A numerical assessment of variable saturation of the upper layers on the ground borne vibrations from underground trains

A numerical assessment of variable saturation of the upper layers on the ground borne vibrations from underground trains: A case history

Pontani, Nicola (Politecnico di Milano)
Martinelli, Luca (Politecnico di Milano)
Acquati, Marco (MM S.p.A.)
Jommi, C. (TU Delft Geo-engineering; Politecnico di Milano)

2023

Ground borne vibrations generated by the passage of underground trains may change over time due to objective causes, such as increasing weight and speed of trains or ageing of the infrastructure components, as well as a variation in the dynamic response of the soil surrounding the tunnel. Among the possible causes of changes in the soil dynamic response, its hydrologic state has been seldom investigated. In this contribution, the role played by the conditions of the soil above the water table is addressed, starting from a case history in the city of Milano. Two-dimensional plane strain numerical models have been developed for the infrastructure. The models were calibrated on the results of two geophysical investigations performed at the same site in the city centre, but at two different times, which allowed distinguishing different dynamic responses. The system was excited by a synthetic load time history, matching a reference dynamic load spectrum included in Italian recommendations. Limitations of using this input on a 2D plane strain model were assessed by comparing the computed vibrations with experimental acceleration records collected on the tunnel. The results of the two numerical models are compared with those of a simulation performed assuming fully dry conditions above the water table. Overall, the set of analyses shows that even small changes in the dynamic response of the soil, interpretated as a consequence of variable saturation, may result in a change of a few decibels in the acceleration levels. Much larger accelerations are predicted on average with the simpler dry model, clearly showing the advantages of a more accurate modelling strategy.

FE numerical analysis
Geophysical investigation
Ground borne vibrations
Partial saturation
Underground trains

http://resolver.tudelft.nl/uuid:204279bf-f979-47bd-88dc-e6e6b5287108

https://doi.org/10.1016/j.trgeo.2023.100981

2023-09-25

2214-3912

Transportation Geotechnics, 40

Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.

Institutional Repository

journal article

© 2023 Nicola Pontani, Luca Martinelli, Marco Acquati, C. Jommi