Abstract
In civil engineering, in order to improve weak foundations, many sand pillars are frequently struck into underground using a casing pipe. In that case, a smooth construction will be achieved if the sinking velocity of the sand level in the pipe is measured on-line accurately. The measurement of the level is reduced to that of a length of the air pillar in the pipe. The authors thus previously proposed, as the first step, an on-line accurate pipe length measurement system for straight pipes, which applied a bank of Kalman filters and Bayesian theorem to a linear dynamic model of the stationary wave in the pipe.
However, it was found that the pre-proposed system could not be directly applied to the sand level mea-surement in the casing pipe, because several patterns of stationary waves were simultaneously formed in the pipe due to its complicated inner structure.
This paper thus presents an on-line sand level measurement system which introduces a new dynamic model to take into consideration of the two dominant patterns of the stationary waves in the pipe. The criterion to obtain the optimal modes of the stationary wave is also presented to realize a much higher measurement accuracy.
