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The large underground structure in saturated stratum is vulnerable to float during an earthquake. This results in a plethora of problems, such as uneven settlement, large internal force and structure damage. In this study, the seismic behavior of a three-story, two-span subway station in complex saturated stratum was investigated through water-soil fully coupled 3D finite element method. In the analysis, the nonlinear soil behavior was described by a cyclic mobility model and the structure was calculated using a nonlinear constitutive model which can consider the influence of axial force on its bending moment. Joints elements were used to model the contact surface between soil and structure. The development of the soil displacement and internal force of the station structure at different times during a huge earthquake was examined. The bearing capacity of the station structure members was analyzed. The results indicated that the vertical displacement was spatially distributed. The larger additional seismic stresses appeared in the bottom slab and side wall. Failed elements were observed in both the walls and slabs, and the walls were more easily damaged than the slab. The results provide useful reference for the large underground structure seismic design in the construction of urban underground space. [ABSTRACT FROM AUTHOR]

• A novel Bayesian inference method was proposed to study deep excavations. • Machine learning with Bayesian Network could predict soil-structure interactions. • The Bayesian Network model could predict ground/wall responses accurately. • The sequential updating process could improve model performance effectively. • The Bayesian framework could be applied to various geological settings reasonably. The demand for deep excavations to construct underground infrastructure has been growing in metropolitan cities due to rapid urban development and limited land space. In this original research, a machine learning technique based on Bayesian Network is proposed to evaluate and predict soil-structure interactions caused by braced excavations. A novel framework based on Bayesian Network incorporating the Bayesian updating process was proposed to study the ground and wall responses induced by deep excavations. Three established case studies collected from the literature were used to implement and showcase the novel concept. Besides, original two-dimensional finite element models were developed to simulate the first two case studies involving deep excavations in clay in order to generate sufficient ground and wall response data for the training and updating phases of the proposed Bayesian model. The third deep excavation case study carried out in a totally different geology (predominantly sand) was then used to assess and verify the robustness of the Bayesian framework in predicting the soil-structure responses. It was eventually established that the developed novel Bayesian Network model managed to successfully predict the wall deflections and bending moments as well as the ground surface settlements of the third case study with good accuracy through using only two case studies as priors via the versatile sequential updating processes, albeit having totally different geological settings. [ABSTRACT FROM AUTHOR]

This research developed a robust Bayesian framework for evaluating geomaterials and soil-structure interactions involving deep excavation, utilizing Bayesian Regression and Bayesian Network methods that combined data training, validation, and updating into a cohesive framework. A methodology based on Bayesian Generalized Linear Model (a variant of Bayesian Regression) was applied to a laboratory-based case study on sustainable cementitious blends. The framework effectively used past research data to estimate design parameters even though the studies involved different mix design requirements. Then, a framework based on Gaussian Bayesian Network (a variant of Bayesian Network) incorporating Bayesian updating was applied to an established case history for deep excavation in clay. Two-dimensional finite element analysis was used to generate data for model training and updating. The GBN models accurately estimated responses such as wall deflections, wall bending moments, and ground surface settlements through a sequential updating process. The research was conducted using R programming language, with a custom R script designed to follow the process flow of the proposed framework. The successful application and validation of this framework demonstrated its potential for characterizing geomaterials and evaluating complex soil-structure interactions in deep excavation, leveraging on the availability of existing data and a reliable sequential updating process. [ABSTRACT FROM AUTHOR]

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This paper presents the dynamic response of soil-piles-mattress-slab and soil-piles-slab systems under seismic loading. In this context, a three-dimensional numerical model using finite elements is proposed; the piles of two systems are embedded in a soft soil. The reinforced soil is surmounted by a load-transfer mattress setup at the rigid piles head level. The piles are embedded in the soft soil and are perfectly connected to a 0.6 m thick slab. The soil-piles-mattress-slab and soil-piles-slab systems are subjected to a horizontal seismic loading. The soil and the mattress are modeled by volume elements, the rigid piles and piles are modeled by beam elements and the slab is by structural elements. The formulation is based on the direct method and the calculations are done considering elastic and elasto-plastic behaviors for the soil mass. The obtained results are compared in terms of horizontal displacements and internal stresses according to the piles length. The obtained results show the effectiveness of the soil-piles-mattress-slab system, the load transfer mattress constituted an energy dissipation zone for the two behaviors. The embedding at the head of the piles induces very high shear forces and bending moments at the level of the pile-structure connection. These efforts could damage the structure. The soil-piles-mattress-slab system eliminates these major efforts at the head of the rigid piles by separating the structure with a mattress. The non-linearity of the ground must be taken into account for further study. [ABSTRACT FROM AUTHOR]

