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Quick Search     Advanced Search MODERN TUNNELLING TECHNOLOGY   2017 Vol.54 Issue.6 Published 2017-12-25 Article 1 Opinions on Amendments to Partial Provisions for Tunnel Structure Calculation in“JTG D70-2010 Guidelines for Design of Road Tunnel” TIAN Zhi-Yu, Yang- Feng, Zhang-Zhao-Jie, WANG Bo, Wang-Wei-Jia Tunnel design is mainly based on empirical analogy method due to the complexity of tunnel structure, and the structure calculation and analysis is auxiliary. It is difficult and complex to study the calculation principle of tunnel structure and load, there are some problems to be found regarding the structural calculation in“Guidelines for Design of Road Tunnel”and revisions are needed. Analysis and discussion are conducted from the aspects of calculation method for loosening pressure on surrounding rock of the deep-buried multi-arch tunnel, arch feet constraint method for primary support and secondary lining calculation model and the bending moment solely borne by steel arch during checking steel arch and shotcrete strength. And some opinions on corresponding amendments are put forward. 2017 Vol. 54 (6): 1-7 [Abstract] ( 1087 ) [HTML 1KB] [ PDF 2306KB] ( 2156 ) 8 Analysis Method for the Longitudinal Equivalent Bending Stiffness of Shield Tunnels LUO Wenlin1,2 HAN Xuan2 HOU Wei2 ZHOU Honglei2 With more and more shield tunnels being constructed, the problems caused by excessive settlement are increasingly prominent, especially by longitudinal uneven settlement. At the present time, the study of longitudinal structural performance and the theoretical calculation model for shield tunnels are still imperfect, and the determination of the longitudinal stiffness of a tunnel is a key and difficult problem. In this paper, the longitudinal stiffness of a tunnel is back analyzed by the deformation monitoring data of the structure beneath an existing tunnel, providing a new analysis method for the longitudinal bending stiffness calculation of shield tunnels. A variety of factors are considered using this new method, such as the segment erection method, the tunnel′s transverse stiffness and the bolt function, which is quite different for the present calculation method. The research shows that the longitudinal stiffness of a shield tunnel varies with tunnel deformation and is nonlinear. A fitting relationship is established between the efficiency ratio of the longitudinal stiffness and the maximum longitudinal deformation of the tunnel structure. 2017 Vol. 54 (6): 8-14 [Abstract] ( 1054 ) [HTML 1KB] [ PDF 2637KB] ( 2056 ) 15 Design and Construction of a Metro Station by Enlarging a Single-Tube Double-Track Shield Tunnel HUANG Mingli1 SHEN Qiaofeng1 SHEN Rongjie2 The disturbance created by the construction of a subway station and running section may be eased by en? larging excavation using the shallow bored construction method for a single-tube double-track shield tunnel, thereby avoiding having to drag the shield machine through the station and reducing the hassle of station construction on the surrounding environment. Based on the Beixinqiao station of the West Extension Line of the Beijing Subway Airport Express, double-arch station and triple-arch station schemes using the PBA construction method are designed,a numerical simulation of these schemes is conducted using MIDAS and ultimately the triple-arch scheme is proposed. An optimization study on the rational design parameters for the three-arch station structure is carried out. 2017 Vol. 54 (6): 15-23 [Abstract] ( 1069 ) [HTML 1KB] [ PDF 5424KB] ( 2249 ) 24 Study on Karst Development in Tunnels by Hydrochemical Kinetics -Fractal Index Evaluation Technology LI Cangsong LIAO Yankai DING Jianfang Geological disasters such as karst water inflow and mud burst in the long tunnel have become an interna? tional problem. And it′s necessary to take further research on the mechanism of karst to have accurate understanding and evaluation of the extent and rules of karst development, to provide a basic theory for the key technology to solve the problem of karst geological disaster. Based on the previous research results, the relationship between karst groundwater and karst morphology is studied, an evaluation model and evaluation standards for karst development by hydrochemical kinetics-fractal index are established from the aspect of characteristics of karst aquifer medium,and an evaluation index system of karst development degree is formed. Using the 2# groundwater river in Wulong tunnel as an example, it shows the evaluation results agree well with the engineering practice. 2017 Vol. 54 (6): 24-31 [Abstract] ( 1097 ) [HTML 1KB] [ PDF 1927KB] ( 2015 ) 32 Application of Controlled Source Audio-Frequency Magnetotellurics (CSAMT) in Highway Tunnel Survey MAO Chengying LI Zuneng YANG Xianjie CSAMT has become an economical and efficient exploration method for deep-buried tunnels, but the static effect, near field effect and electromagnetic interference are prominent problems in CSAMT application.Based on engineering practices, the static effect and near-field effect generation mechanism, along with their characteristics and differences before and after correction, are discussed. If the magnetic field changes slightly in the same geological unit, it is proposed that the magnetic rod is placed far away from cultural noise sources. In the case of exploration in the Longbang tunnel, CSAMT anomalies agree well with the fault fracture zone and karst development zone disclosed by drilling, which illustrates the effectiveness of this method. 