抄録
Cast-in-place concrete piles are made by placing concrete into slurry that fills an excavated hole, and where appropriate control of the physical properties of slime and slurry is necessary. Electric resistivity of suspension generally depends on the content of the suspended substance, so that physical properties such as density, sand fraction and funnel viscosity of slurry and sand fraction of slime, are closely related to resistivity of slurry and slime. In order to control these physical properties, we must measure their depth distributions in excavated holes. Measurement of resistivity in excavated holes continuously by depth is relatively easy, so we attempted to obtain information on physical properties of slurry and slime by measuring vertical distributions of resistivity. Relationships between the resistivity and physical properties of slime and slurry were determined in the laboratory test, and the vertical resistivity distribution of the slime and the slurry in the hole of a cast-in-place pile at excavation was also studied with a sensor capable of recording in-situ resistivity continuously. As a result, it was found that changes of resistivity were widely affected by the bentonite content of slurry and the sedimentation thickness of slime can be estimated with satisfactory precision by the vertical resistivity distribution (depth profile of resistivity) in an excavated hole. The resistivity method can be an effective, promising control method for the physical properties of slurry when the relationship between resistivity and the properties is quantitatively determined.
