DAMAGE EFFECTS OF PILE DRIVING VIBRATION

Abstract

THE INSTRUMENT MOST COMMONLY USED FOR MEASUREMENT OF EARTH OR STRUCTURAL VIBRATION RESULTING FROM PILE DRIVING IS THE PORTABLE THREE-COMPONENT SEISMOGRAPH. THE DAMAGE POTENTIAL OF PILE-DRIVING VIBRATIONS DEPENDS ON DISPLACEMENT AND FREQUENCY OF THE VIBRATION. SEVERAL INVESTIGATIONS REVEALED THAT A VIBRATION LEVEL OF 2.0 IN./SEC /PARTICLE VELOCITY/ IS SAFE WITH REGARD TO PLASTER CRACKS IN RESIDENTIAL-TYPE STRUCTURES. THE SAFE LEVEL OF INTENSITY FOR A STEADY-STATE VIBRATION IS COMPUTED BY THE AUTHOR. ASSUMING A 5.0 IN./SEC /PARTICLE VELOCITY/ SAFETY VIBRATION LEVEL FOR CURED CONCRETE, AND RECOGNIZING THE RATE AT WHICH GREEN CONCRETE ATTAINS STRENGTH, IT IS POSSIBLE TO RELATE THE PERMISSIBLE SAFE VIBRATION LEVEL TO THE TIME SINCE PLACING THE CONCRETE. WHEN THE DECREASE OF VIBRATION WITH DISTANCE HAS BEEN EVALUATED FOR A PARTICULAR SITE, THE DISTANCE AT WHICH PILE DRIVING MAY BE PERMITTED /FOR A CERTAIN SIZE HAMMER/ CAN THEN BE DETERMINED AS A FUNCTION OF CURING TIME. THE SAFE LEVEL OF INTENSITY FOR A STEADY-STATE VIBRATION COULD CONCEIVABLE BE BETWEEN ONE-HALF AND ONE-FIFTH OF THE SAFE LEVEL FOR TRANSIENT EXCITATIONS DUE TO THE POSSIBLE MAGNIFICATION AT RESONANCE WHICH DEPENDS PRIMARILY ON THE INHERENT DAMPING CHARACTERISTICS OF THE STRUCTURE.