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This study aims to investigate the behavior of ground surface settlement in TBM double-line tunnels constructed under existing buildings and to devise a calculative representation for that behavior. Numerical simulation and field monitoring methods were used to examine the Zhongcong Tunnel in Chongqing Metro Line 9. The ground surface settlement was analyzed using an orthogonal test of 3D numerical simulation methods. The results showed that ground surface settlement was influenced by TBM tunneling parameters and the location of the existing building in the following manner. The existing building reduced the settlement trough width. Surface settlement was increased by frictional and palm surface thrust forces but reduced by grouting pressure. The settlement trough width of the first excavation iz correlated with that of the last excavation iy. To accommodate the influence of existing buildings, the tilt factor of the settlement trough TR was introduced to improve the formula for calculating the ground surface settlement of TBM double-line tunnels. The improved formula was validated by comparing the calculated results with actual measurements.

During high speed railway construction, shield-tunnel undercrossing frequently induces subgrade settlement, which threatens project safety and progress. Existing settlement monitoring methods struggle to provide timely early warnings due to unclear data features and inadequate long-term dependency modeling.To address this, we propose a settlement early warning method for high-speed railway subgrades based on TD Transformer. Firstly, we utilize temporal-spatial enhanced attention (TSEA) for feature extraction from high-speed railway settlement data, effectively resolving the problem of vague features post-extraction. Secondly, dynamic global temporal attention (DGTA) is employed to dynamically capture and represent the long-term dependencies of settlement data. Experimental results demonstrate that TD Transformer achieves Accuracy, Precision, Recall, and F1-Score of 93.39%, 93.10%, 93.40%, and 93.24%, respectively, outperforming other advanced settlement early warning methods for high-speed railway subgrade with relative improvements of 1.24%, 1.3%, 1.3%, and 1.27%.This method effectively forecasts subgrade settlement and exhibits significant superiority in the task of multi-factor settlement early warning for high-speed railway subgrades.

The number of pit-in-pit foundation pit is increasing quickly because of the continuous utilization of underground spaces in urban areas. Based on the co-construction project of Shanghai Museum of Natural History foundation pit and Shanghai Metro Line 13 foundation pit in Shanghai, China, the deformation characteristics of pit-in-pit foundation pit are researched by field observation and centrifugal model tests. The lateral wall displacement of inner foundation pit includes global deformation caused by the outer foundation pit excavation and deflection caused by the excavation of itself. The effect of inner foundation pit excavation on the lateral wall displacement of outer foundation pit and ground-surface settlement is smaller. The two factors affecting the deformation characteristics of pit-in-pit foundation pit, the distance between inner and outer foundation pits ( D ) and the excavation width of inner foundation pit ( W in ), are analyzed by centrifugal model tests. The result shows that the maximum lateral wall displacements of inner and outer foundation pits decrease nearly linearly with the increase of D , but increase with the increase of W in .

The present study aims to investigate the excavation method, excavation sequence, and optimum trailing distance between excavation stages of the tunnel face to control ground settlement caused by constructing the Tehran Subway Tunnel-Line 6 in the northern part. To this end, 3D numerical modeling is performed, and settlement data validate the obtained results. The results showed that among the sequential excavation methods, the ring-cut (RC) and central diaphragm (CD) have more appropriate control over the surface settlement. The maximum settlement resulting from the RC method and CD is within the permissible settlement range. Considering the better control of the RC method compared to the CD method in limiting the ground settlement, the RC method was chosen to determine the excavation sequence and optimum trailing distance between excavation stages of the tunnel face. Increasing the number of excavation sequences and excavation support core in the final stages of the face can play an effective role in limiting ground settlement. Also, the results showed that when the trailing distance between excavation stages is more than one-time the tunnel diameter, due to the less interference of the stress distribution zones, the settlement of the ground surface declines dramatically and falls within the permissible settlement range.

The construction disturbance caused by pipe jacking is an index that must be strictly controlled in the project. With the wide application of curved pipe jacking in urban underground construction, predicting its ground surface settlement characteristics has become an increasingly important research topic. Based on finite element numerical simulation, a three-dimensional model of curved pipe jacking was established to simulate the construction stage. Compared with the straight pipe jacking, the normal component of jacking force is set in the outer tunnel of the curved pipe jacking to simulate the extrusion of the outer soil caused by the corner of the pipe joint, and the surface settlement characteristics of the curved pipe jacking are explored by changing the pressure value. The research results show that the surface settlement of the curved pipe jacking conforms to the normal distribution as a whole. Compared with the linear pipe jacking, the surface settlement is not symmetrical about the design axis of the tunnel. With the increase of the pressure outside the tunnel, the maximum settlement value of the surface and the difference between the two sides of the axis increase. Compared with the Peck formula, the width of the settling tank of the curved pipe jacking is larger, the convergence rate outside the width of the settling tank is slower, and the settlement trend is more in line with the Verruijt formula. The calculation formula is modified by axis offset distance and ovalization coefficient and modified formula can better reflect the measured engineering data. The research results can provide guidance and reference for the prediction and control of surface settlement of curved pipe jacking.

