diameter microtunneling and pipe jacking projects, the jacking pipes have a great axial load carrying capacity and longer drives can be accomplished. Furthermore, smaller diameters for the tunnel affect the possibilities available for muck removal - with slurry systems and augers being used in the smaller diameters and conveyor systems or muck cars being possibilities in the larger diameters.

Person-entry pipe jacking allows a wide range of tunneling excavation and face support methods to be employed. Typically, a steel cylindrical tunnel shield is used at the face and is pushed ahead of the jacking pipes. Depending on tunnel size and ground conditions, various types of mechanical excavation equipment may be used and face support may include breasting plates, sand shelves and other forms of partial face support. Muck removal can be accomplished using a variety of methods – including muck cars or conveyor belts. Also, rectangular pipe jacking is becoming more widely used with its cross-sectional shape being particularly suitable for common utility tunnels or pedestrian underpasses.

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