The deformation caused by tunnel excavation is quite important for safety,especially when it is adjacent to the existing tunnel.Nevertheless,the investigation of deformation characteristics in overlapped curved shield...The deformation caused by tunnel excavation is quite important for safety,especially when it is adjacent to the existing tunnel.Nevertheless,the investigation of deformation characteristics in overlapped curved shield tunneling remains inadequate.The analytical solution for calculating the deformation of the ground and existing tunnel induced by overlapped curved shield tunneling is derived by the Mirror theory,Mindlin solution and Euler-Bernoulli-Pasternak model,subsequently validated through both finite element simulation and field monitoring.It is determined that the overcutting plays a crucial role in the ground settlement resulting from curved shield tunneling compared to straight shield tunneling.The longitudinal settlement distribution can be categorized into five areas,with the area near the tunnel surface experiencing the most dramatic settlement changes.The deformation of the existing tunnel varies most significantly with turning radius compared to tunnel clearance and grouting pressure,especially when the turning radius is less than 30 times the tunnel diameter.The tunnel crown exhibits larger displacement than the tunnel bottom,resulting in a distinctive‘vertical egg'shape.Furthermore,an optimized overcutting mode is proposed,involving precise control of the extension speed and angular velocity of the overcutting cutter,which effectively mitigates ground deformation,ensuring the protection of the existing tunnel during the construction.展开更多
The construction of the new tunnel under the existing railway will break the original stress balance in the engineering area, resulting in the secondary redistribution of surrounding rock stress. The large amount of e...The construction of the new tunnel under the existing railway will break the original stress balance in the engineering area, resulting in the secondary redistribution of surrounding rock stress. The large amount of excavation unloading of the soil below is also easy to induce the uneven settlement deformation of the existing structure above, affecting the safety of driving. Based on the shield tunnel project between Caoqiao Station and Lize Business District Station of Beijing Metro, this paper restores the construction site by constructing the finite element numerical model of the project area, calculates and analyzes the deformation and stress of the existing railway structure before and after the construction of the tunnel, and determines the safety impact of the new structure on the existing railway. The results show that the shield tunnel undercrossing construction will cause the “concave” settlement of the railway subgrade above. Under the condition of grouting reinforcement, the “concave” settlement curve is slower and the distribution range is wider. With the advancement of the construction step, the settlement deformation of the subgrade gradually increases. When the tunnel approaches and passes directly below the subgrade, the settlement deformation curve of the subgrade changes from slow to steep. After the tunnel passes away, the curve changes from steep to slow, and the deformation of the subgrade reaches the maximum after the tunnel is connected. Under the grouting condition, the maximum settlement deformation of the subgrade is 2.08 mm, which is about 45% of the settlement deformation of the subgrade under the non-grouting condition. The ground grouting reinforcement can effectively control the subgrade settlement, and the field monitoring verifies the rationality of the calculation results. After the tunnel passes underneath, the most unfavorable section of the existing railway frame bridge is located at the top plate of the structure, and the maximum crack width is 0.178 mm. After grouting reinforcement, the stress environment of the structure is improved, the crack width generated by the structure is smaller, the reinforcement area required for calculation is less, and the structural safety meets the requirements.展开更多
Shield tunnel,composed of several segments,is widely used in urban underground engineering.When the tunnel is under load,relative displacement occurs between adjacent segments.In the past,distributed optical fiber sen...Shield tunnel,composed of several segments,is widely used in urban underground engineering.When the tunnel is under load,relative displacement occurs between adjacent segments.In the past,distributed optical fiber sensing technology was used to perform strain monitoring,but there is an urgent need to determine how to transform strain into displacement.In this study,optical frequency domain reflectometry was applied in laboratory tests.Aiming at the shear process and center settlement process of shield tunnel segments,two kinds of quantitative calculation methods were put forward to carry out a quantitative analysis.Meanwhile,the laboratory test process was simulated numerically utilizing the discrete element numerical analysis method.Optical fiber,an atypical geotechnical material,was innovatively applied for discrete element modeling and numerical simulation.The results show that the measured displacement of the dial gauge,the calculated results of the numerical model,and the displacement quantitatively calculated from the optical fiber data agree with each other in general.The latter two methods can potentially be utilized in engineering application of deformation monitoring at shield tunnel joints,but need to be further calibrated and adjusted in detail.展开更多
This paper proposes a longitudinal vulnerability-based analysis method to evaluate the impact of foundation pit excavation on shield tunnels,accounting for geological uncertainties.First,the shield tunnel is modeled a...This paper proposes a longitudinal vulnerability-based analysis method to evaluate the impact of foundation pit excavation on shield tunnels,accounting for geological uncertainties.First,the shield tunnel is modeled as an Euler Bernoulli beam resting on the Pasternak foundation incorporating variability in subgrade parameters along the tunnel’s length.A random analysis method using random field theory is introduced to evaluate the tunnel’s longitudinal responses to excavation.Next,a risk assessment index system is established.The normalized relative depth between the excavation and the shield tunnel is used as a risk index,while the maximum longitudinal deformation,the maximum circumferential opening,and the maximum longitudinal bending moment serve as performance indicators.Based on these,a method for analyzing the longitudinal fragility of shield tunnels under excavation-induced disturbances is proposed.Finally,the technique is applied to a case study involving a foundation pit excavation above a shield tunnel,which is the primary application scenario of this method.Vulnerability curves for different performance indicators are derived,and the effects of tunnel stiffness and subgrade stiffness on the tunnel vulnerability are explored.The results reveal significant differences in vulnerability curves depending on the performance index used.Compared to the maximum circumferential opening and the maximum longitudinal bending moment,selecting the maximum longitudinal deformation as the control index better ensures the tunnel’s usability and safety under excavation disturbances.The longitudinal vulnerability of the shield tunnel nonlinearly decreases with the increase of the tunnel stiffness and subgrade stiffness,and the subgrade stiffness has a more pronounced effect.Parametric analyses suggest that actively reinforcing the substratum is more effective on reducing the risk of tunnel failure due to adjacent excavations than passive reinforcement of the tunnel structure.展开更多
