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Quick Search     Advanced Search MODERN TUNNELLING TECHNOLOGY   2020 Vol.57 Issue.2 Published 2020-04-25 1 Progress in Research of the Rockburst Hazard WEI Xinjiang1,2 CHEN Taotao2 WANG Xiao2 YU Xingfu1 ZHOU Lianying1 In order to clarify the mechanism of rockburst and reduce this hazard, the definition, classification, re? search methods, characteristics, forming conditions, prediction methods and prevention and control measures of rockburst are elaborated systematically. On the basis of previous research work and engineering practice both at home and abroad, the temporal and spatial characteristics of rockburst and the lithological characteristics of occurrence location of rockburst are analyzed, reasonable classification and brief introduction of the existing research and prediction methods of rockburst are conducted, the defects of some existing research methods and the development trend of rockburst prediction are pointed out. The comprehensive research shows that: there is no uniform standard for rockburst classification currently, and their research methods are improvable; the rockburst prediction methods applicable to most engineering projects are still in exploration and improvement; effective measures to prevent and control rockburst need to be optimized and further studied. 2020 Vol. 57 (2): 1-12 [Abstract] ( 852 ) [HTML 1KB] [ PDF 1126KB] ( 2898 ) 13 Machine Recognition Method of Tunnel Lining Voids Based on SVM Algorithm QIN Hui1 TANG Yu2 XIE Xiongyao3, 4 WANG Zhengzheng1 Ground penetrating radar (GPR) is one of the most effective detection methods for tunnel lining voids. However, the difficulties in data explanation are always the key to restrict its wide application. Based on support vector machine (SVM) algorithm, a set of machine recognition method of GPR image for tunnel lining voids is established. This method includes pre-processing of GPR data, feature extraction and SVM recognition. Firstly, the GPR image needs to be preprocessed by time-zero correction, filtering, migration and gain and so on to improve the signal-noise ratio (SNR). Secondly, each time-domain trace of GPR image is segmented and three statistics, namely variance, mean absolute deviation and fourth-order moment are extracted from the segmented signal as image features. Finally, the SVM model is trained by using the known data, and the data from a numerical simulation and a model experiment are used to test the trained SVM model. The results show that the proposed method can not only accurately recognize all voids in the tunnel lining and surrounding rock, but also accurately estimate the cover depths and lateral ranges of the voids. 2020 Vol. 57 (2): 13-19 [Abstract] ( 871 ) [HTML 1KB] [ PDF 2251KB] ( 1796 ) 20 Prediction of Tunnel Coal and Gas Burst Hazard Based on Nonlinear Support Vector Machine ZHU Baohe ZHENG Bangyou DAI Yijun LIU Can In order to effectively predict the risk of coal and gas outburst in a coal seam disclosed section of Taozi? ya tunnel, nine key factors affecting coal and gas burst are determined in light of the comprehensive hypothesis about coal and gas burst and the Regulation of Preventing Coal and Gas Burst. Because of the complex nonlinear mapping relationship between evaluation factors and risk degree of burst, a nonlinear support vector machine (SVM) method is adopted to predict the risk of tunnel coal and gas burst. The specific parameters of all training samples are determined, a comparison of risk prediction of coal and gas burst is conducted to the selected training samples by single index method, optimal classification decision function and the MATLAB SVM Toolbox software based on the actual situation. The prediction results of the two measuring points of N7 and N8 show that there are risks of coal and gas outburst in the disclosed coal section of Taoziya tunnel, so it is necessary to take relevant measures to prevent coal outburst. 2020 Vol. 57 (2): 20-25 [Abstract] ( 956 ) [HTML 1KB] [ PDF 1010KB] ( 1642 ) 26 Prediction Model of TBM Net Advance Rate Based on Parameters of Rock Mass and Tunnelling YAN Changbin JIANG Xiaodi Net advance rate is a main evaluation index of TBM construction speed and it has something to do with the mechanical behavior of surrounding rocks and tunnelling parameters. Taking the double shield TBM adopted in the water diversion tunnel of Lanzhou water source construction project as the research background, a correlation analysis on single factor between TBM net advance rate and relevant influential parameters is conducted in terms of uniaxial compressive strength, tensile strength, modulus of deformation, Poisson′s ratio and CAI value of rock wear resistance as well as cutterhead thrust and rotation speed, and the corresponding fitting formula is obtained based on the field data. A prediction model of TBM net advance rate is established by multivariate nonlinear regression method in light of a correlation among TBM net advance rate, rock mass properties and tunnelling parameters. By comparing the measured TBM net advance rate and the predicted results of the water conveyance tunnel in Lanzhou water source construction project, the