20 October 2018, Volume 31 Issue 10
    

  • Select all
    |
  •  
    China Journal of Highway and Transport. 2018, 31(10): 0-0.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
     
  •  
    China Journal of Highway and Transport. 2018, 31(10): 0-0.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
     
  • State and Trends of Dangerous Rock Prevention and Control During Tunnel Construction
    LI Shu-cai, LIU Hong-liang, LI Li-ping, SHI Shao-shuai, HU Jie, SUN Shang-qu
    China Journal of Highway and Transport. 2018, 31(10): 1-18.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    The prevention and control of dangerous rocks rolling down is a significant theoretical and technical problem faced during tunnel construction. Owing to an unclear mechanism and lack of effective detection methods, achieving effective prevention and control is difficult. The state and trends of the prevention and control of dangerous rocks are summarized according to available data in three aspects-information acquisition and integration, stability identification of dangerous rock, and monitoring and control of dangerous rock. With respect to information acquisition and integration, digital compass measurement technology, close-range photogrammetry, and laser scanning technology have been developed and a three-dimensional rock mass information integration analysis method based on structural surface network simulation has been initially established. With respect to stability identification of dangerous rocks, a static and dynamic combination method for identifying dangerous rocks has been preliminarily established. Although some research has been conducted on the monitoring and control of dangerous rocks, an effective method for monitoring and controlling dangerous rock in tunnels has not yet been established. Based on existing research work being carried out by the author's team, this article systematically elaborates the existing problems with regard to the prevention, control theory and technology related to dangerous rocks in tunnels. We also discussed the trends for the prevention and control measures for dangerous rocks and considered that the following three aspects denote research priorities and trends:The combination detection method for geophysical exploration, drilling, and surface scanning for rock structure detection. The cross-scale modeling method for rock mass structure. The synchronous monitoring method of key point and dangerous zone and targeted control technology of dangerous rocks. This paper provides a reference for the research in this field and also provides a basic framework for discussion with various researchers and applicators.
  • Review on Seismic Response Analysis and Test Methods for Long and Large Tunnels
    YU Hai-tao, YUAN Yong
    China Journal of Highway and Transport. 2018, 31(10): 19-35.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    The seismic analysis of tunnel structures for disaster prevention is an important topic in the field of underground engineering. Nowadays, long and large tunnels with complex joints are widely constructed. Critical issues such as the longitudinal seismic design theory, large-scale seismic response analysis method, and non-uniform earthquake excitation effects are challenging for the seismic analysis of large and long tunnels. Based on literature review and urgent demands for the seismic design of tunnel structures, this paper focuses on seismic analysis theories and test methods of long tunnels subjected to non-uniform seismic loadings. First, several simplified models for seismic design of long tunnels were developed and analytical solutions for longitudinal responses of long tunnels under arbitrary dynamic loads were derived, and degraded solutions were obtained for the special load case of travelling waves. These solutions can be conveniently used to obtain the overall response of a tunnel structure subjected to seismic loading. Based on the proposed multi-mass-spring-beam model, a simplified method was also developed for the longitudinal seismic design of long tunnels. Second, a multiscale method was developed for the large-scale seismic analysis of long tunnels, with coarse and refined finite element meshes, or with the discrete element method and the finite difference method. The proposed multiscale method was used to compute the overall seismic response of the tunnel while including detailed dynamic responses at positions of potential damage or of interest. This multiscale method did not have spurious wave reflections at the fine/coarse interface and did not require filtering procedures. Third, a multi-point shaking table test method is proposed for long tunnels subjected to non-uniform excitations. The multi-point shaking tables worked in coordination as a large linear shaking table array. A discrete multi-point input mechanism was derived to accomplish a continuous and coordinated excitation over a long tunnel. A long segmental model container was also developed to realize an equivalent transformation from independent shaking tables into continuous excitations. The proposed analytical, numerical, and test methods were applied to major projects such as the immersed tunnel of Hongkong-Zhuhai-Macau Bridge to demonstrate their applicability. Finally, seismic mitigation methods for critical joints in long tunnels were also developed. This paper can lead to state-of-the-art longitudinal seismic design and analysis of long and large tunnels and provide suggestions for future seismic research.
  • Technical Review of Cutter Replacement in Shield Tunneling
    CHEN Jian, LIU Hong-jun, MIN Fan-lu, LIU Hai
    China Journal of Highway and Transport. 2018, 31(10): 36-46.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Shield tunneling machines are often used in complex hydrogeological environments and have to be frequently shut down owing to excessive wear of the cutters. This has become one of the important problems affecting construction during tunneling operations. Cutter replacement is the primary method of solving this problem and restoring tunnel shields. However, a scientific system of cutter replacement has not yet been formulated for the engineering field. On the basis of understanding and summarizing existing research, a technique and classification of shield cutter replacement were expounded. Three main techniques of cutter replacement, namely exchanging cutters under normal pressure after formation reinforcement, exchanging cutters based on the design of permanent pressure replaceable cutter, and exchanging cutters under pressure, were utilized frequently in construction sites. The principles, processes, key technologies, applications, advantages, and disadvantages were analyzed and summarized based on typical cutter replacement operations and research results of the project. Moreover, the latest cutter replacement techniques used in Japan were introduced, and the cutting tool replacements for shield tunneling in China were evaluated. The results show that, the cutter replacement techniques under normal pressure after formation reinforcement and under pressure were formulated for conventional cutterhead design, and the key requirements were to ensure the stability of the excavation face. The differences between these were that, the former was performed under normal pressure after stabilizing the excavation face to achieve self-stability, whereas the latter was conducted under the condition of air pressure support using the auxiliary technology of slurry infiltration and filter cake formation to improve the air-tightness of the excavation face. The stability of the excavation face was not considered for the cutter replacement owing to the design of the permanent pressure replaceable cutterhead. The significance of this technique is the special design of the hollow cutter arm and the permanent pressure replaceable cutter for the shield machine.
