Boring to recommend a local excavation approach, first picks or excavation at the top put a small gun in place of the top of the excavation, the top of the first u-steel temporary support, and then dig two walls, walls, dug in place, install the u-steel legs. u-steel after the completion of the temp

Boring suggested that take partial excavation of the first method, with jackhammers or small guns on the top, and dig dug up top to top, first with steel U temporary support, and dig dug two walls, walls in place, installing U steel legs. Steel U temporary support is complete, then dug middle part.

The tunneling suggested adopts excavates the method partially, after uses the air pick first or puts the small artillery the method to excavate the crown, the crown excavates the arriving, the crown uses the U section temporary supports and protections first, then digs two walls, the wall digs the a

Driving the local excavation methods are recommended, with a pick or small Cannon top of the excavation, excavating at the top in place, top u-temporary support, to dig two walls, dig the walls in place, install the u-shaped steel legs. U-temporary support is complete, you dig the middle part. Excav