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Quick Search     Advanced Search MODERN TUNNELLING TECHNOLOGY   2015 Vol.52 Issue.4 Published 2015-08-25 Article 1 General Design and Key Technologies of the Nanjing Weisan Road River-Crossing Tunnel Project Tuo Yongfei, Guo Xiaohong The general design proposal and key technologies of the Nanjing Weisan Road river-crossing tunnel project are introduced with respect to the engineering characteristics and difficulties encountered, such as a very large diameter, ultra-high water pressure, complex geological and environmental conditions, driving in high strength rocks, high-precision construction control and so on. By synthetically analyzing the original design options of the tunnel plane, longitudinal profile, cross-section and civil structures and studying the key technologies for survey and design, the optimized final design option is proposed so that the overall function and safety of construction and operation can be best achieved. This paper is a significant reference for improving the construction of large-scale highway underwater shield tunnels. 2015 Vol. 52 (4): 1-6 [Abstract] ( 3078 ) [HTML 1KB] [ PDF 1067KB] ( 2184 ) 7 Study of the Longitudial Profile Optimization of Large-Diameter Shield Tunnels in Mixed Ground with Very High Water Pressure Lin Xin1, Shu Heng1, Zhang Yaguo2, Yang Linsong1, Li Jin1, Guo Xiaohong1 Using the Nanjing Weisan Road river-crossing tunnel, which is a large-diameter shield-driven tunnel in mixed ground with very high water pressure, as an example, the rational overburden thickness and anti-floating requirements for a tunnel structure during the construction and operation phases were studied in order to address such problems as unfavorable mixed ground, great depth and length of the entering rock layer and very high water pressure in the original design option. An optimized profile scheme is presented by combining the permanent weight scheme in the tunnel with the predicted and observed river-bed erosion data. Fewer construction difficulties and risks, a shorter construction period and easier driving can be achieved by adopting this optimization scheme while meeting the requirements for the tunnel plane and longitudinal profile index and assuring tunnel safety during construction and operation. 2015 Vol. 52 (4): 7-14 [Abstract] ( 2650 ) [HTML 1KB] [ PDF 1280KB] ( 1892 ) 15 Key Construction Technology for the Nanjing Weisan Road River-Crossing Tunnel Project Yao Zhanhu1, Yang Zhao2, Tian Yi1, Hu Huitao1 The Nanjing Weisan Road river-crossing tunnel has some of the most complex geological conditions and engineering technical difficulties of any existing and under-construction large-diameter slurry shield tunnels. During the construction process, the large-diameter slurry shield machine has successfully passed hrough shallow ground as well as soft upper and hard lower mixed ground, and has directly passed under the ventilation shaft. Furthermore, hyperbaric chamber intervention technology with a saturated helium-oxygen mixed gas was successfully introduced for this project. In this paper, the key construction technologies used in this project are studied regarding engineering characteristics and construction difficulties; the safety concept and excavation principles for the shallow ground, soft upper and hard lowe rmixed ground are proposed; and a complete set of safe, reliable technology for extra-large diameter slurry shield launching and saturated hyperbaric chamber intervention is summarized, providing a significant reference for the development of extra-large diameter slurry shield-driven tunnel technology. 2015 Vol. 52 (4): 15-23 [Abstract] ( 2777 ) [HTML 1KB] [ PDF 1381KB] ( 1930 ) 24 On Water Burst Patterns in Underwater Tunnels Li Xinyu, Zhang Dingli, Fang Qian, Song Haoran Water bursts, the result of the combined effects of regional geological conditions, hydrological conditions and construction disturbances, are the main risk during construction of underwater tunnels. Their occurrence is based on the source and channel of the water and is affected significantly by unfavorable geology. In this paper, typical water-burst cases both at home and abroad are analyzed, and four patterns for water burst are concluded: a hydraulic fracture pattern, a seepage failure pattern, an interface opening pattern and a rock failure pattern. Corresponding geological and hydrological conditions are presented as well. Using the Nanjing Weisan Road river-crossing tunnel as an example and utilizing the acquired geological and hydrological information, a water burst prediction is carried out and relevant measures are taken accordingly, thus preventing a water-burst disaster during tunnel construction. 