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Quick Search     Advanced Search MODERN TUNNELLING TECHNOLOGY   2018 Vol.55 Issue.2 Published 2018-04-25 Article 1 Defect Investigation and Operation Management of Highway Tunnels in Henan Province ZHOU Jiabin1,2 With increased traffic mileage and operation time of highway tunnels in Henan province, tunnels are having increasing numbers of defects. In order to provide a basis for treatment and to improve the maintenance mangement of highway tunnels in Henan province, the main tunnel defects are analyzed and a technical evaluation of tunnel operation statuses is carried out. Problems, suggestions and countermeasures concerning tunnel maintenance concepts and systems as well as proper treatments are presented based on research, inspections, sampling and statistics and investigations of highway tunnels with different grades and maintenance levels in Henan province. The prospects for tunnel operation management are projected in terms of "life cycle management and maintenance", "customized tunnels", "preventive maintenance", "intelligent maintenance " and so on. 2018 Vol. 55 (2): 1-10 [Abstract] ( 1001 ) [HTML 1KB] [ PDF 3682KB] ( 1460 ) 11 Application and Development of a Sprayed Waterproof Membrane for Tunnels JIANG Yajun1 YANG Qixin1 LIU Dongmin2 SHENG Caoying3 The application and development trends of the sprayed waterproof membrane technology used in tunnel? ling are discussed based on an analysis of development stages, basic principles and application in tunnels both at home and abroad. The sprayed waterproof membrane technique includes the material, polymerization mechanism,spray apparatus and construction technology, and this technique can be used in bored tunnels with compound linings,immersed tunnels, cut-and-cover tunnels, other underground works and for treatment of tunnel leakages. It has not been applied extensively yet, though it has been introduced to more and more tunnels all over the world recently.the prospects for this technique are bright as it is increasingly applied to various tunnels, and more achievements regarding related research work are expected in the near future. 2018 Vol. 55 (2): 11-19 [Abstract] ( 1032 ) [HTML 1KB] [ PDF 1582KB] ( 2860 ) 20 Principles and Application of a Smart Tunnel Laser Convergence Gauge for Monitoring Tunnel Crown Settlement XIA Caichu1,2 NA Tongxing1 ZHANG Pingyang1 HUANG Man1,2 ZENG Gehua Monitoring tunnel crown settlement is a way to evaluate the stability of surrounding rock during tunnel construction and to ensure tunnel construction safety. However, it is difficult to operate a grade rod for the precise leveling instrument and it is quite intense work. Though total station trigonometric leveling can be accurate to a millimeter, it is not often applied in engineering. In order to improve the efficiency of crown settlement monitoring in tunnels, non-contact measurement using a smart tunnel laser convergence gauge to monitor tunnel crown settlement is proposed, and the monitoring steps are briefly introduced in this paper. Through theory analysis, the repeated monitoring and measuring tests both in the laboratory and onsite indicate that the precision of crown settlement monitoring using the smart tunnel laser convergence gauge can reach 0.70 mm. Compared with results from a DS05 percussive leveling instrument and a Leica TS15 total station on the construction sites of a cavern project in the Qindao and the Dangjinshan tunnel on the Dunge railway, the monitoring accuracy and stability of the smart tunnel laser convergence gauge are verified. The application prospects are vast using the smart tunnel laser convergence gauge to measure and monitor tunnel crown settlement thanks to its reliable precision, high efficiency, minimized construction disturbance and ability to simultaneously monitor peripheral convergence. 2018 Vol. 55 (2): 20-27 [Abstract] ( 968 ) [HTML 1KB] [ PDF 1904KB] ( 2339 ) 28 Surrounding Rock Deformation Control for Deep-Buried Soft-Rock Tunnels ZHANG Chuanqing1,2 ZHANG Yang3 ZHOU Hui1,2 YANG Fanjie1,2 LIU Ning3 Deformation control is a main measure for controlling the stability of soft-rock tunnels. Control indexes and methods for deformation and deformation rate are proposed in relevant specifications and literatures, but most of them focus only on convergence identification and are summarized based on construction experience in shallow tunnels, which makes them less appropriate as a basis of adjustment and control of stability during construction and not very suitable for deep- buried tunnels with high rock deformation pressure. Based on an analysis of the rock mass deformation characteristics of the squeezing section of a deep- buried chlorite schist tunnel, a multi-index rock stability control method that considers the indices and modes of deformation and deformation rate is proposed,and timely adjustment measures for rock mass stability are available in light of the time-space effect during construction, eliminating squeezing deformation of the surrounding rock in the deep-buried soft rock tunnel. 