PURPOSE: To support the excavation reaction force of an excavating machine with a timbering member and easily remove it with the excavating machine by integrally forming a lining member and support rods preventing the collapse of the ground with steel-nonreinforced concrete.

CONSTITUTION: A reaction force receiving timbering member 10 is constituted of a lining member 11 fitted on the excavation inner periphery of a tunnel in a ring shape to prevent the collapse of the ground and support rods 12 radially provided on the inner periphery of the lining member 11. The lining member 11 is made of steel-nonreinforced, fiber-reinforced concrete, and multiple arc- shaped pieces 13 are integrated into a ring shape. The lining members 11 integrated into a ring shape are connected in the axial direction of the tunnel, and the inner periphery is made a lining with the preset length. The support rods 12 are molded with steel-nonreinforced concrete, they are fixed to the lining member 11 with fixing bolts 14, and they are connected in the axial direction to support the excavation reaction force of the jacks of an excavating machine. When a pilot tunnel is to be expanded after its excavation is completed, the reaction receiving support member 10 is crushed removed by the excavating machine together with the surrounding ground.