rationality of prediction model for TBM net advance rate is verified. The research results show that: (1) in complex and various geological conditions, the TBM net advance rate has a negative correlation with uniaxial compressive strength, tensile strength, modulus of deformation, CAI value of rock wear resistance, thrust and rotating speed of cutterhead while it has a positive correlation with the Poisson's ratio; (2) the moisture state has certain effect on CAI value of rock wear resistance, and there is a closer correlation between CAI value of rock wear resistance and TBM net tunneling rate under saturation condition; (3) this multivariate nonlinear regression prediction model with a high precision can be used to estimate the TBM net advance rate under similar geological conditions. 2020 Vol. 57 (2): 26-33 [Abstract] ( 957 ) [HTML 1KB] [ PDF 2019KB] ( 1812 ) 34 Research of Shield Big Data Preprocessing ZHANG Longguan1 DUAN Wenjun1 ZHUANG Yuanshun1 ZHANG Zhonghua1 LIU Suimei1 ZHANG Feng2 During the construction of shield tunnel, reasonable determination of operating parameters of shield ma? chine is significant regarding process control to ensure that shield machine can drive at a certain speed. Aiming at the unsatisfactory prediction results due to the lacking of systematic data analysis and processing of existing prediction method for shield parameters, a full set of new data preprocess flow is proposed. This new preprocess flow is divided into two stages of data analysis and data processing, the first stage involves feature selection by analyzing principal component and Pearson correlation coefficient, and the second stage involves data smoothing by interpolation smoothing and convolution smoothing. After processing of original data, the data with more obvious features and higher valued can be extracted from the massive data generated by the shield machine. Contrast experiment is conducted by selecting real data sets, and the result shows that the proposed data preprocessing flow can effectively improve the accuracy of shield parameter prediction model. 2020 Vol. 57 (2): 34-41 [Abstract] ( 884 ) [HTML 1KB] [ PDF 2068KB] ( 1971 ) 42 Design and Implementation of the Tunnel Overbreak and Underbreak Detecting Information System LIAO KAI1 LI LIN2 WU JIAN1 Aiming at the detecting of key factors to control tunnel overbreak and underbreak and evaluation of blasting effect, a drillhole detecting rod is developed, and the APP and B/S version information management platforms for tunnel overbreak and underbreak are developed. Connecting drillhole detecting rod with total station by means of the APP, the information of blasting hole 3D angle, position and tunnel profile after blasting are detected,calculated and transmitted, realizing detecting of blasting process and effect evaluation of blasting profile and providing reference for the following adjustment of blasting parameters and control of tunnel overbreak and underbreak. 2020 Vol. 57 (2): 42-48 [Abstract] ( 902 ) [HTML 1KB] [ PDF 4420KB] ( 1787 ) 49 Quality Management Practice of Tunnel Secondary Lining Construction of Chongqing Section of Zhengzhou-Wanzhou High-speed Railway ZHANG Jun1 WANG Minghui1，2 XIANG Daoyin1 ZHANG Qiao1 JIANG Shuping1 LIU Weibang1 Quality of the tunnel secondary lining is related to operation safety of railway. Based on secondary lining construction of the Chongqing section of Zhengzhou-Wanzhou high-speed railway, the construction installation equipment, construction technology and management measures are optimized aiming at the defects of lining quality,especially a series of improvement measures are taken regarding the flatness of primary support, laying of waterproof board, concrete distribution of trolley, quality of concrete vibration, monitoring of vault void, treatment of construction joint, waterstop installation, realizing effective management of construction of secondary lining and standardizing operation standards, improving the construction quality and achieving good construction results. 2020 Vol. 57 (2): 49-54 [Abstract] ( 879 ) [HTML 1KB] [ PDF 1926KB] ( 2184 ) 55 New Progress in Grouting Technology for Underground Works QIN Pengfei Grouting is a key technique for anti-seepage and reinforcement in the construction of civil engineering, water conservancy and mining engineering. Based on the research literatures concerning grouting techniques both at home and abroad, theoretical achievements of "percolation effect" and "time-space variability of viscosity" of the granular slurries like cement are summarized, application status and development prospect of new materials of nonaqueous reactive polymers and CW epoxy resin as well as microbial bacterial liquid are discussed, and the breakthrough of numerical simulation on mesomechanics is introduced. 