2017 Vol. 54 (6): 32-37 [Abstract] ( 938 ) [HTML 1KB] [ PDF 3373KB] ( 1912 ) 38 Collapse and Water Inflow Characteristics of a Tunnel in Metamorphic Schist in the Nappe Structure Region WANG Zhangqiong1,2 WANG Yajun1 YAN E′chuan2 Collapse and water inflow often occurs in regions with unfavorable geological conditions, and it is necessary to study this mechanism from a geological point of view. Taking the collapse and water inflow event in the Tongsheng Tunnel of the Shiyan-Fangxian Highway as an example, the development process of the disaster is analyzed and the typical phase characteristics of the deformation,collapse, water inflow and mud bursting in the surrounding rock are summarized. Based on the geological condition analysis, the geologi? cal survey for inside the tunnel and on the ground surface, and the TRT detection, the mechanism of tunnel collapse and water inflow is discussed from the perspectives of engineering geology and hydrogeology. The following conclusions are reached: 1) the tunnel passes through the compressive fault fracture zone, which is composed of broken rock and clay containing water, and it directly leads to the occurrence of collapse, water inflow, and mud bursts after tunnel excavation; 2) the nappe structure causes layering and fracturing in the surrounding rock; 3) with a high content of clay minerals in the schist, mud is easily created when water is encountered; and 4) the fault fracture zone contains confined groundwater. Finally suggestions for strengthening geological predictions and geological analyses are proposed. 2017 Vol. 54 (6): 38-44 [Abstract] ( 922 ) [HTML 1KB] [ PDF 3103KB] ( 2007 ) 45 Soil Conditioning Experiments for EPB Shield Tunneling in Water-Rich Sandy Cobble Strata HU Changming1 ZHANG Yanjie1 TAN Bo2 MU Shixu2 MEI Yuan Based on the shield tunneling of the Chengdu Metro line 3, the soil conditioning experiment for waterrich sandy cobble strata is conducted. In light of the laboratory experiments, a reasonable mix proportion of the modifier and the optimized mixing proportion range of the foam improvement are obtained for different moisture content conditions. In a field test, the main parameters for the shield are used as indicators to evaluate the effects on soil improvement and to analyze the feasibility of soil conditioning with a foaming agent in the water-rich sandy gravel stratum dominated by slightly dense pebbles in order to ensure the quality of the soil modifier. Through a FEM numerical simulation, the laboratory and field soil conditioning test results are further verified, and the research results of the optimized mix proportion of the improvement agent and the principal excavation parameters of shield tunneling can be used as a reference for similar construction scenarios. 2017 Vol. 54 (6): 45-55 [Abstract] ( 1019 ) [HTML 1KB] [ PDF 3970KB] ( 1998 ) 56 Full-Scale Model Test for Sand-Filling Foundation Construction Technology in the Nanchang Honggu Tunnel GUO Jun1 WU Gang2 SHEN Yongfang2 XI Xiaozhou2 As for the Nanchang Honggu immersed tunnel—the largest domestic immersed tunnel, a full-scale mod? el for the sand-filling of the foundation is designed, an equipment system and sand-filling monitoring system are established. Through sand-filling model tests for four cases, the real-time expansion process of the sand deposit, the law of pressure variation at the bottom of the model, the whole construction effect and the relative density of the sand deposit after sand filling are obtained. The feasibility and rationality of the construction technology design for the sand-filling method are verified. 2017 Vol. 54 (6): 56-62 [Abstract] ( 952 ) [HTML 1KB] [ PDF 2380KB] ( 1702 ) 63 Differences of Freezing Temperature Field under Opening and Closing Conditions LI Min1,2 DU Hongpu3 LI Zhu4 SHEN Furong3 YANG Yu3 The artificial freezing method is commonly applied to the construction of subway cross passages and for shield receiving. The formation and characteristics of the freezing curtain are influenced by factors such as the cold source and geological conditions. The engineering properties of frozen soil and frozen structures are reflected by the distribution and evolution of the temperature. Through a low-temperature heat transfer bench, the variation characteristics of temperature and moisture fields are tested for an opening system and a closing system with a water supply device, and the differences of the two fields with or without the water supply device are analyzed. The results show that the integral value along the tube length should be considered during calculation of the average temperature in the freezing region; the development process of the temperature with a water supply device is slightly faster than that without a water supply device; and the freezing front varies exponentially with time and moves faster with a water supply device. 