The influence of surrounding structures on ground-borne vibration from railways

Abstract

Railway transportation is widely recognised as an environmentally friendly and sustainable mode of transport, with extensive global development over recent decades. However, train-induced ground vibration has become a subject of increasing concern. To address this, various prediction methods, including empirical, analytical/semi-analytical, and numerical approaches, have rapidly evolved. Despite these advancements, most methods presume a free-field transmission path, disregarding the influence of buildings located between the excitation source and receiver points. This simplification highlights the need for more detailed investigations into the impact of surrounding structures on ground-borne vibration.
Ground vibration is fundamental to the vibration response of the target building. To improve computational efficiency and simplify the model, the ground vibration is investigated. The aim of this thesis is to explore and analyse the influence of surrounding structures located in the transmission path on ground vibration induced by railways. This investigation begins with a fundamental problem: the interaction between a single pile and the surrounding soil and its subsequent impact on ground response. To address this, a semi-analytical model has been developed to study the effects of a single pile on ground vibration. The finite element method is used to simulate a piled foundation structure. The surrounding soil is modelled by using the dynamic stiffness matrix method. The model's accuracy and reliability are examined across various conditions. Additionally, the ground velocity levels behind the pile and the corresponding insertion loss results are thoroughly investigated. The influence of the single pile on ground vibration is quantitatively analysed under varying conditions, including different soil wave velocities, frequencies, and layer parameters.
A semi-analytical model of a pile group embedded in soil is constructed by considering the transfer receptances between distinct piles, based on the single pile-soil dynamic interaction model. The model accuracy range is investigated. Then different pile configurations are investigated. These include two piles aligned transverse to the line from source point to the receiver point, two piles arranged axially to this line, and four piles arranged in a square 2×2 configuration. The ground response and the ground vibration mitigation effects are investigated and summarised.
Next, an analysis is conducted on the ground response behind a building structure with piled foundation. The ground velocity level response and the insertion loss results for a fixed unit load are presented. Furthermore, the excitation source is substituted with a railway train load operating within an embedded tunnel structure. The tunnel structure is simulated using the Pipe-in-Pipe method. The study summarises responses under varying train loads and distances between the railway and the building, providing a comprehensive analysis of the impact of the structure located in the transmission path.
Finally, within the framework of a hybrid ground vibration prediction model, the impact of five different foundation types on ground response is explored. These are a raft foundation, strip foundations oriented both perpendicular and parallel to the direction of train movement, a pile foundation, and a box foundation. The excitation sources encompass both surface and underground railway force density levels. The line source transfer mobility for the different types of building foundation is computed using a set of incoherent point loads and combined with force densities to represent train excitation. The line source transfer mobility of the various foundation types is simulated using the finite element method. Leveraging high-performance computing and batch processing, the line source transfer mobility results are investigated. The findings reveal that deep foundations generally offer more significant ground vibration mitigation effects. However, when the train load is embedded below the surface, zones of amplified ground vibration may occur behind the building.
Overall, the presence of structures in the transmission path significantly influences ground vibration. When point loads or train loads are applied on the ground surface, the ground response is typically mitigated. However, when the loads are embedded in the ground, the vibration may be amplified in certain zones. Therefore, it is crucial to account for structures within the transmission path when predicting ground vibration impacts. Consequently, this approach is expected to yield more accurate predictions.

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Identifiers

ORCID for Xiangyu Qu: orcid.org/0000-0002-6651-929X

ORCID for David Thompson: orcid.org/0000-0002-7964-5906

ORCID for Evangelos Ntotsios: orcid.org/0000-0001-7382-0948

ORCID for Giacomo Squicciarini: orcid.org/0000-0003-2437-6398

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