2020 Vol. 57 (2): 55-60 [Abstract] ( 862 ) [HTML 1KB] [ PDF 1947KB] ( 1893 ) 61 Structure Design and Parameter Analysis of a Large-section Sea-crossing Shield Tunnel ZHANG Jinlong1 GOU Changfei2 YE Fei3 In order to obtain a refined and rational structural design method of large-section shield tunnel, the structure selection and structure parameters are analyzed based on a large-section sea-crossing shield tunnel. The selection method of segment structure is analyzed in terms of segment erection method and segmentation, segment connection method and segment material; the numerical simulation calculation methods of segment cross-section and tunnel longitudinal structure and its applicability are analyzed in terms of selection of calculation model, determination of calculation conditions and loads, selection of parameters and calculation results. The results show that the internal force distributions in the calculation of segment cross-section by the beam-spring model or homogeneous ring model are not the same, the design should consider the main calculation result while the latter should be used for recheck in actual design; it is easy to produce large longitudinal bending moment and shear between segment rings of the shield tunnel located in the place where the foundation changes violently, and it can be solve by setting deformation joints, crushing hard rock block and so on. 2020 Vol. 57 (2): 61-67 [Abstract] ( 854 ) [HTML 1KB] [ PDF 3875KB] ( 1512 ) 68 Preliminary Study on Design Method of Waterproof Curtain Considering Ecological Environment Effect ZHENG Bangyou1 CHEN Fudong2 LEI Mingfeng2 WU Zhigang1 PENG Cheng1 YAO Yu1 When a tunnel passes beside a large water conservancy project, the waterproof curtain between them is of? ten designed as a structure with a certain opening, the size of the opening is directly related to its waterproof capacity and its influence on the surrounding groundwater environment. Based on practical engineering, the influence of opening size (buried-depth and density) on dewatering effect and recovery time of the water level is discussed by numerical simulation. The results show that: (1) it can be divided into three zones regarding the impact of opening size on drawdown, i.e. non-affected zone, gradual changing zone and abrupt changing zone; it can be divided into two zones regarding the impact of opening size on recovery of water level, i.e. gradual changing zone and abrupt changing zone; (2) the larger of buried depth of waterproof curtain, the better the dewatering effect but the longer of water level recovery time. In light of dewatering effect, water level recovery time, construction cost and so on, the selection of design parameters of waterproof curtain should be within the gradual changing zone; (3) based on its hydrogeologi? cal conditions, the design parameters of waterproof curtain are proposed, that is to say the depth and density should be within 14-20 m and 0-0.8 respectively, and the validity is verified by engineering app 2020 Vol. 57 (2): 68-72 [Abstract] ( 910 ) [HTML 1KB] [ PDF 1991KB] ( 1529 ) 73 Application of Electrostatic Precipitation Technology to Shengli Tunnel in Tianshan GUO Zhijie1,2 ZHANG Cancheng1,2 Ventilation scheme for the super-long highway tunnel has direct effect on construction cost, operation safety and efficiency. The adoptability of a combination of electrostatic precipitation and ventilation of blowing and exhausting in the super-long tunnel is analyzed, and the advantages and disadvantages of this proposed ventilation scheme are discussed. The results show that this scheme is easy to operate and economic in terms of the cost of civil engineering construction, and especially the polluted air can be purified at site, which is favorable for protecting atmospheric environment and reducing ambient pollution. 2020 Vol. 57 (2): 73-79 [Abstract] ( 843 ) [HTML 1KB] [ PDF 1913KB] ( 1769 ) 80 Six-stage Ventilation Techniques for the Large and Long Gas Tunnel with Trackless Transportation and Advance Construction of Parallel Adit YAN Su1，2 Reasonable ventilation design is significant to reduce the risk of serious gas disaster when a tunnel pass? es through the coal measure strata with a long distance. Aiming at the ventilation problem of the of Laofangzi tunnel on Chengdu-Guiyang high-speed railway passing through gas-rich stratum, a six-stage ventilation scheme with forced ventilation at the first and second stage and gallery ventilation at the later stages, which can be adjusted with the construction progress, is designed. The simulation analysis is conducted by Fluent software, and it is verified with practical measured results. The results show the effect of the fourth stage ventilation is the poorest and most unfavorable condition; the gas concentration during the fourth stage ventilation is smaller than the threshold of 0.5 % and the max. gas concentration during the other ventilation stages is 0.08 %, meeting the requirements of specification. It can be seen that the effect of six-stage ventilation scheme is positive. 