2015 Vol. 52 (4): 24-31 [Abstract] ( 2479 ) [HTML 1KB] [ PDF 1111KB] ( 1658 ) 32 Health Monitoring Design for Extra-Large Diameter Underwater Shield Tunnels Shu Heng, Wu Shuyuan, Li Jian, Guo Xiaohong Considering that an underwater shield tunnel with defects or affected by a disaster may result in heavy economic losses and harmful social impacts during operation due to complex geological conditions and the environments outside and inside the tunnel, and using the Nanjing Weisan Road river-crossing project as an example, this paper systematically discusses the composition of a health monitoring system. Included in this discussion are the following topics: the selection of monitoring items, the typical section, the acquisition and transmission system of the monitoring data, the central database subsystem, the safety pre-warning and comprehensive evaluation subsystems, and the software system for the user interface. The results show that the health monitoring system, integrated with sensor testing, computer techniques, remote intelligent control, damage detection, signal analysis and safety evaluations, has the advantages of advancement, rationality, practicability, compatibility and convenience. 2015 Vol. 52 (4): 32-40 [Abstract] ( 2402 ) [HTML 1KB] [ PDF 1407KB] ( 1642 ) 41 Identification of Investment Risks for River-Crossing Tunnels Based on Grey Fuzzy Multi-Attribute Group Decision Making Liu Guangfeng1, Chen Fangwei2, Zhou Zhi1, Zhang Shilong3, Liu Mingqiang1 To help control the investment risks regarding three commonly over-budget items in river-crossing tunnels, a risk-identification model based on grey fuzzy multi-attribute group decision making was established with respect to fuzzy, grey-level, multi-attribute and group risk characteristics. The model's feasibility and effectiveness were verified by using the Nanjing Weisan Road river-crossing project as an example. The results show that it is possible for the model to achieve risk sequencing by making use of expert opinions in a comprehensive and realistic way, helping decision makers to identify the key, major and general potential risks more accurately. 2015 Vol. 52 (4): 41-48 [Abstract] ( 2968 ) [HTML 1KB] [ PDF 998KB] ( 2485 ) 49 Construction Risk Assessment for the Shield-Driven Section of the Nanjing Weisan Road River-Crossing Project Yao Zhanhu Because of the complexity and uncertainty of geological conditions, risk assessments for the construction safety of underwater shield tunnels have become an important research topic in underground engineering. Based on the Nanjing Weisan Road river-crossing tunnel construction, this paper analyzes the identification of construction risk factors and evaluation of construction risks in the shield-driven section and formulates control measures for the various risk factors. The analysis results show that hyperbaric intervention in the shield chamber is the primary goal of risk control for such shield tunnels as the Nanjing Weisan Road river-crossing tunnel, which passes through mixed ground with high water pressure and permeability for long distances. Risk may be reduced by reducing the changing times of cutters, setting a reasonable face support pressure and ensuring the formation of a stable filter cake on the working face. Risk during the process of shield tunnelling is mainly controlled by the detection of shield tunnelling parameters and cause analysis of parameter anomalies while the shield machine is shut down; complete risk control measures, such as a risk emergency plan and emergency supplies, are also important measures for reducing risks. 2015 Vol. 52 (4): 49-54 [Abstract] ( 2678 ) [HTML 1KB] [ PDF 870KB] ( 1631 ) 55 Risk Control for Saturated Hyperbaric Intervention in Slurry Shield Tunnelling Zhang Boyang1, Zhao Xiaopeng1, Zhang Yaguo2, Chen Yu1 Saturated hyperbaric intervention technology has the advantages of high efficiency and security, but it also has many risks. Based on the Nanjing Weisan Road river-crossing tunnel project, the technological process of saturated hyperbaric intervention is introduced in detail, and the risks concerning geology, unstable pressure on the tunnel face, physical effects and equipment failure are analyzed, with corresponding countermeasures given. The practices show that these risks in the process of saturated hyperbaric intervention are controllable and suitable solutions can be made according to various existing risks and engineering features. 