Novel Open Trench Techniques in Mitigating Ground-Borne Vibrations due to Traffic under a Wide Range of Ground Conditions

This study proposes the novel geometrical design of open trenches in contrast to the traditional rectangular type of open trench, in order to improve the efficiency in mitigating the traffic-induced ground vibrations. The novel geometric design involves the variation in cross-sectional shape, cross-sectional area, sidewall inclination, depth of trenches, and the number of trenches. In addition, the efficiency of the multirow trenches with shallower depths, in contrast to the single-row deep trench, is also assessed for further mitigating the low-frequency ground vibrations. It is argued that these novel open trenches would change the wave propagation direction while also weakening the wave propagation capability in the original direction. A two-dimensional (2D) finite-element study is performed to investigate the isolation efficiency of novel open trench techniques with varying cross sections in a linear elastic, isotropic, and homogeneous half-space. A steady-state vertical harmonic excitation of the ground surface was simulated. The numerical results show that compared with the rectangular open trench, the part of the area behind the new cross section trench has better isolation efficiency, Cross section 6 seems to be the most efficient of the six cross sections, and the isolation efficiency is improved by nearly 10.2% compared. Increasing the cross-sectional area could not effectively improve the isolation efficiency of the open trenches. Selection of inclination of the hypotenuse to an appropriate angle, increasing the number and depth of open trenches could improve the isolation efficiency. The vibration isolation performance of the trenches in the soft soil was better than the stiff soil. Besides, an excessively high groundwater table is usually detrimental to the isolation efficiency of the trenches.