2020 Vol. 57 (2): 80-85 [Abstract] ( 838 ) [HTML 1KB] [ PDF 2419KB] ( 1695 ) 86 Analysis of Mechanical Behaviors and Deformation Characteristics of the Loess Tunnel Reinforced by Lime-soil Compaction Piles SHAN Chao1,2 GAN Lu2,3 WANG Yadong2 CAO Xiaoyong1,2 LAI Jinxing2 The loess in Lanzhou is characterized by severe collapsibility, high compressibility and dynamic vulner? ability due to its loose texture, large void ratio and low strength, and it′ s easy to cause failures at tunnel floor and building foundation whenever the positive pressure or pore water pressure increase. Aiming at the deformation of a large-section loess tunnel in Lanzhou, reinforcement is conducted by the lime-soil compaction pile, and a three-dimensional numerical method is adopted to study the characteristics of deformations and mechanical behaviors before and after reinforcement with lime-soil compaction piles. The results show that before reinforcement with limesoil piles the heaving occurs and gradually increases along with the direction of excavation, subsidence occurs at arch spring, the maximum displacement occurs at the center of tunnel bottom; after reinforcement with lime-soil piles, the pile axial force, pile stress and pile displacement are small on both sides and large in the middle in horizontal direction, and they increase gradually along with the excavation direction, the piles bear most of the load produced by tunnel excavation, and the force and deformation at tunnel bottom decrease, and the displacement at tun? nel floor is reduced by 32%-34.4%, which shows the lime-soil compaction pile can improve the bearing capacity and resistance to deformation at tunnel bottom of the loess tunnel. 2020 Vol. 57 (2): 86-95 [Abstract] ( 949 ) [HTML 1KB] [ PDF 4848KB] ( 1745 ) 96 Study on Mechanical Effect of Steel Arch of Soft Rock Tunnel Based on Structural Characteristic Curve ZHAO Wei1,2 LEI Shengxiang1,2,3 XIAO Qinghua1,2 LIU Jifeng4 CHEN Qiaofeng1,2 In light of that traditional anchor-shotcrete support is difficult to adapt to large deformation of soft rock tunnel, the steel arch and shotcrete supporting structure is divided into two work stages: individual work stage of steel arch and combination work stage of steel arch and shotecrete. The mechanical behaviors and the mechanical effects of solid web steel arch and spatial steel truss arch in individual work stage are analyzed by using SAP2000 finite element program. Considering the material nonlinearity and geometric nonlinearity, the ultimate bearing capacity and deformation capacity of steel arches under different support conditions are studied. The results show that: (1)It is feasible for the steel arch to work alone as a support stage; (2) lateral support and restraint of arch springing have a decisive influence on action effect of the solid web steel arch; (3) the overall stiffness of the spatial steel truss arch is higher than that of the solid web steel arch, and it is less affected by lateral support; (4) the methods to im? prove the bearing and deformabilities of steel arch are proposed to provide more time and space for the implementation of shotcrete and other support measures. 2020 Vol. 57 (2): 96-103 [Abstract] ( 863 ) [HTML 1KB] [ PDF 2294KB] ( 1766 ) 104 Influence of Earth-Rock Interface Height on Safety of Primary Support Structure of the Shallow-buried Loess Tunnel YU Li1,2 WANG Zhuhong1,2 ZHANG Yiteng1,2 JIANG Yongtao1,2 Wang Mingnian1,2 In order to understand the influence of earth-rock interface height of the shallow-buried loess tunnel on safety of primary support structure, the effect of earth-rock interface height and position on safety of primary support is studied by numerical simulation based on the Linxian tunnel. The results show that: the earth-rock interface results in sudden change of safety factor of the primary support structure and the distribution of safety factor is asymmetric when the interface is inclined. Under the same buried depth, the asymmetric pressure above the earth-rock interface decreases while the asymmetric pressure below the earth-rock interface increases with downward movement of the earth-rock interface. Under the same interface depth, the asymmetric pressures of the left and right sections of the primary support increase with the increase of the buried depth. When the earth-rock interface is located in upper heading,middle heading and lower heading, and the interface inclination is 10°, the load can be calculated by increasing the load by 20% on the left side of tunnel or reducing resistance coefficient by 20% on the right side of tunnel. 2020 Vol. 57 (2): 104-109 [Abstract] ( 810 ) [HTML 1KB] [ PDF 1487KB] ( 1816 ) 110 Safety Evaluation of Support Structure of the Tunnel Excavated by Mining Method with Arching and Backfilling GUI Dengbin1，2 TONG Jianjun1,2 WANG Mingnian1,2 DENG Kun1,2 ZHAO Siguang1,2 Based on the Jingshengwu tunnel of the Quzhou-Jiujiang railway, the construction steps of mining meth? od with arching and backfilling are introduced, an calculation formula for the rock load sharing proportion of the arching structure and primary support arch structure is deduced by elastic theory, a mechanical model of surrounding rocks at sidewall is established by ultimate equilibrium theory, and a formula for calculating additional surrounding rock pressure on the sidewall of primary support is derived, the internal force and safety factors of arching structure and primary support structure are calculated by establishing a load-structure model, and the safety of arching structure and primary support structure is evaluated. The results show that: rock load sharing proportion of primary support is related to elastic modulus and thickness of arching structure and primary support structure, the rock load sharing coefficient of primary support of Jingshengwu tunnel is about 30%; the vertical pressure at arch spring of arching structure causes the rocks above sidewall slide along the fracture surface and horizontal additional surrounding rock pressure is produced at the upper sidewall of primary support; the arching structure and primary sup? port structure of Jingshengwu tunnel are in safe state, the safety of primary support slightly decreases with the increase of rock load sharing factor. 