2018 Vol. 55 (2): 28-35 [Abstract] ( 958 ) [HTML 1KB] [ PDF 3006KB] ( 1956 ) 36 Analysis and 3D Visualization of Surrounding Rock Stability during TBM Tunnelling in Jointed Rock Masses ZHANG Zixin1,2 WANG Shuaifeng1,2 HUANG Xin1,2 The intrinsic geological characteristics of a jointed rock mass include rock mass structure, in-situ stress of the primary rock mass and groundwater, which results in unfavorable geological conditions like fracture zones, soft rocks with large deformation and zones with abundant groundwater. TBM driving in the jointed rock mass is affected by these rock mass characteristics and geological conditions, while the rock mass is disturbed by the TBM construction, leading to instability of the surrounding rock. Unfavorable factors such as improper geological exploration and inappropriate selection of TBM types can also trigger or facilitate instability of the surrounding rock. The instability of rock masses may occur in front of the excavation face or around the periphery of the tunnel, or a combination of the two. A 3D visualization model of a jointed rock mass is established to simulate TBM tunneling in jointed rock masses using the developed software package BLKLAB based on block theory. Removable blocks and key blocks of surrounding rock on the excavation face and around tunnel periphery are identified. 2018 Vol. 55 (2): 36-43 [Abstract] ( 891 ) [HTML 1KB] [ PDF 2522KB] ( 2270 ) 44 Frost Damage Mechanisms and Anti-Freezing Measures for Tunnels in a Seasonally Frozen Soil Region WEI Xingxing1,2 ZHENG Bo2 WANG Renjie1,2 Affected by temperature, water, crevices and other external conditions, a freeze-thaw cycle between the lining and surrounding rock may occur for a newly built tunnel in a region with seasonally frozen soil. With the change of seasons, the freeze-thaw cycle would produce frost heaves due to constraint of the lining and surrounding rock, causing lining cracking and freezing damage. Studies of the mechanism of frost heaves and the influential factors of frost damage have been conducted for many years, with three kinds of frost heave theory and a variety of antifreeze measures proposed from the micro and macro points of view; however, the problem of frost damage to tunnels in seasonally frozen regions still continues to occur. Countermeasures against freezing disasters in cold regions are presented by summarizing frost damage and analyzing the mechanism and measures for freeze prevention both at home and abroad in terms of temperature, water and crevices. 2018 Vol. 55 (2): 44-50 [Abstract] ( 1020 ) [HTML 1KB] [ PDF 1345KB] ( 3108 ) 51 Preliminary Analysis of Causes of Closing Type Blockage Disasters during Tunnel Construction QU Haobo1,2 LI Lin2 Based on investigation of closing type blockage disasters and analysis of their relationship to geological disasters, seven structures affected by deformation-induced collapse of the surrounding rock, six structures affected by mud bursts and two structures affected by debris flows inside the tunnels are introduced, and the causes of the disasters are analyzed. The examination shows that: 1) the grade of the surrounding rock where the instability occured due to deformation and collapse were not corrected and either the primary supports were not constructed in time or the the primary support was not intense enough; 2) the soil disc of the soil-isolating rock was broken through because the autologous mud isolating soil disc and compound soil disc were not thick enough or strong enough, or the conditions of the disasters causing mud bursts varied, which led to mud bursts and debris flows; 3) shear fracture failure occurred along the preferred structure planes at mud- isolating joint fractured rock discs and led to mud bursts; and 4) vibrations induced by tunnel construction resulted in instantaneous sinking of clay fill in karst caves and caused mud-isolating rock discs to break and mud bursts to occur. 