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Quick Search     Advanced Search MODERN TUNNELLING TECHNOLOGY   2015 Vol.52 Issue.2 Published 2015-04-25 Article 1 Guidelines for Good Working Practice in High Pressure Compressed Air (Part II) ')" href="#"> ITA Working Group No.5 "Health & Safety in Works" 2015 Vol. 52 (2): 1-7 [Abstract] ( 1825 ) [HTML 1KB] [ PDF 1102KB] ( 1532 ) 8 Dynamics Issues Regarding High-Speed Railway Crossing Tunnels Li Yufeng1,2, Peng Limin1, Lei Mingfeng1,2 In this paper, key dynamics problems regarding crossing tunnels on high-speed railways are presented based on their classification and combination, and the current state and existingproblems of research on train vibration, aerodynamic effects, seismic shock, etc. are summarized. This study indicates that future research should focus on the following: 1) a quantitative safety assessment using a 3D train-track-crossing tunnel model and considering the strata parameters and the structures of the cross-linked tunnels; 2) train-tunnel aerodynamic research for providing safe construction measures and tunnel safety assessment under the superposition of aerodynamic load and other loads; 3) seismic response research for providing the dynamic characteristics of crossing tunnels and relevant aseismic design schemes; and 4) the establishment of a calculation model considering rock dynamic damage and its constitutive relationship with concrete. 2015 Vol. 52 (2): 8-15 [Abstract] ( 1948 ) [HTML 1KB] [ PDF 1161KB] ( 1477 ) 16 Study of Driving Safety in a Highway Tunnel with New Interior Applied Materials Liang Bo1, He Shiyong2, Pan Guobing1, Xiao Yao2, Cui Lulu1 The eye fixation characteristics of drivers can properly express their visual information processing, and therefore the change rules of thedriver's eye fixation characteristics can be used to evaluate safety and comfort while driving in a highway tunnel with various interior materials applied on the sidewalls. For the Lushan Tunnel project on the Baoteng highway in the Yunnan Province, the Smart Eye Pro 5.7 non-intrusive eye tracking system was used to create an evaluation index of the eye fixation characteristics of drivers in the highway tunnel. The fixation duration, fixation area, pupil changes and change rates regarding 3 kinds of interior materials were used as the research objects to carry out real vehicle driving tests, and the changes of drivers' eye fixation characteristics under 3 testing conditions were consequently derived. Testing results show that the eye fixation characteristics for driving in a highway tunnel with applied energy-saving self-illuminated interior material are superior, featuring minimal and smooth changes of pupil diameter. It is thereby verified that the energy-saving self-illuminated interior applied material could remarkably improve the safety and comfort level of drivers in the highway tunnel. 2015 Vol. 52 (2): 16-21 [Abstract] ( 1863 ) [HTML 1KB] [ PDF 885KB] ( 1468 ) 22 Impacts of the Main Fault Zones on the Construction of the Qinling Water Conveyance Tunnel Li Limin The extra-long deeply buried Qinling water conveyance tunnel, located under the ridge of Qinling, passes through dozens of faults; of these faults, three regional faults have the greatest impact on the tunnel's construction. In this paper, the characteristics of the main fault zones are discussed from the aspects of tectonics, kinematics, fabric, geometry, etc., and the relevant impacts on tunnel construction are studied based on fault activity, rock strength and integrity, structural plance condition, underground water condition, occurrences of main structural planes and physical parameters. The results show that the characteristics of tectonics, kinematics, fabric, geometry and the formation mechanism of surrounding rock deformation can be used as a geological basis for predicting a spatial distribution rule. Through a comprehensive assessment of the engineering characteristics of rocks in fault zones, the surrounding rock classfication and lining support parameters can be optimized, providing effective guidance for tunnel design and construction. 2015 Vol. 52 (2): 22-29 [Abstract] ( 1757 ) [HTML 1KB] [ PDF 1136KB] ( 2289 ) 30 Elasto-Plastic Analysis of the Surrounding Rock of a Tunnel/Roadway Based on the Zienkiewicz-Pande Criterion Zhang Han1,2, Li Yingming1,3, Ren Fangtao2, Yang Mingdong3 In this paper, based on the Zienkiewicz-Pande criterion, which is a modification of the Mohr-Coulomb criterion, and considering the effects of intermediate principal stress, analytic solutions for the elastic-plastic stress of the surrounding rock of a tunnel/roadway, as well as the radius and displacement of the plastic zone, are deduced using an equilibrium equation. The influence of the intermediate principal stress on the Zienkiewicz-Pande criterion solution is analyzed through a given example, and the plastic zone radius and the distribution of surrounding rock stress are analyzed based on the Zienkiewicz-Pande and Mohr-Coulomb criterions, respectively, showing that the Zienkiewicz-Pande criterion is applicable to the elasto-plastic analysis of the surrounding rock in a tunnel/roadway. 