The quasi-rectangular tunnel represents a novel cross-section design,intended to supersede the traditional circular and rectangular tunnel formats.Due to the limited capacity of the tunnel vault to withstand vertical ...The quasi-rectangular tunnel represents a novel cross-section design,intended to supersede the traditional circular and rectangular tunnel formats.Due to the limited capacity of the tunnel vault to withstand vertical loads,an interior column is often installed at the center to enhance its load-bearing capacity.This study aims to develop a hyperstatic reaction method(HRM)for the analysis of deformation and structural integrity in this specific tunnel type.The computational model is validated through comparison with the corresponding finite element method(FEM)analysis.Following comprehensive validation,an ensemble machine learning(ML)model is proposed,using numerical benchmark data,to facilitate real-time design and optimization.Subsequently,three widely used ensemble models,i.e.random forest(RF),gradient boosting decision tree(GBDT),and extreme gradient boosting(XGBoost)are compared to identify the most efficient ML model for replacing the HRM model in the design optimization process.The performance metrics,such as the coefficient of determination R2 of about 0.999 and the mean absolute percentage error(MAPE)of about 1%,indicate that XGBoost outperforms the others,exhibiting excellent agreement with the HRM analysis.Additionally,the model demonstrates high computational efficiency,with prediction times measured in seconds.Finally,the HRM-XGBoost model is integrated with the well-known particle swarm optimization(PSO)for the real-time design optimization of quasi-rectangular tunnels,both with and without the interior column.A feature importance assessment is conducted to evaluate the sensitivity of design input features,enabling the selection of the most critical features for the optimization task.展开更多
The recent upsurge in metro construction emphasizes the necessity of understanding the mechanical performance of metro shield tunnel subjected to the influence of ground fissures.In this study,a largescale experiment,...The recent upsurge in metro construction emphasizes the necessity of understanding the mechanical performance of metro shield tunnel subjected to the influence of ground fissures.In this study,a largescale experiment,in combination with numerical simulation,was conducted to investigate the influence of ground fissures on a metro shield tunnel.The results indicate that the lining contact pressure at the vault increases in the hanging wall while decreases in the footwall,resulting in a two-dimensional stress state of vertical shear and axial tension-compression,and simultaneous vertical dislocation and axial tilt for the segments around the ground fissure.In addition,the damage to curved bolts includes tensile yield,flexural yield,and shear twist,leading to obvious concrete lining damage,particularly at the vault,arch bottom,and hance,indicating that the joints in these positions are weak areas.The shield tunnel orthogonal to the ground fissure ultimately experiences shear failure,suggesting that the maximum actual dislocation of ground fissure that the structure can withstand is approximately 20 cm,and five segment rings in the hanging wall and six segment rings in the footwall also need to be reinforced.This study could provide a reference for metro design in ground fissure sites.展开更多
Sandy cobble soil exhibits pronounced heterogeneity.The assessment of the uncertainty surrounding its properties is crucial for the analysis of settlement characteristics resulting from volume loss during shield tunne...Sandy cobble soil exhibits pronounced heterogeneity.The assessment of the uncertainty surrounding its properties is crucial for the analysis of settlement characteristics resulting from volume loss during shield tunnelling.In this study,a series of probabilistic analyses of surface and subsurface settlements was conducted considering the spatial variability of the friction angle and reference stiffness modulus,under different volumetric block proportions(Pv)and tunnel volume loss rates(ηt).The non-intrusive random finite difference method was used to investigate the probabilistic characteristics of maximum surface settlement,width of subsurface settlement trough,maximum subsurface settlement,and subsurface soil volume loss rate through Monte Carlo simulations.Additionally,a comparison between stochastic and deterministic analysis results is presented to underscore the significance of probabilistic analysis.Parametric analyses were subsequently conducted to investigate the impacts of the key input parameters in random fields on the settlement characteristics.The results indicate that scenarios with higher Pv or greaterηt result in a higher dispersion of stochastic analysis results.Neglecting the spatial variability of soil properties and relying solely on the mean values of material parameters for deterministic analysis may result in an underestimation of surface and subsurface settlements.From a probabilistic perspective,deterministic analysis alone may prove inadequate in accurately capturing the volumetric deformation mode of the soil above the tunnel crown,potentially affecting the prediction of subsurface settlement.展开更多
Current machine learning models for predicting geological conditions during earth pressure balance(EPB)shield tunneling predominantly rely on accurate geological conditions as model label inputs.This study introduces ...Current machine learning models for predicting geological conditions during earth pressure balance(EPB)shield tunneling predominantly rely on accurate geological conditions as model label inputs.This study introduces an innovative approach for the real-time prediction of geological conditions in EPB shield tunneling by utilizing an unsupervised incremental learning model that integrates deep temporal clustering(DTC)with elastic weight consolidation(EWC).The model was trained and tested using data from an EPB shield tunneling project in Nanjing,China.Results demonstrate that the DTC model outperforms nine comparison models by clustering the entire dataset into four distinct groups representing various geological conditions without requiring labeled data.Additionally,integrating EWC into the DTC model significantly enhances its continuous learning capabilities,enabling automatic parameter updates with incoming data and facilitating the real-time recognition of geological conditions.Feature importance was evaluated using the feature elimination method and the Shapley additive explanations(SHAP)method,underscoring the critical roles of earth chamber pressure and cutterhead rotation speed in predicting geological conditions.The proposed EWC-DTC model demonstrates practical utility for EPB shield tunneling in complex environments.展开更多
An efficient determination of the geological characteristics and soil-rock type ahead of a tunnel face is critical for adjusting construction parameters during shield tunnelling.In general,operational engineers rely o...An efficient determination of the geological characteristics and soil-rock type ahead of a tunnel face is critical for adjusting construction parameters during shield tunnelling.In general,operational engineers rely on visual observations of mucky soil types from belt conveyors.This results in shield halting and involves both time and cost implications.This paper proposes a deep learning approach designed to identify mucky soil by monitoring a video installed on the strut of a belt conveyer.The proposed approach comprises four steps:(1)image acquisition,(2)enhanced you-only-look-once(YOLO)modelling,(3)model performance evaluation,and(4)soil identification based on an optimal analysis.The enhanced YOLO model is a deep image detection algorithm.It was introduced by integrating two innovative strategies:data augmentation and imbalance learning.This enhancement accelerates the speed of image identification and improves the overall classification performance.A case study of shield tunnelling in the soil-rock mixed strata of the GuangzhoueFoshan intercity railway line was conducted to validate the proposed approach.The results indicate that the enhanced YOLO model achieves a classification performance comparable to that of the highly optimised AlexNet and GoogleNet.Additionally,the proposed approach more effectively detects the muck soil content than manual observation.This demonstrates its potential for real-time applications in shield tunnelling operations.展开更多
Maintaining the stability of the excavation face is key for ensuring the safety of underwater shield tunnel construction.However,the majority of current studies on the stability of excavation face focus on the homogen...Maintaining the stability of the excavation face is key for ensuring the safety of underwater shield tunnel construction.However,the majority of current studies on the stability of excavation face focus on the homogeneous strata,with limited research conducted on the upper loose and lower dense strata.Active instability tests are conducted in this study,in concert with the digital image correlation(DIC)technique,to investigate the effects of different water pressure ratios in upper loose and lower dense water-rich strata.The accuracy of these model tests is verified using numerical simulations.The results indicate that as water pressure ratio decreases,there is an increase in both the peak displacement of surface settlement and the seepage path range of water ahead of the excavation face expands.In contrast,decreasing water pressure ratio will break the limit equilibrium state of the strata faster,cause the earth pressure on the cutterhead to change more rapidly,and increase the instability range of the strata.展开更多