2015 Vol. 52 (4): 55-61 [Abstract] ( 2691 ) [HTML 1KB] [ PDF 1079KB] ( 1827 ) 62 Effects of Filter Cake Charateristics on Airtightness during Hyperbaric Intervention in Slurry Shield Tunnelling Zhang Ning1,2 Yao Zhanhu3 Zhu Wei1,2 Min Fanlu1,2 Jiang Teng1,2 For an underwater tunnel driven by a slurry shield machine, the formation of an airtight filter cake is key to the success of hyperbaric intervention under complex geological conditions. Great differences exist among filter cakes formed under different conditions, yet the effects on airtightness are unclear. In this paper, a formation and airtightness test was performed on 9 different filter cakes by a self-made testing unit, and the effects of porosity and thickness of the filter cake on airtightness (airproof time and air pressure limit) were analyzed. The results show that: 1) porosity is the major influence affecting airtightness, and performance is better with less porosity; 2) filter cakes formed in the same stratum have similar porosities, and airtightness can be improved by increasing the thickness of the filter cake to acertain extent; 3) nearly 95% of the filtration water emerges from the compression of the filter cake, while the rest is generated by air penetrating the pores and stratum compression; therefore the three stages of filter-cake compression, air penetration into pores and water flow into the filter cake are adopted to provide a better understanding of the process of the filter cake. 2015 Vol. 52 (4): 62-67 [Abstract] ( 2776 ) [HTML 1KB] [ PDF 863KB] ( 2413 ) 68 Airtightness of Filter Cakes Formed under Different Slurry Infiltration Modes Min Fanlu1,2 Zhao Xiaopeng3 Zhu Wei1,2 Zhang Ning1,2 Aiming at the airtightness of filter cakes on the excavation face during hyperbaric chamber intervention in slurry shield tunnelling, and using the sandy cobble stratum through which the Nanjing Weisan Road river-crossing tunnel passes as anexample, airtightness tests were carried out for filter cakes formed under different slurry infiltration modes by a self-developed airtightness apparatus. The results show that when the slurry infiltrates into the stratum, some of the mud particles plug the pores of the stratum and effectively reduce the permeability; if the stratum is first infiltrated by a pure bentonite slurry with a density of 1.05~1.07g/cm3 and then the filter cake is formed by a slurry with a density above 1.15g/cm3, the period of airtightness will be several times longer than that of the filter cake only formed by the denser slurry. This study plays a significant role in slurry adjustments and filter cake schemes for slurry shields during hyperbaric interventions in highly permeable strata. 2015 Vol. 52 (4): 68-73 [Abstract] ( 2720 ) [HTML 1KB] [ PDF 845KB] ( 2050 ) 74 Research and Application of Airtight Fliter Cakes to Saturation Intervention in Hyperbaric Slurry Shield Chambers Yao Zhanhu1 Min Fanlu2,3 Zhang Yingming1 Shao Hailong1 As a new type of intervention technology for hyperbaric conditions, the saturation intervention method has the advantages of high efficiency and security; the key to success of this method is the formation of a good, airtight filter cake. Based on the Nanjing Weisan Road river-crossing project, and considering that effective working time inside the chamber is about 3 to 4 hours, on-site tests were carried out regarding slurry preparation, formation of the filter cake and air tightness, and a slurry performance index was determined for each stage of filter cake formation. Relevant quantitative judgment standards are summarized in this paper. 2015 Vol. 52 (4): 74-79 [Abstract] ( 2260 ) [HTML 1KB] [ PDF 884KB] ( 1724 ) 80 Experimental Study on Segment Durability in the Nanjing Weisan Road River-Crossing Tunnel Liu Jiguo1 Song Kanglin1 Guo Xiaohong1 Zhang Yaguo2 Usingthe Nanjing Weisan Road river-crossing tunnel as an example, a durability test of reinforced concrete segments was carried out considering the effects of different mineral additive parameters, with the results showing that:1) the carbonation depth increases with an increase of carbonization age under the same water/cement ratio, for which the increment speed at each age is slow and the total carbonation depth is small; 2) the carbonation depth increases with an increase of the water/cement ratio under the same additive amount; 3) the carbonation depth increases with an increased additive amount under the same water/cement ratio when both fly ash and mineral powder are added; and 4) the carbonation depth increases with an increase of fly ash and a decrease of mineral powder under the same additive amount and water/cement ratio when both fly ash and mineral powder are added. 