Based on the Zhengzhou–Xuchang Intercity Railway tunnel project passing beneath Terminal 1 of Xinzheng International Airport, this study employs a three-dimensional numerical analysis model to investigate the effects of tunnel depth and pile foundation structure on ground surface settlement and pile foundation response during twin-line shield tunnelling in typical cohesive soils under tunnel side-crossing and under-crossing conditions. The results indicate that during tunnel side-crossing, the ground surface settlement profiles evolved from V-shaped to W-shaped before and after twin-tunnel breakthrough. With increasing tunnel depth, the lateral displacement profiles of the left-row and right-row piles transformed from spindle-shaped to X-shaped. With increasing pile count, the maximum axial force per pile decreased from 320.1 kN in the single-pile configuration to 197.4 kN in the six-pile configuration, a reduction of 38.3%. During tunnel under-crossing, the lateral displacement profiles of both left-row and right-row piles exhibit X-shaped profiles at different tunnel depths, and the pile-top displacement varies slightly with a maximum of 1.1 mm. With increasing pile count, the maximum axial force per pile decreased from 202.2 kN to 132.1 kN, a reduction of 34.7%. The findings provide valuable reference for design and construction control of twin-line shield tunnels crossing existing airport pile foundations in cohesive soil.

In this paper, a simplified prediction formula of ground settlement induced by deep foundation pit excavation is proposed, especially suitable for ground overloading near a foundation pit, such as embankment surcharge load, which is carefully considered via the means of load equivalence. The ground settlement induced by foundation pit excavation and embankment surcharge load is determined by the modified skewness prediction formula and the simplified Boussinesq solution, respectively, and it is assumed that no coupling effect exists between the two settlement sources. In addition, this paper improves the determination of the maximum settlement location by combining calculus and curve fitting, replacing the existing prediction formula which relies heavily on engineering experience to determine the maximum settlement point. The predicted value obtained using this method comes close to the measured value, and the deviation of the maximum surface settlement value is controlled within about 5% in the three cases introduced, of which the accuracy is higher than the existing prediction formula.

Double-O-tube shield tunneling has attracted increasing attention because it offers cost-efficiency in underground construction. Prediction of ground surface settlement and the variety of additional stresses induced by shield construction is crucial to underground construction in metropolises since excessive settlement could trigger potential damage to the surrounding environment. The additional stresses induced by the propulsion of double-O-tube shields are calculated by means of the Mindlin’s equations of elasticity. The characteristics of additional stresses are analyzed with compound Gauss-Legendre integral arithmetic, and the frontal additional thrust, the lateral friction, and the ground loss are taken into account. Subsequently, based on field measurements, the maximum settlement coefficient and width of the settlement trough coefficient of the typical Peck formula are modified. The predictive curve of the Peck formula is closer to the engineering measured data than that of the typical formula. The cut-off functions of ground surface settlement caused by double-O-tube tunnel shield construction are proposed and can predict the shape of ground surface settlement, such as single peak or double peak. The correctness of the proposed functions is verified based on an engineering project.

We address the effect of three groups of factors on supplementary ground surface displacements during tunnel construction. The first group of factors includes the engineering and geological properties of the massif in which the tunneling is conducted; the second group includes the structural features of the designed tunnels and surrounding buildings, and the third group includes the engineering parameters of the tunneling process. The research takes advantage of the geotechnical monitoring data obtained during the construction of underground facilities and the engineering parameters of shield tunneling during construction of single- and double-track Moscow underground lines by using EPB (earth pressure balance)–TBM (tunnel boring machines) in different soils. The dependence of additional displacements, occurring above the designed tunnel, on the TBM pressure, is addressed in detail. The presence of a close interdependence is evidenced by a correlation coefficient equal to 0.77. No dependence of the settlement on the diameter or depth of the designed tunnel, the distance from the tunnel axis to the monitored object, the loading that comes from a building in the affected area, or the boring rate was identified. The consideration of this parameter can be used to predict the soil displacement around the tunnel at construction facilities having similar geological profiles and boring parameters.

Three-bench seven-step excavation method (TSEM) has been widely used in large-section loess tunnels for high-speed railway in China. As the most commonly applied pre-supports, pipe roofs and leading ductules are broadly used in the ground reinforcement of loess tunnels. Their application is to ensure face stability and prevent tunnel collapse during construction. This study focused on the impacts of the TSEM on the ground surface settlement (GSS), as well as the tunnel displacement characteristics for the high-speed railway tunnels with large cross-sections in loess ground. Furthermore, the reinforcement effects of the two kinds of pre-supports were compared in this study. In-situ tests for a total of 12 sections were conducted to reveal the GSSs and displacement characteristics for the shallow-buried large-section loess tunnels. The monitoring results showed that the excavation process plays a significant role on the GSSs and tunnel displacements. A maximum value was observed for the tunnel displacement rate at the excavation of the upper and middle benches, where the face instability or collapse were prone to occur. The GSS trough curves were deviated to the early excavation side, with no conformation to the Gauss distribution. After a series of comparisons, we concluded that the pre-reinforcement effect of the pipe roof is better than that of the leading ductule for the loess tunnels.