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Quick Search     Advanced Search MODERN TUNNELLING TECHNOLOGY   2015 Vol.52 Issue.5 Published 2015-10-25 Article 1 Calculation Methods for the Bearing Capacity of SFRC Underground Structure Members WANG Shuaishuai GAO Bo LI Zhiye ZHANG Bohua This paper presents the deficiencies of the calculation method for the bearing capacity of SFRC underground structures in Chinese code, compares it with the Eurocode through case studies and gives relevant suggestions. The results show that: 1) the design methods and calculation formulas in the Chinese code and Eurocode are roughly the same in respect to the ultimate bearing capacity of normal sections, while they are different in the bearing capacity of oblique sections-the shearing resistance of the bending beam under the Chinese code is greater than that under the Eurocode, and the higher the beam height and the concrete grade, the greater the difference; 2) the Eurocode not only considers the shearing resistance of longitudinal tensile reinforcement but also has a greater influence coefficient of axial compressive force compared with the Chinese code; and 3) crack width can be reduced by 10% at a serviceability limit state under the national code, but much less than 60% under the Eurocode, and this is one of the main influence factors of the reinforcement ratio. 2015 Vol. 52 (5): 1-9 [Abstract] ( 1834 ) [HTML 1KB] [ PDF 1181KB] ( 1806 ) 10 Construction Difficulties and Countermeasures for the Lanzhou-Chongqing Railway Tunnels in Complicated Geological Conditions LI Guoliang The stratum passed by the Lanzhou-Chongqing railway is mainly loess, tertiary mudstone and sandstone, slate, carbonaceous slate and phyllite rock with regional faults, developed folds and high or extremely high geostress; therefore, the geological conditions are very complicated. In light of the technical problems during construction of the Lanzhou-Guangyuan section of the Lanzhou-Chongqing railway, this paper emphatically describes the construction problems encountered in tertiary weak consolidated pelitic fine water-rich siltstone, adopts countermeasures and analyzes characteristics of the soft rock squeezing deformation and stress state regarding tunnels in soft rock with high geostress. The grading standards and major control measures are presented for the large deformation of soft rock tunnels on the Lanzhou-Chongqing railway. 2015 Vol. 52 (5): 10-15 [Abstract] ( 1562 ) [HTML 1KB] [ PDF 947KB] ( 1840 ) 16 Application and Prospect Analysis of Large-Diameter Shield-Driven Tunnels Combined with Enlarged Metro Stations LI Hong'an Considering that complex construction environments bring more and more challenges to metro construction, and based on the construction of the large-diameter shield-driven tunnel and enlarged station at the North Dongfeng Bridge - Jingshun Road section of Beijing Metro line 14, this paper discusses the problems encountered in the preliminary planning and design stage, such as a limited selection of alignments, a limited selection of construction methods, and rigorous external environment requirements. In this context, the combined construction method of a large-diameter shield-driven tunnel with an enlarged metro station is presented. Based on design optimization, process control, and a construction cost comparison, this construction method is proved to be technically feasible and cost effective. 2015 Vol. 52 (5): 16-23 [Abstract] ( 1495 ) [HTML 1KB] [ PDF 1294KB] ( 2319 ) 24 Application Status and Prospects for the Casting Support Tunnelling System Using TBM ZHANG Long1,2 GAO Juru2 ZHANG Bo2 YUAN Wei2 TU Wenxuan2 Rational selection of the type of lining structure in tunnel construction is one of the major measures for improving tunnel construction quality, shortening the construction period and reducing comprehensive construction costs. Based on the introduction of domestic and international lining structure types for shield tunnels and their application statuses, this paper puts emphasis on a new tunnel lining system, the Casting Support Tunnelling System Using TBM (CSTSUT),which has been presented and successfully applied in Japanese shield tunnelling. The technical and economic analysis for existing shield-tunnel lining types reveals that the CSTSUT has unique advantages in terms of economy and technology compared to traditional lining structures in shield tunnels when the tunnels are longer and deeper, especially for construction in water-rich non-consolidated formations. 