2015 Vol. 52 (4): 80-85 [Abstract] ( 2299 ) [HTML 1KB] [ PDF 765KB] ( 1574 ) 86 Research on the Influence of Segment Reinforcement Corrosion on the Mechanical Behaviors of Shield Tunnel Lining Structures Liu Sijin He Chuan Feng Kun An Zheli He Zhengshu Under the long-term action of a water-soil load and ion-erosive environment, the mechanical behavior of a shield tunnel structure will be degenerated gradually. Based on the degeneration mechanism, a test regarding the corrosion of segment members under loading was carried out and the evolution law about the mechanical behaviors of segments under the combined action of a high water-soil load and erosive environment was analyzed. A decline model for the bending stiffness of the deteriorated segment was established. The structural mechanical behavior of the deteriorated segments of the Nanjing Weisan Road river-crossing tunnel was analyzed, with the results showing that: 1) a high water-soil load creates favorable conditions for the rapid deterioration of the lining structure under an erosive environment; 2) in the process of deterioration of the segment, the occurrence and development of tensile cracks is accompanied by that of corrosion cracks, which presents the characteristics of non-uniform corrosion along the reinforcement; 3) under a constant water-soil load, segment deformation develops in a non-linear way with an increase of the reinforcement corrosion rate, while the bending stiffness of the segment declines significantly with an increase of the corrosion rate; and 4) the structural mechanical behavior is represented by the evolution law of a structural stiffness decline, a deformation increase, a bending moment decrease and a basically unchanging axial force under the four structural deterioration conditions of 0%, 10%, 20% and 30%, respectively. The study results provide guidance and reference for precisely evaluating the long-term safety of a shield tunnel lining structure under the combined action of a water-soil load and erosive environment during the design reference period. 2015 Vol. 52 (4): 86-94 [Abstract] ( 2386 ) [HTML 1KB] [ PDF 1374KB] ( 1695 ) 95 On the Mechanical Properties of Consolidated-Undrained Shearing for Backfill Grouting in the Nanjing Weisan Road River-Crossing Tunnel Wang Rui1,2 Yao Zhanhu3 Zhu Wei1,2 Chen Xikun1,2 Based on backfill grouting in the Nanjing Weisan Road river-crossing tunnel, a consolidated-undrained shearing test was conducted with an improved triaxial apparatus for non-self-supporting materials; the pore pressure dissipation law for the backfill grout, the volumetric strain law and the stress-strain relationship during the consolidation process were studied; and the early undrained shear strength and shearing strength were measured, providing some helpful parameters regarding the control of surface subsidence and prevention of segment uplift. The results show that the volumetric strain of the two kinds of mortar is very low in the consolidation process because of their high density and the cemented mortar has little influence on the development of the consolidation volumetric strain, undrained shear strength and shearing strength due to low cement content. 2015 Vol. 52 (4): 95-100 [Abstract] ( 2432 ) [HTML 1KB] [ PDF 857KB] ( 1683 ) 101 Study and Application of Synchronous Grouting Techniques in the Launching Section of an Extra-Large Diameter Shield Tunnel Yao Zhanhu Zhang Boyang Chen Yu Shao Hailong Tian Yi During shield tunnelling gaps will emerge between segment rings and surrounding rock, which will affect rock stability and structural safety of the segment. In this paper, considering the geological characteristics and synchronous grouting requirements of the Najing Weisan Road river-crossing tunnel, a test was carried out regarding one-component inert grouting material to study the working capacity and compression strength of grouts with different cement/sand ratios. The test results show that the grout working capacity meets the requirements of synchronous grouting if its cement/sand ratio is over 0.55. Considering strength requirements and economical factors, the one-component inert grout with a mix proportion of group D4 was ultimately adopted. The monitored surface settlements were not beyond the alarm range during shield tunnelling, which proves that the synchronous grouting achieved the expected results. 