ABSTRACT
Scope of application: a. earth pressured shield machine can be suitable for most kinds of geological conditions, ranges from soft sand soil stratum to sandy gravel stratum. Excavated soil layers are separated into soil particles and muddy water when they are transported to the ground as slurry status. The separation equipment set on the ground occupy such a large area that the recent use has been limited; b. earth pressure balanced shield machine is suitable for plastic liquid clay with less sediment concentration which can be excavated by cutters; c. soil pressured shield machine is equipped with added materials like bentonite, CMC, clay, super absorbent resin, vesicant and so on, which can be selected by different soil properties. This kind of machine is suitable for a wide range of geological conditions such as alluvial clay, pluvial clay, sandy soil, gravel, grait and alternation of beds among these stratums. At the back of cutter of soil pressured shield machine is equipped with agitating vane which can stir the whole soil space compulsively. Excavated soils are mixed with bentonite, CMC, clay or foam materials to transfer into plastic liquid clays with impermeability. Such clays are full of soil space and screw conveyer, can balance earth pressure and water pressure in excavation face. This machine with spoke cutter can be applied to a wide range of soil [7]; c. slurry shield machine transform excavated soils into slurries by adding materials. This is more suitable for huge gravel bed and is less used in practical project. Figure 1 shows some typical types of shield machines.