2015 Vol. 52 (5): 24-31 [Abstract] ( 1496 ) [HTML 1KB] [ PDF 1195KB] ( 1455 ) 32 Numerical Analysis of the Rock Mass Conditions for Rock Burst Occurrences in Deep Underground Caverns ZHAO Hongliang1,2 ZHOU Youhe1,2 Structural properties of rock masses are the material basis and main factors for rock burst occurrences. In deep tunnels, most rock bursts occur in hard surrounding rock characterized by elasto-friability. Sound conditions for rock masses, such as high strength, fewer original joint fissures and good integrality, are conducive to elastic strain energy accumulation in rock masses. In order to quantitatively analyze the influence of rock mass conditions on the possibility of rock bursts in surrounding rocks, and using the deep tunnel of the Jinping II hydropower station as an example, the uniaxial compressive strength of a rock mass is selected to represent the strength of the surrounding rock and the geological strength index (GSI) is selected to represent the integrality of the surrounding rock mass. With an unchanged surrounding rock geo-stress, different uniaxial compressive strengths and various geological strength indexes, the stress behaviors and ultimate stress state at the stress concentration zones during tunnel construction are calculated by a numerical simulation. The numerical calculation results indicate that intense rock bursts mostly occur in surrounding rock masses of Class II characterized by high strength (uniaxial compressive strength＞120 MPa) and good integrality (geological strength index＞55). 2015 Vol. 52 (5): 32-39 [Abstract] ( 1582 ) [HTML 1KB] [ PDF 1147KB] ( 2337 ) 40 Seismic Response Analysis of Surrounding Rocks Around Underground Works Adjacent to Bank Slopes ZHANG Yuting1 DING Xiuli1 ZHOU Shuda2 Because of the motion during an earthquake, terrain such as high mountains and canyons may affect the seismic response characteristics of surrounding rocks around underground works adjacent to bank slopes, and structures on the bank slopes may also have adverse effects on the stability of the surrounding rock due to dynamic loads. On this basis, the main factors affecting surrounding rock stability are analyzed and the key problems regarding the calculation analysis of its seismic response are discussed and compared quantitatively by means of numerical simulation. Then, using the underground caverns of the Wudongde hydropower station as an example, a time-history analysis of the stability of the surrounding rocks is performed, with earthquake inputs determined by the fortification criterion. The factors of cavern excavation, high mountainous and canyon terrain and the dynamic loads of structures on bank slopes are considered in the calculation. The research results show that earthquakes have a little influence on the underground structures because of the sound rock lithology, the stability of the surrounding rock is mainly governed by cavern support, and the dynamic loads of the arch dam foundation base do not have a controlling influence on surrounding rock stability. 2015 Vol. 52 (5): 40-47 [Abstract] ( 1833 ) [HTML 1KB] [ PDF 1162KB] ( 1517 ) 48 Z-P Yield Criterion Based Analysis of the Element Safety Factor for the Stability of Surrounding Rock YUAN Mu1,2 XIAO Ming1 LIU Huibo3 YANG Yang3 The traditional failure evaluation criterion for the stability of surrounding rock can only be used for determining if surrounding rock failure will occur, but it can not quantitatively reflect the extent of damage to the surrounding rocks. By introducing the safety factor concept used in engineering, and based on the Z-P yield criterion and a unified expression of generalized Von Mises yield criterion, a 3D elastoplastic finite-element based element safety factor expression considering rock mass damage properties is deduced by a theory analysis, a quantitative index is established for the evaluation of stability of the tunnel surrounding rock, a tunnel excavation model is set up and a numerical simulation is carried out based on engineering case studies. The calculation results show that: 1) the closer to the excavation face, the greater the rock damage and the less safe the rock mass, and the greater the failure degree of the rock mass; and 2) when the element safety factor is less than one, its scope is approximately the same as the calculated surrounding rock plastic failure scope and damage area, which verifies the correctness of the deduced Z-P yield criterion-based element safety factor formula. 