| 摘要 |
PROBLEM TO BE SOLVED: To provide an underdrain-forming apparatus by which a vertical port passage is kept even if both opposite surfaces of bored groove trace is made closely narrow and blocked by passage of time, capable of favorably keeping draining property and air ventilation of an underdrain by presence of the vertical port passage. SOLUTION: This underdrain-forming apparatus is obtained by connecting a machine frame 3 to a traveling machine body 1 by a connecting mechanism 2, swingably vertically installing boring beam 4 in advancing direction by a swinging mechanism 5 in the machine frame and installing a bullet body 14 capable of forming the underdrain in the soil in the lower part of boring beam, installing an enlarging member 15 capable of forming, alternately to right and left, a vertical port passage T opening on the ground surface by enlarging the opposite surfaces of a boring trace groove S extended and formed in the vertical direction in the soil by the boring beam at the backward position in the advancing direction of the boring beam and installing an alternately enlarging mechanism 16 for carrying out alternate enlarging action of the enlarging member. COPYRIGHT: (C)2003,JPO
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