Advances in intelligent shield machines reflect an evolving trend from traditional tunnel boring machines(TBMs)to tunnel boring robots(TBRs).This shift aims to address the challenges encountered by the conventional sh...Advances in intelligent shield machines reflect an evolving trend from traditional tunnel boring machines(TBMs)to tunnel boring robots(TBRs).This shift aims to address the challenges encountered by the conventional shield machine industry arising from construction environment and manual operations.This study presents a systematic review of intelligent shield machine technology,with a particular emphasis on its smart operation.Firstly,the definition,meaning,contents,and development modes of intelligent shield machines are proposed.The development status of the intelligent shield machine and its smart operation are then presented.After analyzing the operation process of the shield machine,an autonomous operation framework considering both stand-alone and fleet levels is proposed.Challenges and recommendations are given for achieving autonomous operation.This study offers insights into the essence and developmental framework of intelligent shield machines to propel the advancement of this technology.展开更多
Twin curved tunnels are often encountered in shield tunnelling,where significant complexities in densely exploited underground space are observed.In this study,the ground settlement and tunnel deformation due to twin-...Twin curved tunnels are often encountered in shield tunnelling,where significant complexities in densely exploited underground space are observed.In this study,the ground settlement and tunnel deformation due to twin-curved shield tunnelling in soft ground were investigated using numerical simulation and field monitoring.Different curvature radii of twin curved tunnels and subsequent effects of tunnel construction were considered to reveal the tunnelling effect on ground surface settlement and tunnel deformation.The results show that the settlement trough yields one offset towards inside of curved shield tunnelling.The location of settlement trough and maximum settlement were affected by curvature radius but except for the shape and width of settlement trough.Adjacent parallel twin-curved shield tunnelling could increase the offset of existing settlement trough and maximum settlement.Then,an empirical prediction of surface settlement trough due to twin-curved shield tunnelling with same tunnel diameters in soft clay was proposed,which was applicable to curvature radius less than 800 m.Finally,a minimum radius of 600 m of curvature tunnel was proposed in terms of allowable convergence deformation of tunnel.The result could provide guidance on safety evaluation for twin curved shield tunnelling construction.展开更多
This study focuses on the analytical prediction of subsurface settlement induced by shield tunnelling in sandy cobble stratum considering the volumetric deformation modes of the soil above the tunnel crown.A series of...This study focuses on the analytical prediction of subsurface settlement induced by shield tunnelling in sandy cobble stratum considering the volumetric deformation modes of the soil above the tunnel crown.A series of numerical analyses is performed to examine the effects of cover depth ratio(C/D),tunnel volume loss rate(h t)and volumetric block proportion(VBP)on the characteristics of subsurface settle-ment trough and soil volume loss.Considering the ground loss variation with depth,three modes are deduced from the volumetric deformation responses of the soil above the tunnel crown.Then,analytical solutions to predict subsurface settlement for each mode are presented using stochastic medium theory.The influences of C/D,h t and VBP on the key parameters(i.e.B and N)in the analytical expressions are discussed to determine the fitting formulae of B and N.Finally,the proposed analytical solutions are validated by the comparisons with the results of model test and numerical simulation.Results show that the fitting formulae provide a convenient and reliable way to evaluate the key parameters.Besides,the analytical solutions are reasonable and available in predicting the subsurface settlement induced by shield tunnelling in sandy cobble stratum.展开更多
Due to the network planning of subways and their surrounding structures,increasingly more overlapping shields with a small curve radius have been constructed. A newly constructed upper tunnel partly overlaps a lower o...Due to the network planning of subways and their surrounding structures,increasingly more overlapping shields with a small curve radius have been constructed. A newly constructed upper tunnel partly overlaps a lower one, leading to the extremely complex uplift of the lower tunnel caused by the construction of a new tunnel. Based on the shield-driven project that runs from the Qinghe Xiaoyingqiao Station to the Qinghe Station in Beijing, which adopts the reinforcement measures of interlayer soil grouting and steel supports on site, in this study, the uplift pattern of the lower tunnel and the stress characteristics of steel supports were investigated through numerical simulations and on-site monitoring.The study results show that among all tunnel segments, the first segment of the shield witnesses a maximum uplift displacement that increases with the horizontal space between tunnels. On using either interlayer soil grouting or steel-ring bracing reinforcement, the uplift of the tunnel lining exceeds the control value;by contrast,when these two measures are jointly applied, the uplift of the tunnel lining does not exceed a maximum value of 4.87 mm, which can satisfy the requirements of deformation control. Under these two joint measures, the soil strength between two stacked shield tunnels can be enhanced and the uplift deformation can be restricted with the interlayer soil grouting. Also, the segmental deformation and overall stability of the existing tunnel can be controlled with the temporary steel supports.The deformation of circumferential supports and segments is closely related to each other, and the segmental uplift is controlled by H-shaped steel supports. With the increase in the horizontal space between twin shields, the effect of the construction would gradually weaken, accompanied by a gradual reduction of the stresses of steel supports. These findings provide a valuable reference for the engineering design and safe construction of overlapping shield tunnels with a small curve radius.展开更多
The problem of shield tunnel uplift is a common issue in tunnel construction.Due to the decrease in shear stiffness at the joints between the rings,uplift is typically observed as bending and dislocation deformation a...The problem of shield tunnel uplift is a common issue in tunnel construction.Due to the decrease in shear stiffness at the joints between the rings,uplift is typically observed as bending and dislocation deformation at these joints.Existing modeling methods typically rely on the Euler-Bernoulli beam theory,only considering the bending effect while disregarding shear deformation.Furthermore,the constraints on the shield tail are often neglected in existing models.In this study,an improved theoretical model of tunnel floating is proposed.The constraint effect of the shield machine shell on the tunnel structure is considered using the structural forms of two finite long beams and one semi-infinite long beam.Furthermore,the Timoshenko beam theory is adopted,providing a more accurate description of tunnel deformation,including both the bending effect and shear deformation,than existing models.Meanwhile,the buoyancy force and stratum resistance are calculated in a nonlinear manner.A reliable method for calculating the shear stiffness correction factor is proposed to better determination of the calculation parameters.The proposed theoretical model is validated through five cases using sitemonitored data.Its applicability and effectiveness are demonstrated.Furthermore,the influences of soil type,buried depth,and buoyancy force on the three key indicators of tunnel floating(i.e.the maximum uplift magnitude,the ring position with the fastest uplift race,and the ring position with the maximum uplift magnitude)are analyzed.The results indicate that the proposed model can provide a better understanding of the floating characteristics of the tunnel structure during construction.展开更多