2015 Vol. 52 (2): 30-35 [Abstract] ( 2017 ) [HTML 1KB] [ PDF 772KB] ( 1316 ) 36 Study of the Mechanical Characteristics of the Support Structure of a Deeply Buried Diversion Tunnel in Soft Rock Zhou Zelin, Chen Shougen, Li Yansong In-situ tests were carried out regarding the mechanical characteristics of the support system of a diversion tunnel in soft rock by using one project as an example, and a calculation method is presented for calculating the bearing capacity and strength safety coefficients of secondary linings in the construction of soft rock tunnels based on the strength reduction theory and numerical simulation analysis. Additionally, the stability of the surrounding rock and secondary lining is estimated and analyzed. The results indicate that: 1) the sidewall rock bolts play an important role in anti-pulling-out capacity, and the plastic zone of weak surrounding rock determined by the neutral point of rock bolts tends to develop and expand continuously; 2) in the primary support, the supporting effect of a steel arch will take effect immediately after it is erected, which plays a major role in surrounding rock support; 3) the secondary lining shall bear 12% of the surrounding rock load released during the construction period; 4) the stress concentrated area at the foot of the wall has the lowest safety coefficient; and 5) the calculation results of the secondary lining bearing characteristics basically agree with the in-situ test conclusions regarding secondary lining contact pressure. 2015 Vol. 52 (2): 36-43 [Abstract] ( 2068 ) [HTML 1KB] [ PDF 1205KB] ( 2211 ) 44 Model Test of the Relationship between the Face Support Pressure and Ground Surface Deformation of a Shield-Driven Tunnel in Sand Stratum Jin Dalong, Li Xinggao In order to study the relationship of the face support pressure and the ground surface deformation of a shield-driven tunnel, a self-made model testing system is used to measure the ground surface deformation and the face support pressure of a sand sample, and the relationship between the two is then analyzed. A failure model for soil settlement and heaving ahead of the excavation face is established by measuring the disturbance area at different overlying depths. Based on the gained relation curves of the face support pressure and the ground surface deformation, a deformation of 0.2% of the excavation diameteris taken as a reference value for setting the face support pressure, and the upper and lower limits of the ultimate support pressure for maintaining face stability are given by considering the Rankine earth pressure formula. For convenience of application, the required support pressure values for keeping specific ground surface deformation are suggested. 2015 Vol. 52 (2): 44-51 [Abstract] ( 2090 ) [HTML 1KB] [ PDF 1082KB] ( 1360 ) 52 A Diagnosis Method for Lining Structure Conditions of Operated Tunnels Based on Asymmetric Closeness Degree Wang Yaqiong1,2, Zhou Shaowen1, Sun Tiejun3, Xie Yongli1 In order to evaluate the condition of tunnel lining structures in operation, a diagnosis index system composed of a target layer, factors layer and index layer was established by applying the concept of analytic hierarchy process to determine four evaluation grades for operated tunnel lining structure conditions. The non-dimensional evaluation criteria for each diagnosis index was determined by using the range transformation method, and an evaluation model for judging the condition of the tunnel structure based on the asymmetric closeness degree was set up by applying the fuzzy theory, the gray system theory and the information entropy theory. The project demonstrates that the evaluation model can properly reflect the real condition of the tunnel lining structure. The comprehensive index weights determined by the improved gray relevancy method and entropy value method can overcome the shortcomings of subjective arbitrariness and increase the reliability of weight coefficients, and the analysis based on the asymmetric closeness degree guarantees that the diagnostic results are more consistent with the objective reality. 