ABSTRACT
Because of diversified social demands, urbanization and environment preservation concerns, strict conditions have been imposed on mountain tunneling projects, with restrictions on the alignments of tunnels. Recently, injection type long steel forepiling has been widely used, aimed at stabilizing the face and limiting displacement ahead of the face. However, under the requirement that impact of tunnel excavation should be minimized, this method fails to satisfactorily control loosening ahead of the face in some ground conditions, because this technique reinforces the portion around the crown ahead of the face but it does not strengthen the face.