To address the seismic face stability challenges encountered in urban and subsea tunnel construction,an efficient probabilistic analysis framework for shield tunnel faces under seismic conditions is proposed.Based on ...To address the seismic face stability challenges encountered in urban and subsea tunnel construction,an efficient probabilistic analysis framework for shield tunnel faces under seismic conditions is proposed.Based on the upper-bound theory of limit analysis,an improved three-dimensional discrete deterministic mechanism,accounting for the heterogeneous nature of soil media,is formulated to evaluate seismic face stability.The metamodel of failure probabilistic assessments for seismic tunnel faces is constructed by integrating the sparse polynomial chaos expansion method(SPCE)with the modified pseudo-dynamic approach(MPD).The improved deterministic model is validated by comparing with published literature and numerical simulations results,and the SPCE-MPD metamodel is examined with the traditional MCS method.Based on the SPCE-MPD metamodels,the seismic effects on face failure probability and reliability index are presented and the global sensitivity analysis(GSA)is involved to reflect the influence order of seismic action parameters.Finally,the proposed approach is tested to be effective by a engineering case of the Chengdu outer ring tunnel.The results show that higher uncertainty of seismic response on face stability should be noticed in areas with intense earthquakes and variation of seismic wave velocity has the most profound influence on tunnel face stability.展开更多
We develop assembled reinforcement structures(ARSs)composed of connection parts,connecting rods,and straight bolts to strengthen segmental joints in the lining of shield tunnels.Through full-scale bending experiments ...We develop assembled reinforcement structures(ARSs)composed of connection parts,connecting rods,and straight bolts to strengthen segmental joints in the lining of shield tunnels.Through full-scale bending experiments and numerical simulations,we investigate the deformation and failure characteristics of segmental joints strengthened by ARSs,and propose a novel optimization method for ARSs.The experimental results show that the ARSs can effectively limit the opening of a segmental joint,but also that separation can occur during loading if the connection between the ARSs and segments is not designed properly.Importantly,this connection can be improved by embedding anchor parts in the concrete.In numerical modeling,we investigate the failure modes of segmental joints strengthened by ARSs for both positive bending and negative bending loading cases.In the case of positive bending loading,first the concrete around the anchor parts cracks,and subsequently the concrete on the external side of the joint is crushed.The joint failure is caused by the crushing of concrete on the external side of the joint.While the un-strengthened segmental joint fails with an opening of 5.884 mm,the strengthened segmental joint only opens by 0.288 mm under the same loading,corresponding to a reduction of 95.1%.In the case of negative bending loading,the concrete around the anchor parts first cracks,and then the amount of joint opening exceeds a limiting value for waterproofing(6 mm),i.e.,the joint’s failure is caused by water leakage.While the opening of the un-strengthened segmental joint is 9.033 mm and experiences waterproofing failure,the opening of the strengthened segmental joint is only 2.793 mm under the same loading,corresponding to a reduction of 69.1%.When constructing a new shield tunnel,anchor parts could be embedded in the concrete segments in tandem with ARSs for improved resistance to joint opening.For existing shield tunnel linings,anchor parts cannot be embedded in the concrete segments;therefore,the connections between the ARSs and concrete need to be optimized to strengthen the segmental joint.展开更多
Waterproof performance of gaskets between segments is the focus of shield tunnels.This paper proposed an analytical method for determining seepage characteristics at tunnel-gasketed joints based on the hydraulic fract...Waterproof performance of gaskets between segments is the focus of shield tunnels.This paper proposed an analytical method for determining seepage characteristics at tunnel-gasketed joints based on the hydraulic fracturing theories.First,the mathematical model was established,and the seepage governing equation and boundary conditions were obtained.Second,three dimensionless parameters were introduced for simplifying the expressions,and the seepage governing equations were normalized.Third,analytical expressions were derived for the interface opening and liquid pressure.Moreover,the influencing factors of seepage process at the gasketed interface were analyzed.Parametric analyses revealed that,in the normalized criterion of liquid viscosity,the liquid tip coordinate was influenced by the degree of negative pressure in the liquid lag region,which was related to the initial contact stress.The coordinate of the liquid tip affected the liquid pressure distribution and the interface opening,which were analyzed under different liquid tip coordinate conditions.Finally,under two limit states,comparative analysis showed that the results of the variation trend of the proposed method agree well with those of previous research.Overall,the proposed analytical method provides a novel solution for the design of the waterproof in shield tunnels.展开更多
Severe shield jamming events have been reported during excavation of Uluabat tunnel through adverse geological conditions, which resulted in several stoppages at advancing a single shielded tunnel boring machine(TBM)....Severe shield jamming events have been reported during excavation of Uluabat tunnel through adverse geological conditions, which resulted in several stoppages at advancing a single shielded tunnel boring machine(TBM). To study the jamming mechanism, three-dimensional(3D) simulation of the machine and surrounding ground was implemented using the finite difference code FLAC3D. Numerical analyses were performed for three sections along the tunnel with a higher risk for entrapment due to the combination of overburden and geological conditions. The computational results including longitudinal displacement contours and ground pressure profiles around the shield allow a better understanding of ground behavior within the excavation. Furthermore, they allow realistically assessing the impact of adverse geological conditions on shield jamming. The calculated thrust forces, which are required to move the machine forward, are in good agreement with field observations and measurements. It also proves that the numerical analysis can effectively be used for evaluating the effect of adverse geological environment on TBM entrapments and can be applied to prediction of loads on the shield and preestimating of the required thrust force during excavation through adverse ground conditions.展开更多
For a tunnel driven by a shield machine,the posture of the driving machine is essential to the construction quality and environmental impact.However,the machine posture is controlled by the experienced driver of shiel...For a tunnel driven by a shield machine,the posture of the driving machine is essential to the construction quality and environmental impact.However,the machine posture is controlled by the experienced driver of shield machine by setting hundreds of tunneling parameters empirically.Machine learning(ML)algorithm is an alternative method that can let the computer to learn from the driver’s operation and try to model the relationship between parameters automatically.Thus,in this paper,three ML algorithms,i.e.multi-layer perception(MLP),support vector machine(SVM)and gradient boosting regression(GBR),are improved by genetic algorithm(GA)and principal component analysis(PCA)to predict the tunneling posture of the shield machine.A set of the parameters for shield tunneling is extracted from the construction site of a Shanghai metro.In total,53,785 pairwise data points are collected for about 373 d and the ratio between training set,validation set and test set is 3:1:1.Each pairwise data point includes 83 types of parameters covering the shield posture,construction parameters,and soil stratum properties at the same time.The test results show that the averaged R2 of MLP,SVM and GBR based models are 0.942,0.935 and 0.6,respectively.Then the automatic control for the posture of shield tunnel is illustrated with an application example of the proposed models.The proposed method is proved to be helpful in controlling the construction quality with optimized construction parameters.展开更多
基金financially supported by the National Natural Science Foundation of China(Grant No.52078334)the National Key Research and Development Program of China(Grant No.2017YFC0805402)the Tianjin Research Innovation Project for Postgraduate Students(Grant No.2021YJSB141).
