Segment attached to the cutter head, cutter disc is a key part of the pipe, the pipe jacking front-end, direct contact with the soil layer, the main function is to break the rock and soil. Usually there are four forms of the knife dish, 1. The vertical plate type: more used in the soft soil such as clay, silt 2, conical: early pipe using 3, shaft taper Suitable for sand, gravel bearing layer and hard soil layer, spherical 4: used in tunneling in hard rock.