2017 Vol. 54 (6): 63-69 [Abstract] ( 839 ) [HTML 1KB] [ PDF 2403KB] ( 1896 ) 70 Deformation Prediction for a Tunnel Rock Mass Based on the Multi-Scale Combination Kernel Extreme Learning Machine Model QIANG Yue1,2 LI Shaohong3 LIU Chaoqiong4 Tunnel rock deformation sequences are nonlinear and it is therefore difficult to obtain satisfactory preci? sion in predictions by conventional methods. To improve the prediction accuracy of tunnel surrounding rock deformation, a model of a multi-scale extreme learning machine with a combination kernel is proposed based on measured deformation data. The measured deformation data is divided into different scale sequences using the empirical mode decomposition technique, a sequence of each component is predicted by the combination of the extreme learning machine and the final forecast value is obtained by combining the results of each component. For the improved model, a compound kernel parameter is obtained by the linear weighting of the radial basis function and polynomial kernel function, kernel parameters and weighting coefficients are optimized by particle swarm optimization,the prediction results of the model are discussed using Markov Chain and the prediction accuracy for tunnel surrounding rock deformation is improved. The predicted surrounding rock deformation of the Daxiangling tunnel shows that higher accuracy can be achieved in both the one-step prediction and multi-step prediction of tunnel surrounding rock deformation using the improved model, the proposed model is better than the Bayesian regularization BP neural network and the deformation is acceptable compared to the measured deformation. 2017 Vol. 54 (6): 70-76 [Abstract] ( 918 ) [HTML 1KB] [ PDF 1177KB] ( 1661 ) 77 Calculation Method for the Radial Displacement of a Circular Tunnel Considering the Time Effect of the Viscosity Coefficient XIAO Zunqun1,2 WANG Xin1 TANG Dongsang1 LI Zhiping3 XU Caiyun4 ZHOU Pei5 LIU Yiming Based on a K-B Model, an analytic expression for the radial viscoelastic displacement of surrounding rock under an asymmetric load is established by way of the correspondence principle. Based on the records of the time-dependent creep parameters for the K-B model in relevant literatures, a viscoelastic solution for the radial displacement of the rock mass considering the time effect of the creep parameters of the K-B Model is obtained. A comparison of data shows that the maximum radial displacement considering the time effect of the creep parameters is larger than that which doesn′t consider it, and this indicates that it takes longer for the rock mass to reach a steady state in the former case compared with the latter one. According to a comparison between practical monitoring results and theoretical calculation results, it is determined that the laws of variation with time for both cases are consistent and the actual displacement is larger than the theoretical one, with an error scope of 18% to 26% . 2017 Vol. 54 (6): 77-84 [Abstract] ( 857 ) [HTML 1KB] [ PDF 1974KB] ( 1751 ) 85 Relationship between the Peripheral Displacement of a Tunnel and the Displacement of the Deep Surrounding Rock MA Shiqiang1,2 Based on a two-lane expressway tunnel, FLAC3D numerical analysis software is adopted to simulate dif? ferent rock deformation evolution processes under four conditions with different depths and different surrounding rock grades. Two kinds of large deformation of the surrounding rock are determined—a convergent one and a nonconvergent one. Meanwhile, data regarding the deep surrounding rock displacements at different peripheral displacements are recorded. The relationship between the peripheral displacement and the displacement of the deep surrounding rock is obtained by analyzing the curve of the surrounding rock displacements of different positions. The results show that, as for the same type of deformation, the relationship between the peripheral displacement and the displacement of the deep surrounding rock is consistent, while it is inconsistent for different types of deformation.Based on the knowledge of the deformation type determined by numerical simulation, the loose zones and plastic areas can be determined by the correlation curve of the peripheral displacement and the displacement of the deep surrounding rock. Compared with the field-measured loose zone under large deformation, the research results prove to be rational. The regression function is obtained by a multiple regression analysis to facilitate practical application. 2017 Vol. 54 (6): 85-92 [Abstract] ( 904 ) [HTML 1KB] [ PDF 3819KB] ( 1098 ) 93 On Frost-Heave Calculation Model Based on a Broken Freeze-Thaw Circle and Its Influential Factors ZHANG Yuwei1 LI Youyun1,2 XIE Yongli1,2 ZAN Wenbo3 The force created by frost heaves is one of the major influential factors for tunnels in cold regions, and it is very important to study this frost-heave force. Several kinds of calculation models and mechanisms for this frost-heave force are analyzed and summarized, and a model of frost heaving in a broken freeze-thaw circle is established based on a frost-heaving model for a weathered layer. A frost-heave force calculation formula is deduced according to displacement continuity conditions, the relation of frost-heave force and influential factors are analyzed by the control variable