Underwater Shield Tunnel Research Articles

Application of data mining to lagging deformation prediction of the underwater shield tunnel

Owing to the limitation of inner space of the shield machine, it is difficult to arrange the monitoring elements within a certain distance behind the excavation face. As a result, the deformation of the segments may not be detected in time. For underwater shield tunnels, the consequences of the lack of deformation data of the supporting structure are more serious. In this paper, the FLAC3D and the regression analysis method are used to obtain the lagging deformation data that cannot be monitored. Eight influencing factors of segments deformation and the two deformation indexes are selected to establish a BP neural network model for predicting the lagging deformation of the underwater shield tunnel. The feasibility of the prediction method is verified through engineering application. Among the three prediction methods used, namely regression analysis, neural network model, and numerical simulation, the neural network model has the highest prediction accuracy and the fastest calculation speed. Totally, the findings of this study can act as a reference for deformation prediction in similar underwater shield tunneling engineerings.

A structural health monitoring system for data analysis of segment joint opening in an underwater shield tunnel

The opening of segment joints is considered critical for the stability analysis of a shield tunnel lining. In order to prevent tunnel disasters, an integrated framework was developed in this study based on the laboratory experiment, real-time monitoring, and statistic theory. As a case study, this presented method was employed in a typical underwater shield tunnel to prevent leakage disasters. The water pressure experiment was used to analyze the importance of joint openings for the tunnel waterproofing. Then, an automatic structural health monitoring system was installed in the study site to have real-time monitoring of segment joint opening and the variation of external load applied to the structure. Based on the monitoring data, a multiple linear regression model was developed to explain the response of joint opening to water pressure and temperature at the important positions of arch crown, spandrel, and hance of the tunnel. The multiple linear regression results were verified to be in agreement with those of the numerical simulation; they denote that (1) joint opening decreased with the rise in temperature, but increased with the rise in water pressure at arch crown and hance, and (2) the segment joint opening decreased with the rise in water pressure at spandrel. As a potential application, the developed model was applied to predict future behaviors of structure, which is vital to prevent disasters and provides a reference to underwater constructions.

Fast vibration characteristics analysis of an underwater shield tunnel using the accelerometer network enhanced by edge computing

Edge computing can reduce the latency induced by the long communication path from end users to the cloud center in the Internet of Things (IoT). In this paper, we implement a vibration test of an underwater shield tunnel using a wired accelerometer network enhanced by edge computing to verify a vibration edge computing architecture that we propose. The cloudlet for edge computing can temporarily store raw data and analyze them simultaneously. It can also serve as the hub of the accelerometer. The acquired acceleration data and their results can be viewed on mobile devices in real time from the cloudlet. The results of measurements show that the amplitude of vibrations of components of the tunnel decreased distinctly from the pavement lane to the segment lining and the base. Moreover, the dominant frequency of a low-frequency band was determined by the tunnel–soil interaction, and represents the overall vibration characteristics of the tunnel–soil system along the Z-axis. The quickly analyzed online results agreed well with those of an offline simulation in terms of general trends. This study highlights the potential of the proposed vibration edge computing architecture for underwater shield tunnels.

Study on load distribution characteristics of secondary lining of shield under different construction time

With the massive construction of underwater shield tunnels, the single segmental lining is unable to meet long-term safety requirements in many cases; thus, the double-lining shield tunnel has attracted increasing attention in recent years. The construction time of the secondary lining is a key factor for the mechanical properties of a double lining. In this paper, taking the Shiziyang shield tunnel as the example, we investigate the interaction between shield segment and secondary lining under different construction times by similar model tests. According to the load variation characteristics of the segment and secondary lining structures under different construction times, the load distribution law of a secondary lining structure under the condition of different external loads is analyzed in detail. The results show that (a) the ability of the double-lining structure to bear the external load as a whole will not be changed by a different construction time of the secondary lining, although the bearing capacity at different locations is influenced. (b) Due to the nonuniformly distribution of the stiffness of each part of the segment, the segment and secondary lining have a noncoordinated deformation under the external load. The distribution pattern of the earth pressure outside the segment gradually changes from a uniform distribution to a nonuniform distribution with the delay of the construction time of the secondary lining. In the meantime, the distribution of contact pressure of the joint surface tends to gradually transform from an irregular distribution to a symmetrical distribution along the circumferential direction. (c) The bearing performance of the secondary lining is more stable with the delay of the construction time of the secondary lining during construction, which is more beneficial to the bearing performance of the double-lining structure. In the actual project, it is recommended that the secondary lining be applied when the external loads of the segments are up to 83–100% of the design load, which is beneficial to the bearing performance of the secondary lining.