  • Research Progress of Shield Cutter Cutting and Analysis of Abnormal Wear Cases（in English）
    MIN Fan-lu, BAI Yu-xin, LIU Lai-cang, CHEN Jian
    China Journal of Highway and Transport. 2018, 31(10): 47-58.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    The force and wear condition of shield cutters during the cutting of rock and soil is a key factor in determining whether a construction project is successful or not. However, when shield machines cross highly abrasive sand pebble strata and soil-rock composite formations, they often cannot bore properly due to excessive wear on the tool. In order to solve the problem of force and wear from the soil-rock mass cutting process, the research progress of cutter wear monitoring methods, cutting mechanisms, and experiments and numerical simulations of stress in the cutting process are summarized in this paper. Through typical engineering cases, the abnormal wear problems of the tools seriously disturbed by shield tunneling are analyzed. Regarding tool wear monitoring methods, electrical and ultrasonic monitoring technologies are widely used in shield construction, and photogrammetry and DCRM technology for continuous imaging have been gradually developing. With respect to the tool cutting mechanical model, this paper focuses on the tensile-fractured model and the CSM mechanical model of the disc cutter, as well as the flow cutting model and the Mckyes-Ali model of the scraper. Tool cutting and wear experiments are studied in three aspects:geotechnical erosion unit experiments, single tool cutting experiments, and tool overall cutting model experiments. Numerical simulation studies focus on the study of the stress state and the fracture morphology of rock and soil under different cutting conditions. The abnormal wear of the tool directly shortens the service life of the tool, and is also abrupt and irregular. It is the most typical tool wear model in engineering practice. Finally, looking at the cutting and wear forms of shield cutters, this paper provides an outline of the developing trend of cutters in tool monitoring mode, shape and arrangement, alloy materials, and the welding process.
  • Characterizing and Identifying Types of Water and Mud Inrush Utilizing Magnetic Resonance Sounding for Tunneling Through Karst Areas with Filling Materials
    FAN Ke-rui, LI Xiu, LI Ning-bo, LIU Zheng-yu
    China Journal of Highway and Transport. 2018, 31(10): 59-68.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Water and mud inrush hazards can occur when tunneling through water-bearing karst strata. To predict these hazards, the distribution of volumetric water content, permeability, and hydraulic conductivity should be observed during tunneling operations. Magnetic resonance sounding (MRS) is a direct geophysical method for investigating these hydrogeological parameters. In this study, an MRS approach was developed for identifying different types of water and mud inrush hazards and characterizing the filling materials that can cause such hazards. Using a Log-Gauss distribution function, an MRS relaxation distribution function was proposed for characterizing different kinds of inrush hazards. These hazard sources were modeled using a 3-D discretization of the resistivity, volumetric water content, and MRS relaxation time distribution. Subsequently, the MRS responses for different inrush hazard types were stimulated and analyzed, and these responses were combined with the volumetric water content and MRS relaxation time to obtain a type factor that provides a direct judgment for characterizing water and mud inrush hazards.
  • Comprehensive Inversion Analysis Method and Application of Deep Buried Long Tunnel Geo-stress Field
    LIU Ning, ZHANG Chun-sheng, CHU Wei-jiang, WU Jia-yao, CHEN Ping-zhi
    China Journal of Highway and Transport. 2018, 31(10): 69-78.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    When analysis on the geo-stress field of deep buried long tunnel, many factors such as large buried depth, long tunnel line and complex geological conditions increase the complexity of the geo-stress field and cognitive difficulty, and affect the accuracy of the results. Jinping mountain ultra-deep buried and ultra-long traffic tunnel is the largest deep buried traffic tunnel in our country, and the maximum depth is 2 375 m and the length reaches 17.5 km. The conventional direct in-situ stress test methods such as Hydraulic fracturing method, stress relief method applies, only can be applied to shallow buried deep, and is difficult to directly measure the geo-stress values. The judgment of the whole regional stress field will be affected. Because of the lack of objective information, the state of stress field must be evaluated from other multiple angle. Firstly, by using the peak strength and residual strength stress envelope, the stress state corresponding to the excavation response of surrounding rock in different locations around the tunnel is revealed. The process of analyzing the stress field of deep buried and long line tunnel is proposed. In the construction process of Jinping traffic tunnel, the methods of macroscopic geological judgment, the failure phenomenon analysis, test results indicate, high stress concentration area estimation were combined to evaluate and interpret the stress field distribution characteristics. In addition, because the petrofabric, fold, structure, terrain conditions lead to local ground stress anomaly, the discrete numerical analysis method was used to analyze the structural plane and fold factors impact on the local stress field. Finally, based on the above research results, the high-precision three-dimensional model was established, including the whole terrain, main fault and fold. The subdivision of the geo-stress along the line is revealed by the response of the fold structure and the fault structure under the current tectonic compression. It provides a more accurate and convenient method to judge the geo-stress field of the deep buried and long line tunnel engineering.