2020 Vol. 57 (2): 110-116 [Abstract] ( 725 ) [HTML 1KB] [ PDF 2252KB] ( 1448 ) 117 Study on Structural Stability of Mined Large-Span Tunnels Constructed by Two Arch-Cover Methods in Upper-Soft and Lower-Hard Rock Stratum of Qingdao Area SHI Yujing As for the upper-soft and lower-hard rock stratum with larger stiffness differences in vertical depth, the arch-cover method is developed based on the cover-excavation method and double side heading method. The archcover method includes the arch-cover method with double-layer primary support and the arch-cover method with secondly lining. Taking a mined large-span station of Qingdao metro as an example, a numerical analysis on structural stability of the tunnel constructed by two arch-over methods is conducted in light of the characteristics of the upper-soft and lower-hard rock stratum. The results show that: (1) as for the arch-cover method with secondary lining, when tunnel is constructed at a safe strut dismantling distance of 9 m in longitudinal direction, the "spatial stiffness effect" of shed protection of outer primary support can′ t make up for the "arch" effect of arch-cover, the construction technology of arch-cover method with double-layer primary support is more conducive to tunnel deformation control; (2) the arch-cover structure has significant bearing and protection functions during excavating the lower part of the tunnel, however, the plastic damage of rock mass at arch springing is more obvious during the construction by arch-cover method with secondary lining under the same geological conditions, in other words, the arch springing of secondary lining requires higher strength and rigidity of the rock foundation; (3) the internal force con? trol positions of structure by arch-cover method with double-layer primary support are spandrel and arch springing,and the control position is the arch springing for the structure by arch-cover method with secondary lining, the control internal force of arch springing of the latter is about 1.56 times of that of the former, the "beam" effect of the former is more obvious while the "foot" effect of the latter is more obvious; (4) from the perspective of safety, it is suggested that the arch-cover method with double-layer primary support should be adopted. 2020 Vol. 57 (2): 117-126 [Abstract] ( 780 ) [HTML 1KB] [ PDF 5316KB] ( 1761 ) 127 Study on Slope Support Instability Evaluation for Open Cut Tunnel Section in Seasonal Frozen Area Based on FLAC3D QIN Jianchun1 FANG Zhijie1,2 XING Jingzhi1 MO Man1 CHEN Cheng1 In order to study the law of freeze-thaw induced deformation of the slope support of open cut tunnel sec? tion in seasonal frozen area under the coupling effect of stress field, temperature field and moisture field, the FLAC3D finite difference software is used to analyze the failure of slope support with shotcrete and anchor bolts for the open cut tunnel section of the Jiaoxi tunnel. The result shows the temperature field and excavation slope are the important factors affecting slope stability; the deformations of slope support are different under different temperatures but the deformation law is the same; the largest deformation induced by frost heave and thawing settlement occurs at the slope shoulder and the deformation fluctuates greatly near soft rock and soil; the optimal excavation slope is 1∶1 in terms of satisfying stability and economic rationality under freeze-thaw effect. The research results are consistent with the measured ones, which shows the instability evaluation model can predict the safety state of slope support of open cut tunnel accurately and scientifically. 2020 Vol. 57 (2): 127-133 [Abstract] ( 753 ) [HTML 1KB] [ PDF 3054KB] ( 1524 ) 134 Structure Safety Analysis of a Newly Built Expressway Crossing over an Operating High-speed Railway Tunnel XIAN Zhengping The line intersection will change the mechanical behavior of existing tunnel during the construction of an expressway crossing over an operating high-speed railway tunnel and endanger the operation safety of the railway tunnel. Based on a practical engineering case, a numerical simulation analysis on the overcrossing intersected section is conducted by MIDAS GTS/NX finite element software, and the changes of mechanical behavior and safety factors of high-speed railway tunnel are studied before and after the load applying of expressway. The results show that the amplitude of stress increase and safety factor decrease of existing tunnel are small after load applying of expressway, and it has a little effect on safety of tunnel structure. 