2015 Vol. 52 (4): 101-104 [Abstract] ( 2529 ) [HTML 1KB] [ PDF 631KB] ( 2325 ) 105 Model Test on Construction Loads of Prefabricated Structural Elements for a Double-Deck Shield-Driven Tunnel Xia Pengju1 Hu Huitao1 Chen Yu1 Chen Xuguang2 This paper focuses on the reliability of prefabricated structural elements for the Nanjing Weisan Road river-crossing tunnel, which is a double-deck large-diameter tunnel, during the construction stage. Midas/Civil software is used to carry out a numerical simulation for studying the loads appled by the frame girder machine when it erects prefabricated elements and to analyze the load bearing capacity of structural elements under different loading conditions during construction. Additionally, a 1∶1 model test is carried out for verifying and evaluating the safety of recommended construction loads. The results show that the deflection correction coefficients and strain correction coefficients of the carriageway deck and longitudinal beam are both between 0.7~1.0 but less than 1.05; the integral rigidity and bearing capacity of the structure, which is in the elastic deformation state, meets the design requirements and has less structural residual deformation and strain; and no obvious defects are found in the carriageway deck, brackets, columns and the test sections involved in the load testing site. 2015 Vol. 52 (4): 105-110 [Abstract] ( 2697 ) [HTML 1KB] [ PDF 854KB] ( 2440 ) 111 Seismic Response Analysis of Large-Diameter Shield Tunnels Considering the Segment Joint Effect Dong Fei Zhang Dingli Fang Qian Zhu Wenjun Chen Liping Tai Qimin Considering that segment joints have a great influence on the deformation and seismic response of shield tunnels, a real segment connection model with FLAC 3D software was established and the rotation angles of the joints as a function of the designed positive and negative moments were calculated along with axial forces considering three segment layout patterns using the Nanjing Weisan Road large-diameter river-crossing shield tunnel as an example. Based on a simplified continuous and heterogeneous ring model, the material stiffnesses at the weak parts of the segment joints were equivalently modified according to the rotation angles, and the seismic responses of the tunnel structures affected by the EI Centro wave were analyzed with respect to different segment layout patterns. The results show that: 1) the segment layout pattern may affect the tunnel dynamic characteristics within 1.2 s after an earthquake; 2) the time-history curve magnitudes of the horizontal acceleration at the crown and bottom decrease with a decrease of the angle of the key segment; 3) regarding the three segment layout patterns, the greatest tensile stress may occur in a range of 60° on each side of the crown and bottom after a seism; and 4) the distribution and magnitude of the maximum principle stress are affected by the joint area distribution pattern and the key segment dimension, respectively. 2015 Vol. 52 (4): 111-120 [Abstract] ( 2304 ) [HTML 1KB] [ PDF 1338KB] ( 1618 ) 121 Aseismic Behavior Analysis of a Multi-Deck Intersected Tunnel Structure System at an Urban Transport Node Zhao Guang1 Zhang Tao1 Xu Xiang2 Dai Huilan1 Because underground structures are wholly embedded in the subsoil, their seismic response is mainly affected by the surrounding soil; therefore, the anti-earthquake analysis method used for structures on the ground is not applicable in this context. Regarding the intersection node of the double-deck main tunnel and the double-deck underground ramp at the Jiangnan open-excavation section of the Nanjing Weisan Road river-crossing tunnel project, this paper establishes a tunnel structure/foundation soil interaction model using the dynamic FEM method and conducts a dynamic elastoplastic time history analysis using the EL Centro seismic wave, Lomap seismic wave and Kebo seismic wave. The results show that: 1) when the foundation soil vibrates along direction y, the tunnel structure experiences the most unfavorable force conditions; 2) under the action of the three seismic waves, the peak values of the tunnel strain response are close to each other, with the maximum strain response induced by the EL Centro wave that causes partial concrete cracking; however, 3) the interstory drift ratios under frequent earthquakes and rare earthquakes are within the limits, represented by the fact that the steel bars do not yield, and the tunnel structure is still in the elastic deformation state. Based on this, the design scheme of the intersection node structure composed of a double-deck tunnel and a double-deck ramp can satisfy the specified requirements for aseismic performance. 