文摘The deformation caused by tunnel excavation is quite important for safety,especially when it is adjacent to the existing tunnel.Nevertheless,the investigation of deformation characteristics in overlapped curved shield tunneling remains inadequate.The analytical solution for calculating the deformation of the ground and existing tunnel induced by overlapped curved shield tunneling is derived by the Mirror theory,Mindlin solution and Euler-Bernoulli-Pasternak model,subsequently validated through both finite element simulation and field monitoring.It is determined that the overcutting plays a crucial role in the ground settlement resulting from curved shield tunneling compared to straight shield tunneling.The longitudinal settlement distribution can be categorized into five areas,with the area near the tunnel surface experiencing the most dramatic settlement changes.The deformation of the existing tunnel varies most significantly with turning radius compared to tunnel clearance and grouting pressure,especially when the turning radius is less than 30 times the tunnel diameter.The tunnel crown exhibits larger displacement than the tunnel bottom,resulting in a distinctive‘vertical egg'shape.Furthermore,an optimized overcutting mode is proposed,involving precise control of the extension speed and angular velocity of the overcutting cutter,which effectively mitigates ground deformation,ensuring the protection of the existing tunnel during the construction.
文摘The construction of the new tunnel under the existing railway will break the original stress balance in the engineering area, resulting in the secondary redistribution of surrounding rock stress. The large amount of excavation unloading of the soil below is also easy to induce the uneven settlement deformation of the existing structure above, affecting the safety of driving. Based on the shield tunnel project between Caoqiao Station and Lize Business District Station of Beijing Metro, this paper restores the construction site by constructing the finite element numerical model of the project area, calculates and analyzes the deformation and stress of the existing railway structure before and after the construction of the tunnel, and determines the safety impact of the new structure on the existing railway. The results show that the shield tunnel undercrossing construction will cause the “concave” settlement of the railway subgrade above. Under the condition of grouting reinforcement, the “concave” settlement curve is slower and the distribution range is wider. With the advancement of the construction step, the settlement deformation of the subgrade gradually increases. When the tunnel approaches and passes directly below the subgrade, the settlement deformation curve of the subgrade changes from slow to steep. After the tunnel passes away, the curve changes from steep to slow, and the deformation of the subgrade reaches the maximum after the tunnel is connected. Under the grouting condition, the maximum settlement deformation of the subgrade is 2.08 mm, which is about 45% of the settlement deformation of the subgrade under the non-grouting condition. The ground grouting reinforcement can effectively control the subgrade settlement, and the field monitoring verifies the rationality of the calculation results. After the tunnel passes underneath, the most unfavorable section of the existing railway frame bridge is located at the top plate of the structure, and the maximum crack width is 0.178 mm. After grouting reinforcement, the stress environment of the structure is improved, the crack width generated by the structure is smaller, the reinforcement area required for calculation is less, and the structural safety meets the requirements.
基金National Natural Science Foundation of China,Grant/Award Numbers:41977218,42222707State Key Laboratory for GeoMechanics and Deep Underground Engineering,Grant/Award Number:SKLGDUEK2117。
文摘Shield tunnel,composed of several segments,is widely used in urban underground engineering.When the tunnel is under load,relative displacement occurs between adjacent segments.In the past,distributed optical fiber sensing technology was used to perform strain monitoring,but there is an urgent need to determine how to transform strain into displacement.In this study,optical frequency domain reflectometry was applied in laboratory tests.Aiming at the shear process and center settlement process of shield tunnel segments,two kinds of quantitative calculation methods were put forward to carry out a quantitative analysis.Meanwhile,the laboratory test process was simulated numerically utilizing the discrete element numerical analysis method.Optical fiber,an atypical geotechnical material,was innovatively applied for discrete element modeling and numerical simulation.The results show that the measured displacement of the dial gauge,the calculated results of the numerical model,and the displacement quantitatively calculated from the optical fiber data agree with each other in general.The latter two methods can potentially be utilized in engineering application of deformation monitoring at shield tunnel joints,but need to be further calibrated and adjusted in detail.
基金Project(52178402) supported by the National Natural Science Foundation of China。
文摘This paper proposes a longitudinal vulnerability-based analysis method to evaluate the impact of foundation pit excavation on shield tunnels,accounting for geological uncertainties.First,the shield tunnel is modeled as an Euler Bernoulli beam resting on the Pasternak foundation incorporating variability in subgrade parameters along the tunnel’s length.A random analysis method using random field theory is introduced to evaluate the tunnel’s longitudinal responses to excavation.Next,a risk assessment index system is established.The normalized relative depth between the excavation and the shield tunnel is used as a risk index,while the maximum longitudinal deformation,the maximum circumferential opening,and the maximum longitudinal bending moment serve as performance indicators.Based on these,a method for analyzing the longitudinal fragility of shield tunnels under excavation-induced disturbances is proposed.Finally,the technique is applied to a case study involving a foundation pit excavation above a shield tunnel,which is the primary application scenario of this method.Vulnerability curves for different performance indicators are derived,and the effects of tunnel stiffness and subgrade stiffness on the tunnel vulnerability are explored.The results reveal significant differences in vulnerability curves depending on the performance index used.Compared to the maximum circumferential opening and the maximum longitudinal bending moment,selecting the maximum longitudinal deformation as the control index better ensures the tunnel’s usability and safety under excavation disturbances.The longitudinal vulnerability of the shield tunnel nonlinearly decreases with the increase of the tunnel stiffness and subgrade stiffness,and the subgrade stiffness has a more pronounced effect.Parametric analyses suggest that actively reinforcing the substratum is more effective on reducing the risk of tunnel failure due to adjacent excavations than passive reinforcement of the tunnel structure.
基金funded by the Hanoi University of Mining and Geology(Grant No.T23-44)The research is also funded by the German Research Foundation(DFG e Project number 518862444)in collaboration with the Vietnam National Foundation for Science and Technology Development(NAFOSTED)under grant number DFG.105e2022.03The third author was funded by the Postdoctoral Scholarship Program of the Vingroup Innovation Foundation(VINIF)(VINIF.2023.STS.15).
文摘The quasi-rectangular tunnel represents a novel cross-section design,intended to supersede the traditional circular and rectangular tunnel formats.Due to the limited capacity of the tunnel vault to withstand vertical loads,an interior column is often installed at the center to enhance its load-bearing capacity.This study aims to develop a hyperstatic reaction method(HRM)for the analysis of deformation and structural integrity in this specific tunnel type.The computational model is validated through comparison with the corresponding finite element method(FEM)analysis.Following comprehensive validation,an ensemble machine learning(ML)model is proposed,using numerical benchmark data,to facilitate real-time design and optimization.Subsequently,three widely used ensemble models,i.e.random forest(RF),gradient boosting decision tree(GBDT),and extreme gradient boosting(XGBoost)are compared to identify the most efficient ML model for replacing the HRM model in the design optimization process.The performance metrics,such as the coefficient of determination R2 of about 0.999 and the mean absolute percentage error(MAPE)of about 1%,indicate that XGBoost outperforms the others,exhibiting excellent agreement with the HRM analysis.Additionally,the model demonstrates high computational efficiency,with prediction times measured in seconds.Finally,the HRM-XGBoost model is integrated with the well-known particle swarm optimization(PSO)for the real-time design optimization of quasi-rectangular tunnels,both with and without the interior column.A feature importance assessment is conducted to evaluate the sensitivity of design input features,enabling the selection of the most critical features for the optimization task.