• Refined FE analyses were conducted to study the seismic responses of shield tunnels. • The peak value of the dynamic bending moment of each segment was consistent. • Seismic analysis of shield tunnel by the stiffness reduction method may result in errors. • Lining segment exhibits considerable rotation under earthquake loading. The segment joints of a shield tunnel are generally the weak components of the structure, and they can be considerably damaged under strong seismic loading, thus influencing the overall seismic behavior. In this study, Finite Element simulation analyses of centrifuge shaking table tests and a shield tunnel project are carried out to investigate the influences of the segment joints on the seismic responses and the associated mechanisms. First, the reliability of the numerical procedure is validated by using the centrifuge shaking table test results. The numerical procedure is then used, together with the refined simulation approach for segment joints, to carry out extensive numerical analyses of the seismic responses of a shield tunnel project under different horizontal earthquake loadings. The research results show that due to the influence of the segment joints, the peak value of the dynamic bending moment of each segment tends to be more uniform. When the stiffness reduction method is used to consider the influence of the segment joints, the peak values of the dynamic bending moments can be too large, while the peak values of the dynamic axial forces may be too small. In addition, the tunnel segment rotates during an earthquake, resulting in relatively large relative displacements of the segment joints. [ABSTRACT FROM AUTHOR]

• Instrumentation program of the world's largest-span soil-steel structure. • Three-dimensional nonlinear FE modeling for all soil and structural elements. • The influence of steel mesh and circumferential concrete collar to buried steel structures. • Investigating the performance of soil-steel structures with beveled ends. Soil-steel structures (SSS) are increasingly used as a solution for roadway and waterway overpasses. The inlet and outlet of the buried steel structure may encounter different end treatments and bevelling slopes to accommodate different design aspects. Current design codes require precise numerical analysis of SSS considering soil-structure interaction to evaluate the stability of the steel structure and unbalanced surrounding backfill. The current study evaluates the performance of large-span SSS considering different end treatment conditions. The numerical modeling approach was validated by conducting three-dimensional nonlinear finite element model for the world's largest-span soil-steel structure and comparing the model predictions with field observations. The steel structure has a span of 32.40 m and was constructed using a corrugation profile of 237 mm depth and 500 mm pitch. The ends of the structure were strengthened by attaching 400 mm X 1090 mm circumferential reinforced concrete collars. The numerical analysis predicted the same deflection trends as the field measurements at different construction stages. Furthermore, the validated numerical approach was employed to evaluate the performance of bevel-ended SSS. The benefits of stiffening SSS by using circumferential concrete collars and steel mesh reinforcements buried in the surrounding soil are evaluated in terms of the stability of steel structure and surrounding soil. The results indicated significant longitudinal bending moment induced in the steel plates that were affected by the slope of the beveled ends. It was also found that the steel mesh reinforcement and concrete collars reduced the induced straining actions in the steel structure by 30–50%. The obtained results demonstrate the necessity of rigorous numerical simulation in controlling the design and cost of SSS. [ABSTRACT FROM AUTHOR]

As a result of wind power's expansion over the globe, offshore wind turbines (OWTs) are being projected in seismic prone areas. In parallel, the industry develops increasingly larger and more powerful generators. Many of the seismic response analyses of wind turbines conducted so far only consider smaller units. In this paper, a finite element substructuring model in frequency domain is used to compute the seismic response of four reference OWTs from 5 to 15 MW founded on monopiles embedded in several homogeneous soil profiles with shear wave velocities from 100 to 300 m/s and subjected to different accelerograms. The foundation behaviour is obtained through a continuum model including kinematic and inertial interaction. The relevance of soil-structure interaction and main trends of the seismic response of OWTs are inferred from the presented results. Although the seismic maximum bending moments increase with the size of the OWT system, their relevance with respect to the ones produced by design loads decreases as the turbine gets bigger. The same effect is observed for the shear forces if the soil is soft enough. The inclusion of SSI effects almost duplicates the seismic response when compared to the rigid base scenario. [ABSTRACT FROM AUTHOR]