Due to tool wear,the tunneling section of the shield machine in the hard rock stratum is under-excavation,and the length of the longitudinal under-excavation is about 2.5 m,resulting in the left and right line of the shield machine being stuck in the rock stratum at the same time.In order to get the shield out of trouble,the section of the upper half of the tunnel in the under excavated section is expanded by blasting.Before expanding the section,it is necessary to excavate a certain length of blasting on the front face of the shield machine,so as to create operation space for drilling and blasting construction(reverse blasting) in the under-excavated part.The first round blasting close to the tunnel face of the shield machine knife plate is the most difficult.Firstly,the distance between the cutter head and the blasting body is the smallest,so the damage to the cutter head caused by blasting impact should be avoided; The second is to consider the crushing damage to the cutter head caused by the increase of rock crushing volume after blasting.Therefore,short footage,less charge and zone blasting are adopted to reduce the damage of the aforementioned harmful effects on the cutter head.In the reverse excavation blasting,the cutting blasting with the largest impact force should be arranged far away from the shield shell,and measures such as non-coupling charge,symmetrical initiation and charge control should be adopted to finally blast the section of the under-excavation part into place,so that the shield machine can safely escape.Under the condition of hard rock(compressive strength greater than 150 MPa),in a narrow space with a width of 0.6 m(between shield shell and rock) and a hole depth of 2.8 m,the reverse excavation blasting can make the blasting rate reach more than 90%,which is inseparable from the use of cutting of annular empty hole(6 empty holes are arranged around the middle charging hole).This method can be used to solve the problem of shield machine being stuck under medium hard rock and hard rock conditions.