2015 Vol. 52 (2): 52-58 [Abstract] ( 1952 ) [HTML 1KB] [ PDF 916KB] ( 1336 ) 59 Parameter Analysis Considering the Impacts of the Support Structure on Ground Settlement and Inner Force During Center Drift Construction Ji Xinbo1, Zhao Wen1, Han Jianyong1, Zhou Yongwei2, Yu Hongfu3 Considering that the center drift method is widely used in the construction of large-span tunnels and using a subway station utilizing this method in Dalian as an example, the impacts of the longitudinal spacing between two mid-columns, the curvature of the vertical temporary support and the stiffness of the temporary support on tunnel and ground deformations, as well as the inner force transformation of the support, were researched. The results show that: 1) the accumulated ground settlement increases gradually with an increase of mid-column spacing after dismantling the temporary support below the medial plate; 2) the mid-column spacing has more effect on the axial forces of the mid-column and primary lining, but less effect on the bending moment of primary lining; 3) the minimum ground deformation can be obtained using the optimal curvature radius of the vertical temporary support; 4) side drift excavation plays an important role in the inner force transformation of the vertical temporary support; and 5) the stiffness of the temporary support has less effect on the deformations at various points and the final support inner force, but more effect on its own inner force. 2015 Vol. 52 (2): 59-66 [Abstract] ( 1959 ) [HTML 1KB] [ PDF 1217KB] ( 2209 ) 67 Stability Analysis of Tunnels under Horizontal and Vertical Joint Developments Sang Yunlong1, Li Jun2, Liu Xuezeng3 In this paper, based on the construction of the Yaogou tunnel in Hohhot, the characteristic parameters of approximate horizontal and vertical developed joints are collected for areas of the typical section; additionally, the kinematic behaviors and force characteristics of the overlaying rock are analyzed and the deformation and instability patterns of the surrounding rock are studied by adopting field monitoring, a laboratory model test and numerical simulation. The results show that: 1) without support, the stability of the strata is very poor during construction with the caving and loosening zones concentrated above the vault, of which the maximum caving height is 0.48 times the tunnel width, the caving area is 0.51 times the section area, the equivalent load of the vault is 0.084 MPa and the loosening zone extends to the ground surface in an almost triangular distribution; and 2) with a primary lining, the loosening range of the strata is significantly reduced, with a maximum caving height of 1.1 times the tunnel width, and the maximum settlement of the vault is reduced to 7.7 mm and the sidewall convergence becomes 3.4 mm. 2015 Vol. 52 (2): 67-71 [Abstract] ( 2223 ) [HTML 1KB] [ PDF 779KB] ( 2116 ) 72 Effect of Geostress on the Permeability of a Fractured Rock Mass in the Huangdao Underground Water-Sealed Storage Cavern Wang Zhangqiong1, Yan E'chuan2, Wang Lunan2, Long Lihong2, Zhou Nan2 The permeability of a fractured rock mass is a key parameter for evaluating the water-sealing effect of water curtain systems in underground water-sealed storage caverns. As fractured rock masses always exists under the conditions of stress and seepage fields, it is important to study the effects of the geostress of underground water-sealed storage caverns on the permeability of fractured rock masses. Using the Huangdao underground water-sealed storage cavern as an example, this paper presents the basic law of seepage flow in a fractured rock mass and the influence mechanism of stress on the seepage effect. The geostress and permeability parameters of a rock mass in the studied area and their distribution rules with an increase of hole depth are obtained by hydraulic fracturing and pump-in tests, and a relational expression of the geostress and permeability coefficient is established by a regression analysis. The results show that the permeability coefficient decreases with an increase of geostress and presents a negative exponential law. Consequently, the main causes for the negative exponent relationship between the permeability coefficient and geostress are analyzed. 2015 Vol. 52 (2): 72-77 [Abstract] ( 1838 ) [HTML 1KB] [ PDF 773KB] ( 1534 ) 78 Prediction Analysis of Fissure Water in Metro Tunnels Based on Groundwater Dynamics Hua Fucai With respect to mined metro tunnelling in mixed ground, a combined phreatic water and fissure water media analysis model is established based on the continuous porous media model for a phreatic aquifier, a formula and specific parementer values used to predict fissure water inflow are derived in light of the dynamics of groundwater, and the application method for the above formula for predicting water inflow at the grouting-reinforced section of metro tunnels is put forward. Using the Qingdao metro tunnel as an example, the water inflow is predicted by the analytical method and the numerical analysis method, respectively, and is compared with the measured values at the site. Analysis results show that the estimation error is lower for the analytical method. In addition, the effects of different tunnel shapes on water inflow are analyzed and it is concluded that the section type has little effect on the water inflow. Thus, the derived analytic formula has high applicability for predicting water inflow in mined metro tunnels in combined rock and soil strata. 