2020 Vol. 57 (2): 134-140 [Abstract] ( 735 ) [HTML 1KB] [ PDF 4157KB] ( 1373 ) 141 Research on Ground Deformation Induced by Pipe Jacking Construction in Sandy Gravel Stratum HE Lei1 LIU Huaqing1 CUI Ming jie2 WU Bing3 This paper discusses the deformation of ground surface induced by pipe jacking construction in sandy gravel stratum. Based on the existing theoretical calculation methods of deformation in granular soil, theoretical calculation and analysis of ground deformation in sandy gravel stratum induced by pipe jacking construction in an electric power tunnel are conducted; the rules of ground deformation induced by pipe jacking construction in sandy gravel stratum are obtained through theoretical analysis and field monitoring; a formula for calculating the width coefficient of settlement trough induced by pipe jacking construction in sandy gravel stratum is put forward by using the programming solver based on the existing theory and monitoring data. The results show that ground loss is the main factor causing ground settlement and the dynamic changes of ground loss during pipe jacking must be considered in settlement calculation; the proposed formula can be used to calculate the ground settlement induced by pipe jacking construction in sandy gravel stratum. 2020 Vol. 57 (2): 141-148 [Abstract] ( 781 ) [HTML 1KB] [ PDF 3620KB] ( 1941 ) 149 Numerical Simulation of the Propagation Law of Blast-induced Vibration in the Tunnel under Frequent Blasting YE Hongyu1 YANG Xiaolin1,2 ZHUO Yue3 In order to reveal the law of propagation and attenuation of vibration in tunnels under frequent blasting, a 3D tunnel model is built by LS-DYNA based on the Duanjiaping tunnel on the Inner Mongolia-Jiangxi Railway, and the propagation laws of blast-induced vibration in the near area, medium and far area are simulated and analyzed. The results show that the vertical peak vibration velocity of the particle decreases with the increase of distance and blasting times except for a few exceptions; the attenuation of vibration velocity in the near area is faster than that in the medium and far areas; the value of α in the medium and far area is at least 12.5% smaller than that in the near area, and as a whole the values of α in this two areas increase slowly with the increase of blasting times;the coefficient K decreases with the increase of number of blasting, the reduction rate of K in the near area is generally greater than that in the medium and far area and the value of K in the near area is at least 29.1% higher than that in the medium and far area; the parameters of the medium and far area are more consistent with the Sadovsky empirical formula than that in the near area under frequent blasting. 2020 Vol. 57 (2): 149-156 [Abstract] ( 666 ) [HTML 1KB] [ PDF 2463KB] ( 1349 ) 157 Development and Application Research of a Model Test of Different Collapsible Deformation Modes of a Metro Tunnel in the Loess Area WANG Shuming1,2 LIANG Qingguo1,2 WANG Erlei3,4 In order to study the settlement laws of soil mass around the metro tunnel in loess area with different pat? terns of deformations caused by collapse, a model test device, which consists of a model box, a flow rate control system and a settlement measurement system, is developed to measure loess settlements under even and uneven collapse modes. The collapse induced deformation of loess upon encountering water is summarized by indoor test, and the deformation law of tunnel surrounding rocks in loess area under two different submerging modes is analyzed. The experiment results show that the final accumulated settlements under uneven collapse is greater than that under even collapse, it means the uneven collapse causes more damages to the metro tunnel; the settlements near tunnel center line are the largest under the two types of collapse induced deformations, therefore, the monitoring of displacement at central line should be emphasized during construction. The influence of even and uneven collapse on the deformation of metro tunnel is analyzed by indoor model test. The research results are of great significance to the construction control and disaster avoidance during the tunnel construction in loess area. 2020 Vol. 57 (2): 157-162 [Abstract] ( 624 ) [HTML 1KB] [ PDF 2933KB] ( 1394 ) 163 Thermal Physical Parameters Test on the Surrounding Rocks of Lanzhou Underground Rail Transit ZHEN Zuolin1,3 ZHU Jianghong1 YU Gui3 GAI Yuxi1 ZHANG Huyuan1,4 The optimum design of HVAC system in metro station is closely related to the thermophysical parame? ters of surrounding rocks of Metro tunnel. Taking the original soil sample of Lanzhou metro station as the research object, the thermal physical properties of the surrounding rocks of Lanzhou metro station are investigated by using Hot Disk thermal constant analyzer. The results show that the thermal conductivity of the surrounding rocks of Lanzhou metro increases with the increase of depth, the thermal conductivity and thermal diffusivity of the medium sand layer at 13 m depth are the largest and they are obviously larger than that in loess and silty soil, while the volume specific heat of the medium sand is small; the thermal conductivity coefficient increases linearly with the increase of water content, and the volume specific heat decreases first and then increases with the increase of water content, the thermal diffusion coefficient increases first and then decreases slowly with the increase of water content. 