Efficiency of Open and Infill Trenches in Mitigating Ground-Borne Vibrations

In the present-day context, man-made sources of ground-borne vibration are rising at a very rapid rate due to increasing construction work, blasting activities, and rapidly expanding rail and road traffic systems. As a consequence, amplified levels of ground-borne vibration occur, causing annoyance to residents living in nearby areas, posing a threat to the stability of old structures, and interfering with instrumentation works in industries. This paper discusses an investigation into the use of trenches as a means of mitigating ground vibration caused by propagation of surface (Rayleigh) waves. Two- and three-dimensional (2D and 3D) finite-element models were developed using PLAXIS for identifying key factors affecting the vibration isolation efficiency of open and infill trenches. Parametric studies were carried out, and the results were analyzed to arrive at optimum values of geometrical and material properties of trenches. Numerical analysis showed that, for open trenches, normalized depth is the decisive factor and width is of importance in trenches that are very shallow. For infill trenches, it was observed that low-density materials perform exceedingly well as infill materials but their performance is highly sensitive to the relative shear-wave velocity between the infill material and the in situ soil. Finally, an in-depth analysis was carried out to investigate the performance of polyurethane foam trenches in mitigating vibrations caused by harmonic loads. The analysis was extended to study the effectiveness of these geofoam barriers in damping out the vibrations generated by a moving train. In this case, barrier efficiency was shown to increase with increasing train speed. The key findings suggest that trenches are a simple and effective solution for reducing ground-borne vibrations. (C) 2018 American Society of Civil Engineers.