2015 Vol. 52 (2): 78-86 [Abstract] ( 2076 ) [HTML 1KB] [ PDF 1287KB] ( 1569 ) 87 Win-Win Effect of Ground Consolidation Grouting on the Interaction between Tunnel and Grounwater Liu Zhichun1,2, Wan Liangyong1,3 Semi-enclosed waterproofing is adopted for mountain tunnels in most cases; this effectively decreases water pressure against the lining, but also results in a loss of groundwater resources. Based on a tunnel transient seepage model and under the condition of semi-enclosed waterproofing, the water drainage volume and water level variation during tunnel construction and operation are researched and the distribution law of water pressure against a lining in operation is established. Furthermore, the influence of the range and parameters of curtain/radial grouting on the water drainage volume, water level and water pressure are examined, showing that ground consolidation grouting can reduce both the water pressure against the lining and the loss of groundwater resources, achieving a win-win effect on the interaction between the tunnel and the groundwater. Finally, whether a drainage system for an invert is set or not is also discussed. 2015 Vol. 52 (2): 87-96 [Abstract] ( 2249 ) [HTML 1KB] [ PDF 1451KB] ( 1434 ) 97 Analysis of the Effect of Advanced Consolidation Grouting on Water Diversion Tunnels in Fractured Zones Li Lingzi1,2, Xiao Ming1,2, Geological disasters such as collapse and large deformation often occur when a water diversion tunnel passes through a water-abundant zone and soft fractured rock stratum. Aimed at this complex geological environment, a calculation method of 3D seepage stress damage coupling and an explicit fault simulation method with thin-lamina elements are put forward. The excavation and support process of an underground diversion tunnel after advanced consolidation grouting is simulated, the relative stability of a rock mass passed by the water-diversion tunnel under different conditions is quantitatively evaluated, and a contrast analysis of the rock mass failure area distribution and deformation law of the surrounding rock around tunnels with and without advanced consolidation grouting is conducted. The results show that the rock mass failure volumes and the displacements around the cavern are obviously reduced by 43.98% for the former (namely 1 252.9 m3 ) and 54.92% for the maximum displacement around a tunnel after advanced consolidation grouting. Thus, the advanced consolidation grouting significantly improves the overall stability of fault-fractured rock. 2015 Vol. 52 (2): 97-104 [Abstract] ( 2320 ) [HTML 1KB] [ PDF 1237KB] ( 2188 ) 105 A Mathematical Model for Fracture Grouting in Underground Engineering Xie Taofeng1,2, Xie Wenbing2, Jing Shengguo1,2, Zhou Xiaoting3 Based on research regarding rock fracture propagation in hydro-fracturing, a fluid-solid coupled rock failure process analysis system (RFPA) is used to establish a mathematical model for fracture propagation and slurry diffusion, as well as consolidation during fracture grouting. A numerical analysis is conducted for fracture grouting in a rock mass. The results show that: 1) in the process of fracture grouting, the width of the fracture does not increase indefinitely with rising pressure, and the required pressure for expanding the fracture decreases with an increase of the fracture length; 2) in the same rock mass, the fluid diffusion distance is positively correlated with the grouting time, fracture width and grouting pressure while it is negatively correlated with the resistance coefficient of the rock mass, the fracture length and the grout's kinematic viscosity; and 3) because of the fluid-solid coupling effect of the rock mass, the permeability of the rock mass decreases with a rise in the confining pressure and increases with propagation of the fracture, but when the confining pressure is unloaded, the permeability of the rock mass increases again. 