Application of Analytical Solution to Steady‐State Temperature Field by Double‐Row‐Pipe Freezing and Verification with Field Measurement: A Case Study of Connected Aisle

In order to solve the problem of sealing water and bearing capacity of a connected aisle in an underwater shield tunnel, a double‐circle horizontal freezing method was adopted for ground reinforcement in the connected aisle of Maliuzhou Tunnel, which is China’s first shield tunnel with superlarge diameter built in a composite stratum. This paper proposed a new double‐row‐pipe freezing model for the calculation of frozen wall thickness based on analytical solution to steady‐state temperature field. Besides, field measurement and transient numerical studies of the active freezing period were also carried out to study the freeze‐sealing effect. The results show that frozen wall thickness obtained by analytical solutions agrees well with numerical simulation results, which verifies the applicability of the newly proposed calculation method. Field analysis indicates that soil temperature gradually approaches a stable value which is far below the freezing point, and a reliable water‐sealing curtain can be formed around the designed connected aisle. Maximum impact of soil excavation on the frozen wall is about 10°C, and reducing exposure time of excavation surface can effectively alleviate the weakening of frozen wall. To obtain comprehensive analysis for freezing wall thickness, a more reasonable arrangement of temperature‐measuring holes is expected in future freezing engineering.

Evacuation experiments in vertical exit passages in an underwater road shield tunnel

Evacuation experiments were conducted to examine the movement speed and evacuation capacity in an underwater shield road tunnel where vertical evacuation passages were installed. Behavioral results were collected through several field experiments aimed at investigating vehicle evacuations, the time required to open vertical evacuation passages, slide and stairs descending with and without counter flows. The results show that the individual movement speed in staircase was lower than the speed in slide, but the average Occupant Flow Rate (OFR) in staircase was higher than the OFR in slide. The probable reasons were discussed and analyzed. Females had worse performance when opening the exit door than males. The upstairs movement of firefighters was observed not negatively affect the evacuation performance of occupants down stairs. The replicated experiments showed that appropriate training or drills can help improve the movement speed of occupants. The results of this study will be essential to evaluate evacuation capacity and occupant behavior on stairs and slides of underwater shield tunnels.

Formulation and performance of grouting materials for underwater shield tunnel construction in karst ground

Grouting is one of most important techniques for underwater tunnelling in karst ground which is actually difficult to be resolved due to the presence of underground water flow. This paper proposed a new grouting material to fill karst caverns when there is flowing underground water prior to shield tunnel construction. The grout uses bentonite and cement as the base material, and a curing agent were added to form excellent fluidity, stability and scour resistance. The effects of the composition and formulation on the performance of the grouting material, and the optimal formulations were determined through a series of laboratory experiments. The recommended parameters for the grout are a specific gravity for the bentonite slurry from 1.30 to 1.35, a cement content of 30%, a meta-aluminate content of 1.25% and a lignin content of 0.20%. The effectiveness of the hardened cement-bentonite grouting material (HCBGM) was checked by a field grouting application for a underwater shield tunneling in karst area, and the results illustrated that the proposed grouting material not only can fulfill the engineering requirements but also turns out cost effective and eco-friendly.

A computational framework to predict the water‐leakage pressure of segmental joints in underwater shield tunnels using an advanced finite element method

SummaryThe construction of shield tunnels under riverbeds and seabeds has considerably increased over the past decades. Due to the ultra‐high water head, water leakage through tunnel joints is a major concern during a tunnel's service life. One practical solution to prevent groundwater penetration is to implement ethylene‐propylene‐diene‐monomer gaskets at the segmental joints. However, numerical simulation of fluid pressure penetration into rubber materials remains a challenging problem in computational mechanics. Severe mesh distortions can occur due to large deformation. Consequently, a convergent solution is difficult to achieve. This paper presents an Abaqus‐based numerical framework to solve the previously mentioned problem using the implicit finite element solver. The key aspects of this framework are twofold: (1) a remesh and re‐map algorithm to overcome the excessive mesh distortion, and (2) simulation of fluid penetration into the contact interface of the gaskets to reproduce the water‐leakage process at the tunnel joints. The proposed framework is first tested to simulate the gasket‐in‐groove mechanical behavior and is then validated using experimental data and the solution produced by an explicit finite element solver. The developed framework is then adopted to predict the water‐leakage pressure at gasketed tunnel joints to illustrate the practical applications. Finally, the numerical results are compared with experimental data to demonstrate the accuracy and robustness of the proposed method and confirm its superiority and effectiveness over existing methods. This novel method can be used by tunnel designers to analyze and estimate the waterproof behavior of gasketed joints in shield tunnels without performing extensive experimental testing works.

