Chengdu shield mortarOne kind of hand-dug shield is the original kind of shield, which is simple in structure, less equipped and low in cost, and is still widely used in engineering with better geological conditions。The top of the shield has a movable front eaves to support the upper soil。Excavation is carried out manually from the top down, and an operation platform is set every 2 ~ 3m, which can adapt to various complex strata. The excavation face can be all open according to geological conditions, and the front support can also be used to support the excavation。The construction personnel can observe the formation changes, and it is easier to deal with the underground obstacles such as piles and solitons, easy to carry out shield correction, and easy to construct in the curve section。