DETECTION METHOD FOR UPPER PILE-MEMBER SURFACE POSITION IN PILE-PLACING PROCESS

摘要

PURPOSE:To increase the measuring accuracy of an upper pile surface position, by determining the length of an intratube air column from the resonance frequency based on the detection of sound waves introduced into an intratube air column formed by a casing and an upper pile surface. CONSTITUTION:A whitish noise sound is introduced, from a speaker 16A, into an intratube air column formed by a casing 2 penetrated into a soft/weak ground 1, an upper casing end 20, and an upper pile surface 10, thereby to detect intratube resonance by means of microphones 19, 26. Then, the resonance frequency is analyzed by a frequency analyzer 21, the output of which is transferred to an intratube air column calculation section 22. Subsequently, a distance covering from a pile introduction port upper/lower boundary 25 to the upper pile surface 10 is calculated from the two intratube air column resonance frequencies and the distance between the upper casing end 20 and the boundary 25. This enables determination of a highly accurate upper pile surface position independently of the intratube temperature distribution.