基金supported by the National Key Research&Development Program of China(Grant No.2023YFC3008404)the Key Laboratory of Earth Fissures Geological Disaster,Ministry of Natural Resources,China(Grant Nos.EFGD20240609 and EFGD20240610).
文摘The recent upsurge in metro construction emphasizes the necessity of understanding the mechanical performance of metro shield tunnel subjected to the influence of ground fissures.In this study,a largescale experiment,in combination with numerical simulation,was conducted to investigate the influence of ground fissures on a metro shield tunnel.The results indicate that the lining contact pressure at the vault increases in the hanging wall while decreases in the footwall,resulting in a two-dimensional stress state of vertical shear and axial tension-compression,and simultaneous vertical dislocation and axial tilt for the segments around the ground fissure.In addition,the damage to curved bolts includes tensile yield,flexural yield,and shear twist,leading to obvious concrete lining damage,particularly at the vault,arch bottom,and hance,indicating that the joints in these positions are weak areas.The shield tunnel orthogonal to the ground fissure ultimately experiences shear failure,suggesting that the maximum actual dislocation of ground fissure that the structure can withstand is approximately 20 cm,and five segment rings in the hanging wall and six segment rings in the footwall also need to be reinforced.This study could provide a reference for metro design in ground fissure sites.
基金supported by the Natural Science Foundation of Beijing Municipality(No.8222004),Chinathe National Natural Science Foundation of China(No.51978019)+3 种基金the Natural Science Foundation of Henan Province(No.252300420445),Chinathe Doctoral Research Initiation Fund of Henan University of Science and Technology(No.4007/13480062),Chinathe Henan Postdoctoral Foundation(No.13554005),Chinathe Joint Fund of Science and Technology R&D Program of Henan Province(No.232103810082),China。
文摘Sandy cobble soil exhibits pronounced heterogeneity.The assessment of the uncertainty surrounding its properties is crucial for the analysis of settlement characteristics resulting from volume loss during shield tunnelling.In this study,a series of probabilistic analyses of surface and subsurface settlements was conducted considering the spatial variability of the friction angle and reference stiffness modulus,under different volumetric block proportions(Pv)and tunnel volume loss rates(ηt).The non-intrusive random finite difference method was used to investigate the probabilistic characteristics of maximum surface settlement,width of subsurface settlement trough,maximum subsurface settlement,and subsurface soil volume loss rate through Monte Carlo simulations.Additionally,a comparison between stochastic and deterministic analysis results is presented to underscore the significance of probabilistic analysis.Parametric analyses were subsequently conducted to investigate the impacts of the key input parameters in random fields on the settlement characteristics.The results indicate that scenarios with higher Pv or greaterηt result in a higher dispersion of stochastic analysis results.Neglecting the spatial variability of soil properties and relying solely on the mean values of material parameters for deterministic analysis may result in an underestimation of surface and subsurface settlements.From a probabilistic perspective,deterministic analysis alone may prove inadequate in accurately capturing the volumetric deformation mode of the soil above the tunnel crown,potentially affecting the prediction of subsurface settlement.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.52378392,52408356)Foal Eagle Program Youth Top-notch Talent Project of Fujian Province,China(Grant No.00387088).
文摘Current machine learning models for predicting geological conditions during earth pressure balance(EPB)shield tunneling predominantly rely on accurate geological conditions as model label inputs.This study introduces an innovative approach for the real-time prediction of geological conditions in EPB shield tunneling by utilizing an unsupervised incremental learning model that integrates deep temporal clustering(DTC)with elastic weight consolidation(EWC).The model was trained and tested using data from an EPB shield tunneling project in Nanjing,China.Results demonstrate that the DTC model outperforms nine comparison models by clustering the entire dataset into four distinct groups representing various geological conditions without requiring labeled data.Additionally,integrating EWC into the DTC model significantly enhances its continuous learning capabilities,enabling automatic parameter updates with incoming data and facilitating the real-time recognition of geological conditions.Feature importance was evaluated using the feature elimination method and the Shapley additive explanations(SHAP)method,underscoring the critical roles of earth chamber pressure and cutterhead rotation speed in predicting geological conditions.The proposed EWC-DTC model demonstrates practical utility for EPB shield tunneling in complex environments.
基金funded by Guangdong Province Scientific Research Project for Young Innovation Talent(Grant No.2022KQNCX239)The Pearl River Talent Recruitment Program(Grant No.2019CX01G338),Guangdong Province.
文摘An efficient determination of the geological characteristics and soil-rock type ahead of a tunnel face is critical for adjusting construction parameters during shield tunnelling.In general,operational engineers rely on visual observations of mucky soil types from belt conveyors.This results in shield halting and involves both time and cost implications.This paper proposes a deep learning approach designed to identify mucky soil by monitoring a video installed on the strut of a belt conveyer.The proposed approach comprises four steps:(1)image acquisition,(2)enhanced you-only-look-once(YOLO)modelling,(3)model performance evaluation,and(4)soil identification based on an optimal analysis.The enhanced YOLO model is a deep image detection algorithm.It was introduced by integrating two innovative strategies:data augmentation and imbalance learning.This enhancement accelerates the speed of image identification and improves the overall classification performance.A case study of shield tunnelling in the soil-rock mixed strata of the GuangzhoueFoshan intercity railway line was conducted to validate the proposed approach.The results indicate that the enhanced YOLO model achieves a classification performance comparable to that of the highly optimised AlexNet and GoogleNet.Additionally,the proposed approach more effectively detects the muck soil content than manual observation.This demonstrates its potential for real-time applications in shield tunnelling operations.
基金supported by the National Natural Science Foundation of China(No.51978019)the Natural Science Foundation of Beijing Municipality(No.8222004),China.
文摘Maintaining the stability of the excavation face is key for ensuring the safety of underwater shield tunnel construction.However,the majority of current studies on the stability of excavation face focus on the homogeneous strata,with limited research conducted on the upper loose and lower dense strata.Active instability tests are conducted in this study,in concert with the digital image correlation(DIC)technique,to investigate the effects of different water pressure ratios in upper loose and lower dense water-rich strata.The accuracy of these model tests is verified using numerical simulations.The results indicate that as water pressure ratio decreases,there is an increase in both the peak displacement of surface settlement and the seepage path range of water ahead of the excavation face expands.In contrast,decreasing water pressure ratio will break the limit equilibrium state of the strata faster,cause the earth pressure on the cutterhead to change more rapidly,and increase the instability range of the strata.
