PURPOSE: To form a dry space in an inside enclosed by a caisson by setting the caisson furnished with an opening section at the bottom surface, which coincides with a channel on riprup mound furnished with the channel connected to a rock mass, and thereby integrating both of them into one by means of concrete placing in water.
CONSTITUTION: A riprup mound 1 is first formed with a channel 2 by the use of a cut-off block 3 made of concrete, which is made up out of double wall panels faced to each other, and of a periphery plate. In the second place, a cut-off zone 33 made of impermeable material is set by making use of a spacer consisting of the cut-off block 3. On the other hand, in constructing the caisson, an opening section is provided at a position which coincides with the channel 2 when the caisson is rested on a mound 1, the caisson is carefully lowered down therefore in such a way that both of them mutually coincide with, so that it is thereby rested on the mound 1. Following which, reinforcing bars are then placed while both of the channel 2 and the opening section are being penetrated through, and when concrete is placed in water until it reaches an under water rock mass, the mound 1 is completely integrated with the caisson, so that a cut-off wall is thereby formed.
KISHI YASUHIRO
SUGIYAMA KAZUYA