  • Hazard-causing Structures for Water and Mud Inrush in Tunnels and the Corresponding Detailed, Multiscale Observation Technology
    LI Xiao-zhao, HUANG Zhen, XU Zhen-hao, FAN Jing, SONG Jin-long, ZHANG Pei-xing, LU Jun-jie
    China Journal of Highway and Transport. 2018, 31(10): 79-90.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Hazard-causing structures, which are complex and multiscale, are the key ways to control water and mud inrush in tunnels. However, the depth and length of tunnels excavated in high mountains result in the maladjustment and low accuracy of traditional field geological surveys. Hazard-causing structures are classified as fractured zones and karst caves with abundant water and mud. The fractured zones are associated with either abundant water or abundant mud. The karst zones consist of deep karst caves filled with water, fracture-induced karstified zones, and filled karst caves. In this study, the typical geological features of these structures were summarized, and methods for the theoretical identification of different types of hazard-causing structures were proposed. Water and mud inrush may be caused by an Epi-Fracture-Karst-Zone in carbonate rocks under warm and humid climatic conditions. The detailed, multiscale observation of hazard-causing structures for controlling water and mud inrush in tunnels was explored using an unmanned aerial vehicle, digital photography, drilling television imaging, and other advanced technologies. The observation method for geological surveys included air, outcrop, borehole, and tunnel (AOBT), and this method was used in several tunnels. The results show that the AOBT observation technology meets the demands of different measurement scales, provides fast and high-precision measurements of hazard-causing structures, and improves on the traditional field geological survey methods. The results provide a valuable reference for prevention and control of water and mud inrush in tunnels.
  • Risk Rating Index and Evaluation Method for Water Inrush in Long-deep Tunnels
    XU Zeng-guang, WANG Ya-ping, XIAO Yu, LI Li-min, LI Yan-long, LI Yu-bo
    China Journal of Highway and Transport. 2018, 31(10): 91-100.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Long distance and deep burial have become features of future tunnel projects, and water inrush is one of important factors that influencing the speed of excavation advancement. The Qinling water conveyance tunnel of the Hanjiang-to-Weihe River Valley Water Diversion Project is approximately 81.8 km long with a maximum depth of 2 000 m, and the geological structure is complex. The risk evaluation of the inrush water hazard is therefore of great scientific and practical value. Based on the analysis of a large number of inrush water disasters in underground caverns, the characteristics of inrush water in long and deep (long-deep) tunnels were studied. A method of evaluating the hazard level of water inrush in long-deep tunnels was established. Formation lithology, orientation of bedrock, unfavorable geology, surface confluence conditions, head pressure at the bottom of the tunnel, contact zone of soluble and insoluble rocks, and combination degree of interlayer (interlaminar) fissures and surface rivers were selected as seven risk rating indexes of water inrush hazard in a index system for long-deep tunnels. A scoring method was used to quantify the degree of disaster of the index factors. An analytic hierarchy process (AHP) method was used to construct the judgment matrix between the indexes. The weight of each index was obtained by the maximum eigenvalue method. Applying a cloud model to the rating made the synthetic attribute measurement of rating more objective. The corresponding relationship between the risk level of the water inrush and range of single-point maximum volumes of water inrush was established. From this, the range of water inrush volumes could be predicted on the basis of the risk assessment in the early stages of design. The results are in good agreement with the actual situation in the excavated section of the Qinling tunnel (approximately 60 km long), which shows that the method of rating the risk of the water inrush hazard is reliable. Evaluation of the risk of water inrush for the non-excavated section of the Qinling tunnel (approximately 20 km long) can provide a foundation for effective prevention of water inrush.
  • Tunnel Route Selection and Water Inrush Precontrol Analysis for Underground River Development Areas（in English）
    HUANG Xin, LI Shu-cai, XU Zhen-hao, LIN Peng, CHEN Yu-cheng, NIE Li-chao, PAN Dong-dong, WANG Wen-yang
    China Journal of Highway and Transport. 2018, 31(10): 101-117,140.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    To control the risk of water inrush in a tunnel passing through an underground river development area, 21 cases of water inrush engineering were collected and analyzed. The development law and geological identification characteristics of an underground river were studied. A three-stage underground river identification method was proposed, which involved searching the extension of the river in the horizontal direction, confirming the elevation of the river in the vertical direction, and detecting the relative location of the river in the tunnel. Further, route selection principles when a tunnel passed through an underground river development area were defined. The influence factors of the hierarchical assessment model for water inrush were selected and the weight of the factors were obtained. Tunnel route selection and water inrush precontrol in underground river development areas were studied. The results show that the three-stage underground river identification method is a synthetic method of geological survey, engineering analogy, tracer testing, and geophysical prospecting, which can successively verify the flow direction, elevation of the underground river, and relative position of the underground river and the tunnel. The assessment results show that the main control factors of water inrush risk in the underground river area are development intensity, water flow, relative position of the underground river and the tunnel. The less significant factors include advance geological forecast, development forms of the underground river, and hydraulic gradient of the underground river. And the least important factors include precursory information, monitoring measurement, and tunnel excavation and support. The research findings were successfully applied to the identification and risk assessment of Deshengchang underground river at Qiyueshan Tunnel site on the line of Lichuan-Wanzhou Expressway, and the subsequent results prove that the proposed method is rational and feasible, and it can provide a reference for similar engineering activities.