method, and the influence of different factors on the frost-heave force are analyzed by the partial correlation method. The results show that: 1) the frost-heave force value is related to the frozen depth, the frostheave ratio of the freeze-thaw circle, the lining and the resistance coefficient of the original rock mass; 2) the frostheave ratio of the freeze-thaw circle has a close relationship to the degree of breakage, moisture content and water supply conditions; 3) the orders of effects of various factors on the frost-heave force are: the frozen depth > the frostheave ratio of the freeze- thaw circle > the elastic equivalent resistance coefficient of lining. A case calculation shows that the frost-heave force scope is 7.43~11.05 MPa when the frozen depth is 2~3 m, and the calculated frostheave force is larger than that of the measured values. Countermeasures to mitigate the frost-heave force are discussed based on influential factors. 2017 Vol. 54 (6): 93-102 [Abstract] ( 898 ) [HTML 1KB] [ PDF 2524KB] ( 1887 ) 103 On Criterion for Tunnel Rock Mass Slippage along a Structure Surface and Its Impact Factors LIU Jianguo ZHOU Xiaojun XIAO Qinghua WANG Jinghe GAO Bo Based on the continuity hypothesis and Mohr-Coulomb criterion, a criterion to evaluate whether rock mass slippage along a structure surface will occur or not is proposed for a circular tunnel adopting the elastic mechanics method, and the minimum slippage zones of the rock mass under different internal friction angels of the structural surface are predicted. The proposed criterion is verified by the shear displacements of the rock mass along the structural surface with different internal friction angles through UDEC. The impact factors on the minimum internal friction angle to keep the rock mass stable and prevent slippage—including the lateral pressure coefficient, dipangle of the structural surface and the vertical distance from the tunnel center to the structural surface—and the mathematical relation among them are determined, and the impact law for the three factors on the minimum internal friction angle is analyzed. The results show the lateral pressure coefficient, the dip angle of the structural surface mainly influence the minimum internal friction angle of the structural surface that is far from the tunnel and required by keeping the rock mass stable, and the vertical distance only effects the minimum internal friction angle of the structural surface close to the tunnel excavation boundary but has no obvious effect on the region at a distance of more than 2.5 times the excavation radius. 2017 Vol. 54 (6): 103-110 [Abstract] ( 796 ) [HTML 1KB] [ PDF 2786KB] ( 1880 ) 111 Equivalent Constitutive Relationship of Steel Lattice Girder and Sprayed Concrete Composite Structures WANG Tao1 DONG Changsong1 JIANG Binsong2 Due to the complicated mechanism of steel lattice girder and sprayed concrete composite supporting structures, it is diffiuclt to conduct a mathematical description directly. An equivalent transverse isotropic model is proposed based on the mechanical equivalent principle, in which the mechanical property in the isotropic plane is the same as that of concrete and the mechanical property in orthogonal direction is the same as the axial mechanical propertiy of the steel lattice girder concrete. According to the principles of strain coordination, strain energy equivalency and strength equivalency, the axial deformation parameters and strength parameters are obtained. Based on the actual mechanical behavior of the steel lattice girder concrete, an equivalent constitutive relation is put forward and the constitutive relation curves are drawn to describe the complex mechanical properties of steel lattice girder concrete indirectly. The numerical comparison proves that the equivalent constitutive relation is well approximated with the elastic mechanical properties of steel lattice girder concrete. 2017 Vol. 54 (6): 111-116 [Abstract] ( 830 ) [HTML 1KB] [ PDF 1611KB] ( 1982 ) 117 Analysis of Ground Settlement Induced by Shield Tunnel Construction in a Soft Layer MENG Guowang1 ZHOU Jiamei2 GAO Bo2 MA Min3 The construction of the Kunming Metro Line marks the first time China has built a tunnel in a soft layer containing peat soil using the shield method. Focusing on the engineering practices for this metro line, a corrected Peck formula is set up to calculate the ground surface settlement considering the influence of the construction of the first tunnel tube on the second tunnel tube in a soft layer containing peat soil. The law of ground settlement caused by shield construction is studied and compared to the empirical formula for ground settlement prediction. The results from this method and the numerical simulation agree very well with the measured data and can be used to analyze the shield-induced deformation law of soft ground containing peat soil. Compared to the change rate of ground surface settlement outside of the second tunnel tube, the change rate is larger for the first tunnel tube and its transverse settlement range is smaller, while the maximum settlement occurs between the center line of the two tunnel tube axes and first tunnel tube axis, and is caused by the construction of the first tunnel tube. Based on monitoring data from shield construction, the technical countermeasures against ground deformation caused by shield construc? tion in soft stratum containing peat soil are proposed. 