Reasonable overburden thickness for underwater shield tunnel

A reasonable overburden thickness is of importance for the stability of underwater shield tunnels. Based on the analysis of existing theoretical methods, this paper presents a modified method for the estimation of the minimum overburden thickness during underwater shield tunnelling. As the existing methods neglect the effects of grouting pressure, the modified method takes into account the grouting pressure and the hardening of grouting mortar. The modified method is compared with existing methods based on a practical underwater tunnelling project of Beijing Subway Line 14. Parametric analysis of the proposed method considering the dimension of the tunnel, the geological condition and the grouting behavior is performed. The results show that tunnel diameter, friction angle and cohesion of soil, and grouting pressure have significant impacts on the results of modified methods. The results of this study can provide a reference for similar projects.

Experiment study on chloride corrosion deterioration of load-bearing concrete segment

In order to study the combined action of compression-bending load and surrounding ion erosive environment on underwater shield tunnel, a series of cofferdam-type electrochemical-accelerated corrosion tests of mini segments are carried out to investigate the segment reinforcement corrosion under different compression-bending loads and the change of internal force and rigidity of mini segments under different load-bearing and corroding conditions. Then, the failure pattern of mini segments under different loading and corroding states are recorded and analyzed. The results indicate that the following: (1) the larger the external load, the shorter the initial rust time of the steel bar; (2) the corrosion rate of steel bar increases linearly with time, and the ratio of corrosion of steel bar increases quadratically with time, the larger the load, the more obvious the increase will be; (3) after the corrosion of steel bar, the change rate of the strain for the steel bar increases as the external load augments, and as a matter of fact, the change rate of the strain increases as well, besides, the degree of strain change for compressive steel is obviously lower compared with that of tensile steel bar; (4) the effect of electric corrosion on the deflection of the segments is more obvious with the increase of external load, and a quadratic increase relationship between the deflection and the corrosion is observed in the process of corrosion; (5) It can be concluded that plastic failure is observed for the segments without loading and for those without cracks in the initial stage of loading, which can be indicated directly by the relatively smaller loss rate of steel section, while brittle failure is presented as the failure pattern for the segments with cracks after loading for certain period, which means the loss rate of steel section is relatively larger. The results can briefly provide useful reference for rational design and durability assessment of shield tunnel segmental linings.

Full-scale tests on bending behavior of segmental joints for large underwater shield tunnels

This paper presents an experimental and numerical study on the bending behaviour of segmental joints for large underwater shield tunnels. A series of full-scale tests of segmental joint for underwater shield tunnel are carried out to investigate the bending performance under compression-bending loads. And comparative numerical simulations are conducted to compare with the test results and analyze the occurrence and development process of joint failure. The results indicate that the joint opens linearly and deforms nonlinearly after the visible concrete cracking occurred, the shape of joint interface is a curved surface during joint opening. The time when the bolt becomes stressed depended on axial force, and the bolt stress increased linearly with the growth of bending moment. Joint bending stiffness can be divided into three stages according to turning point of 'visible concrete cracking' and 'bolt yield', large axial force has a great influence on keeping it. The joint waterproof material could hardly promote the bending stiffness and capacity of segmental joint for its small rigidity. The failure process of segmental joint was different between under positive and negative bending moment, the compressive capacity of concrete in compression zone near the intrados played a vital role in the process of improving the bending capacity of segmental joint. The numerical results of joint opening and bending stiffness were in good agreement with tests during small deformation stage, while after visible cracking the results differ relatively. It is reasonable to simulate joint bending performance before visible concrete cracking, and estimated joint failure mode and its approximate range by using the proposed numerical model.

水下盾构隧道近接既有隧道掘进参数控制技术研究

水下盾构隧道近接既有隧道掘进参数控制技术研究

Numerical analysis of the cracking and failure behaviors of segmental lining structure of an underwater shield tunnel subjected to a derailed high-speed train impact

Extended finite element analysis was performed to investigate the cracking and failure characteristics of the segmental lining structure of an underwater shield tunnel upon a derailed high-speed train impact, allowing for the optimization of tunnel design under accidental conditions. Dynamic crack analysis of this study focuses on the crack morphology, crack initiation and opening of the concrete segmental lining, along with joint bolts in the circumferential and longitudinal directions. The results showed that impacting the segmental lining structure leads to V-shaped continuous and penetrating cracks in the segment and to continuous long strip or polygonal-shaped cracks in the joint surfaces around the impacting area of the segments as well as their outer surfaces near the joint surface. The major cracks initiate in the center of the impact region, and their maximum openings take place at the impact load peak stage, whereas the cracks in other region mainly occur at the shock stage. All cracks close to different degrees when subjected to subsequent loading. Curved bolt cracks at the longitudinal joint are annular and closed, while those of straight bolts at the circumferential joint are irregularly stripped and closed along the length of the screw. The former may cause screw fracture, while the latter could easily induce peeling of the screw surface layer, consequently decreasing the cross sectional area of the bolt. Increasing train impact speeds may result in an increase in the degree of crack openings occurring at both segmental lining and joint bolts. Interestingly, the cracking damage of the segments and joint bolts at the rear of the impact region seem to be more severe than those occurring at the front with respect to the direction of train travel.