2018 Vol. 55 (2): 51-55 [Abstract] ( 859 ) [HTML 1KB] [ PDF 569KB] ( 1730 ) 56 Determination Method for a Reasonable Installation Time of the Tunnel′s Secondary Lining YANG Feng The key to determine a reasonable installation time for a tunnel′s secondary lining is to evaluate when the deformation of the surrounding rock reaches a stable state. Site measured data contain the information about the development and evolution of the surrounding rock, which directly reflects the state of stress and deformation. In this context, a monitoring index based dynamic comprehensive evaluation model for the deformation state of surrounding rock is set up, which overcomes the defects of a traditional evaluation method that only takes static evaluation at a certain time node. In this new model, evaluation indices are weighted dynamically based on the principle of maximum deviations, for which the indices′weights vary with its stability in certain time domains, and the larger the deviations,the larger the weights. Furthermore, the status and the trend of the variation speed of monitoring indices are taken into consideration by introducing the concept of an acceleration correction coefficient. And such concepts as time weight vector and time degree are also introduced to make sure the collected monitoring data are weighted properly according to different acquisition times (the weights of recent monitoring data are higher than those of long term monitoring data). Finally, the feasibility of the model is verified by a test section in the Zizhi Tunnel in Hangzhou. 2018 Vol. 55 (2): 56-64 [Abstract] ( 885 ) [HTML 1KB] [ PDF 2286KB] ( 1944 ) 65 Longitudinal Force Transfer Law of TBM Tunnel Segments HOU Gongyu1 YANG Yue1，2 LI Xiaorui1 CUI Yongke1 ZHOU Menghui1 In the process of TBM tunneling, the jacks produce reverse thrusts on the segment lining structure be? hind the shield tail, and the backfill layer around the outside of the segment structure produces a longitudinal shear force on them. Based on the construction of the TBM tunnel at the Shenhuataigemiao mine area, the whole variation process of intensity of the backfill layer is determined considering the time effect, and the shear resistance of the outer surface of the segment structures at different positions is further determined. Through force balance analysis, the affected scope of the jacks on segment structures, distribution rules of the longitudinal compressive stress of each segment lining ring and longitudinal shear stress of the lateral surface are studied. The results show that the reverse thrust transfer stops after the 17th segment ring; the thrust decreases in a nonlinear way between the 1st segment ring and the 17th segment ring; and the shear stress increases in a linear way between the 5th segment ring and the 17thsegment ring. 2018 Vol. 55 (2): 65-71 [Abstract] ( 931 ) [HTML 1KB] [ PDF 1514KB] ( 1924 ) 72 On Characteristics of Combined Support with TBM Segment and Pea Gravel JIANG Zhiyi WANG Mingnian YU Li LIU Dagang WU Shengzhi Under certain assumptions, a rigidity formula for a combined support composed of a segment and pea gravel is derived based on elastic strain theory for a thick-wall cylinder, proving a theoretical foundation for the application of the convergence-confinement method in the design of a shield type TBM segment structure. In order to further study the mechanical action of pea gravel backfilling layer in this combined support, three indexes (the stress sharing ratio Up, the deformation ratio of the pea gravel backfilling layer Uu, and the reduction coefficient of the combined support rigidity K) are defined. The case study and parameter analysis suggest that: 1) the grouted pea gravel backfilling layer could neither effectively bear the pressure nor absorb the deformation of the surrounding rock, and its main function is to transfer the pressure and deformation between the surrounding rock and segment lining; and2) there is a critical elastic modulus for the backfilling layer, which leads to abrupt changes to the combined support rigidity, while an increase of the backfilling layer′s thickness increases rigidity of the combined support. 