METHOD FOR MEASURING DISCHARGE QUANTITY OF PILE MATERIAL IN PILE PLACING CONSTRUCTION

PURPOSE:To improve measurement accuracy of exhaust quantity of the pile material by feeding sound wave from the outside to an inline air column, which is formed by a casing and the top surface of the pile material, and obtaining the top surface position of the pile material on the basis of a resonance frequency, which is obtained on the basis of the detection of that sound wave, and the sound speed of the inline air pressure column. CONSTITUTION:Under the condition that a cover of a hopper 4 is closed, white noise is radiated from a speaker 32 into a casing 2. Next, the resonance sound of this sound wave inside of the inline air column is detected by a microphone 34, and the resonance number f0 is analyzed by a frequency analyzer 36 on the basis of this output signal, and is transferred to an inline air column computing unit 38. On the other hand, a temperature (t) inside of the inline air column read out by a temperature sensor 35 is transferred to the inline air column computing unit 38 through an inline temperature measuring circuit 37. Length lof the inline air column is computed on the basis of a resonance frequency f0 and the sound speed (v), which is obtained on the basis of the temperature (t), with a formula l=v/(2.f0).