2017 Vol. 54 (6): 117-125 [Abstract] ( 922 ) [HTML 1KB] [ PDF 3034KB] ( 1700 ) 126 Deformation Law of a Metro Tunnel underneath an Existing Urban Road in Combination Soft/Hard Stratum WU Ke1 ZHANG Wen2 WU Haotian3 WANG Yajun3 YU Yalin1 Large surface settlement is often caused by tunnel construction in a stratum with a soft upper part and hard lower part, and this endangers any existing buildings. Based on the Antuo-Mountain Entrance/Exit Line project of Shenzhen subway line 7 underneath the North Ring Road, a numerical calculation model is set up by three-dimensional finite differential software FLAC3D under combination of numerical simulation and field monitoring to analyze the characteristics of ground surface settlement and stratum settlement during construction of the V-shaped tunnel underneath the existing road, and a comparison and demonstration is conducted by field monitoring and measurement. The results show: 1) the ground settlement trough mainly presents in a Y shape; 2) the superposed effect of the crown settlement trough is obvious when the interval of two tunnels is less than 2.0D, and the superposition of ground surface settlement increases greatly when the interval of two tunnels is less than 4.0D; and 3) the influential scope of overlying ground deformation decreases with an increase of the depth. The effect of advanced support on ground surface settlement is described and a comparative study of the parameters for advanced grouting is conducted so that the construction method and support measures are optimized. 2017 Vol. 54 (6): 126-135 [Abstract] ( 918 ) [HTML 1KB] [ PDF 5120KB] ( 1857 ) 136 Simulation Technology for Superimposed Cover-Arch Reinforcement Based on Composite Beams LIU Xuezeng1，2 LIU Xingen2 SANG Yunlong2,3 LIU Wenyi1 Based on the force characteristics of reinforcement by a superimposed cover arch and the rigidity equiva? lent theory for highway tunnels, parameters are combined and modified for section characteristics of the lining and cover-arch reinforced structure, and the internal force distribution method of a compound section in a beam element is discussed. The composite structure of the lining and superimposed cover arch are simulated using composite beam elements with a sharing node, and the output of the internal force values of lining, cover arch and composite structure are determined by the analysis results. The feasibility and correctness of the calculation model is verified by comparing the numerical validation example, the analytic solution and the ANSYS solution. Based on actual highway tunnel engineering, a finite-element analysis is conducted using composite-beam simulation technology, and the analysis results confirm that the effects of a superimposed cover-arch reinforcement based on composite-beam analysis is rational and intuitive, providing a reference for evaluating the reinforcement effects of similar projects. 2017 Vol. 54 (6): 136-142 [Abstract] ( 904 ) [HTML 1KB] [ PDF 2046KB] ( 1791 ) 143 Numerical Simulation of the Bearing Capacity of a Shield Tunnel Structure in Unloading Conditions LU Liang HE Yanqing HAO Xiaobin The large horizontal deformation of lining rings caused by adjacent unloading has a serious impact on the security and normal operation of a tunnel structure, so an efficient and highly accurate method must be developed to simulate the whole process from unloading to failure. A numerical simulation of the internal force and deformation of the lining ring for different joint stiffnesses indicates that joint stiffness has little effect on the axial force distribution and magnitude of the lining ring, so the axial force of the segment joint is calculated using the equivalent stiffness ring method, which is used to determine the bending stiffness curve of the bend-resistant spring. A fine analysis is performed using the three-dimensional straight beam solid element method and a bending stiffness model for the segment joint under different axial forces is obtained. Parameters for the bending-stiffness model are used as the pa? rameters for the spring of the two-dimensional beam-spring model, and the internal force and deformation of the lining structure under different load levels is calculated by the two-dimensional beam-spring method, with results that are consistent with those of the experiment. A whole-process numerical analysis shows that the bending moment increases and the axial force decreases continuously at the joint section with the bending stiffness of the joints during the unloading process, with the bending stiffness at the joint decreasing rapidly and the structure reaching a state of failure. 