2018 Vol. 55 (2): 72-77 [Abstract] ( 830 ) [HTML 1KB] [ PDF 1607KB] ( 1962 ) 78 3D Numerical Simulation for Predicting Water Inflow Volume in Deep and Long Tunnels JIANG Simin1 WANG Yaoming2 LI Xianwen3 ZHOU Nianqing1 Improper treatment of water inflow in tunnel construction might lead to serious destruction to the ecologi? cal and social environments, so it is necessary to accurately predict the volume of tunnel water inflow. Using the Mingtangshan tunnel as a case study, the watershed of surface water, boundary conditions, initial conditions, generalization of fault factors and groundwater simulation methods are analyzed. A finite-difference program MODFLOW is adopted to simulate the water inflow volume for the deep-buried, long tunnel in water-bearing bedrock fissures, and the impact of tunnel construction on the surrounding groundwater environment is assessed. The results show that the instantaneous water inflow volume at fault F7 is reduced to a stable value after 1 000 days, and the calculated stable water inflow volume is close to the measured value; the influence of tunnel excavation on the adjacent groundwater environment is mainly concentrated at the tunnel axis near the fault and locally on the ridge. 2018 Vol. 55 (2): 78-83 [Abstract] ( 963 ) [HTML 1KB] [ PDF 1853KB] ( 1945 ) 84 Deformation Characteristics of a Shallow Tunnel in Soft Rock REN Yuzhen DU Jun ZHANG Lunhua MAO Ning WU Yong A tunnel in soft rock is affected by construction disturbances and the deformation is very obvious, with tunnel collapse occurring if any mistake is made. Based on the branched tunnel A of the Lianyue tunnel in Xiamen and the geological conditions, the deformation characteristics of the shallow tunnel in soft rock is studied by numerical simulation and site monitoring. The results show that the order of deformation magnitude is: extruded displacement at the work face, crown settlement, surface displacement and convergence around the tunnel for a tunnel in soft rock by full-face excavation or the bench construction method. Surrounding rock deformation is divided into antecedent deformation in front of the work face and deformation at the rear of the work face, and the more unfavorable the surrounding rock the larger the antecedent deformation, with antecedent deformation occupying 10%-30% of the total deformation. Bench construction reduces the affected scope and deformation in front of the work face. More strict pre- reinforcement measures should be taken to control deformation caused by tunnel construction if more strict requirements for control of surrounding deformation of the soft rock tunnel are specified, in order to ensure the safety of tunnel construction and its surroundings. 2018 Vol. 55 (2): 84-90 [Abstract] ( 871 ) [HTML 1KB] [ PDF 2819KB] ( 1735 ) 91 Deformation Prediction for Surrounding Rock of a Deep Roadway Based on a Non-Equidistant GM(1,1) Model Group DENG Kangyu1 XUE Xinran2 ZHUGE Lianbing3 NIU Gang1 In order to overcome surrounding rock deformation problems for a deep roadway with different intervals, a full data non-equidistant GM(1,1) model and a partial data non-equidistant different-dimension GM(1,1) model are established, a 5-dimensional partial data non-equidistant GM(1,1) model with smallest relative error is obtained after error analysis, and displacements of the roadway roof and floor, as well as two sides, are predicted. The result shows the smaller the dimension, the smaller the average relative error of the non-equidistant GM(1,1) model within a certain range, making it a good method for predicting surrounding rock deformation of a roadway. 2018 Vol. 55 (2): 91-95 [Abstract] ( 884 ) [HTML 1KB] [ PDF 1356KB] ( 1600 ) 96 3D Numerical Simulation of Tunnel Blasting Vibration Laws under Axial Uncoupled Charge with Water Medium WANG Lichuan1,2 ZHANG Xuemin2,3 MA Mingzheng4 CHEN Junbo4 HUANG Qinwei2 HAN Zengzeng5 Based on the Qifengshan tunnel on the Zhengzhou-Wanzhou railway, field tests and the 3D dynamic nu? merical simulation method are adopted to study the propagation law of the blasting vibration of the cut hole under the conditions of axial uncoupled charge with the air medium and water medium. The attenuation features of the vibration velocity of the primary support at different distances and positions at the rear of the working face are compared and analyzed. The results show that: 1) the peak vibration velocity at the vault caused by upper bench blasting is the highest and the peak vibration value at the haunch is second highest, with the smallest vibration velocity occuring at the side wall under the same distance from the blasting center; 2) it′s not safe when the measurement results of side wall vibration are adopted to optimize the largest charge for upper bench cut blasting; and 3) for the case of the same total charge of the cut hole, the blasting vibration velocity under axial uncoupled charge with water medium is less than that of the air medium. 