2020 Vol. 57 (2): 163-168 [Abstract] ( 778 ) [HTML 1KB] [ PDF 2499KB] ( 1957 ) 169 Study on the Construction Parameters of Shallow Buried Shield Tunnels under Bungalows in Water-rich Sand Stratum CHEN Qingzhang1 QI Weiqiang2 JIANG Yusheng2 ZHANG Changshu1 CHEN Xiafei1 LIU Rui1 Blow-out, large ground surface settlement, quick sand and so on are encountered during shield construc? tion in water-rich sand stratum, which will bring many problems and difficulties. It is extremely important to control the parameters of shield construction in water-rich sand stratum. Based on the practice of a running tunnel between Shuixi station and Changping station of Guangzhou metro line 21, an analysis on shield construction measures and parameters of the test section is conducted in light of the shield construction passing through water-rich sand stratum and underneath the bungalows with poor foundation in Shuixi village, and the parameters of shield construction are determined thereof. The monitoring results show that: the actual control values are close to the fitting values of analysis, the settlements of ground surface and building can be controlled within 5 mm and 10 mm respectively, and the correctness of the selected parameters is verified. The actual pressure in earth chamber is higher than the static earth pressure, the amount of simultaneous grouting shouldn′ t be less than 1.6 times of the theoretical value, increasing of earth pressure and thrust can effectively reduce settlement. 2020 Vol. 57 (2): 169-175 [Abstract] ( 709 ) [HTML 1KB] [ PDF 3683KB] ( 1508 ) 176 Engineering Measures and Safety Evaluation of Baizhang Tunnel Passing through Flow Plastic Water-rich Fracture Zone TIAN Zhiyu1 TIAN Shangzhi1 YANG Feng1 ZHANG Zhaojie1 WANG Bo2 Collapse and clearance invasion events occurred repeatedly during the construction at the section of ZK152+433-ZK152+463 of left tube of Baizhang tunnel passing through a flow-plastic fracture zone with abundant water, which brought unprecedented challenges to the engineers. The various measures adopted in the construction are described in detail, and an analysis on structure safety is conducted by numerical method. The results show that:(1) as for the flow-plastic water-rich fracture zone, dense advance support is the most effective measure to prevent large deformation or collapse of surrounding rocks during excavation, a ring of ?51 self-drilling anchor bolts with unit length of 3.5 m are installed between steel arches (with the steel arch interval of 50 cm), that is to say there are 7 layers of advance support for each tunnel section, effectively controlling the rock mass deformation after excavation, avoiding collapse and clearance invasion of tunnel lining; (2) it is significant to reinforce the surrounding rocks,especially at sidewall and tunnel floor, since it can effectively decrease the integral subsidence of tunnel lining during construction. A combination of jackstone treatment and grouting is adopted to reinforce the surrounding rocks at sidewall and tunnel floor and the effect is much better than that only with grouting; (3) as for the tunnel with explicit external load, the parameters of lining support should be determined by both calculation analysis and engineering experience, which will guarantee the safety of tunnel structure and also make it economical and reasonable; (4) as for the two-lane tunnel, three-bench method is taken and the bench length should be shortened as much as possible in order to form an enclosure of primary support in time so as to control the deformation of surrounding rocks better. 2020 Vol. 57 (2): 176-183 [Abstract] ( 763 ) [HTML 1KB] [ PDF 2777KB] ( 1518 ) 184 Research on Construction Optimization of Single-span Four-lane Municipal Tunnel Based on Construction Period Target YANG Zhiqiang1 FANG Jing2 LIU Xianglin1 ZHENG Yuchao2 The No. 3 tunnel on Nanya Road in Guiyang is a twin-tube independent single-span four-lane munici? pal tunnel with the maximum excavation span of 21.878 m and the maximum excavation area of 245.7 m2 as well as developed underground karst and joint fissure since it is located in karst area, the , and the rock mass is fractured and construction time is tight. A research on the construction optimization of single-span four-lane municipal tunnel in weak and fractured surrounding rocks is conducted based on the construction period target. The strength reduction method is used to quantitatively evaluate the surrounding rock stability of the unsupported cavern and it is found that the unsupported rock of grade IV has the conditions to reach self-stability but the unsupported rock mass of grade V doesn′t meet the requirement of safety factor; based on the construction simulation and construction period deduction of different construction methods, the construction scheme is optimized, and it is determined for theNo. 3 tunnel at Nanya Road to adopt three-bench five-step excavation method in the surrounding rock of grade Ⅳand double side drift method for the rock mass of grade V; the switch of construction method for the main tunnel in rocks of grade Ⅳ and Ⅴ is optimized, and the construction period is shortened by 9 months. 