2015 Vol. 52 (4): 121-127 [Abstract] ( 2415 ) [HTML 1KB] [ PDF 1028KB] ( 2417 ) 128 Analytical Study of the Flexural Behaviors of Non-Gasket Segment Joints in Shield Tunnels Chen Biguang1 Guo Xiaohong1 Cheng Weizhong2 Based on the Nanjing Weisan Road river-crossing tunnel, and by means of a rational simplified assumption, a calculation model for the flexural behaviors of non-gasket segment joints in shield tunnels is established with and without considering bolt action, and an explicit analytic solution is derived for the joint moment/rotation relationship under different axial forces in different loading stages. Accuracy of the simplified assumption used in the theoretical analysis is verified by comparing the analytic solution without considering bolt action with that of a finite-element numerical calculation model. Additionally, the analytic solution is used to analyze the differences of joint flexural mechanical behavior under an axial force with or without a bolt, to compare the ultimate bending moment of the joints and summarize the function of the bolt, providing a reference value for engineering design. 2015 Vol. 52 (4): 128-135 [Abstract] ( 2217 ) [HTML 1KB] [ PDF 1014KB] ( 1470 ) 136 Service Life Prediction for the Lining of a Large-Diameter Underwater Shield Tunnel Based on Reliability Theory Li Xin Li Jian Fan Fangfang Tuo Yongfei Using the Nanjing Weisan Road large-diameter underwater shield tunnel as an example and based on the similarity rule and reliability theory, a service-life prediction was carried out for the tunnel lining in light of its durability design using the Monte Carlo method, Matlab calculation program and two prediction methods: the crack limit and bearing capacity limit criteria. The results show that the lining service life is expected to be 124 years under the crack limit criterion, 9 years less than that under the bearing capacity limit criterion, if the newly built tunnel is in an erosive environment with no protection measures.This meets the requirements for structural applicability and safety regarding the crack and bearing capacity. 2015 Vol. 52 (4): 136-142 [Abstract] ( 2286 ) [HTML 1KB] [ PDF 1029KB] ( 1627 ) 143 Study on the Transverse Force and Deformation of Large-Diameter Shield Tunnels under Complex Geological Conditions with High Water Pressure Wei Longhai1 Zheng Shaohua1 Zhang Yaguo2 Zhang Dongmei3 In order to explore the impacts of non-uniformity of the stratigraphic distribution and high water pressure on the force borne by tunnel linings, the law of force borne by tunnel structures in the transverse direction under different geological conditions was studied using a typical section of the Weisan Road large-diameter river-crossing shield tunnel as an example. A single-ring beam/spring model, multi-ring beam/spring model and shell/spring model were adopted, respectively, and the simulation results of these three methods are analyzed and compared in this paper. The study results indicate that: 1) the bending moment of the tunnel is mainly affected by the stratum resistance based on the single-ring beam model without considering interaction between rings; 2) the erecting angle has a slight effect on internal force distribution-like the bending moment-and a strong effect on deformation in the single-ring beam/spring model, and the effect of the adjacent ring can not be ignored while a staggered joint is adopted; and 3) the deformation of the tunnel is somewhat decreased if the shear action between rings is considered, even at the segment joints. 2015 Vol. 52 (4): 143-150 [Abstract] ( 2555 ) [HTML 1KB] [ PDF 1128KB] ( 2493 ) 151 Analysis of Stratum Deformation and Stability: A Case Study of the Nanjing Weisan Road River-Crossing Tunnel Passing under the Yangtze River Embankment Zhang Yazhou1, 2 Xia Pengju3 Zhu Wei1, 2 Min Fanlu1, 2 Stratum deformation and the overall stability of river embankments are key points in river-crossing shield tunnelling. Using the north river embankment section of the Nanjing Weisan Road river-crossing tunnel as an example, a numerical simulation of the construction process was made using finite difference software. This paper analyzes the influences of shield tunnelling on stratum deformation and overall stability of embankments, and compares settlement and stability differences under different grouting effects, slope coefficients and buried depths. The results show that: 1) the maximum settlement occurs at the center point of the top of the embankment and the maximum longitudinal displacement of the slope towards the water occurs near the midpoint of the slope; 2) the safety factor decreases with shield tunnelling at the slope towards the water, for which the trend is most significant at the front half of the slope; 3) the influence of the grouting effect on embankment settlement is significant, less so regarding the buried depth and minimal regarding the slope coefficient; and 4) the slope coefficient has the greatest influence on slope stability while it has the smallest influence on the grouting effect. 