2018 Vol. 55 (2): 96-102 [Abstract] ( 932 ) [HTML 1KB] [ PDF 2674KB] ( 1966 ) 103 Study of the Invert Installation Issues for a Three-Lane Road Tunnel in Surrounding Rock of Grade Ⅲ1 WANG Keyi1 XU Dongqiang2 SUN Xiaoshan2 For a three-lane road tunnel in surrounding rock of grade Ⅲ, the concrete invert with the thickness of 45 cm should be installed according to the requirements specified in the Code for Design of Road Tunnels. However,as per the Guidelines for Design of Highway Tunnels the invert can be eliminated. Based on Shengjie expressway tunnel project, flat and inverted arch structures in grade Ⅲ1 surrounding rock are simulated and compared using finite-difference software. The results show that the differences between the vertical displacement, vertical stress and volume of the plastic zone of the two support structure patterns are within the scope of 5%; a flat arch structure can be used instead of an inverted arch for the three-lane tunnel in grade Ⅲ 1 surrounding rock, and the flat arch structure can meet the requirements of structure stability. 2018 Vol. 55 (2): 103-109 [Abstract] ( 944 ) [HTML 1KB] [ PDF 3351KB] ( 1857 ) 110 Fractal and Hydro-Chemical Characteristics of Microscopic Karst Morphology Based on Dissolution Experiments LI Cangsong1 WU Fengshou1 ZHAO Yanjie2 WANG Fugang2 CAO Yuqing2 In order to effectively prevent and control the geological hazards of water inflow and mud bursts in large and long karst tunnels, it is necessary to study the karst development law and the karst dissolution mechanism.Based on the existing research achievements, experimental devices are developed independently, and dissolution experiments are conducted for different working conditions. Based on a preliminary analysis of the results of the dissolution experiments, the micro-karst fractal characteristics are analyzed by fractal theory, and the hydro-chemical dynamic parameters and the hydro-chemical fractal characteristics of the solution are studied by hydro-chemical dynamic theory. The correlation between the fractal characteristics of karst morphology and the hydro-chemical dynamic characteristics is further explored. The study shows that the correlation between the hydrochemical-fractal evaluation index and the micro-karst fractal index is significant, which lays an experimental and theoretical foundation for understanding the karst groundwater mechanism and performing in-depth research on karst development evaluation techniques 2018 Vol. 55 (2): 110-120 [Abstract] ( 843 ) [HTML 1KB] [ PDF 4386KB] ( 1895 ) 121 Research on the Spatial Distribution Laws of Shear Force of Immersed Tunnel Segment Joints HU Zhinan1,2 BIN Shenglin3 XIE Yongli2 YANG Wanjing4 In order to study the spatial distribution laws of the shear force of shear keys on segment joints along the longitudinal and transverse directions, a 1∶4.69 large-scale segment joint model test is conducted on a settlement test platform by taking differential settlement as a control variable. A full-scale 3-D numerical simulation is carried out with consideration to the bilinear material characteristics of shear key rubber blankets and the contact effects between segment joints, as well as segment and soil. A comparison of the model test and numerical simulation results shows that: 1) there is an imbalance in the shear force distributions along the transverse direction, and for the design it is unreasonable to distribute shear force equally or distribute shear force according to the contacting area between the shear key tenon and shear key groove; 2) the shear force of a segment joint is transferred vertically in the form of the left part of a quadratic curve with an upward opening, and the attenuation rate of the shear force increases with an increase of the differential settlement; and 3) the shear force′s influential scope of the segment joint equals 3 segments for the vertical differential settlement and 4 segments for the longitudinal differential settlement. 2018 Vol. 55 (2): 121-126 [Abstract] ( 891 ) [HTML 1KB] [ PDF 2211KB] ( 1725 ) 127 Model Test of Strain Development in Cement Soil under Subway Loading CHEN Fangmin1 DING Zhi2 LI Shaolang2 ZHANG Mengya2 ZHOU Lianying2 Cement soil reinforcement is widely used in metro construction in soft clay zones since it can effectively improve foundation strength and reduce settlement. Due to the initial consolidation of the compound soils caused by construction disturbance, the strain development and long term deformation is affected under the function of cyclic loading. A dynamic test is conducted on cement soil by means of an indoor GDS dynamic triaxial test, and the effects of the cement mixing ratio and the initial consolidation degree on strain development are analyzed. Based on the research and experiment results, a strain development model considering the cement mixing ratio and initial consolidation degree is established. The experiment results show: 1) the lower the initial consolidation degree, the faster the strain development rate; 2) when the initial consolidation degree is low, the strain development rate of the cement soil with a low cement mixing ratio is high; and 3) the strain development of cement soil is in a non-failure form, and it is approximately a linear relationship between the dynamic strain of the cement soil and the logarithm lgN of cyclic times under different consolidations. 