An experimental study on vibration isolation by open and in-filled trenches

Abstract

The mitigation of vibrations due to a harmonic load induced by a mechanical oscillator is studied experimentally. The vertical components of soil particle velocities are measured (via geophones) at different locations apart from the source, where various frequencies (30–70 Hz) are generated. For normal conditions where no mitigation means are used, it is found that the measured peak particle velocities are proportional to the excitation frequencies. The mitigation effect of constructing an active (near source) open (0.4 m wide × 3 m long × 2 m deep) trench barrier is also studied. The measurements revealed velocity increase at the points in front of the trench due to the reflected waves. This increase is proportional to the vibration frequency. Although the presence of the barrier greatly reduced the peak particle velocities beyond it, it is found that the efficiency of screening is more pronounced at high vibration frequencies. Increased and fluctuated trends of the amplitude reduction ratio are reported away from the barrier. It is realized that passive (near target) screening is less effective for all frequencies except at 30 Hz. Active and passive trenches, filled with native soil–rubber mixture at various ratios (20–40% rubber), are also considered. The rubber material is in a form of tire chips purchased from the Unit of Recycling Scrap Tires in Al-Diwaniyah Tires Factory. Although the in-filled trenches are less effective in screening the vibrations, similar trends and behavior to the open trenches are noted. It is found that the mitigation efficacy is increased with the rubber content.

Keywords

• vibration screening
• vibration mitigation
• in-filled trenches
• rubber material
• scrap tire