2015 Vol. 52 (4): 151-157 [Abstract] ( 2718 ) [HTML 1KB] [ PDF 969KB] ( 2515 ) 158 Discussion of a Practical Calculation Method for the Maximum Support Pressure of Slurry Shield Tunnels in Sand Strata Hu Yunhua1 Zhang jianmin2 Zhengshaohua1 The upper and lower limits of support pressure are key for determining the reasonable support pressure of slurry shields. Based on an analysis of the stability mechanism of the working face during slurry shield operation, it is determined that there are three necessary conditions for ground breakdown failure in shallow-buried sand strata: 1) severe slurry dehydration or slurry penetration directly into the ground, causing a drastic increase of the extra-static pore water pressure; 2) good directionality of the slurry with a great pressure difference compared with that of static water pressure in the ground due to higher support pressure; and 3) a permeability coefficient of the overburden that is too small to cause slurry directly seeps and diffuses into the ground, creating an extremely high water pressure gradient at the contact site of the soil particles, which means that the extra-static pore water pressure increases along with the high-pressure slurry permeating directly into the ground, and seepage failure occurs thereafter due to large water head difference. Accordingly, a practical calculation method of maximum support pressure, which is convenient and requires fewer parameters, is proposed. The maximum support pressure is calculated and a comparison with a practice case is carried out based on a certain river-crossing tunnel project, verifying the rationality and effectiveness of the method. 2015 Vol. 52 (4): 158-164 [Abstract] ( 2235 ) [HTML 1KB] [ PDF 1069KB] ( 1760 ) 165 Application of Photogrammetry in Wear Detection for Shield Cutters Shi Zhenming1,2 Liu Liu1,2 Deng Fei3 Guan Shenggong1,2 Zhao Xiaopeng4 Yao Zhanhu4 Cutter wear is a key problem that affects construction quality and the progress of shields due to the high-risk, high-cost and long operation period of hyperbaric intervention. Aiming at the disadvantages of common detection methods, such as high risk, poor effects and low accuracy, and combined with the characteristics of slurry shield tunnelling, this paper proposes a new visualized detection method for shield cutters based on the development of photogrammetry technology. By using this new method, image data of shield cutters may be collected during construction via a video camara calibrated by a 3D control field. With directed operation of the precise 3D shield model, a quantitative detection can be conducted in terms of cutter wear conditions by utilizing the 3D visualized platform and image analysis, thus making possible the virtual integrated display and digital evaluation of cutter wear. 2015 Vol. 52 (4): 165-172 [Abstract] ( 2303 ) [HTML 1KB] [ PDF 1219KB] ( 1579 ) 173 GPR Forward Simulation for Shield Tunnel Conditions Based on the Consistent Information Removal Method Zeng Chenchao1 Chen Fangwei2 Wu Jianli1 Xie Xiongyao3 Wang Shangao4 Ground Penetrating Radar (GPR) is widely used for the detection of shield tunnel defects, but multiple reflection waves produced by lining rebars cause great difficulties for data interpretation. This paper analyzes common defects in shield tunnels and presents GPR forward simulations that were carried out using GprMax2D software based on two typical conditions: uneven backfill grouting and segment cracking. By using the consistent information removal method, the characteristics of the radar images were obtained successfully without the influence of multiple reflection waves. 2015 Vol. 52 (4): 173-178 [Abstract] ( 2145 ) [HTML 1KB] [ PDF 837KB] ( 1531 ) 179 Study of Shield Cutterhead Hyperbaric Intervention with Diving in Slurry Zhai Shihong1 Yang Zhao1 Ju Yicheng2 Yang Qing1 Yu Cun1 Currently, for shield construction under complicated geological conditions, hyperbaric intervention is an important way to solve the problems of shield cutters. In this paper, the technology of hyperbaric intervention with diving in slurry is analyzed and studied regarding the problem of excavation face instability and collapse experienced in the process of hyperbaric intervention in the Nanjing Weisan Road river-crossing tunnel N. Face support with slurry pressure under normal excavation conditions and the saturation diving technique are used together to carry out cutter tool replacement, so problems regarding hyperbaric intervention can be solved in cases where supporting the working face with compressed air is impossible. 