DEVELOPMENT OF AN EFFECTIVE FOREPILING METHOD WITH MIDDLE LENGTH PIPES

Recently, NATM method has been adopted in tunneling under shallow and unconsolidated ground. In order to stabilize the face and control the ground surface settlement, a variety of forepiling methods have been proposed. Above all, long-sized forepiling is evaluated as the effective one for its ability to reinforce the ground. However, this method is not economical, and has a bad influence on the total construction period. Therefore, authors proposed a new forepiling method using middle-sized forepiling as the more effective one, based on a series of laboratory tests. In this paper, the outline of this new method, the results of laboratory tests and its application to actual work are presented.