2015 Vol. 52 (5): 48-54 [Abstract] ( 1713 ) [HTML 1KB] [ PDF 838KB] ( 2223 ) 54 Analytical Solution to the Squeezing Deformation of Highway Tunnels Under Asymmetrical Loads CHEN Chao LI Tianbin CHEN Guoqing GAO Meiben With the development of tunnel projects, problems related to the squeezing deformation of highway tunnels under asymmetrical loads are more prominent. In this paper, based on Rubinnat's solution for the plastic zone of a circular tunnel section and by means of rotating the direction of the maximum principal stress, an analytical formula for the radius of the plastic zone of surrounding rock around a non-circular portal of a deep buried tunnel section was derived by the complex variable function theory. Furthermore, referencing the analytical solution to the elastic-plastic displacement of a circular tunnel under an asymmetrical load and using the mapping function and transformation law, a calculation formula for the actual squeezing deformation of tunnel surrounding rock was deduced accordingly. The analysis indicates that the actual plastic zone distribution of a tunnel's surrounding rocks is related to the maximum principal stress and shape of the tunnel, and the actual distribution scope of the plastic zone of a tunnel's surrounding rocks can be obtained by analysis and calculation, which provides a reference for the design and construction of similar tunnels. 2015 Vol. 52 (5): 54-60 [Abstract] ( 1645 ) [HTML 1KB] [ PDF 1009KB] ( 1539 ) 61 Study and Application of the Equivalent Parameters of Full-Length Anchored Rock Masses in DDARF CHEN Yunjuan1, 2 ZHU Weishen2 WANG Zhishen2 WANG Wen3 In the discontinuous deformation analysis of rock failure (DDARF), it is assumed that the rock mass is reinforced by end-anchored bolts. The study of the rock masses reinforced by full-length anchored bolts is still in its early stages. In light of the equivalent anchoring effect, and considering the variation of mechanical parameters of the rock mass supported by full-length anchored bolts, a method was proposed to perform an anchoring-effect analysis of full-length anchored bolts in DDARF. Based on construction of the Yimeng power station project, and using FLAC software, this paper analyzed the plastic zone of surrounding rocks under three conditions of excavation: no support; support with improved equivalent mechanic parameters; and rock mass support with full-length anchored bolts. Furthermore, the crack development of the rock masses was analyzed by DDARF. The results show that: 1) in FLAC analysis, fewer plastic zones occurred in surrounding rocks under conditions of support with improved equivalent mechanic parameters and those reinforced with full-length anchored bolts compared with excavation with no support, and the calculation results under the conditions of 1.18 times cohesive force and full-length anchoring are matched especially well; and 2) in DDARF analysis, the cracks in the surrounding rocks using anchors with improved mechanic parameters and full-length anchoring are controlled more effectively compared to those in rock masses with no support, with roughly the same development scale and number of cracks. Thus, using the improved equivalent mechanic parameters for anchored rock masses to simulate the full-length anchoring effect in DDARF can not only reduce the complexity of the calculation but also improve its accuracy. 2015 Vol. 52 (5): 61-66 [Abstract] ( 1579 ) [HTML 1KB] [ PDF 855KB] ( 1324 ) 67 Comparative Study on Prediction Methods for Tunnel Surrounding Rock Deformation YANG Changmin1 GENG Pengfei2 In order to precisely predict the deformation of a tunnel's surrounding rocks, the principles of radial basis function neural network and non-equal time-interval GM (1,1) grey system theory were adopted to establish prediction models. The fitting programs for two prediction models were compiled by way of the MATLAB-2010b platform. Based on the measured rock deformation data from the Linli tunnel on the Zhangzhuo Highway, the deformation prediction was carried out by model training. According to a comparative analysis of the predicted values and measured values and a model error verification test, it was revealed that the prediction results of a radial basis function neural network (RBFNN) model are more precise and that the predicted deformation curve agrees better with that of measured one, truly reflecting the variation law of surrounding rock deformation. 2015 Vol. 52 (5): 67-73 [Abstract] ( 1572 ) [HTML 1KB] [ PDF 929KB] ( 1390 ) 74 Accuracy and Influence Factors of the Verhulst Model for the Prediction of Surrounding Rock Deformation WANG Yiguo1 JI Anjun2 Considering that the Verhulst model has a sound basis for modeling and good prediction results for the final deformation of surrounding rocks, this paper discusses its serviceability and accuracy in the prediction of rock deformation and compares it with the traditional model. The results show that the prediction accuracy increases with a decrease of parameter a in the Verhulst model, and its variation law will contribute to the selection of the optimum time for secondary lining installation without any external disturbances. 