Method of determining proper air supply pressure to caisson working room in pneumatic caisson construction method

摘要

PROBLEM TO BE SOLVED: To obtain a relation between air supply pressure and an inflow volume of groundwater in a manner that: reproduces a construction state of a pneumatic caisson method by excavating a borehole in an almost vertical direction in inspection object ground; increases pressure inside the borehole as is the case with actual construction; and measures the inflow volume of the groundwater into the borehole in a state where a certain volume of the groundwater is allowed to flow into the borehole from the inspection object ground.SOLUTION: A relation between air supply pressure P and an inflow volume Q of groundwater can be obtained in a manner that measures: the air supply pressure P which keeps an influent level of groundwater at a predetermined value by supplying air toward a lower end of a casing 20 through a gap between pressurizing piping 30 and drainage piping 40 in a state where the groundwater is allowed to flow into the casing 20 from inspection object ground; and the inflow volume Q of the groundwater into the casing 20 by draining the underground water flowing into the drainage piping 40 with drainage means (a submerged pump 60).