| 摘要 |
A vertical pit having a sufficient radius to carry the necessary equipments for forming the cavity is dug upto the common bottom level of the cavities. Then the horizontal tunnels are dug upto the desired positions for the cavities. From those positions, the cavities are formed by digging the subterranean upwardly. The first vertical pit is used as a water feeding pit for balancing the liquified gas level by compensating water pressure after the cavities are completed to form.
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