2018 Vol. 55 (2): 127-133 [Abstract] ( 822 ) [HTML 1KB] [ PDF 2580KB] ( 1663 ) 134 Experimental Test of Support Effect of Different Tunnel Support Systems TIAN Zhiyu1 LIN Guojin1 YANG Feng1 JIANG Yi2 WANG Bo2 In order to study the support effects of different tunnel support systems, a 1∶30 model test is conducted to study the bearing capacities of different support systems based on a two-lane highway tunnel in surrounding rock of grade Ⅳ by using an external load with crown displacement of 20 mm (equal to 60 cm for the real tunnel) for the ultimate bearing capacity of the surrounding rock-support system. Test results show that: 1) the ultimate bearing capacity is much higher than that of an unlined tunnel for the conditions of surrounding rock + system anchor bolt +shotcrete, surrounding rock + shotcrete, or surrounding rock + system bolt, and the percentages of the bearing capacity increases are 56.8%, 48.3% and 47.8%, respectively, regarding the above three support system; 2) the support effect of system bolts + shotcrete is the best, followed by shotcrete and system bolts, with little difference between the support effects of system bolts and shotcrete; and 3) the combined support of system bolts and shotcrete has not reached the effect of 1+1=2 or ＞2, and it can be optimized. 2018 Vol. 55 (2): 134-139 [Abstract] ( 866 ) [HTML 1KB] [ PDF 2427KB] ( 2102 ) 140 Multi-Scale Comprehensive Detection Technique to Identify Water Burst Causes in Karst Tunnels QIN Cheng1,2 ZHANG Yudong2 LI Hao2 DENG Chunwei2 Water inflows occur frequently during tunnel construction in water-rich Karst areas, thereby endanger? ing tunnel construction. Accurate and rapid analysis of water bursts are the premise of and key to water burst treatment. Based on the concept of multiple scales, a multi-scale comprehensive detection technique for identifying the causes of water bursts in karst tunnels is proposed, using the Huayingshan tunnel on the Yuguang expressway as an example. Based on hydrological dynamic observation data before and after water burst in light of the time scale, a comprehensive analysis is conducted from a point (working face) to a plane (area) in light of the spatial scale; it is determined that an interlayer fissure at 3.0-7.6 m in front of the working face connects the horizontal cyclic karst water within the elevation scope of +180 -+420 m, which causes water inflow in general water supply conditions. This conclusion provides a basis for the treatment measure of radial grouting after tunnel excavation. 2018 Vol. 55 (2): 140-145 [Abstract] ( 820 ) [HTML 1KB] [ PDF 3159KB] ( 1639 ) 146 Relative Coordinate Measuring System Applied in the Geological Advanced Prediction with Tunnel Reflection Tomography LIU Zhaoyong WANG Yilei YANG Wei Tunnel reflection tomography (TRT) is a brand new method of tunnel geological prediction and it is play? ing an increasingly important role in tunnel geological prediction. As for the traditional TRT technique, a tunnel survey model is set up based on the geodetic coordinate system, which is time consuming onsite and affects construction progress. Based on an application of the relative coordinate measuring system in the geological advanced prediction of a power station tunnel, the results of geological prediction using geodetic coordinate measuring system and relative coordinate measuring system are compared and analyzed. The results show that the prediction effects of the two measuring systems are the same, with the one using the relative coordinate measuring system having better consistency with actual conditions. 