Evaluation of the Ground-Borne Vibration Reduction Properties of Tire Derived Aggregate Installed on the Denver RTD Light Rail System

摘要

This paper presents the results of field tests performed to evaluate the ground-borne vibration reduction properties of tire derived aggregate (shredded tires, also known as TDA) as installed beneath ballast-and-tie track on the Denver Regional Transit District (RTD) Southeast Corridor (T-REX) Light Rail Transit (LRT) line in Denver, CO (USA). The vibration tests were carried out at four (4) locations where TDA has been installed beneath the tracks as well as at one control site without TDA underlayment. At each of the sites, ground-borne vibration measurements were made during multiple operations of a dedicated two-car train at three different speeds. In addition, impact tests were conducted to determine the local vibration propagation characteristics of the ground in an effort to normalize the train vibration data for the effects of local geology. A comparison of the test results at the TDA sites with the results at the control site provided a measure of the TDA vibration reduction. The results of the study indicate that, on average, the TDA underlayment at RTD provides a ground-borne vibration reduction of about 3 dB in the one-third octave frequency bands centered at 25 Hz and 31.5 Hz and reductions of 8 to 14 dB at frequencies between 40 Hz and 160 Hz. These results are similar to those obtained from pre-operation vibration tests at the T-REX corridor and to those obtained from recent TDA vibration tests conducted at the Santa Clara Valley Transportation Authority (VTA) light rail system in San Jose, CA (USA). Compared to other types of vibration mitigation measures tested at the San Francisco, CA (USA) Muni light rail system, the vibration reduction performance of the TDA treatment at RTD was found to be equal or superior to that of a ballast mat and not as effective as a floating slab track installation.