2015 Vol. 52 (5): 74-78 [Abstract] ( 1618 ) [HTML 1KB] [ PDF 693KB] ( 1944 ) 79 Experimental Study on Smoke Temperature Distribution in Immersed Tunnel Fire Scenarios XU Pai1 JIANG Shuping2 ZHOU Jian2 CHEN Dafei2 XIE Yaohua2 Using the Hong Kong-Zhuhai-Macao subsea immersed tunnel as an example, a tunnel fire test was performed by establishing a full-scale experimental platform, the variation law of the smoke temperature over time under different working conditions was researched and the temperature distribution characteristics along the tunnel at the stable combustion stage were analyzed. The results show that the longitudinal ventilation velocity, fuel type, fire scale and location of the ignition source are the main factors affecting smoke temperature distribution characteristics. Additionally, the hazardous areas for trapped people are presented and the recommended installation heights for rescue facilities are given after analyzing the influence of the spreading scope of high-temperature smoke on the escape of personnel and facility arrangement at the fully burning stage. 2015 Vol. 52 (5): 79-83 [Abstract] ( 1429 ) [HTML 1KB] [ PDF 785KB] ( 1507 ) 84 On the Critical Air Velocity for Fire Smoke Control in a Curved Tunnel WANG Feng1, 2 DONG Guohai2 WANG Mingnian1 Using the construction of double-spiral tunnels as an example, this paper discusses the critical air velocity and the smoke-flow law in a curved tunnel with a diameter of 600 m determined by numerical calculations. The results given by the numerical calculations agree well with those given by a fire test in the Memorial tunnel: the critical air velocity for fire smoke control is 2.5 m/s for a fire of 10 MW in the curved tunnel; smoke backflow occurs, and the backflow length and thickness increase significantly, when the ventilation velocity decreases; the deflection angle of the flame and the maximum temperature of the vault increase with an increase of the ventilation velocity; and at the downstream of a fire, the smoke around the fire source forms an asymmetric distribution and is followed by an obviously layered smoke. 2015 Vol. 52 (5): 84-89 [Abstract] ( 1581 ) [HTML 1KB] [ PDF 806KB] ( 1500 ) 90 Study on Hybrid Ventilation Modes for Urban Tunnel Fires ZHAO Dong1,2 JIANG Juncheng1,2 ZHAO Canguan3 ZHAO Shengping1,2 Aimed at the problem of not being able to fully guarantee safe evacuation in case of urban tunnel fires with semi-open natural ventilation, the Fire Dynamic Simulation(FDS) software and a wind tunnel experimental platform were used to carry out a numerical simulation and experimental study on how smoke diffuses under natural ventilation and hybrid ventilation modes. The results show that natural ventilation used in a semi-open urban tunnel is unable to solve the problems of fire safety, but hybrid ventilation can effectively control smoke when the exhaust coefficient reaches 3.3, which assures the safe evacuation of personnel and vehicles. Additionally, the exhaust coefficient presented in this paper and applied in the study of the hybrid ventilation mode for semi-open urban tunnels may provide a theoretical basis for similar tunnels regarding safety during fires. 2015 Vol. 52 (5): 90-94 [Abstract] ( 1494 ) [HTML 1KB] [ PDF 722KB] ( 1467 ) 95 A Measurement Method for Grout Injection Rate Based on Digital Image Processing GUO Yanwei HE Shaohui GUAN Xiaoming LIU Yangpeng To find a convenient, economic and reliable method to measure actual grout injection rate and provide important parameters for grouting volume acceptance and quality inspection, this paper uses the digital image processing(DIP) technique to obtain information for the cross section diagram based on the section method. First it introduces basic principles and steps of this technique and discusses the feasibility of digital images for equivalently substituting the actual grouting section under the type of theoretical fracture grouting diffusion, then it analyzes the reliability of this technique through an onsite single-hole grouting test. The results show that the grout injection rate judged by the DIP technique has little variability and good repeatability, and the grouting volume calculated based on the DIP technique is about 1.1~1.2 times the measured one, showing a sound agreement between them. Lastly, in light of the advantages of Photoshop in selecting the target area and MATLAB in batch programming, this method is generalized to be more effective and suitable for engineering applications. 