Tunnel boring machine and tunnel reverse expanding method

The invention provides a tunnel boring machine and a tunnel reverse diameter expanding method, and relates to tunneling equipment, the tunnel boring machine comprises a diameter expanding cutterhead with a cutterhead body, the front end face of the cutterhead body is provided with a front rolling cutter, the rear end face of the cutterhead body is provided with a back rolling cutter, and the side face of the cutterhead body is provided with a side face cutting cutter; when the tunneling machine conducts tunneling in the reverse direction, the front face rolling tool and the side face cutting tool crush rock soil, when the tunneling machine conducts tunneling in the reverse direction, the back face rolling tool and the side face cutting tool crush the rock soil and enlarge the excavation diameter, and reverse reaming can be achieved by arranging the back face rolling tool on the rear end face of the cutter head body. During reverse reaming, the tunnel face is transferred to the back face of the expanding cutte