TUNNEL EXCAVATION DEVICE, AND TUNNEL CONSTRUCTION METHOD

PROBLEM TO BE SOLVED: To reduce an outbreak amount while securing an excavation speed.SOLUTION: A tunnel excavation device 10 for executing finish excavation of a peripheral edge part 1a of a pile 1 formed by blast excavation is capable of traveling on a construction base face 3, and includes a full revolving type base machine 20, a boom arm 30, and a cutter head 43. The cutter head 43 is rotatable with a direction almost the same as the extending direction of the boom arm 30 as a rotary axis P. A contour of a moving area of a bit in the case of projecting the moving area of the bit when the cutter head 43 is rotated on a surface in parallel with the rotary axis P is roughly a chevron shape whose peak is a distal end of the cutter head 43. An angle 1 formed by a straight line connecting the peak of the contour of the moving area of the bit and a tip end of the bit most separated from the peak and a straight line orthogonal to the rotary axis P is within the range of 40° to 50°. Also, an angle 2 formed by a ridge line of the contour of the moving area of the bit and a straight line orthogonal to the rotary axis P is equal to or smaller than 60°.