2017 Vol. 54 (6): 143-180 [Abstract] ( 922 ) [HTML 1KB] [ PDF 3596KB] ( 1987 ) 151 Deformation Characteristics of a Segment Lining Structure for a Shield Tunnel Adjacent to Piles SHAN Shengbiao1 SHI Qiang2,3 WANG Yixian3 DENG Fang2 QIAN Yelin3,4 LV Weike4 As for one running section of Hefei Metro Line 1 adjacent to a pile group foundation, the shield driving process is simulated using the finite- element software Midas, with a focus on segment deformation and internal force change. The tunneling process of a shield machine under different grouting pressures and approaching or not approaching a pile group is simulated and a comparative analysis of the effect on the segment′s internal force and deformation is conducted. The results show that: when grouting pressure is within the range of 0.1 MPa to 0.4 MPa, the internal force and deformation of the tunnel segment increase with an increase of the grouting pressure during shield tunnelling; and the internal force and deformation of the tunnel segment are restrained by piles during shield tunnelling adjacent to a pile group foundation, and these are related to the distance between the tunnel segment and the piles, with apparent restraint of the horizontal displacement for the tunnel segment closest to the pile group foundation. 2017 Vol. 54 (6): 151-157 [Abstract] ( 897 ) [HTML 1KB] [ PDF 2398KB] ( 1798 ) 158 Aseismic Analysis of a Shallow-Buried Large-Span Single-Arch Station with No Column LI Gang1 MENG Xiaowei2 The advantages, disadvantages and applicability of common calculation methods for aseismic analysis of metro tunnels are briefly described. A finite-element model is established based on the People′s Hall Station of Qingdao metro line 4, and the dynamic characteristics of a metro station under a seismic load is calculated and analyzed.A comparison of the internal force and displacement at each point of the structure shows: 1) the seismic response results calculated by the response displacement method and response acceleration method are generally larger than those calculated by the time- history method, and the greater the station stiffness, the larger the difference; 2) in light of a large elastic-plastic constitutive error of the structure under an E3 state, the elastic-plastic interlayer displacement can be obtained by multiplying the elastic interlayer displacement and ductility coefficient for the station in the simple stratum; 3) the results calculated by the inertia force method are generally larger than those calculated by the response displacement method, while the difference is small if the station inertia force plays a leading role (i.e.,the station stiffness is very great with respect to the soil mass); 4) the Qingdao station is basically located in granite,with 90% of the structure dynamic response caused by shear force, so the aseismic analysis results of the soil mass are different from those of Kunming, Changzhou and Zhengzhou; and 5) the interlayer displacement angle of the metro structure increases with an increase of the station overburden but decreases with an increase of the rise-span ratio, elastic modulus of the rock mass and thickness of the secondary lining, while the thickness of the secondary lining has little effect on the angle of the interlayer displacement and the station overburden has greatest effect on the angle of the interlayer displacement. 2017 Vol. 54 (6): 158-165 [Abstract] ( 864 ) [HTML 1KB] [ PDF 2893KB] ( 1907 ) 166 Study on Properties of Cutting Rock and Soil Medium by Pre-cutting Cutters XIA Yimin1,2 ZHANG Xuhui1,2 TAN Qing1,2 WU Caizhang1,2 QIAN Cong1,2 LIU Jie3 In order to study the characteristics of cutting two kinds of typical rock and soil media using a pre-cut? ting cutter, a two-dimensional numerical simulation model of the cutting rock and soil media is established with a particle flow code. The characteristics of the dynamic process, force and specific energy consumption are analyzed.The results show that: 1) it will lead to a packing effect in front of the cutter blade, with the force applied on the whole front blade while cutting soft soil; 2) the force is only applied to the tip of the cutter blade when cutting soft rock; 3) the horizontal cutting force is much higher than the vertical cutting force when cutting these two kinds of media, with a more intense force fluctuation during soft-rock cutting than soft-soil cutting and a different crack growth trend; 4) the failure scope and failure mode of the two kinds of media change with different cutting depths and rake angles; 5) the force of cutting two media increases with an increase of the cutting depth and decreases with an increase of the rake angle, but for soft soil the rake angle will have a significant effect on the cutting force when the cutting depth reaches a certain extent, so the force is more affected by the cutting depth rather than the rake angle; and 6) the specific energy consumption decreases with increases of the cutting depth and rake angle and the reduction range becomes larger and larger. 2017 Vol. 54 (6): 166-173 [Abstract] ( 864 ) [HTML 1KB] [ PDF 3830KB] ( 1505 ) 174 Frequency Domain Dynamic Response of a Submerged Floating Tunnel Anchor Cable under Random Wave Force Excitation A theoretical study of the frequency domain dynamic response of an anchor cable of a submerged floating tunnel under random wave force excitation is presented and a mathematical method is established by the pseudo-excitation and Galerkin methods, and the non-linear motion equation is solved by the equivalent linearization method.The effects of parameters for wave and structure under non-stationary and stationary random excitation on the dynamic response parameters for the vibration system are analyzed. Compared with the results obtained from the Sunshengnan method and the hydrodynamic software AQWA, it shows that the proposed method can truly reflect the actual oceanographic conditions for meeting the requirement of accuracy. 