2018 Vol. 55 (2): 146-151 [Abstract] ( 777 ) [HTML 1KB] [ PDF 2627KB] ( 1797 ) 152 Array Horizontal Sound Probing (HSP) Technology for Tunnel Geological Prediction LIU Jibin1 CAI Jianhua1 ZHANG Fang2 PENG Yue1 Array horizontal sound probing is a new geological prediction method that can detect adverse geologic bodies (belts) based on energy excited by hammers or electric sparks during tunnel construction. Its technical advantages are summarized by a description of its application in prediction of karst caves, joint-dense fracture zones and fault zones. An introduction to the basic principles, data processing software, instrumentation and test layouts for the array horizontal sound probing method is presented. 2018 Vol. 55 (2): 152-157 [Abstract] ( 854 ) [HTML 1KB] [ PDF 2495KB] ( 1824 ) 158 Thickness Detection for Reinforced Concrete Inverts of Railway Tunnels ZHAO Qianjin Nondestructive testing of the thickness of a reinforced concrete invert of a new railway is carried out using the broadband multi-channel transient Rayleigh wave method. A contrastive analysis of the key parameters of optimal settings regarding the geophone, earthquake source, zero-offset and group interval is conducted through an experiment. The global optimal method is used to invert the Rayleigh dispersion curve to avoid the problem of the local optimal solution of objective function and reduce the accuracy requirement of the initial model. Engineering practices show that the results are consistent with the core sampling data and effectiveness of the detection method is verified. 2018 Vol. 55 (2): 158-163 [Abstract] ( 955 ) [HTML 1KB] [ PDF 1798KB] ( 1819 ) 164 Construction Techniques and Safety Analysis for a Deep Vertical Shaft and Vertical Shaft Shifting to Main Tunnel AN Yonglin1 OUYANG Pengbo1 PENG Limin2 WU Bo3 HU Wenxuan1 Considering the geological conditions and problems encountered in construction, the vertical shaft con? struction technique and construction program for vertical shaft shifting to the main tunnel are proposed based on the No.2 shaft of the Liuyang river tunnel, for which the top-down construction method is adopted for the vertical shaft;an enclosed circular horizontal force- bearing structure with great stiffness is formed by the retaining piles, shotcrete-bolt support and lining; and the construction of the vertical shaft shifting to the main tunnel and the vertical shaft construction at the bottom are performed simultaneously, solving the problem of a high operating platform during main tunnel excavation. A simulation model is established, and the safety of this construction method is analyzed considering the onsite monitoring results. Implementation result shows that the ground displacement, the force on initial support and secondary lining of the vertical shaft and the force on the initial support of the main tunnel meet the safety requirements, and the large bending moments of the initial support of the main tunnel are mainly concentrated near the tunnel arch spring during the construction of the vertical shaft shifting to the main tunnel, with the maximum bending moment increasing with excavation. 2018 Vol. 55 (2): 164-173 [Abstract] ( 977 ) [HTML 1KB] [ PDF 5895KB] ( 1761 ) 174 Construction Control Technology for an Urban Subway Shield Tunnel underneath an Operational Railway LI Jun1 LEI Mingfeng2 LIN Dayong2 With the large-scale construction of urban rail transit, it′s very common to approach various types of construction works, which poses great construction challenges. A study on the construction control of shield tunneling beneath an existing railway is conducted based on the running tunnel from Tujiachong station to Tiedaoxueyuan station of Changsha Metro Line 1. Construction control programs such as rotary pile reinforcement and overhead line reinforcement (longitudinal lifting of the existing railroad using cantilevers of I-beams) are proposed, and a numerical simulation is carried out. The results indicate that the deformations of the subgrade and existing railroads can meet the requirements of railway operation safety when the above construction control measures are used and that the proposed control measures are effective and reliable. 2018 Vol. 55 (2): 174-179 [Abstract] ( 840 ) [HTML 1KB] [ PDF 2668KB] ( 1870 ) 180 On Configuration and Optimization of Cutting Tools for the Supper-Large Shield Passing through the Upper-Soft and Lower-Hard Stratum ZHANG Yaguo1 YAO Zhanhu2 With the development of domestic highway, railway and urban rail transit projects, the super- large shield has been widely used in the underwater tunnelling, with the difficulty of reasonable selection and configuration of the cutting tools for the shield used in underwater tunnels. Based on the Weishan Road river-crossing project in Najing, the primary design concept of cutting tools for the shield machine is introduced, the mechanism of abnormal wear of cutting tools in upper-soft and lower-hard stratum with abundant quartz is analyzed, the life time of cutting tools is prolonged by optimizing the type of disc cutter and main cutting tools, and the times of cutter replacement by hyperbaric intervention are reduced, increasing the adaptability and durability of cutting tools. 