基金supported by the National Natural Science Foundation of China(No.52105074)the Open Project of State Key Laboratory of Shield Machine and Boring Technology(No.SKLST-2021-K02),China。
文摘Advances in intelligent shield machines reflect an evolving trend from traditional tunnel boring machines(TBMs)to tunnel boring robots(TBRs).This shift aims to address the challenges encountered by the conventional shield machine industry arising from construction environment and manual operations.This study presents a systematic review of intelligent shield machine technology,with a particular emphasis on its smart operation.Firstly,the definition,meaning,contents,and development modes of intelligent shield machines are proposed.The development status of the intelligent shield machine and its smart operation are then presented.After analyzing the operation process of the shield machine,an autonomous operation framework considering both stand-alone and fleet levels is proposed.Challenges and recommendations are given for achieving autonomous operation.This study offers insights into the essence and developmental framework of intelligent shield machines to propel the advancement of this technology.
基金financially supported by the National Natural Science Foundation of China(Grant No.42307260)the Sichuan Natural Science Foundation(Grant No.2023NSFSC0882)the Open Project of the Research Center of Tunnelling and Underground Engineering of Ministry of Education(Grant No.TUC2022-03).
文摘Twin curved tunnels are often encountered in shield tunnelling,where significant complexities in densely exploited underground space are observed.In this study,the ground settlement and tunnel deformation due to twin-curved shield tunnelling in soft ground were investigated using numerical simulation and field monitoring.Different curvature radii of twin curved tunnels and subsequent effects of tunnel construction were considered to reveal the tunnelling effect on ground surface settlement and tunnel deformation.The results show that the settlement trough yields one offset towards inside of curved shield tunnelling.The location of settlement trough and maximum settlement were affected by curvature radius but except for the shape and width of settlement trough.Adjacent parallel twin-curved shield tunnelling could increase the offset of existing settlement trough and maximum settlement.Then,an empirical prediction of surface settlement trough due to twin-curved shield tunnelling with same tunnel diameters in soft clay was proposed,which was applicable to curvature radius less than 800 m.Finally,a minimum radius of 600 m of curvature tunnel was proposed in terms of allowable convergence deformation of tunnel.The result could provide guidance on safety evaluation for twin curved shield tunnelling construction.
基金This study was supported by the National Natural Science Foundation of China(Grant Nos.51538001 and 51978019).
文摘This study focuses on the analytical prediction of subsurface settlement induced by shield tunnelling in sandy cobble stratum considering the volumetric deformation modes of the soil above the tunnel crown.A series of numerical analyses is performed to examine the effects of cover depth ratio(C/D),tunnel volume loss rate(h t)and volumetric block proportion(VBP)on the characteristics of subsurface settle-ment trough and soil volume loss.Considering the ground loss variation with depth,three modes are deduced from the volumetric deformation responses of the soil above the tunnel crown.Then,analytical solutions to predict subsurface settlement for each mode are presented using stochastic medium theory.The influences of C/D,h t and VBP on the key parameters(i.e.B and N)in the analytical expressions are discussed to determine the fitting formulae of B and N.Finally,the proposed analytical solutions are validated by the comparisons with the results of model test and numerical simulation.Results show that the fitting formulae provide a convenient and reliable way to evaluate the key parameters.Besides,the analytical solutions are reasonable and available in predicting the subsurface settlement induced by shield tunnelling in sandy cobble stratum.
基金National Natural Science Foundation of China,Grant/Award Number:52168059Program for Young Talents of Science and Technology in Universities of Inner Mongolia Autonomous Region,Grant/Award Number:NJYT23103Fundamental Research Funds in Universities of Inner Mongolia Autonomous Region,Grant/Award Number:2023QNJS159。
文摘Due to the network planning of subways and their surrounding structures,increasingly more overlapping shields with a small curve radius have been constructed. A newly constructed upper tunnel partly overlaps a lower one, leading to the extremely complex uplift of the lower tunnel caused by the construction of a new tunnel. Based on the shield-driven project that runs from the Qinghe Xiaoyingqiao Station to the Qinghe Station in Beijing, which adopts the reinforcement measures of interlayer soil grouting and steel supports on site, in this study, the uplift pattern of the lower tunnel and the stress characteristics of steel supports were investigated through numerical simulations and on-site monitoring.The study results show that among all tunnel segments, the first segment of the shield witnesses a maximum uplift displacement that increases with the horizontal space between tunnels. On using either interlayer soil grouting or steel-ring bracing reinforcement, the uplift of the tunnel lining exceeds the control value;by contrast,when these two measures are jointly applied, the uplift of the tunnel lining does not exceed a maximum value of 4.87 mm, which can satisfy the requirements of deformation control. Under these two joint measures, the soil strength between two stacked shield tunnels can be enhanced and the uplift deformation can be restricted with the interlayer soil grouting. Also, the segmental deformation and overall stability of the existing tunnel can be controlled with the temporary steel supports.The deformation of circumferential supports and segments is closely related to each other, and the segmental uplift is controlled by H-shaped steel supports. With the increase in the horizontal space between twin shields, the effect of the construction would gradually weaken, accompanied by a gradual reduction of the stresses of steel supports. These findings provide a valuable reference for the engineering design and safe construction of overlapping shield tunnels with a small curve radius.
基金the National Natural Science Foundation of China (Grant Nos.52379111,51979270 and 52208380).
文摘The problem of shield tunnel uplift is a common issue in tunnel construction.Due to the decrease in shear stiffness at the joints between the rings,uplift is typically observed as bending and dislocation deformation at these joints.Existing modeling methods typically rely on the Euler-Bernoulli beam theory,only considering the bending effect while disregarding shear deformation.Furthermore,the constraints on the shield tail are often neglected in existing models.In this study,an improved theoretical model of tunnel floating is proposed.The constraint effect of the shield machine shell on the tunnel structure is considered using the structural forms of two finite long beams and one semi-infinite long beam.Furthermore,the Timoshenko beam theory is adopted,providing a more accurate description of tunnel deformation,including both the bending effect and shear deformation,than existing models.Meanwhile,the buoyancy force and stratum resistance are calculated in a nonlinear manner.A reliable method for calculating the shear stiffness correction factor is proposed to better determination of the calculation parameters.The proposed theoretical model is validated through five cases using sitemonitored data.Its applicability and effectiveness are demonstrated.Furthermore,the influences of soil type,buried depth,and buoyancy force on the three key indicators of tunnel floating(i.e.the maximum uplift magnitude,the ring position with the fastest uplift race,and the ring position with the maximum uplift magnitude)are analyzed.The results indicate that the proposed model can provide a better understanding of the floating characteristics of the tunnel structure during construction.