  • Water Inrush Criterion and Catastrophe Process of a Karst Tunnel Face with Non-persistent Joints
    GUO Jia-qi, LUO Yan-bin, CHEN Fan, LUO Yan-bin, LIU Qin
    China Journal of Highway and Transport. 2018, 31(10): 118-129.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    This study aims to provide theoretical support for early warning and prevention for water inrush of a karst tunnel face. As to the water-resistant rock mass with non-persistent joints ahead of a karst tunnel face, the compressive shear cracking property of non-persistent cracks and the changing law of stress intensity factor at the branch crack tip with water pressure and its extended length were analyzed under karst water pressure and geo-stress from the perspective of fracture mechanics. The critical water pressure of a rock mass with non-persistent joints under axis-tension coalescence mode was deduced. The water inrush and instability criterion of water-resistant strata with non-persistent joints ahead of a karst tunnel face, based on the minimum safety thickness, was established by using the two-band theory and the deduced formula of critical water pressure. The influence of the karst water pressure, length of non-persistent cracks, array pitch of non-persistent cracks, and angle between the crack and the maximum principal stress on the minimum safe thickness of water-resistant strata was discussed. A 3D DEM, considering the fluid-solid coupling effect and structural characteristics of the rock mass, was adopted to study the evolution rule of displacement and seepage fields in the water-resistant rock mass ahead of the tunnel face. The precursory features in sequential excavation of the tunnel working face close to the high pressurized karst cave before it. Based on the results of numerical simulation, the transition from the single effect of unloading on the extrusion displacement of the karst tunnel face to the combined action of unloading and karst water pressure occurs when the karst tunnel face advances. The displacement and its amplitude at each measuring point in the water-resistant strata continue to increase in the excavation process. The extrusion displacement and water flow velocity in the tunnel face suddenly increase when the water inrush pathway is about to form, and this is important precursory information for preventing a water inrush disaster.
  • Investigation into Parameter Optimization of Existing Metro Tunnel for Shield Tunnel Closely Undercrossing It at Small Angle in Sand Stratum（in English）
    LAI Hong-peng, ZHENG Hai-wei, HE Qiu-min, LIU Hai-yang
    China Journal of Highway and Transport. 2018, 31(10): 130-140.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    New tunnels that closely undercross existing tunnels at small angles cause problems that need to be solved. The left line of the shield tunnel section that starts from Zhangjiacun station to Houweizhai station in the Xi'an Metro Line 1 is constructed in close proximity to the existing Line 1 above it. Thus, field investigations, numerical simulation, and field monitoring were used to analyze the influence of construction parameters on the settlement and distance between two tracks of the existing tunnels. This study chose the construction parameters to be soil pressure, grouting pressure, and grouting amount, and the grouting amount was indirectly measured through grouting thickness. A three-dimensional numerical simulation model was constructed. By analyzing the results of the simulation, reasonable values of shield construction parameters were obtained. Field monitoring was carried out to verify the control effect of the proposed construction parameters on the track height difference. The results show that with the increase of chamber pressure and grouting pressure, both the settlement of existing metro tunnels and the distance between two tracks will continue to decrease; however, when the chamber pressure increases to 0.10 MPa and grouting pressure increases to 0.22 MPa, the control effects are no longer significantly improved. Therefore, the settlement of existing lines and the distance between two tracks decrease with the increase of the grouting thickness, which shows an approximately linear relationship. Thus, increasing the grouting range is an effective method to control the settlement and orbital difference of existing tunnels. From the numerical simulations, the recommended values of the construction parameters are 0.10 MPa for chamber pressure, +0.22 MPa for grouting pressure, and +0.23 m for grouting thickness. Through field monitoring, on the existing subway tunnel bed, the maximum settlement of the four measured lines C, B, G, and F are found to be approximately 6 mm, less than 20 mm, and the maximum rail height difference is 1.2 mm, less than 4 mm. These are all seen to be less than the control values required by the specifications, indicating that the suggested construction parameters have a good control effect on the existing tunnel settlement and rail height difference.
  • Mechanics Model to Determine the Minimum Safe Thickness of Tunnel-face Rock Slab at a Fracture Zone
    ZHANG Qian, BAI Song-song, GAO Yu, DU Yan-liang, ZHAO Wei-gang, LIANG Guan-ting
    China Journal of Highway and Transport. 2018, 31(10): 141-149,219.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    The stability and safety of tunnels passing through fault fracture zones are the difficulties in tunnel construction today. Typical working conditions in fracture zones with loose soil masses are constraints in tunnel construction. Considering these conditions and the mechanical properties of surrounding rock, and using theoretical calculation, numerical simulation, and engineering practices, a method to calculate the minimum safe thickness of tunnel-face rock for rock mass stability was developed. Further, fracture zone pre-reinforcement and suitable treatment schemes were explored in this study. First, a fracture zone-rock slab mechanics model was established, in which the rock mass equivalent for rock slab loads was the constraint. This model calculated the pressure on a fracture zone due to rock slab minimum safe thickness and obtained an effective equation for the calculation of the relationship between rock slab thickness, strata dip angle, and fracture zone height. Further, the curtain grouting processing parameters were optimized in this model. Then, based on the results of this theoretical analysis, a comparison was done between a typical case of construction of a tunnel through an unstable fracture zone where the thickness of the rock mass on the tunnel-face was not controlled and one where the thickness was controlled. Finally, the Comsol Multiphysics software was used to perform numerical simulations, and the effects of various rock dips, tunnel depths, and grouting pretreatment parameters on the minimum safe thickness of a tunnel-face rock slab were analyzed. The results show that:the results of the theoretical calculation, engineering practice, and numerical simulation are in good agreement. During normal construction, the minimum safe rock slab thickness of the tunnel face increases with increase in the effective height of the crushing zone and decreases with increase in the dip angle of the rock layer. When the curtain grouting method is used for pretreatment of the fracture zone, the minimum safe rock slab thickness decreases with increase in the rock dip angle. Thus, large minimum safe thicknesses should be reserved in the grouting process while controlling the grouting pressure.