Case Study of Rehabilitation of a Damaged Underwater Tunnel in the Construction Phase

AbstractA case was examined in which an underwater shield tunnel was rehabilitated during the construction phase. An unexpected methane eruption resulted in an inrush of water and silt, which damaged the tunnel. Because of this situation, the sleeve method was adopted to repair the tunnel and to mitigate the environmental influence. The process and technologies for rehabilitation are explained in this work. The finite-element approach was also used to simulate the repair procedure and to analyze the risks in the construction phases to ensure the safety of the tunnel. This presentation of rehabilitation in key construction phases can serve as instructions for similar engineering accidents that occur in the future.

Study on the Mechanical Behavior of Lining Structure for Underwater Shield Tunnel of High-Speed Railway

Referring to the Shiziyang Tunnel – the first underwater shield tunnel for high-speed railway (HSR) in China, model tests and field tests are carried out to study the mechanical properties of the single-layer and double-layer lining structures under hydrostatic water pressure and the interaction between the lining and the stratum. The impact of assembling modes, various ground conditions and water level change on the mechanical behavior of the single-layer lining structure, the influence of the secondary lining construction time, the interface working modes of the double-layer lining structure, and their failure characteristics are investigated and explored in this study. The rationality and reliability of using double-layer lining structure is also discussed.

Study on Selection of Segment Lining Structure for Large Profile Underwater Shield Tunnel

Based on Nanjing Yangtze River Tunnel project, the selection of segment lining of large profile underwater shield tunnel was analyzed. Considering from structure force, construction and economic, the comparison and selection for assembling modes, joint form, blocking modes, thickness and width of segment lining was carried out, The better segment lining structure was obtained. The study results can offer references for the design of segment lining of similar large profile underwater shield tunnel.

Model Test on Impact of Surrounding Rock Deterioration on Segmental Lining Structure for Underwater Shield Tunnel with Large Cross-Section

Based on Guangzhou Shiziyang Tunnel, a large-scale model test of segment lining structure was conducted to study the impact of surrounding rock deterioration. The results showed the outflow or deterioration of surrounding rock at the hence could make the stress state at the bottom and crown more serious. And it is very important to provide effective surrounding rock resistance to ensure the safety of tunnel structure.

Transverse Response of Underwater Shield Tunnel to Incident P Waves

In this paper, the seismic response of underwater shield tunnel to incident P waves is investigated by using the Fourier-Bessel series expansion method. On the basis of the exact analytical solution, it is studied that the seismic response of the system which is made up of tunnel lining structure, underwater soil and water. The influence that water depth and buried depth of shield tunnel put on the seismic response of tunnel lining is given. The analytical result shows that the seismic response of tunnel lining unobvious varies with water depth change when incident P waves have a small incident angle, nevertheless, opposite conclusion appears when oblique incident P waves have a big incident angle. At a certain incident angle, the seismic response of tunnel increases with the increasing of the water depth; and the seismic response decreases with the increasing of the buried depth of underwater tunnel.

Model Test on Structural Behaviour of Underwater Shield Tunnel with Large Cross-Section Considering Assembling Modes

Taking Nanjing Yangtze River Shield Tunnel with large cross-section (Φ14.5m) as background, the mechanical characteristic of lining structure under high hydrostatic water pressure for different segmental assembling modes is studied by large-scale similar model test. The test system can control earth pressure, uniform and non-uniform water pressure acting on lining respectively and cooperatively. The study results show that the values and distribution of deformation and internal force vary with different assembling modes. The rigidity of the whole ring for straight joint assembling is less, inducing the deformation larger and internal force smaller, which is unfavorable for waterproofing requirements. The peak positions of bending moment change with the difference of staggered joint assembling modes. Due to the smaller rigidity of K segment, the value of bending moment on that position is less. The most favorable and unfavorable assembling modes are proposed for construction design for Nanjing Yangtze River Shield Tunnel; meanwhile it can also provide important reference to the correlative project.

A Loading Test Method of Prototype Structure for Nanjing Changjiang Tunnel

Considering the features of underwater shield tunnel with large cross-section, a prototype test of segmental lining structure for Nanjing Changjiang Tunnel (Φ14.5m) is carried out by using a new loading test method. And with “Multi-function Shield Tunnel Structure Test System” developed according to this test method, the effect of high hydraulic pressure can be equivalently imposed upon the structure by hoop, and then the earth pressure can be equivalently applied to the structure by radial concentrated force. The structures were loaded by the device according to a certain hydraulic and earth pressure. Meanwhile, the mechanical characteristics can be further studied. In a word, it can provide reliable test means for research, design and construction of underwater shield tunnel project.