2015 Vol. 52 (5): 95-101 [Abstract] ( 1746 ) [HTML 1KB] [ PDF 1097KB] ( 1474 ) 102 Study of the Formation Process of Mud and Water Bursts During Tunnel Construction and the Influence of Fault Dip Angles GENG Ping1 QUAN Qianlong2 WANG Shaofeng1 AN Junji1 YAN Qixiang1 Mud and water bursts are common phenomena when tunnels pass through water-rich fault zones and are serious disasters encountered during tunnel construction. In order to explore the formation process of mud and water bursts in tunnels and the influence of fault dip angles on the formation process in order to avoid serious engineering disasters, the processes of mud and water bursts induced by tunnelling in water-rich fault zones with different dip angels were simulated by Discrete Element Method(DEM) based on coupling the particle and fluid. In the simulation process, the development of fractures in surrounding rocks and the amounts of inrushing mud and water were traced and recorded, the formation processes of the mud- and water-bursting channels were analyzed, and the influence of fault dip angles on mud and water bursts was revealed. The study shows that the smaller the fault dip angles, the shorter the vertical distances between the fault and tunnel, and the more likely that mud and water bursts will occur and concentrate at the bottom of the working face. The study results provide a reference for the design of tunnel excavations in water-rich fault zones as well as for the forecast and prevention of mud and water bursts. 2015 Vol. 52 (5): 102-109 [Abstract] ( 1604 ) [HTML 1KB] [ PDF 1219KB] ( 1360 ) 110 A Conceptual Water Inflow Model and Characteristics of the Hydraulic Pressure of Water-Stopping Points in the Mingtangshan Tunnel's Fractured Zone LIU Tuo1 CAO Xiaoxiang1 LI Xianwen2 Considering that improper treatment of water inflow during tunnel construction may seriously affect local ecological and social environments, and using a typical water-inflow section of the Mingtangshan tunnel as an example, this paper proposes a conceptual hydrogeological model for water inflow in a fractured zone based on a small-scale test for hydraulic pressure at a water-stopping point on a typical section. It presents three fissure water-distribution models for the fractured zone before and after excavation. The results show that: 1) a perched water saturated zone in the surface weathered fissure rock layer will appear or disappear after water inflows with the coming of the wet season or dry season; 2) the hydraulic pressure of the water-inflow point increases rapidly after water stopping and then slows down, which can be reflected by a logarithmic model; 3) a water-head depression cone is formed near a single water inflow point, and a balance will be reached by connecting to other interlinked points of water inflow after water stopping; and 4) seven-day monitoring indicates that a stable hydraulic pressure can be achieved after 24 hours of water stopping. 2015 Vol. 52 (5): 110-116 [Abstract] ( 1782 ) [HTML 1KB] [ PDF 1106KB] ( 2020 ) 117 Prediction of Water Inflows in Underground Caverns Based on the Random Field Theory JIA Chao1 WANG Lunxiang2 WANG Zhechao1 QIAO Weili2 ZHANG Tengchao2 Regarding the predictive analysis of water inflows in tunnels and underground caverns, the permeability coefficients of seepage fields have great spatial differences induced by developed geological structures such as joints and fissures around rock masses. It is difficult to accurately simulate an actual situation by a deterministic method, and it is more realistic to regard it as a random field. In this paper, a numerical calculation was conducted using the FLAC3D finite difference software and considering random characteristics of the permeability coefficient caused by the randomness of joints and fissures in a rock mass, and based on the random field theory, the permeability coefficient was introduced as a random variable to carry out a numerical simulation analysis on seepage by giving a random permeability coefficient to each unit of the random field. The results show that the prediction of water inflows in the seepage field in underground caverns will be more accurate and reasonable when considering the spatial anisotropy. Based on a comparison of simulation results, calculation results by the empirical formula and field monitoring statistics, the application conditions of the random seepage field simulation are presented, providing a reference for water inflow prediction in practical engineering. 