2015 Vol. 52 (2): 105-109 [Abstract] ( 2277 ) [HTML 1KB] [ PDF 641KB] ( 1337 ) 110 Prediction of the Longitudinal Uplift of an Underwater Shield Tunnel During Canal Excavation Wang Daoyuan1,3,4, Wang Xichao2,4, Yuan Jinxiu3, Zhu Zhengguo4 A prediction model for the longitudinal uplift of an underwater shield tunnel during the excavation of a canal was set up and solved based on the bending differential equation of the elastic foundation beam, compatibility equations of deformation, rotation angle, shearing force and bending moment, and its boundary conditions. The results show that the analytical solutions obtained by the prediction model are consistent with the numerical solutions within a maximum error of 2.7%, and can therefore be used to predict uplift in similar projects. The longitudinal uplift of the shield tunnel decreases nonlinearly with the increase of the ground reaction coefficient, while it is not affected by the reaction coefficient when the ground reaction coefficient reaches 10 000 kN· m-3. In practical engineering, it is possible to keep the ground reaction coefficient around 10 000 kN·m-3 by backfill grouting to realize a balance between economy and safety. 2015 Vol. 52 (2): 110-114 [Abstract] ( 1991 ) [HTML 1KB] [ PDF 740KB] ( 1474 ) 115 Theoretical Prediction of the Thermal Parameters of a Roof Close to a Fire Source in a Tunnel with a Concentred Smoke Extraction System Xu Lin1,2,3, Chang Jian1, Wang Zhen1 Because a concentred smoke extraction system enables the diffusion range of upstream and downstream smoke to be better controlled, it is widely used in the design of long tunnels. In this paper, a theoretical model of defined diffusion of a fire plume in a tunnel with a concentred smoke extraction system is established for a small-scale fire scenario, and these theoretical results are compared with experimental results to verify the theoretical model and predict such thermal parameters as the maximum temperature rise and the offset distance of smoke underneath the tunnel roof. The prediction results show that: 1) the maximum temperature rise of smoke drops sharply with an increase of equivalent wind velocity when the fire intensity is unchanged, and the fire intensity has a remarkable effect on the temperature rise; 2) when the equivalent wind velocity is over 1.5 m/s, the rising temperature will slow down until it becomes constant; 3) however, the plume has no obvious offset when the wind velocity is small, as its offset increases with an increase of wind velocity but its change rate decreases with an increase of fire intensity. Based on the regression method, a dimensionless criterion correlation is obtained regarding the maximum temperature rise and offset distance of smoke underneath the tunnel roof. 2015 Vol. 52 (2): 115-119 [Abstract] ( 1816 ) [HTML 1KB] [ PDF 702KB] ( 1375 ) 120 Back Analysis of the Incremental Displacement of a Long-Span Bored Metro Station Sun Keguo1,2, Lu Feng1,2, Qiu Wenge1,2, Zhang Liang3, Xu Weiping1,2, Gong Lun1,2, Zhang Jingwei1,2 In this paper, a uniform design method is adopted to design a numerical simulation test with 16 levels of 5 factors（surrounding rock density, elasticity modulus, Poisson ratio, cohesive force and internal friction angle）and a 3D calculation is conducted for the construction of a long-span bored metro station by the finite difference method to obtain the values of surface subsidence for different experimental conditions and different procedures. The incremental displacements of 11 observation points induced by the demolition of the temporary support and corresponding rock-soil parameters are used as the input set, and the output set of a BP neural network helps to complete the training and learning. Additionally, the measured displacements induced by the demolition of the temporary support are taken as input parameters and the corresponding rock-soil parameters were inversed. The displacements of the rock-soil mass were obtained by putting all the inversion parameters into FLAC3D for a 3D-simulated calculation, and the rationality of those parameters are verified by measured increments of surface subsidence at 7 measuring points. The results show that the equivalent physical and mechanical parameters of the surrounding rock of a long-span bored metro station can be effectively obtained by a uniform design method and BP neural network in light of the surface subsidence increments induced by the temporary support demolition. 