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Surface settlement is one of the key engineering issues during shield construction process. In order to accurately predict surface settlement, this paper proposes a new machine learning method based on relevance vector machine (RVM), principal component analysis (PCA), and particle swarm optimization (PSO). Taking Beijing Metro Line 6 as a case study, the PCA-PSO-RVM model is used to make the prediction and compared with the prediction results of the RVM model using the same samples. In order to evaluate the reliability of the model, three evaluation indexes including mean relative error (MRE), root mean square error (RMSE), and Theil inequality coefficient (TIC) were calculated, and sensitivity analysis was carried out on them. The results show that the minimum relative error between PCA-PSO-RVM and the actual value is only 0.06%. The calculated MRE, RMSE, and TIC are 0.17%, 0.0714 mm, and 0.027%, respectively, which shows that PCA-PSO-RVM model has higher prediction accuracy, smaller deviations, and higher reliability compared with the three other models. Through sensitivity analysis, it is found that the weighted average internal friction angle (φ) has the most significant impact on the surface settlement, which should be focused on in relevant research. [ABSTRACT FROM AUTHOR]

• Monitoring results of 30 stations using PBA approach in Beijing are clarified. • Surface settlement characteristics of two types of PBA approach are illustrated. • Effects of different factors on surface settlement are elaborated. This paper illustrates the surface settlement characteristics of subway station construction in the shallow-buried soft ground using the pile-beam-arch (PBA) approach of the shallow tunnelling method. The geological conditions, cross sections and measured surface settlements of 30 subway stations constructed by the PBA approach in Beijing are presented. The total surface settlements of the strip foundation station and the pile foundation station using the PBA approach mainly range from 40 mm to 80 mm and from 30 mm to 40 mm, respectively. The superposition of the surface settlements in Stage 1 and 3 of the PBA approach accounts for about 90% of the total surface settlement, and that in Stage 2 and 4 accounts for about 10%. The mean of the surface settlements produced in silty clay is smaller than that in silty sand, and is approximately 1.4 times as large as that in gravel. The surface settlement generally decreases with the increase of the overburden depth. The surface settlement could more than double due to the effect of groundwater. The surface settlement induced by the excavation of the latter level of drifts is commonly larger than that of the former level of drifts. In addition, the quality of workmanship has significant impacts on the surface settlement. This research is conducive to update the database of the world subway projects and can serve as a practical reference for future similar projects. [ABSTRACT FROM AUTHOR]

In metropolitan areas, the static load of high-rise buildings may result in uneven settlement, which seriously threatens residents' living safety. Studying the response relationship between the additional stress of high-rise buildings and foundation settlement plays an important role in ensuring the safe development of metropolitan cities. Firstly, based on Persistent Scatterers Interferometric Aperture Radar (PS-InSAR) technology, we used 68 descending TerraSAR-X images to obtain the surface settlement in the study area from April 2010 to October 2018, which were validated with leveling benchmark monitoring results. Secondly, we calculated the additional stress of the building loads to quantify its effect on the uneven settlement in the Central Business District (CBD) of Beijing. Finally, two sets of characteristic points were selected to analyze the response relationships between foundation settlement and additional stress generated by building loads. The findings show: (1) The surface settlement rate varied from −145.2 to 24 mm/year in the Beijing Plain. The InSAR results agree well with the monitoring results derived from the leveling benchmark; the Pearson correlation coefficients were 0.98 and 0.95 in 2011–2013 and 2015–2016, respectively. (2) The stress results show that the depth of the influence of the static load of high-rise buildings was 74.9 m underground in the CBD. (3) The spatial distribution pattern of the additional stress is consistent with the foundation settlement. A characteristic point with greater additional stress in the same group has a higher foundation settlement rate. This relationship has also been found between the uneven foundation settlement and additional stress gradients. These findings provide scientific support for mitigating economic losses due to foundation settlement caused by additional stresses derived from building loads. [ABSTRACT FROM AUTHOR]

• The role of TBM tail-grouting on surface settlement in coarse-grained soils was investigated. • The field test was executed to show how surface settlement is controlled by TBM tail-grouting. • Influence of asymmetric tail-grouting on settlement trough was explored. This paper examines the role of TBM tail-grouting on surface settlement of coarse-grained soils in urban area. The influence of tail grouting on the ground surface settlement is firstly demonstrated through a challenging shield-driven tunnel project in Beijing City, China. FEA modelling incorporating the excavation sequence and tail grouting details is then set up to support the field observations, based on which the influences of different TBM tail-grouting parameters on ground settlement are investigated, especially the asymmetric tail-grouting in which one of the two grouting openings at the upper part of the shield tail is malfunctioned. It is shown that the grouting volume variation is inconsistent with the development of the grouting pressure, and the ground deformation in coarse-grained soils is directly related to the tail-grouting pressure rather than the grouting volume ratio. Asymmetric tail-grouting will result in notable offset of the maximum surface settlement point in settlement trough from tunnel centerline which correlates exponentially with the parameter ξ defined to represent the asymmetry ratio of the grouting pressure. [ABSTRACT FROM AUTHOR]

Large size shield tunnels have been constructed with the increasing demands, because it offers cost efficiency in urban areas. One major problem created by shield tunnelling is that ground settlement occurs, which is crucial to existing structures. A detailed case study of surface settlement induced by the operation of a large-diameter earth pressure balance (EPB) shield tunnel in Beijing was presented. This study provides important new insights into the values of settlement trough parameters of empirical methods. The narrower transverse settlement trough was observed in large size tunnels. The development of longitudinal settlement can be divided into four stages, and methods were further proposed to assess the associated four components of volume loss. Results demonstrate that the proposed methods can efficiently predict the volume loss and the associated ground settlement within a reasonable accuracy by comparing with the collected field observations. In addition, a bandwidth of achievable surface settlement for future large EPB shield tunnels is suggested via performing analysis on real settlements. [ABSTRACT FROM AUTHOR]