2015 Vol. 52 (5): 117-124 [Abstract] ( 1536 ) [HTML 1KB] [ PDF 1170KB] ( 1625 ) 125 Dynamic Simulation of Water Inflows During Tunnel Excavation LI Yuxin XIA Qiang XU Mo ZHANG Qiang A secondary development of the groundwater flow simulation program MODFLOW was conducted with MATLAB software in this paper, which regards the continuously driven tunnel as a dynamic boundary condition, achieving a dynamic simulation of tunnel water inflows under ideal conditions. Three kinds of permeability coefficient fields were used as input for the model, and the calculation results show that: 1)the anisotropy of the permeability coefficient field has a great impact on simulation results; 2)a water inflow event will occur when a water-bearing zone in the tunnel is exposed, and the total water inflows will then gradually decrease until the next water inflow; and 3) the maximum water inflow occurs at the beginning of tunnel excavation in a defined location, then the water inflow at this location decreases in a negative exponential function with the attenuation law being related to the initial water flow and distribution of the permeability coefficient field of the simulated area. This study provides a theoretical reference for the prediction of water inflow during tunnel construction, while the model still needs to be improved according to actual formation lithology, structural conditions and construction progress in order to realize the real-time prediction of tunnel water inflow. 2015 Vol. 52 (5): 125-130 [Abstract] ( 1633 ) [HTML 1KB] [ PDF 927KB] ( 1505 ) 131 Analysis of the Optimum Support Dismantling Scheme for Shallow Bored Subway Stations in a Soil-Rock Compound Stratum LIU Tao1 HUANG Yongliang1 LEI Gang2 In tunnel construction, dismantling the temporary strut or steel support will break the original balance of the structural system, especially in shallow tunnels with large sections, which may cause a safety accident by excessive deformation of the primary support or the local overloaded internal force if dismantling of the temporary support is performed in an improper way and at an improper time. A large-span shallow bored subway station in a soil-rock compound stratum is used as an example in this paper to simulate the process of dismantling the longitudinal temporary support in a large-section tunnel by a 3D model, and the effects of different dismantling sequences and one-time demolition lengths on the tunnel structure are analyzed. The analysis results show that the effect of alternating the dismantling sequence and the one-time demolition length of 6 m on factors such as crown settlement and surface subsidence is comparatively small. Additionally, a recommended value for controlling standards of surface subsidence induced by dismantling is presented on the basis of numerical calculations, providing a reference to similar projects. 2015 Vol. 52 (5): 131-137 [Abstract] ( 1435 ) [HTML 1KB] [ PDF 1037KB] ( 2104 ) 138 Impact of Spatial Effects on the Structural Design of Subway Stations LI Yan1 QI Taiyue1 LEI Bo1 WU Yubin2 TENG Zhennan1 As for the current structural design of open-cut subway stations in China, the simplified planar model is generally used to carry out structural analyses in accordance with the relevant specification requirements. Nevertheless, subway stations are spatial structures with changes in the longitudinal direction, and using the simplified plane design according to current specifications is bound to cause calculation deviations. This paper proposes that the reinforcement calculation shall be guided by the calculated equivalent bending moment of the spatial structure based on a comparative analysis of numerical simulation calculations by spatial models with different spans and corresponding planar models. If a simplified planar model is used for structural design, the results shall be discounted; especially for the perpendicular joints, the range of peak clipping shall be increased to ensure the cost effectiveness of the subway stations. 2015 Vol. 52 (5): 138-144 [Abstract] ( 1516 ) [HTML 1KB] [ PDF 909KB] ( 1380 ) 145 Influence of the Approaching Construction of Underlying Shield Tunnels on Overlying Metro Tunnels YANG Chunshan1,2 MO Haihong1,2 CHEN Junsheng1,2 LI Yadong1,2 HOU Mingxun1,2 The effects of shield tunnelling on adjacent buildings have long been a serious problem. In this paper, the approaching construction of an underlying shield tunnel was simulated by the finite element method and the displacement variation law of the existing metro tunnel during construction of the underlying shield tunnel was analyzed. Based on the double-sided elastic foundation beam theory and the shield tunnel longitudinal equivalent continuous model, a calculation equation for the segment openings of the existing metro tunnel affected by construction of the new shield tunnel was deduced and the distribution law for the segment openings was analyzed. The analysis results show that: 1) the area of the overlying, obliquely crossing metro tunnel affected by shield tunnel construction is mainly located in the range of 2D (D=tunnel diameter) on both sides of the new shield tunnel axis; 2)the vertical displacement distribution of the existing metro tunnel is mainly within the range of 2D ahead of the working face and 1.5D behind the shield tail; 3) the segment opening of the existing metro tunnel appears obviously at the two joints(left and right) directly above new the shield tunnel axis and is accompanied by plastic deformation; and 4) the area within 2D of the sides of the existing metro tunnel and the soil layer between the two tunnels should be locally reinforced to prevent longitudinal deformation and excessive segment opening of the existing metro tunnel associated with the new shield tunnelling. 