2015 Vol. 52 (2): 120-127 [Abstract] ( 1802 ) [HTML 1KB] [ PDF 1116KB] ( 1312 ) 128 Field Tests Regaring the Uncertainty of the Calculation Model for Soil Filling Pressure on Open-Cut Tunnels Liu Qiang1, Tan Zhongsheng1, Chen Libao2, Zou Xiaoxin1 Based on field tests of soil filling pressure calculations for the Shimenshan open-cut tunnel, the open-cut tunnel on Chouxia Line 1 and the Daheng open-cut tunnel, and considering the two structures of bias type cutting and single-pressure type half-cutting, a theoretical conculation formula is derived to obtain a certain number of sample values of uncertain random variable ζ in a calculation model for the typical section position of an open-cut tunnel on a double-track railway. The distribution scheme of random variable ζ is checked by using the A-D method and the statistic characteristics of ζ are obtained, then corrections are made through a statistic uncertainty calculation to obtain the statistic characteristics of the uncertainty ζ of the soil pressure calculation mode. Results show that the mean value of ζ is 1.065 and its variation coefficient is 0.127, complying with the normal distribution. As for the adaptation of this calculation model from single-track open-cut tunnels to double-track railway tunnels, it is of great significance that the revision of the code for tunnel structure design be based on reliability. 2015 Vol. 52 (2): 128-134 [Abstract] ( 1835 ) [HTML 1KB] [ PDF 909KB] ( 1452 ) 135 Full-Scale Test of the Early Performance of a Factory-Prefabricated Immersed Tunnel Jiang Wei1, Liu Xin2, Liu Xian2, Luo Yao2, Yuan Yong2, Wang Shengnian3, Su Quanke4 Due to large elements, complex structures and complicated construction technology, immersed tunnels are vulnerable to cracking under the influence of temperature and shrinkage and restriction during prefabrication, which are harmful to the serviceability and durability of the tunnel. This paper monitors the development of temperature and strain on the tunnel's key parts and compares relevant laws of temperature and strain development based on a full-scale test, using the immersed tunnel of the Hong Kong-Zhuhai-Macao Bridge Project currently under construction as an example. The results show that the immersed tunnel element structure will be subject to expanding and tensioning at the early age stage under a temperature rise induced by the hydration heat of concrete, then will shrink with the decrease of temperature after reaching the peak value; the element structure finally will be subject to compression because of autogenous concrete shrinkage. 2015 Vol. 52 (2): 135-142 [Abstract] ( 1905 ) [HTML 1KB] [ PDF 1225KB] ( 1209 ) 143 Friction Test for the Incremental Launching Slippage System of a Prefabricated Immersed Tunnel Segement Liu Zhanguo1,2,3, Tian Wei1,2,3, Chen Fuqiang1,2,3, Zou Longyan1,2, Zhang Zhaokun1,2 To select a suitable material for the friction surface of an incremental launching slippage system of a prefabricated segment of a immersed tunnel, the static and dynamic friction coefficients of four material groups, i.e., stainless steel plate-PTFE, stainless steel plate-NGE, ordinary steel plate-PTFE and ordinary steel plate-NGE, were tested. A 20 000 kN load-shearing test machine was used for the test utilizing the double-shear method. The test results indicate that: the friction coefficient of the combined stainless steel plate and PTFE plate is the smallest, and that of the combined ordinary steel plate and PTFE plate is the largest; and lithium-based lubricant and water have visible effects on reducing the static and dynamic friction between the stainless steel plate and PTFE plate, while the effect of lithium-based lubricant on friction reduction declines with the attenuation of the lubricant layer due to squeezing. The test results provide a significant reference for selecting material for the friction surface of incremental launching slippage systems, as well as for disposal measures for lubrication. 2015 Vol. 52 (2): 143-147 [Abstract] ( 1927 ) [HTML 1KB] [ PDF 740KB] ( 1460 ) 148 Sealing Test and Numerical Simulation for Steel Jacking Pipe Joint under High Water Pressure Gao Haidong, Zhao Tao, Ma Shengli, Fan Xuyang, Guo Yanbing Steel pipe jacking is the foundation and key technology of most large pipe-roofing construction. And yet facing with the complex formation and high groundwater pressure, sealing property of leakproof structure of jacking pipe joint is of great importance. In this paper, laboratory model experiment and ABAQUS finite element modeling are carried out regarding the sealing property of steel jacking pipe joints in the curved pipe-roof section of the Gongbei Tunnel of HongKong-Zhuhai-Macau Bridge. The results show that the pipe joint with two olecranon-shaped rubber sealing rings is capable of withstanding 0.3 MPa water pressure and meeting the in-situ construction sealing requirements; the maximum contact pressure between the rubber ring and the joint socket under pressure of 0.1~1.0 MPa is greater than the applied water pressure, which means the rubber ring will be not invalidated. 