| 摘要 |
PURPOSE:To decrease the floor area to be excavated and reduce a term of setting works, by installing an upper cover to be fixed by an upper cover setting leg, set to the upper surface of a high rigid casing, and enabling a supporting length of an upper cover arm and the setting leg to be reduced. CONSTITUTION:A high rigid casing 5 secures to its upper pat an upper cover setting leg 13, while this setting leg 13 sets an upper cover 7, arranged protruding from a housing 4, to be fixed. In this way, a supporting length of an upper cover arm 7c and the setting leg 13 can be reduced. As a result, the manufacturing cost of a setting part can be reduced while the deformation at concrete placing time can be suppressed because of no necessity for increasing the rigidity as in the past. Further a term of setting works can be reduced because the works both reduce an excavation area of base rock and require only one time concrete placing. |
