EXPANSION EXCAVATION DEVICE AND EXPANSION EXCAVATION METHOD

To solve the problem in which conventionally, since an expansion blade is rotated on a vertical axis, an excavation length of the expansion blade becomes long, which causes a problem that an excavation surface pressure decreases and the applicable ground is limited.SOLUTION: A holding and fixing device 15 for fixing a casing K is provided. An upper part of an expansion head H for excavating an expansion hole 8 having a conical slope portion 11 having a diameter larger than that of a vertical hole 6 and a columnar rising hole portion 35 below the slope portion 11 in a ground W is attached to the holding and fixing device 15. The expansion head H is provided with an expansion blade 12 for excavating the slope portion 11 and the rising hole portion 35 of the expansion hole 8, and a lower support member 30 for supporting a lower portion of the expansion head H. In lower support member 30, with the expansion blade 12 expanded, when an expansion excavator 10 and the casing K are driven and rotated while being raised to a predetermined height, and a columnar rising hole 35 having the same diameter as the maximum diameter of the slope portion 11 at a lower part of the slope portion 11 is excavated, a support 32 abuts and supports a predetermined portion of the bottom of the vertical hole 6.SELECTED DRAWING: Figure 1 【課題】従来、拡大翼を縦軸回動させるので、拡大翼の掘削長が長くなり、そのため、掘削面圧が低下し、適用地盤が限られるという課題がある。【解決手段】ケーシングＫと固定状態とする保持固定装置１５を設け、保持固定装置１５に、地盤Ｗに縦穴６よりも大径の円錐状の斜面部１１と斜面部１１の下方の円柱状の立上がり穴部３５とを有する拡大穴８を掘削する拡大ヘッドＨの上部を取付け、拡大ヘッドＨは、拡大穴８の斜面部１１および立上がり穴部３５を掘削する拡大翼１２と、拡大ヘッドＨの下側部分を支持する下側支持部材３０とを設け、下側支持部材３０は拡大翼１２を拡大させた状態で、拡大掘削装置１０とケーシングＫとを駆動回転させたまま、所定高さまで上昇させて、斜面部１１の下部に斜面部１１の最大径と同径の円柱状の立上がり穴部３５を掘削する際に、支持体３２が縦穴６の底部の所定部分に当接して支持する構成とした拡大掘削装置。【選択図】図１