PURPOSE:To execute works for a sunk well economically by driving the sunk well in division vertically arranged, connecting them by a joint having expanding/contracting function, and thereby lessening generation of a bending moment in the axial direction of a catchment well due to horizontal force. CONSTITUTION:A sunk well 1 divided into divisions in vertical arrangement is set in an excavation hole 19 provided in a ground 3 and connected together by a joint 2 having expanding/contracting function. At the bottom of this sunk well 1 which reaches near a landslide plane, a catchment pipe 4 is arranged which is inserted across in the radial direction in the ground 3 while penetrating the wall of sunk well. Water collected at the bottom 7 of this catchment well is exhausted through an exhaust pipe 5 to outside the landslide zone. Thereby the joint 2 exerts a hinge effect to lessen generation of bending moment in the axial direction of the catchment well due to horizontal force, which should lessen the section rigidity of the sunk well, so that the wall thickness of the catchment well can be lessened to ensure that the execution of works is made economically.
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