  • Rock Fragmentation Mechanism and Efficiency Under Inserted-tooth Roller Cutter by Rotary Cutting Test
    WU Fan, YIN Li-jun, ZHANG Hao, GONG Qiu-ming
    China Journal of Highway and Transport. 2018, 31(10): 150-159.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    With the development of tunnel construction, the inserted-tooth roller cutter has been widely used for many types of excavation machines, including tunnel boring machines, raised drills, roadheaders, etc. Thus, it is significant to study the rock fragmentation mechanism and efficiency under the inserted-tooth roller cutter for improving mechanical excavation efficiency. For this issue, rotary cutting tests for the inserted-tooth roller cutter with diameter of 12 inches were conducted using the mechanical rock fragmentation platform of Beijing University of Technology. The rock sample used in the rotary cutting test was Beishan granite with dimensions 1000 mm×1000 mm×600 mm. A series of rotary cutting tests for the different rows of teeth and the whole cutter were conducted under different penetration depths. During the rotary cutting tests, the cutting force, rock chips, and rock fragmentation efficiency were measured collected and analyzed. Moreover, the distribution characteristics of cracks induced by the cutters were explored by fluorescence experiment to verify the rock fragmentation mechanism. The main conclusions can be summarized as follows. ① The mode of rock fragmentation by inserted-tooth roller cutter in a "progressive" way, in which rock breakage propagated from the adjacent single spherical tooth with small spacing to adjacent rows of teeth with large spacing; ② For the tests on different rows of teeth, the rock fragmentation efficiency of the third row is the highest. For the test of the whole cutter, the rock fragmentation is highest with penetration depth of 1.5 mm; ③ Based on the results of the fluorescence experiment, the distribution characteristics of the cracks induced by the cutter were identified, and there are obvious differences in the propagation direction and range of cracks under each row of teeth. The rock fragmentation efficiency obtained from crack distribution coincided with the analysis of cutter force and rock chips. The conclusions of this study can offer some guidance for the optimization of cutter layout, cutter type, and operating parameters of excavation machines.
  • Internal Structural Characteristics and Permeability of Kata-rocks in Geological Structures Filled with Water and Mud（in English）
    FAN Jing, LI Xiao-zhao, HUANG Zhen, ZHANG Rui, HE Zhi-cheng
    China Journal of Highway and Transport. 2018, 31(10): 160-166.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Geological structures filled with water and mud are the main causes of water inrush during excavations of deep-long tunnels. Research on the internal structural characteristics of fractured rock masses and the permeability of different tectonic units can help avoid accidents during the construction of tunnels. To study the internal structural characteristics and the permeability coefficient of a typical rock mass, a series of experiments were carried out in a typical slot of a fractured core in Gansu province. These tests included a detailed characterization of the recognition of fracture, X-ray diffraction (XRD) for mineral analysis of typical fractured rock, SEM-ED for characterization of the inner structure of the rock fracture, permeability tests in different tectonic units, and indoor permeability tests of typical broken rock mass. We also calculated the mineral composition, inner structure, and permeability coefficient of the fractured rock. The results of microcosmic tests show that the infiltration coefficient increases as secondary mineral content increases, and the percolation coefficient of the fault nucleus is lower than that of the fault. The permeability coefficient of the upper surface is larger than that at greater depth, because the particle size at the fault core is larger than that at depth. The rock mass shows a higher degree of shallow metamorphism on the surface. The effective porosity at the fault core is larger than that at depth. The ratio of the surface area of the core is larger than the damage belt and the surrounding rock. Pressure water tests conducted in the field and indoor penetration tests of typical samples show that the fault core has a high permeability coefficient with a high crack density of about 2×10-6 m·s-1 in horizon. The permeability coefficient reduces as the distance from the fault increases because of the reduction in fracture density. Vertically, the fault zone rock mass can be classified into different tectonic units according to the distribution of the permeability coefficient. The permeability coefficient of fault gouge is low (<10-9 m·s-1), while that of debris and breccia (10-5-10-7 m·s-1) and cataclastic rock (10-4-10-7 m·s-1) varies over a wider range. The permeability coefficient (<10-9 m·s-1) reduces in the undamaged surrounding rock. These results can provide the theoretical and engineering basis for the prevention and control of disasters in tunnels.
  • Influence of Longitudinal Spacing of Double-arch Tunnel on Tunnel Stability in Jointed Rock Mass
    YANG Zhong-min, GAO Yong-tao, WU Shun-chuan, YU Peng-qiang, YANG Song, AI Zu-bin, CAO Zhen-sheng
    China Journal of Highway and Transport. 2018, 31(10): 167-176.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    To study the influence of double-arch tunnel excavation on adjacent tunnel, the Caiguanying tunnel at Jinhong Expressway in Yunnan Province was selected for research. A numerical model was established by setting the bond block model method in the discrete element software named 3DEC. The settlement and the range of failure joints in surrounding rocks were simulated and analyzed. The simulation results show that the model can reasonably characterize the abnormal deformation and structural failure of the Caiguanying Tunnel when the longitudinal spacing is too large or too small. In the process of excavation, the settlement value and the number of tensile and shear failure joints in the surrounding rocks of the adjacent tunnel increase when the advance or the back tunnel is being excavated. The failure joints are mainly caused by shear sliding. Furthermore, based on a number of factors, the influence of different longitudinal spacing between the left and right working face of the tunnel on the stability of the surrounding rocks and supporting structure of the tunnel is studied to determine the suitable longitudinal spacing. The results show that this spacing should be greater than or equal to 30 m according to the variation of the settlement value of the vault near the working face of the advance tunnel. In terms of the number of tensile failure joints, the suitable spacing is 20-40 m. In terms of the sliding state, the suitable spacing is 30-40 m. In terms of the total number of slide failure joints, the suitable spacing is 20-40 m. A spacing less than or equal to 40 m is suitable in terms of the bending moment of lining. On the basis of all these judgments, it is concluded that the vertical spacing between two sides tunnel should be between 30-40 m, which is 2 to 2.5 times the tunnel clearance. In the subsequent construction process, the longitudinal spacing of the left and right working faces is strictly controlled within this range, and the tunnel is smoothly penetrated finally.