2015 Vol. 52 (2): 148-154 [Abstract] ( 1769 ) [HTML 1KB] [ PDF 1025KB] ( 1491 ) 155 Dynamic Response Analysis of the Impact of a Rockfall on a Cantilever Shed Tunnel Pan Changping1,2,3, Wu Qing1,2,3, Zhai Mingang1,2,3, Zou Shun1,2,3 Rockfalls are serious hazards in mountainous areas, and cantilever shed tunnels are a key measure against the impact of rolling stones. While in practical engineering it is very common for cantilever shed tunnels to be damaged by falling rock, few studies on the properties of the cantilever shed tunnel against the impact of falling rock have been conducted so far. In this paper, using ANSYS/LS-DYNA finite-element analysis software, a model of the common cantilever shed tunnel found in mountainous areas was established and a simulated analysis of the dynamic response process of the cantilever shed tunnel against the impact of falling rock was carried out to study the resulting deformation properties. The study results show that: 1) under the impact of falling rock, shock waves are generated in the shed tunnel and the transmission of these waves will result in stress and deforming vibrations; 2) the amount of time to reach the maximum stress at different parts of the shed tunnel is different; 3) the most dangerous places in the cantilever shed tunnel during a rockfall are the junction of the inside top wall and the plate as well as the lower part of wall, so that local strengthening should be adopted in these areas to ensure the safety of the structure; and 4) larger residual stress will remain inside the shed tunnel after the impact of the falling rock, so clearing of the fallen rock at the top of the tunnel should be undertaken in a timely manner. 2015 Vol. 52 (2): 155-159 [Abstract] ( 1917 ) [HTML 1KB] [ PDF 738KB] ( 1852 ) 160 Python-Based Secondary Development of ABAQUS and Its Application in Analyzing Shallow-Buried Unsymmetrical Loading Tunnels Wang Hui1, Li Tingchun2, Wang Qingbiao1, Zhan Yubao1 In order to improve the analysis efficiency of the large FEM software ABAQUS for shallow-buried unsymmetrical loading tunnels, the pre-processing and post-processing of ABAQUS is redeveloped based on Python language, and the concept and general steps of program development are presented. On this basis, a parametric calculation program is developed for simulating the effects of different unsymmetrical loading angles and buried depths on stability of shallow-buried tunnels. In terms of post-processing, the output of user-defined calculation results is realized; the redeveloped program is used to analyze the deformation and load rules of surrounding rock and lining under the conditions of 1°~40° unsymmetrical loading angles and 20~30 m buried depths. The results show that the redeveloped program can efficiently deal with the repetitive work in the pre-processing and post-processing of ABAQUS for studying shallow-buried unsymmetrical loading tunnels and improve analysis efficiency, providing a reference for the application of Python-based secondary development in other fields. 2015 Vol. 52 (2): 160-165 [Abstract] ( 2413 ) [HTML 1KB] [ PDF 854KB] ( 2540 ) 166 Adaptability Design for a Large-Diameter Shield Used in Shenzhen Metro Line 11 Chen Kui1,2, Feng Huanhuan2 Due to the requirement of higher running speeds, large-diameter shield tunnelling is a trend for future urban metro tunnels, and the φ6.98 m large-diameter EPB shield was first used in the construction of Shenzhen Metro line 11. This paper examines the construction difficuilties in Lot 11301 of Shenzhen Metro line 11, such as driving in spheroidal weathered granite, shield attitude control in heterogeneous soft ground and mud caking at the cutterhead due to soft clay, and proposes a specific adaptability design in terms of the main drive configuration, cutting tools, shield body, screw conveyer and muck conditioning system. Furthermore, suggestions are presented for optimization of the large-diameter shield. 2015 Vol. 52 (2): 166-173 [Abstract] ( 2026 ) [HTML 1KB] [ PDF 1200KB] ( 1546 ) 174 TBM Selection for a Long-Distance Inclined Coal Mine Shaft with a Large Gradient in Water-Rich Stratum Li Tiecheng, Zou Chunhua The main problems and challenges of TBM construction for an inclined shaft of a coal mine were analyzed, and the adaptability of various kinds of TBMs were compared. Ultimately, a dual-mode TBM was suggested for the long distance inclined shaft of a coal mine shaft with a large gradient in a water-rich stratum. Considering the specific characteristics of a long distance, a large gradient, a great overburden, presence of toxic gas, and a complex stratum with abundant water and strict construction progress, the main function, selection and configuration of the dual-mode TBM are studied, and the suggested design scheme and equipment configuration are presented. 