Vibration-Isolation Treatment of a Railroad Track Bed

Abstract

A few years ago, a half-mile section of railroad track was given a vibration-isolation treatment under several new buildings in Boston. The treatment consisted of welding all rail joints, inserting molded rubber rail seats under the lower flange of the rail, and installing an extra-deep ballast bed under the ties. Recently, a simple measurement was made of the earthborne vibration reduction provided by this treatment. A vibration pickup was mounted on a concrete wall inside the track, and the signal was tape recorded for passages of several short passenger trains. At one position, the vibration pickup was located beside the welded and isolated track. On the following day, the same passenger trains were recorded with the vibration pickup located beside conventional unwelded and unisolated track, approximately 200 yd from the first position. Train speed, train makeup, wheel loads, earth conditions, and the geometry of the measurement conditions were quite similar for both locations, so it is believed that the measured 10 dB difference was due to the vibration reduction provided by this treatment.