2017 Vol. 54 (6): 174-179 [Abstract] ( 875 ) [HTML 1KB] [ PDF 1337KB] ( 1966 ) 180 Measurement and Numerical Simulation of Deformation of the Cofferdam with Geotextile Sand-Bags in the Zhoutouzui Immersed Tunnel Project HE Zegan1 YANG Chunshan1 WEI Lixin1 MO Haihong2 The deformation development law of cofferdam with geotextile sand bags is explored by field measure? ment based on the construction process of the Zhoutouzui immersed tunnel in Guangzhou. Based on the existing research results, the deformation saltation mechanism is determined, the main control indexes for design and construction of the cofferdam are proposed and the rationality is verified by a refined FEM calculation. The results show that:1) the response law and degree of deformation are different at different positions during the construction of the geotextile sand bag cofferdam, with saltation of the local displacement and a larger influence in the vertical direction than in the horizontal direction; 2) the main reason for deformation saltation of the cofferdam is that the buoyant unit weight turns into a dry unit weight due to the dewatering of the geotextile sand bag, which increases the overlying pressure of the upper geotextile bag to the lower ones and flattens them and causes large deformation; and 3) the foundation soil experiences three phases of vertical pressure consolidation, lateral extrusion and local sliding, which cause the maximum vertical and horizontal displacements to occur at the top and foot of the cofferdam. The numerical calculation results show that: 1) it is stable since no sliding failure occurs at the cofferdam and no cut-through plastic zone is formed, which is consistent with the results deduced by theoretical analysis; 2) the stack height of cofferdam should be taken as the control index; and 3) there are some weak points in using the displacement limit value for traditional foundation pit support structure to judge the mechanical state of the cofferdam with geotextile sand bags, and the design for the slope ratio of the cofferdam should fully consider the reinforcement effect of the geotextile sand bags. 2017 Vol. 54 (6): 180-186 [Abstract] ( 892 ) [HTML 1KB] [ PDF 3325KB] ( 1688 ) 187 Modeling Technology and Stability Analysis of the Complex Bell-Shape Caverns YANG Dan1 HU Xiewen1,2 LI Wei3 Three-dimensional modeling technology is key to the numerical analysis of the stability of large irregu? lar cavern groups using Flac3D. Based on the multiple soft coupling technique, the rapid modeling of the complex irregular caverns of Changyu in Wenling of the Zhejiang Province is realized by comprehensive use of AutoCAD, Surpac, Surfer and Matlab programs under the condition of only using the main parameters of the cavern structure, such as the topographic map, center coordinate of the cavern bottom, tunnel height and tunnel span. A model that is 624m long, 480 m wide, 336 m high and has 6 irregular caverns is modeled with 16 m, 8 m, 4 m, and 2 m sized grids.Under the accuracy requirements, the calculation is completed in only 2.5 hours, improving the calculation speed greatly. The calculation and analysis show the cavern group is stable, but the force state of the surrounding rock at the bottom and the central diaphragm wall is not conducive to stability. Traditionally, there are three kinds of measures for enhancing the stability of the cavern structure during cavern excavation: partial removal of the surrounding rock at the bottom, storing water in the rock pit and partial removal of the rock mass at the central diaphragm. 2017 Vol. 54 (6): 187-194 [Abstract] ( 857 ) [HTML 1KB] [ PDF 4239KB] ( 1746 ) 195 ctive Pre-Support Technology for a Shield Tunnel Approaching to a Proposed Viaduct Pile WANG Guofu SUN Jiecheng LU Linhai LI Gang DONG Hongxing HAN Shuai More and more viaduct and metro tunnels are constructed concurrently or in close succession, and tradi? tional passive support measures have the disadvantages of poor control, severe disturbance and poor selectivity restricted by confined spaces. Using a shield tunnel of Jinan metro line R1 that approaches to the proposed viaduct pile as an example, the active pre-support techniques of a frame structure, three-axis mixing pile structure and diaphragm wall are put forward, and the characteristics of the surface settlement, deformation law of the viaduct pile and principal stress distribution of the segment under different support conditions are analyzed. The study results show that: 1) the tunnel settlements, pile foundation deformation and segment principal stress present various tendencies under different support conditions, and the viaduct pile deformation and segment compressive stress reach their maximums without advance support; 2) with the continuous decrease of the frame structure spacing, the outeredge deformation of the pile cap increases and its center deformation decreases gradually; 3) the separation and control effect of the three-axis mixing pile is poor because of its low stiffness; 4) the reinforcement and control effect of the multi-frame structure, mixing-pile embedded precast pile and diaphgram wall increase gradually; and 5) in ac? tual construction, the multi-frame structure should be given priority due to its uniform control effect on the various control indexes, economy and ease of construction, while the mixing- pile embedded precast pile and diaphragm wall support have advantages in unfavorable geological conditions. 