2015 Vol. 52 (4): 179-183 [Abstract] ( 2347 ) [HTML 1KB] [ PDF 685KB] ( 1544 ) 184 Analysis of and Treatment Technologies for a Piping Accident in the Deep Foundation Pit of a Shield Tunnel Yang Qing1 Liu Yi1 Wang Yong2 Tang Xiaopeng2 Yu Cun1 Piping in deep foundation pits as a result of unsuitable dewatering or improper construction of an enclosing structure happens occasionally and severely affects the safety of construction.This can even lead to the foundation pit being out of service and can endanger the surroundings if such an accident is not treated quickly and properly, causing a great loss. Using the construction of a shield shaft on the south bank of line N in the Nanjing Weisan Road river-crossing tunnel as an example, and based on theoretical calculations and field surveys, the cause of a piping accident that occurred during foundation pit construction is analyzed and a comparison is made between the conventional treatment technologies for piping accidents in foundation pits.The selected final treatment measures include grouting and water blocking assisted by a high-pressure jet-grouted pile, which successfully resolved the problem and ensured smooth construction. 2015 Vol. 52 (4): 184-189 [Abstract] ( 2907 ) [HTML 1KB] [ PDF 912KB] ( 3021 ) 190 Application of Grouting and Water-Blocking Techniques to the Replacement of Shield Tail Seal Brushes in a Permeable Strata with High Water Pressure Shi Jinwei1 Yang Zhao3 Yang Qing3 Ju Yicheng2 Yu Cun3 The integrity and reliability of shield-tail sealing are very important to the safety of shield tunnelling, and tail-seal brushes need to be replaced quickly in case of any damage; therefore the sealing of underground water is key to success in these cases. Taking line N of the Nanjing Weisan Road river-crossing project as an example, and considering the characteristics and requirements of replacing a tail-seal brush in a strong, permeable strata with high water pressure, an improved grouting technique was adopted for stopping water: 1) the primary water-stopping system was formed by strengthening the synchronous grouting; 2) the shield-tail part was consolidated by grouting via two special segments with additional reserved holes; and 3) the B-ring of the shield was grouted with polyurethane to avoid leakage from the front of the slurry chamber. Using this method, a complete water-sealing system characterized by its thickness, high density and strength is formed, ensuring successful replacement of the tail-seal brushes in a dry environent. 2015 Vol. 52 (4): 190-194 [Abstract] ( 2233 ) [HTML 1KB] [ PDF 765KB] ( 1624 ) 195 The Application of Multi-Beam Bathymetry-Based Riverbed Monitoring Technology in a Large-Diameter Shield Tunnel Project Zhao Guang1 Wang Shangao2 Zhang Tao1 Many technical challenges related to hydrological and geological conditions were encountered during construction of large-diameter underwater shield tunnels in the Yangtze River basin due to lack of experience in these areas, especially regarding high water pressure, a shallow overburden and servere erosion conditons. Using the Weisan Road river-crossing tunnel as an example, multi-beam bathymetry-based riverbed monitoring technology is used to take a three-dimensional dynamic measurement of the underwater topography and flow rate and to forecast the staged riverbed erosion condtions based on historical data. With the multi-beam bathymetry-based riverbed monitoring technology, advanced prediction of the hydrological and geological conditions of the underwater shield tunnel is achieved, which provides technical support for the risk control of the shield tunnel. 2015 Vol. 52 (4): 195-200 [Abstract] ( 2484 ) [HTML 1KB] [ PDF 962KB] ( 2258 ) 201 Study of Equipment and Operations Related to Saturated Hyperbaric Intervention Technology Zhang Yingming Hu Huitao Zhang Boyang Some problems, such as forced shutdown and intervention for maintenance, are inevitably encountered when a shield tunnel passes through a complex stratum. The hyperbaric intervention method is often used to overhaul the cutterhead and cutters during construction. Compared to conventional intervention characterized by compressed air, the saturated hyperbaric intervention method largely shortens the construction period and reduces the risk of pressurized and depressurized conditions. Based on the Nanjing Weisan Road river-crossing tunnel, the operating principles of saturated hyperbaric intervention equipment, transportation and connecting equipment are systematically studied in this paper. The core components and operation essentials of key equipment, such as the living habitat and shuttle chamber, are summarized, and this summary can be a reference for intervention operations in similar projects. 2015 Vol. 52 (4): 201-206 [Abstract] ( 2188 ) [HTML 1KB] [ PDF 927KB] ( 1525 )

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