2018 Vol. 55 (2): 180-188 [Abstract] ( 843 ) [HTML 1KB] [ PDF 3906KB] ( 1675 ) 189 On Surface Settlement during Subway Station Construction Using the Center Drift Excavation Method Based on the mined construction of Taoranqiao station of Beijing metro line 14, the law of surface settle? ment induced by construction procedures of the center drift excavation method is analyzed and the experience is summarized by means of geometrical leveling. The results show the settlement mainly undergoes five stages, i.e., 1) settlement stage Ⅰ in primary support construction of the pillar pilot tunnel, 2) settlement stage Ⅱ in secondary lining construction of the central pilot tunnel, 3) settlement stage Ⅲ in construction of the floor and buckling arch of the central pilot tunnel, 4) settlement stage IV in construction of the primary support at the side pilot tunnel, and 5) settlement stage V in secondary lining construction. The settlements of phase I and phase IV account for the largest proportion of the final settlement; the curve of final settlement is axisymmetric, with the central line of the central pilot tunnel to be the axis of asymmetry. 2018 Vol. 55 (2): 189-193 [Abstract] ( 730 ) [HTML 1KB] [ PDF 3906KB] ( 1509 ) 194 Key Technology for Cutting a Pile Group in Front of a Shield in Soft Plastic Flow Strata by Mined Excavation Method SU Ming In the first instance of cutting a pile group in front of a shield using the mined method in a soft plastic flow stratum, the alternative construction in terms of mined excavation and pile cutting is very risky and difficult.Based on a shield tunnel section from the Daminglu station to the Mingfa Square station, which passes underneath the Jiagang street box culvert, and with respect to the characteristics and restricted conditions of the pile group and shield-driven tunnel, it is recommended that the upper tunnel section is excavated by mined method and enclosed at first, and then the shaft is constructed followed by the other lower tunnel section, as well as a pile cutting technique with combination of the splitter and pneumatic pick is adopted. By using these key construction techniques,construction period is shortened and some risks are eliminated, such as: large soft soil deformation due to excavation, large vibrations in pile cutting, and the work face collapse due to long exposure time. 2018 Vol. 55 (2): 194-200 [Abstract] ( 812 ) [HTML 1KB] [ PDF 3069KB] ( 1854 ) 201 Cause Analysis and Treatment Measures of a Collapse Event for a ShallowBuried Mountain Tunnel in Soft Rock ZHANG Xiaojin1 ZHONG Haozhong2 ZHANG Chao3 Based on a shallow-buried mountain tunnel in soft rock, the causes of a tunnel collapse in soft rock are analyzed and summarized. It is concluded that: 1) the index of allowed blasting vibration velocity of 10 cm/s is too large for soft rock mountain tunnels, and repeated blasting vibrations will exceed the tolerance value of the rock blasting vibration during excavation by steps; and 2) the frequency of monitoring and measuring should vary with changes to the tunnel construction method, which is necessary to establish a dynamic warning system for tunnel collapses. The blasting vibration velocity of a mountain tunnel in soft rock can be controlled more effectively using the general principles of stabilizing the collapse cavity, filling the collapse cavity, advance grouting of the collapse cavity and cautious passage. The blasting vibration velocity can be reduced by using different arrangements of drill holes at various sections, simultaneous initiation and millisecond delay initiation, which will facilitate rapid passage in the soft rock section. 2018 Vol. 55 (2): 201-207 [Abstract] ( 871 ) [HTML 1KB] [ PDF 3745KB] ( 1881 ) 208 Common Construction Quality Problems for Railway Tunnel Linings GONG Quhong As the last working procedure of tunnel construction, tunnel lining quality directly affects the functional use of the tunnel. Common quality problems related to tunnel linings are summarized, the causes of problems are analyzed and corresponding treatment and countermeasures are presented. 2018 Vol. 55 (2): 208-211 [Abstract] ( 854 ) [HTML 1KB] [ PDF 1104KB] ( 2195 )

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