2015 Vol. 52 (2): 174-179 [Abstract] ( 1722 ) [HTML 1KB] [ PDF 954KB] ( 2487 ) 180 Key Techniques for the Diffused Oxygen Supply of an Extra-Long Highway Tunnel in a High-Altitude Area Yan Tao1,2, Wang Mingnian1, Guo Chun1, Chen Hanbo1, Xie Wenqiang1 Based on the construction of the Balangshan tunnel with an altitude of 3 800 m and a length of 8 km, a field test regarding the diffused oxygen supply was carried out for the first time, obtaining variation patterns of subjects' physiological symptoms, such as heart rate and blood oxygen concentration, as well as the oxygen concentration inside the tunnel. It was determined that the diffused oxygen supply, having obvious positive effects on the oxygen concentration and human body function in the tunnel, is a sound method for the construction of tunnels in high-altitude areas, and it is recommended for application in the Balangshan tunnel. 2015 Vol. 52 (2): 180-185 [Abstract] ( 2031 ) [HTML 1KB] [ PDF 918KB] ( 1602 ) 186 Comprehensive Monitoring and Analysis of Segment Cracking in Shield Tunnels Lai Jinxing1,5, Qiu Junling1,5, Pan Yunpeng2, Cao Xiaojun3, Liu Chi1,4, Fan Haobo1,5 Segment defects like cracking, damage and dislocation have extremely adverse effects on shield tunnels. Using the water inflow event of a shield tunnel on the Xi'an metro as an example, this paper analyzes the situations and relevant causes of segment defects by utilizing field surveys, GPR detection, ultrasonic crack detection, displacement measurement, etc. The results show that: 1) the damages occurred on the segment at an early stage due to the cavities formed around the segment ring and the irregularly distributed loads upon it; 2) the displacements occurred on the segment because of additional asymmetric loading caused by grouting pressure, the cumulative lateral displacement of which was 3.4 cm with the upward movement reaching 5.5 cm at the end of grouting; and 3) the maximum depth of segment crack was 134.9 mm and its maximum width was 1.0 mm. 2015 Vol. 52 (2): 186-191 [Abstract] ( 2126 ) [HTML 1KB] [ PDF 917KB] ( 2431 ) 192 Comprehensive Geological Prediction and a Relevant Treatment Scheme for a Large Karst Cave in Tunnel Construction Yuan Yongcai, Li Shucai, Li Liping, Shi Shaoshuai, Zhou Zongqing, Lei Ting Based on the hydrological conditions of the observation points, topography, lithology and structural features of the Shangjiawan tunnel, it was determined that large karst caves may be encountered during construction, which could result in geological hazards such as water inflow and mud bursts. Based on an early risk assessment, a comprehensive geological prediction method is adopted in this paper to explore the unfavorable geologic bodies in front of the tunnel, utilizing the seismic prediction (TSP) method for the karst cave at ZK67+835, the ground penetrating radar (GPR) method for the cave at YK67+805 and advance drilling for the specific location, strike and dimensions of the cave under the tunnel floor. The results show that the karst caves in the left and right tunnel tubes are interconnected with each other, forming an extra-large underlying unfilled cave. Aimed at the characteristics of the disclosed caves, such measures as filling and bridging are used for this project; backfilling is appropriate for the left tunnel tube, which has no water passing through during the rainy season, and bridging is appropriate for the right tunnel tube, with the structural load borne by a simple beam and the vehicle load by a cover plate. This treatment scheme is verified by rock deformation monitoring after treatment. 2015 Vol. 52 (2): 192-197 [Abstract] ( 2089 ) [HTML 1KB] [ PDF 947KB] ( 1782 ) 198 Flexible Support Technique for the Weak Roof and Floor of a Roadway in a Coal Seam with a Medium-Thickness and a Large Inclined Angle Zhang Yuning1,2, Tang Jianxin1,2, Shen Ping3, Zhao Zhigang3 It is difficult for old methods of support to meet the stability requirements for a roadway in a semi-thick coal seam with a large inclined angle and to provide "gob-side" entry retaining due to gangue caving. Therefore, a flexible support technique is proposed in this paper: utilizing the protective covering zone formed by gangues that have caved in on specialized steel mesh to allow a certain settlement of the roadway roof and provide support for the combined rock beam structure above the roadway roof. Based on the construction process and field tests, the laws of strata pressure behavior, roof movement, the stacking of collapsed gangues and steel mesh deformation were obtained, proving the availability of this technique on the basis of a bolt-mesh-cable-pillar combined support. 2015 Vol. 52 (2): 198-204 [Abstract] ( 1677 ) [HTML 1KB] [ PDF 986KB] ( 1361 )

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