  • Experimental Research on Destruction Characteristics of Tunnel Mud Inrush Using Transparent Soils
    ZHANG Jia-qi, LI Shu-cai, ZHANG Qing-song, ZHANG Xiao, YANG Lei, LI Peng, LAN Xiong-dong
    China Journal of Highway and Transport. 2018, 31(10): 177-189.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    A fully visualized mud inrush indoor test was developed with transparent soils to understand the catastrophic mechanism of tunnel mud inrush disasters for different amounts of disaster-causing media and groundwater. Numerical simulation with the Particle Flow Code-Computational Fluid Dynamics method was conducted to verify the indoor test results. The feasibility of using transparent soils for geotechnical indoor testing was demonstrated. The "black box" problem of traditional mud inrush tests was solved, the destruction characteristics affecting tunnel mud inrush disasters were annualized, and the parabolic rotator shape was shown to adequately describe the destroyed shapes resulting from the disaster. In addition, the evolution law governing the displacement field inside the medium was studied. The disturbance area of the mud inrush disaster was discovered, and the change regulation of the actual disaster influence area was also revealed. Finally, the mechanism of the tunnel mud inrush disaster was identified according to the destruction characteristics. The results show that the shape of the area destroyed by the mud inrush disaster is that of a parabolic rotator, and that it is not influenced by the amount of disaster-causing media or groundwater. Furthermore, mud inrush disasters give rise to a direct destroyed area as well as a disturbance area, and a disaster's actual influence area comprises the sum of these areas. Both the destroyed area and disturbance area extend with an increase in the amount of disaster-causing media and groundwater. The destroyed area is significantly affected by the amount of disaster-causing medium, whereas the disturbance area is significantly affected by the amount of groundwater. The evolution process of mud inrush disasters can be divided into four types, namely, the start-up migration of the medium, appearance of a free surface, overall transfer of the medium, and steady state at the end of the disaster. The time-varying curve of the mud inrush mass shows the characteristics of the start-up, acceleration, slowdown, and stability. The stress evolution law governing the mud inrush hole is characterized by a sharp increase, followed by a continued fluctuation, and slow decrease.
  • Test of Water and Mud Inrush in Completely Weathered Granite Tunnels Considering Variable Mass Properties
    LIU Jin-quan, CHEN Wei-zhong, ZHEN Wei-hua, YUAN Jing-qiang, NIE Wen
    China Journal of Highway and Transport. 2018, 31(10): 190-196.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    To study the variable-mass seepage properties and disaster mechanism of water and mud inrush in completely weathered granite tunnels, a testing system that can induce mass transfer and apply triaxial stress was designed. The testing system consisted of a load system, a permeability system, and a collection system of water and mud, which could simulate the three-dimensional stress of the stratum and particle transfer properties. Using this system, the effects of water pressure and confining pressure on water inrush evolution properties were investigated. The test results demonstrate three things. First, the evolution of water and mud inrush from completely weathered granite is a seepage-erosion coupled process. The mass particles transfer under the effect of water pressure, thus increasing the porosity and permeability of the stratum. This, in turn, further increases the water flow and particle transfer. Under the transfer of particles, the flow pattern may change from a Darcy to non-Darcy flow, which finally induces the disaster. The experiment shows that particle transfer is the internal cause of disaster, and the changeability of the flow pattern is the key reason for the disaster. Second, the evolution properties of water and mud inrush increase with increase in water pressure. When water pressure increases to 0.6 MPa, the transfer mass may be up to 11% of the sample mass, and the water inflow increases to 395.84 mL·min-1, more than 4.3 times of that at 0.4 MPa, indicating that the critical value that induces the disaster was obtained. Third, the evolution of water and mud inrush, in general, increases with an increase in the confining pressure, particularly in the initial evolution stage, indicating that an increase in the confining pressure accelerates the initial evolution rate and decreases the prevention time. This suggests that monitoring of initial seepage-erosion properties should be addressed under the high confining pressure state.
  • Analysis of Lateral Displacement of Stratum Caused by Shield Tunneling Considering Friction Resistance of Cutter Head
    WU Chong-fu, WEI Chao, CAO Hai-ying, XU Liu-qi, JIE Ying
    China Journal of Highway and Transport. 2018, 31(10): 197-209.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    In order to fully and accurately calculate the total lateral stratum displacement due to shield tunneling based on Mindlin's solution to elasticity and the existing research, the impact of friction force of panel-type and spoke-type cutter head on the lateral stratum displacement was additionally considered to yield a simplified cutter head computing model. Coordinate transformation and integration methods were used to deduce the computing formula for the lateral stratum displacement generated by friction force at the front and circumferential faces of the two types of cutter head. Moreover, a displacement overlapping method was used to obtain the computing formula for the total lateral stratum displacement due to shield tunneling. Computing and analysis and comparison to measured values were conducted on existing engineering examples. The computing results reflect the characteristics of the lateral stratum deformation during shield tunneling. The synchronous grouting pressure and shield friction are the major factors that affect the lateral stratum displacement significantly within certain area of the shield tail. However, within a certain area close to the cutter head, the lateral stratum displacement is affected by the shield friction; the circumferential friction at the circumferential face and the friction at the front face of the cutter head cannot be ignored.The lateral stratum displacement caused by these major factors reduces as the depth increases and gradually spreads to the deeper soil mass. The lateral stratum displacement is less affected by the cutter head with different structures and is distributed in similar rules. Within a certain area surrounding the driving face of the cutter head, the distribution of positive and negative areas of the total lateral stratum displacement is correlated to the rotation direction of the cutter head.
