THE CONTROL OF PILES BY SONIC CORE DRILLING /IN FRENCH/

DETAILS ARE GIVEN OF THE "SONIC CORE DRILLING" METHOD AND ITS APPLICATION TO THE INVESTIGATION OF DEFECTS IN CAST-IN-SITU CONCRETE PILES. ACOUSTIC SIGNALS TRANSMITTED AT DIFFERENT LEVELS BETWEEN AN IMPULSE TRANSMITTER AND A RECEIVER PLACED IN TUBES INSIDE THE PILE ARE RECORDED. THE TUBES ARE FILLED WITH WATER TO ENSURE A SATISFACTORY ACOUSTIC LINK WITH THE CONCRETE. THE CONTINUOUS MEASUREMENTS AND THEIR PRESENTATION FACILITATE THE EASY DETECTION OF CONCRETE DEFECTS AND THE PRESENCE OF MUD OR EARTH IN THE PILE ITSELF, EVEN IF TRANSMISSION DISTANCES ARE NOT CONSTANT. IF THE TUBES USED ARE MADE OF PLASTIC MATERIAL, A MAGNETIC METHOD ENABLES THIS DISTANCE TO BE ACCURATELY MEASURED. FROM THE MEASUREMENTS, THE WAVE PROPAGATION VELOCITY IN THE CONCRETE CAN BE DETERMINED AND AN APPROXIMATE VALUE OF THE IN-SITU MODULUS CAN BE OBTAINED. THE EFFICIENCY OF THIS TYPE OF TEST WAS CONTROLLED ON AN EXPERIMENTAL SITE WHEN 10 CAST-IN-SITU PILES HAD TYPICAL DEFECTS. THE MEASURING EQUIPMENT CONSISTS OF ONE TRANSMISSION SOUNDING APPARATUS, ONE RECEIVER SOUNDING APPARATUS, ONE OSCILLOSCOPE WITH SPECIAL DRAWER AND CAMERA, AND A WINCH FOR LOWERING THE SOUNDING APPARATUS. MENTION IS MADE OF THE USE OF THE METHOD IN CONTROLLING CAST-IN-SITU WALLS, CONCRETE OR MASONRY DAMS, ETC. /LCPC/TRRL/