基金Project([2018]3010)supported by the Guizhou Provincial Science and Technology Major Project,China。
文摘To address the seismic face stability challenges encountered in urban and subsea tunnel construction,an efficient probabilistic analysis framework for shield tunnel faces under seismic conditions is proposed.Based on the upper-bound theory of limit analysis,an improved three-dimensional discrete deterministic mechanism,accounting for the heterogeneous nature of soil media,is formulated to evaluate seismic face stability.The metamodel of failure probabilistic assessments for seismic tunnel faces is constructed by integrating the sparse polynomial chaos expansion method(SPCE)with the modified pseudo-dynamic approach(MPD).The improved deterministic model is validated by comparing with published literature and numerical simulations results,and the SPCE-MPD metamodel is examined with the traditional MCS method.Based on the SPCE-MPD metamodels,the seismic effects on face failure probability and reliability index are presented and the global sensitivity analysis(GSA)is involved to reflect the influence order of seismic action parameters.Finally,the proposed approach is tested to be effective by a engineering case of the Chengdu outer ring tunnel.The results show that higher uncertainty of seismic response on face stability should be noticed in areas with intense earthquakes and variation of seismic wave velocity has the most profound influence on tunnel face stability.
基金supported by the National Natural Science Foundation of China(No.52008308)the China Postdoctoral Science Foundation(Nos.BX20200247 and 2021M692447)the Research Project from Jinan Rail Transit Group Co.,Ltd.and China Railway No.5 Engineering Group Co.,Ltd.(No.R2-ZF-2019-039).
文摘We develop assembled reinforcement structures(ARSs)composed of connection parts,connecting rods,and straight bolts to strengthen segmental joints in the lining of shield tunnels.Through full-scale bending experiments and numerical simulations,we investigate the deformation and failure characteristics of segmental joints strengthened by ARSs,and propose a novel optimization method for ARSs.The experimental results show that the ARSs can effectively limit the opening of a segmental joint,but also that separation can occur during loading if the connection between the ARSs and segments is not designed properly.Importantly,this connection can be improved by embedding anchor parts in the concrete.In numerical modeling,we investigate the failure modes of segmental joints strengthened by ARSs for both positive bending and negative bending loading cases.In the case of positive bending loading,first the concrete around the anchor parts cracks,and subsequently the concrete on the external side of the joint is crushed.The joint failure is caused by the crushing of concrete on the external side of the joint.While the un-strengthened segmental joint fails with an opening of 5.884 mm,the strengthened segmental joint only opens by 0.288 mm under the same loading,corresponding to a reduction of 95.1%.In the case of negative bending loading,the concrete around the anchor parts first cracks,and then the amount of joint opening exceeds a limiting value for waterproofing(6 mm),i.e.,the joint’s failure is caused by water leakage.While the opening of the un-strengthened segmental joint is 9.033 mm and experiences waterproofing failure,the opening of the strengthened segmental joint is only 2.793 mm under the same loading,corresponding to a reduction of 69.1%.When constructing a new shield tunnel,anchor parts could be embedded in the concrete segments in tandem with ARSs for improved resistance to joint opening.For existing shield tunnel linings,anchor parts cannot be embedded in the concrete segments;therefore,the connections between the ARSs and concrete need to be optimized to strengthen the segmental joint.
基金Project(52278421)supported by the National Natural Science Foundation of ChinaProject(2024ZZTS0754)supported by the Fundamental Research Funds for the Central Universities of Central South University,China+2 种基金Project(2023CXQD067)supported by the Central South University Innovation-Driven Research Programme,ChinaProject(2022QNRC001)supported by Young Elite Scientists Sponsorship Program by CASTProject(2023TJ-N24)supported by the Youth Talent Program by China Railway Society and the Hunan Provincial Science and Technology Promotion Talent Project。
文摘Waterproof performance of gaskets between segments is the focus of shield tunnels.This paper proposed an analytical method for determining seepage characteristics at tunnel-gasketed joints based on the hydraulic fracturing theories.First,the mathematical model was established,and the seepage governing equation and boundary conditions were obtained.Second,three dimensionless parameters were introduced for simplifying the expressions,and the seepage governing equations were normalized.Third,analytical expressions were derived for the interface opening and liquid pressure.Moreover,the influencing factors of seepage process at the gasketed interface were analyzed.Parametric analyses revealed that,in the normalized criterion of liquid viscosity,the liquid tip coordinate was influenced by the degree of negative pressure in the liquid lag region,which was related to the initial contact stress.The coordinate of the liquid tip affected the liquid pressure distribution and the interface opening,which were analyzed under different liquid tip coordinate conditions.Finally,under two limit states,comparative analysis showed that the results of the variation trend of the proposed method agree well with those of previous research.Overall,the proposed analytical method provides a novel solution for the design of the waterproof in shield tunnels.
基金Alexander von Humboldt-Foundation (AvH) for the financial support as a research fellowthe financial support of the Scientific and Technological Research Council of Turkey (TüB_ITAK) under Project No. MAG-114M568
文摘Severe shield jamming events have been reported during excavation of Uluabat tunnel through adverse geological conditions, which resulted in several stoppages at advancing a single shielded tunnel boring machine(TBM). To study the jamming mechanism, three-dimensional(3D) simulation of the machine and surrounding ground was implemented using the finite difference code FLAC3D. Numerical analyses were performed for three sections along the tunnel with a higher risk for entrapment due to the combination of overburden and geological conditions. The computational results including longitudinal displacement contours and ground pressure profiles around the shield allow a better understanding of ground behavior within the excavation. Furthermore, they allow realistically assessing the impact of adverse geological conditions on shield jamming. The calculated thrust forces, which are required to move the machine forward, are in good agreement with field observations and measurements. It also proves that the numerical analysis can effectively be used for evaluating the effect of adverse geological environment on TBM entrapments and can be applied to prediction of loads on the shield and preestimating of the required thrust force during excavation through adverse ground conditions.
基金supported by the National Natural Science Foundation of China(Grant Nos.52130805 and 51978516)Scientific Program of Shanghai Science and Technology Committee(Grant No.20dz1202200).
文摘For a tunnel driven by a shield machine,the posture of the driving machine is essential to the construction quality and environmental impact.However,the machine posture is controlled by the experienced driver of shield machine by setting hundreds of tunneling parameters empirically.Machine learning(ML)algorithm is an alternative method that can let the computer to learn from the driver’s operation and try to model the relationship between parameters automatically.Thus,in this paper,three ML algorithms,i.e.multi-layer perception(MLP),support vector machine(SVM)and gradient boosting regression(GBR),are improved by genetic algorithm(GA)and principal component analysis(PCA)to predict the tunneling posture of the shield machine.A set of the parameters for shield tunneling is extracted from the construction site of a Shanghai metro.In total,53,785 pairwise data points are collected for about 373 d and the ratio between training set,validation set and test set is 3:1:1.Each pairwise data point includes 83 types of parameters covering the shield posture,construction parameters,and soil stratum properties at the same time.The test results show that the averaged R2 of MLP,SVM and GBR based models are 0.942,0.935 and 0.6,respectively.Then the automatic control for the posture of shield tunnel is illustrated with an application example of the proposed models.The proposed method is proved to be helpful in controlling the construction quality with optimized construction parameters.