  • Influence of Crack Number on Mechanical Properties of Shield Tunnel Segment Structure
    HE Chuan, LIU Chuan-kun, WANG Shi-min, ZHANG Jun-bo, LU Dai-yue, MA Gao-yu
    China Journal of Highway and Transport. 2018, 31(10): 210-219.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Cracks often develop in the process of producing, maintaining, transporting, and assembling shield tunnel segments, and the overall stress levels are affected by the existence of cracks to some extent. Considering a cross-river shield tunnel project in China as an example, and based on the similarity model test, a systematic study of the influence of crack number on the mechanical properties of segment lining structures was conducted. Additionally, the failure mode of the segment structure was studied through the schematic diagram of failure process. The acoustic emission data, displacements, and internal forces of segment linings were measured and analyzed. The results show that the loading of the segment lining structure can be divided into three stages:elastic bearing stage, plastic bearing stage, and unstable failure stage. Owing to the existence of cracks, the overall load bearing capacity of the structure is reduced. With an increase in the number of cracks, the elastic bearing range of the lining structure increases, and the plastic bearing range decreases; the tendency for the spatial impact range of the damage increases and unstable failures are more sudden. Further, displacements under the same load conditions increase, and the ultimate bearing capacity of the structure reduces. The existence of cracks causes the segment to generate longitudinal through-cracks at the precast crack locations. As the number of cracks increases, the number of longitudinal through-cracks increases, and the damage area develops from a certain location to a banding distribution. This study shows that when the number of precast cracks on the hance of the tunnel reaches three, because the segments between cracks squeeze one another, reticulated cracks are generated, and crushing areas are formed at certain locations in the structure.
  • Failure Modes of Rocks Surrounding Tunnel with Two Weak Interlayers During Excavation
    WEN Hai-jia, HU Jing, XIE Peng, XIE Qi-long
    China Journal of Highway and Transport. 2018, 31(10): 220-229.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    A weak interlayer is an unfavorable geological condition often encountered in mountain tunnels. However, investigations with two weak interlayers are still rare. Both physical model tests and numerical analyses were carried out to investigate the failure modes of rocks surrounding tunnels with two weak interlayers during the process of tunneling. Based on the project background, physical model tests were designed, and by identifying the characteristics of the crack damage, stress, and strain of the test model, three similar results were obtained as follows:First, under shear force, the vault developed plasticity and slipped along the interlayer. Second, plastic deformations occurred at the left and right arch shoulders, and tensile fractures developed. Third, the right arch foot developed plasticity because of shear and tensile stress. Finally, the left arch foot developed plasticity because of shear and tensile stress as well. In addition, FLAC3D was used to simulate the experiment, and the simulation result was in good agreement with the experimental results. Based on the numerical simulations, the comparison of failure mode between tunnels with a single weak interlayer and two weak interlayers was conducted. It is found that the horizontal convergence below the weak interlayer is suppressed, and the dip angle of plastic failure zone over the vault and horizontal plane is smaller owing to the existence of two weak interlayers, which shows a more dangerous failure tendency. Besides, vault areas and connection between the left arch foot and the left middle wall should be considered as unfavorable areas. As the failure mode rule of a tunnel with two weak interlayers is different from that of one interlayer, it is unreasonable to adopt the schemes of design and construction of tunnels with one weak interlayer to meet the stability of those with two interlayers.
  • Mechanical Model Calculations of Tunnel Roof with Horizontal Stratified Rock Mass Tunneling Considering the Interlayer Cohesion
    LUO Yan-bin, CHEN Jian-xun, WANG Li-bao, DENG Xiang-hui
    China Journal of Highway and Transport. 2018, 31(10): 230-237,265.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    The mechanical properties of horizontal stratified rock mass are not only controlled by rock formations and structural planes, but are also closely related to the interlayer cohesion. During the construction process of horizontal stratified surrounding rock mass tunneling, due to improper consideration of interlayer cohesion, it is prone to cause unsuitable support parameters and lead to engineering problems such as abundant overbreaking and rock falling from the arched roof, roof separation, and even partial collapse, which seriously affect the safety of the project, construction quality, and progress. At present, the roofs of tunnels with horizontal stratified surrounding rock are generally simplified as an anchor beam and simply supported beam model, however, interlayer cohesion is not considered. In this paper, according to the different stages of excavation, the tunnel roofs are respectively simplified into the anchor beam model at the initial stage of excavation and the simply supported beam model after construction disturbance, and the coordinated deformation conditions of the roof beam model are used to obtain the formula for calculating the interlaminar cohesion. Based on the field test case in Daliangmao Tunnel, the tunnel excavation span calculations were carried out for beam models about whether to consider interlayer cohesion. The results show that considering the interlayer cohesion has a great influence on the excavation span. Considering the interlayer cohesion, the critical excavation span of the anchor beam model is 3.36-4.75 m, and for the simply beam model is 2.74-3.88 m. When the interlayer cohesion is not considered, the critical excavation span of the anchor beam model is 0.14-0.30 m, and for the simply beam model is 0.12-0.24 m. In combination with the tunnel construction site, when the excavation span is 3-6 m, the flat top phenomenon will be present in the crown, resulting in separation and rock falling. Therefore, the mechanical model of the tunnel roof considering the interlayer cohesion is more consistent with the actual situation of project.