2015 Vol. 52 (5): 145-151 [Abstract] ( 1635 ) [HTML 1KB] [ PDF 1025KB] ( 1357 ) 152 Control of the Shield's Vertical Attitude During Shield Tunnelling in Soft Soils LIANG Rongzhu1, 2 XIA Tangdai1, 2 LIN Cungang3 MENG Wanbin4 It is inevitable for a shield to deviate from the designed route during tunnelling in soft soils, which may result in the concentration of stress in segments, segment cracking and excessive ground settlement. Based on measured data from a shield tunnel of the Hangzhou metro project, this paper analyzes the shield's vertical attitude variation in a typical Hangzhou soft-soil layer and gives corresponding control measures. The results show that: 1) it is inevitable for the shield to be tilted with a negative pitch angle during segment erection; 2) during shield driving, an effective way of adjusting the pitch angle is to control the deviation correction moment since the pitch angle is sensitive to deviation correction moment variation; and 3) adjustment of the shield attitude is a dynamic process, so it needs to be planned in detail and implemented patiently. 2015 Vol. 52 (5): 152-157 [Abstract] ( 1541 ) [HTML 1KB] [ PDF 972KB] ( 1541 ) 158 Comparison of Forces Applied on the Working Shafts of Large-Diameter Shield Tunnels by the Bottom-Up and Top-Down Methods FAN Guogang Compared with the bottom-up method, which is widely used in the construction of shallow, medium and small foundation pits, the top-down method is more complex but has obvious advantages in controlling structural performance and deformation, which contribute to the safety of construction of deep and large foundation pits. Using the receiving shaft on the south line of the river-crossing large-diameter shield tunnel on Nanhu Road of Changsha City as an example, this paper compares and analyzes the forces applied on shafts constructed by the bottom-up and top-down methods, indicating that it's better to choose the top-down method for the working shaft construction of large-diameter shield tunnels. 2015 Vol. 52 (5): 158-164 [Abstract] ( 1564 ) [HTML 1KB] [ PDF 1023KB] ( 2518 ) 165 Study on Soil Conditioning Technology for an EPB Shield in an Argillaceous Siltstone Formation XIAO Chao1 WANG Shuying1 YE Xinyu1 SHI Jiehong2 YANG Junsheng1 Since the ground in the Najing area consists of an argillaceous siltstone formation with high contents of clay minerals, soil conditioning tests were carried out based on the shield tunnelling of Najing Metro Line 1, and a correction factor of FIR was determined by the contrastive analysis of laboratory soil tests and field soil tests. The results show that the moisture content of the soil shall be controlled within 16%~30%, and 20%~35% for the FIR value when the foaming agent is used to improve the argillaceous siltstone, and there are differences between the calculated FIR value and the actual FIR value of the soil in the earth chamber, therefore the theoretical FIR value of the soil shall be corrected with the correction factor of 0.59~0.76. 2015 Vol. 52 (5): 165-170 [Abstract] ( 1535 ) [HTML 1KB] [ PDF 869KB] ( 1389 ) 171 Application of the Comprehensive Geological Prediction Techniques in the Lingjiao Tunnel ZHOU Dong1,2 LIU Zonghui1,2 WU Heng1,2 LUO Genchuan3 HUANG Shiwu4 Affected by the intersection of two regional faults and a water-resistant rock wall induced by magmatic intrusion, various unfavorable geological bodies may exist in front of the working face at FK18+330 on the left line of the Lingjiao tunnel. In light of these complicated geological conditions, a macroscopic tunnel geological prediction was first conducted on the basis of geological analysis, and then an in-situ geological detection was conducted inside and outside of the tunnel by the following methods respectively: land sonar+transient electromagnetic+geological radar and land sonar+differential electrical sounding+transient electromagnetic. Additionally, a comprehensive analysis and prediction was carried out, with the in-situ excavation results showing that the above comprehensive prediction method can effectively reduce the error of in-situ geophysical prospecting in the tunnel's axial and transverse directions as well as precisely determine the location, size and type of the unfavorable geological bodies in front of the tunnel face under complicated geological conditions. 