2020 Vol. 57 (2): 184-191 [Abstract] ( 698 ) [HTML 1KB] [ PDF 3881KB] ( 1388 ) 192 Application of Artificial Freezing Method in Construction of Metro Cross Passage in Gravel Stratum JIANG Jie1,2,3 QIU Jutao1 CHEN Xianzhi1 OU Xiaoduo1,2,3 The cross passages of Jinlang running tunnel section of Nanning metro line 3 are mainly located in round gravel stratum which is characterized by poor self-stability, sand gushing, water inflow and deformation caused by large rock disturbance. In view of this, the artificial freezing method is designed for construction of cross passages. The arrangement of freezing holes, selection of freezing parameters and optimization of grouting parameters to control of settlement of soil mass after thawing is described in detail. The temperature of circulated salt water,temperature of soil mass and pore pressure of pressure relief holes are specially analyzed during construction of active freezing, the rules of temperature change of soil mass and formation of frozen wall are summarized, the excavation time of cross passage is accurately judged, and the countermeasures for the problems in freezing construction of cross passage are proposed. 2020 Vol. 57 (2): 192-197 [Abstract] ( 712 ) [HTML 1KB] [ PDF 2091KB] ( 1623 ) 198 Study on the Construction Techniques for Slurry Balance Shield Passing through Water-rich Sandy Gravel Stratum JIANG Xiaotian ZENG Yingjun LIU Yuhong A slurry balance shield with diameter of ?6 240 mm is adopted for the 1.6 km long Changqingqiao sta? tion-Hunnan Avenue station running tunnel of lot 11 of Shenyang metro line 10 which passes through the stratum mainly composed of water-rich gravel layer with the maximum particle size of 110 mm. The cutter wear is effectively reduced and no replacement of cutterhead is taken in the whole construction process by optimizing and adjusting the type selection of shield cutterhead and slurry parameters. The main conclusions are as follows: a set of targeted slurry shield cutterhead configuration option is put forward through analyzing the type selection and configuration of cutterhead in shield design and the cutter tool wear condition after breakthrough of the tunnel; based on an analysis of driving parameters, it is found that increasing the viscosity can improve the effect of slurry support but it is easy to form filter cake on the front of shield cutterhead, thus the gravel muck at front can′ t enter into earth chamber smoothly, causing occurrence of abnormal torque and thrust; the reasonable indexes of slurry parameters for slurry shield in water-rich gravel layer are summarized by analyzing the changes of torque and thrust of the shield under different viscosities and specific gravities. 2020 Vol. 57 (2): 198-203 [Abstract] ( 687 ) [HTML 1KB] [ PDF 3650KB] ( 1680 ) 204 Research on Water Discharge Capacity of Convex Shell Type Waterproof and Drainage Board for the Railway Tunnel MA Chaofeng MA Weibin GUO Xiaoxiong WANG Zhiwei XU Xueliang YU Dongyang Based on the current technical status and main problems of waterproof and drainage system of the railway tunnel in China, the basic characteristics of convex shell type waterproof and drainage board are introduced, a theoretic calculation and research on equivalent pipe diameter and water discharge capacity are conducted. The results show that the minimum equivalent pipe diameter of convex shell type waterproof and drainage board is 0.062 6 m per unit width (longitudinal linear meter of tunnel) and its water discharge capacity is 376-2 138 m3/d under different conditions; the water discharge capacity of convex shell type is about 18-38 times of that of loop blind pipe; improvement of compressive strength is an effective measure to guarantee its water discharge capacity; the convex shell type waterproof and drainage board can replace the traditional one and the loop blind pipe. 2020 Vol. 57 (2): 204-208 [Abstract] ( 667 ) [HTML 1KB] [ PDF 1023KB] ( 1839 ) 209 Time-dependent Analysis on Cross Section of Macro-fiber Reinforced Concrete FU Chunsong1,2 The use of synthetic macro-fibers for the lining of tunnel segments contributes to increasing strength, but creep and cracking of components may occur over time under continuous bending load. With the improvement of ability to deal with cracks, synthetic macro-fiber will be more and more widely applied in the fabrication of tunnel segments by virtue of its superior economical efficiency and durability. Based on the time-dependent characteristics, this paper analyzes and verifies the creep and shrinkage effects of cross section of macro-fiber reinforced concrete under continuous bending moment and axial stress by numerical examples. The results show that fiber in concrete has limited effect on increasing flexural strength of cross section, but it reduces the creep of component during service and significantly decreases the maximum crack width under interaction of fibers and ordinary rebars. 2020 Vol. 57 (2): 209-217 [Abstract] ( 645 ) [HTML 1KB] [ PDF 3354KB] ( 1030 )

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