| 摘要 |
PURPOSE:To make easier the penetration of a casing as well as prevent the degradation of the pit wall by a method in which in constructing on-site concrete piles, a large-diameter casing having a fluid jet nozzle for aiding excavation and a jet nozzle for a pit wall strengthening agent on the downside and the periphery of its tip. CONSTITUTION:A jet nozzle 30 to jet an excavation aiding fluid downwards is provided to the downside of the tip of a casing 1, and also a jet nozzle 31 to jet a pit wall strengthening agent is provided to the periphery of the tip of the casing 1. The casing 1 is penetrated into the ground E while being turned with static load and at the same time an excavation aiding agent, e.g., air, water, etc., is jetted from the nozzle 30 to slacken the ground in the lower end portion of the casing 1. A pit wall strengthening agent, e.g., bentonite, etc., is jetted from the nozzle 31 and coated on and impregnated into the surrounding ground of the casing 1 to prevent the degradation of the pit wall. The large-diameter casing 1 is completely set and the ground inside the casing 1 is excavated by a hammer grab 5. |