2015 Vol. 52 (5): 171-177 [Abstract] ( 1469 ) [HTML 1KB] [ PDF 1102KB] ( 1413 ) 178 On Grouting Techniques for Preventing Water Inflows in Karst Tunnels SUN Keguo1 LI Shucai2 XU Weiping1 GONG Lun1 The inflow of water may seriously affect normal construction of karst tunnels, therefore the grouting techniques for preventing water inflow in karst tunnels were examined using the Qiyueshan tunnel with water inflow at the floor as an example. Specifically, the concept of "probing before grouting" was proposed based on full knowledge of the hydrogeological characteristics of the water inflow area, and the karst channel distribution and the water runoff path were obtained by high-precision nondestructive detection and high-density geological drilling. During grouting, the chemical grout function was optimized by implementing lessons learned from the shallow chemical grouting, and the grouting schemes were adjusted in time to achieve successful deep grouting using cement mortar. 2015 Vol. 52 (5): 178-183 [Abstract] ( 1613 ) [HTML 1KB] [ PDF 978KB] ( 1296 ) 184 Cutting Performance of Shield Cutters in Soft Rock ZHANG Xuhui1, 2 TAN Qing1, 2 XIA Yimin1, 2 CAI Xiaohua1, 2 ZENG Guiying1, 2 ZHANG Jia3 Based on the rational simplification of the cutting process of shield cutters in soft rock, this paper establishes a 2D numerical model using the particle discrete element method; analyzes a dynamic cutting process; and studies the influence of the rake angle, cutting depth and rock joint on the rock-breaking performance of shield cutters. The results show that cutting the soft rock is a process of "extruding and then tensioning." The force application point of a cutter is gradually shifted from the tip of the cutter to the front edge of the cutter, and then back to the tip of the cutter with variations of the cutting stroke, which is consistent with the change of the cutter force. With the increase of the cutter's rake angle and cutting depth, the broken rock block increases while the specific energy consumption decreases. The rock-breaking modes of the cutter are different under different joint dip angles, and because of more easily forming the broken rock block the rock-breaking efficiency is higher under a joint angle of less than 90° than a joint angle of more than or equal to 90°. The experiments show that the actual process of rock breaking and the force applied on the cutter agree well with those determined via numerical simulation. 2015 Vol. 52 (5): 184-191 [Abstract] ( 1517 ) [HTML 1KB] [ PDF 1131KB] ( 1361 ) 192 Discussion of Temporary Auxiliary Facilities for the Installation of Immersed Tunnels LIN Wei Since the construction of immersed tunnels involves numerous procedures such as prefabrication, floating, transportation, immersion and underwater connections, a series of temporary auxiliary facilities are required for their installation. Based on domestic and international findings regarding temporary auxiliary facilities for the installation of immersed tunnels and referencing the design and construction of the Hong Kong-Zhuhai-Macau Bridge(HZMB) Immersed Tunnel Project, this paper systematically divides the temporary auxiliary facilities into different types and analyzes their features and the items needed to meet element construction requirements. The research results show that temporary auxiliary facilities for the installation of immersed tunnels involve numerous complex systems and professions, and the final scheme should be determined by considering the actual demands of the project with classified problems, facility features, capacity and engineering factors. 2015 Vol. 52 (5): 192-199 [Abstract] ( 1655 ) [HTML 1KB] [ PDF 1250KB] ( 1421 ) 200 Comparative Analysis of Common Guidance Systems with Total Stations Adopted in Shield Machines GAO Shu Based on a domestic market investigation of shield guidance systems, this paper presents the guidance systems with total stations and gyroscopes; discusses the composition and theory based on the classification of shield guidance systems; compares and summarizes six guidance systems with total stations in terms of system background, hardware, software and service; and finally forecasts the development tendency of shield guidance system and puts forward some relevant suggestions. 2015 Vol. 52 (5): 200-205 [Abstract] ( 1516 ) [HTML 1KB] [ PDF 854KB] ( 2466 )

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