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Key Words: portable FWD $B!$(B spring model $B!$(B displacement $B!$(B ballast $B!$(B roadbed

A STUDY ON DISPLACEMENT ESTIMATION MODEL FOR FALLING MASS AND THE GROUND USING A PORTABLE FWD

Masaki KAMIURA$B!$(B Hiroaki OOISHI$B!$(B Nagato ABE$B!$(B Etsuo SEKINE

The whole system of a portable FWD equipment and ground was made to be the spring mass mode as the kinetic energy of the falling weight became impulsive force and it was produced a deflection of the ground. Simultaneous differential equations were deduced .At the next stage$B!$(B it was introduced the model of the ground using rubber board. And$B!$(B the loading was made to be the rubber board by the portable FWD equipment which installed the accelerometer in and the prediction of the displacement of the falling weight by double integral and deflection of the ground were compared with the calculation result from the measurement in respect of the acceleration. The calculation using the ballast of roadbed was similarly compared with the observation in the ground. The validity of the solution deduced from this model was confirmed.