| 摘要 |
PROBLEM TO BE SOLVED: To constitute the bottom section of an underground water storage tank surely and easily while preventing the effect of groundwater when the underground water storage tank is built by a pneumatic caisson construction method. SOLUTION: The bottom section of a cylindrical side wall body 2 buried under a ground by a pneumatic caisson construction method is composed of a bottom slab 3, in which divided bottom slabs 3a, 3b divided into two are combined and unified. Opening sections 37, 37 for pits are formed on the divided bottom slabs 3a, 3b, and the bit components 5 with recesses 40 are fixed onto the divided bottom slabs 3a, 3b while the recesses 40 are communicated with the opening sections 37. Drain inlets 51 are formed to the bottom sections of the recesses, and the lower ends of the drain inlets 51 can be opened and closed by automatic closing valves 57 automatically closed by water pressure. Groundwater is made to flow into the drain inlets 51 by pushing down the automatic closing valves 57 against water pressure, and removed by submerged pumps.
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