2017 Vol. 54 (6): 195-202 [Abstract] ( 926 ) [HTML 1KB] [ PDF 2584KB] ( 1994 ) 203 Rapid Construction Technique for a Large Upper-Section of the Tianping Tunnel in Soft Rocks ZHANG Tao Based on the soft-rock section construction of the Tianping tunnel on the Chongqing- Guizhou high speed railway, the conventional two-bench method is optimized and a large upper-section method is presented in light of the confined work space and unavailability of large mechanical equipment regarding the original designed construction method for the rock mass of grades Ⅲ, Ⅳ and Ⅴ. The construction organization is described and a reasonable drill and blast scheme is established, guaranteeing an optimal combination of progress and cost. The technical measures for a soft-rock tunnel with unfavorable geological conditions are summarized, and ultimately the rapid construction of the Tianping tunnel in a soft-rock section is realized. 2017 Vol. 54 (6): 203-209 [Abstract] ( 916 ) [HTML 1KB] [ PDF 2128KB] ( 2143 ) 210 Control and Monitoring of Ground Deformation during Jacking of a Large-Diameter Curved Tabular Roof LIU Yingliang The bored section of the Gongbei Tunnel on the Zhuhai Link of the Hongkong-Zhuhai-Macao bridge passes beneath the Gongbei Port and is excavated using a combination of a curved tubular roof and artificial ground freezing. Due to the environmental sensitivity of the site, the complexity of the ground conditions and the special nature of the construction method, the ground deformation control during the construction of the curved tubular roof is challenging. Based on an analysis of the influential factors of ground deformation caused by tabular roof construction, countermeasures against ground deformation are proposed, including the selection of a proper jacking machine and its corollary equipment, the dynamic control of the jacking parameters, water leakage control at the entrance,launching and receiving process, pipe stiffness requirements, and a lubrication slurry replacement. In light of the ground deformation monitoring data, the law of ground deformation is analyzed in terms of the ground deformation,ground settlement trough and ground settlement accumulative effects, providing a basis for the construction safety and rationality as well as a reference for similar projects. 2017 Vol. 54 (6): 210-216 [Abstract] ( 879 ) [HTML 1KB] [ PDF 4014KB] ( 1821 ) 217 Clay Cake Prevention for a Slurry Shield Cutterhead in Argillaceous Siltstone Stratum WANG Zhufeng1,2 FENG Huanhuan1,2 Aiming at the problems of abnormal driving parameters (the average advance rate is 6~10 mm/min. and the max. torque of a cutterhead is up to 3 200 kN·m) and the formation of clay cakes and mud pies during shield construction in argillaceous siltstone stratum, a specific design for the configuration of the cutterhead and cutting tools is proposed in terms of the cutterhead opening ratio, cutting tool layout and cutter height optimization based on the Nanchang rail transit line 1 in order to reduce the possibility of developing a clay cake. Based on an analysis of the operating principles of the slurry shield flushing system, an optimized design scheme is put forward by taking the geological characteristics into consideration. The engineering application results show that the advance rate of an optimized shield can reach 20 mm/min. and the total torque can be controlled within 2 000 kN·m, which meets the requirements for engineering construction. 2017 Vol. 54 (6): 217-222 [Abstract] ( 935 ) [HTML 1KB] [ PDF 2397KB] ( 1931 ) 223 Research and Application of Xanthan Gum for Simultaneous Grouting in Shield Tunnel Construction WANG GuoYi JIANG Zongquan The buoyancy and long setting time of the mortar used for simultaneous grouting in shield tunnel con? struction lead directly to the problems of a staggered segment, damage and tunnel clearance invasion, which affect the acception and operation of metro tunnels. The mechanism of segment uplift is analyzed, and the concepts of generalized buoyancy and buoyancy density of segment are put forward. The conventional bentonite is replaced by xanthan gum for simultaneous grouting, and this greatly increases the pseudoplasticity of the mortar. Experiment calculations and analysis show that after ten minutes the generalized buoyancy of the mortar with the xanthan gum decreases greatly compared with that of conventional mortar due to its special pseudoplasticity, and the buoyancy is close to zero. Practical application in the Chengdu metro shows that the mortar with xanthan gum effectively fills the gap between the segment and the excavation profile, and the problem of uplift of the shield tunnel can basically be solved. 2017 Vol. 54 (6): 223-226 [Abstract] ( 854 ) [HTML 1KB] [ PDF 766KB] ( 1855 )

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