Evaluation of ground vibrations due to vibro-compaction of rockfill columns

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Date
2023-08-21
Authors
Justo Fernandes Nobre de Araujo, Silvia Cristina
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Abstract

Rockfill columns are a versatile ground improvement technique that uses rockfill to replace some of the weak soil of the original ground. The performance of the rockfill columns for riverbank and embankment stabilization may be improved by densifying the rockfill. This densification may be done, for example, by vibrating pre-embedded steel casings, while removing them from the column hole. Rockfill columns have been extensively and successfully used to stabilize riverbanks in Manitoba since the 1990s. Riverbank instability was noted in a certain area in Winnipeg, in a region where a centenary aqueduct was buried. To stabilize this bank, a project involving the installation of about 80 rockfill columns was proposed and executed, but the unknown possible impacts of the vibration on the buried aqueduct was a major concern. Constant field monitoring was crucial to guide the installation of the columns in the field. In the end, the final field assessment showed that the integrity of the aqueduct was maintained. However, the understanding of any possible impact of the vibratory waves on the aqueduct remained a grey area to the parties involved in the project, especially because this information is lacking in the literature. To rectify the current lack of information on the impact of ground-borne vibration on buried aqueducts, this study presents a comprehensive numerical study of three columns of this case study. Based on the results obtained through the 2-D finite element models, it became clear that the vibratory and non-vibratory removal of steel casings generate some wave propagation in the ground, which could potentially affect the integrity of the aqueduct. The results in terms of particle velocities were used to increase the guidance available in the literature, using Peak Particle Velocity as limiting factor. However, the results obtained in this thesis demonstrated that particle velocity was not the best factor to be used as the limiting value to protect an aqueduct against vibration, but strains on the aqueduct wall were more representative of possible damage from the vibratory wave and should be used to monitor the vibration in future projects.

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Vibration, Rockfill column, Riverbank stabilization, Aqueduct, Prediction
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