EXCAVATION METHOD OF GROUND UNDER SPREAD FOUNDATION AND BASE-ISOLATING METHOD OF EXISTING BUILDING

PROBLEM TO BE SOLVED: To excavate the ground under a spread foundation without constructing a temporary receiving pile.SOLUTION: After constructing a shaft, excavation of the ground 29 under a spread foundation 22 of an existing building 20 is started from an entrance at the depth to an excavation bottom surface 48. That is, the excavation is advanced from a footing 24A to a footing 24B. When the front side in an excavation direction of the footing 24B is excavated, the footing 24B is obliquely received by an inclined support 54 inclined in the same direction as a slope face 50. The lower part of the inclined support 54 is received by a slide-stop support 56. When the excavation is advanced further to the center part of the footing 24B, the footing 24B is obliquely supported similarly by an inclined support 55, and the lower part of the inclined support 55 is received by a slide-stop support 57. Thereafter, the inclined support 54 and the slide-stop support 56 are detached, and a part which has been received by the inclined support 54 is received again in the vertical direction by a vertical support 60. As a result, the footing 24B is continuously supported by the inclined support 55, the vertical support 60 and the ground 29.