  • Smoke Movement Analysis and Full-scale Experimental Study on Central Smoke Extraction System with Uniform Smoke Rate in Tunnel Fire
    XU Pai, XING Rong-jun, JIANG Shu-ping, YIN Jie
    China Journal of Highway and Transport. 2018, 31(10): 238-245.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    In the process of smoke extraction in a central smoke extraction system, a large amount of smoke may be discharged from the smoke extraction damper close to the extraction fans. In this case, the extraction efficiency is greatly reduced and energy consumption increases. To solve this problem, the concept of smoke extraction with a uniform smoke rate is presented in this paper. Adjusting the smoke extraction damper opening angle can make the extraction rate of each smoke extraction damper uniform, such that the high temperature smoke can be discharged furthest through the smoke extraction damper near the fire source. The prediction models of the relationship between the smoke velocities in the duct and damper, extraction rate, opening angle of dampers, and the wind pressure of the extraction fans in the mode of the uniform smoke extraction system are established by theoretical analysis. Meanwhile, taking the Hong Kong-Zhuhai-Macao immersed tunnel as the prototype, the immersed experimental tunnel with the biggest cross-sectional size in the world is constructed, and full-scale fire experiments have been carried out. The results show that in the mode of smoke extraction with a uniform smoke rate, the extraction rate of each smoke extraction damper could be made equal by controlling the opening angle of each damper. It is also suggested that the damper near the source should be open in the fire, and as long as the smoke velocity limit is not exceeded, the number of dampers could be open as few as possible, which may not only shorten the smoke spread range but also achieve effective energy saving. In the uniform smoke extraction mode, the smoke extraction rate of each dampers is uniform, and the opening angle of dampers gradually increases. The closer to the fire source, the smaller the opening angle of dampers. Finally, taking 10 MW fire as an example, the theoretical prediction results are verified by the full-scale experiment.
  • Influence of Grout Viscosity on the Grouting Reinforcement Effect of Completely Weathered Granite
    YANG Lei, LIN Rong-feng, LI Zhao-feng, LI Shu-cai, ZHANG Qing-song, LIU Ren-tai, ZHANG Xiao, WANG Kai, CHEN Hui
    China Journal of Highway and Transport. 2018, 31(10): 246-254.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Cement grout is a commonly used grouting material for water disaster control and ground reinforcement in various tunnel and underground engineering applications. Due to the limitations of the conventional method in viscosity adjustment of cement grout by changing the water-cement ratio, this study selected the cement grout with a fixed 1:1 water-cement ratio as the research object, and two types of admixtures were used to adjust the properties of the cement grout, to realize the aim of dynamic regulation of the grout's viscosity and fluidity to a certain extent. The typical completely weathered granite was used as a model medium to conduct the grouting experiment, and the diffusion rules of cement grouts with varying viscosities in the completely weathered granite, as well as the influence of grout viscosity on the reinforcement effect, were investigated. The experimental results indicate that the diffusion of cement grout in the completely weathered granite strata presents a fracturing propagation mode; with the increase in the grout viscosity, the pattern of the grout vein transforms gradually from the "three-bifurcation" type to the "polygonal-line" type, and the thickness of the primary grout vein gradually increases. Moreover, an increasing grout viscosity results in the improvement of the overall reinforcement effect, mainly in terms of the compressive and shear strengths of the grouted medium. In addition, as the slurry viscosity reaches 24.6 s, the uniaxial compressive strength of the reinforced soil mass increases by 87%, and the shear strength parameters of cohesive force and internal friction angle increase by 220% and 46.6%, respectively. The change trend of the internal friction angle and the shear strength is basically consistent, which indicates that the increase in the internal frictional angle is a key factor to affect the overall shearing properties of the medium. It is also noted that the viscosity corresponding to approximately 18.8 s is a sensitive value for predicting the change in the grout vein pattern and the variation of rate of improvement of the grouted medium strength. This research can provide references for grout material selection, viscosity regulation, and the evaluation of reinforcement effect in the grouting engineering of completely weathered granite and similar strata.
  • Analytical Solution of Stress and Deformation of Noncircular Tunnel Considering Grouting Circle
    LI Yan-song, CHEN Shou-gen
    China Journal of Highway and Transport. 2018, 31(10): 255-265.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    A new complex variable method is presented for solving stress and displacement problems of noncircular deep tunnels with certain boundary conditions at infinity, and obtaining analytical solutions of stress and deformation of noncircular tunnel under grouting reinforcement. The new method uses complex variables with power series and conformal transformations, and thus, is able to overcome several difficulties arising from the noncircular geometric configurations, lining supports, and grouting circle. Furthermore, multiconnected domain problems caused by the tunnel lining and surrounding rock grouting ring were solved using the power series complex function method and continuity condition of elastic mechanics. The ultimate stress function was incorporated into the stress and displacement equations to obtain the stress and deformation values of the noncircular tunnel under grouting reinforcement. The results obtained using the new method were compared with numerical results as well as results obtained without taking the grouting circle into consideration. The conclusions are as follows:The grouting circle stiffness increases after grouting, thereby improving the stress state of the tunnel. The vault subsidence decreases by approximately 21.8% due to the integral stress of the grouting circle of the lining. The arch bottom uplift and normal stress in the lining decrease by approximately 18.1% and 19.9%, respectively. The peak value of the circumferential stress in the lining decreases by 8.9% after the grouting. The surrounding rock grouting can effectively reinforce the rock mass, seal the cracks, improve the stress state of the lining, and improve the ability of the tunnel to resist deformation and damage. The analytical solutions are in good agreement with the corresponding numerical solutions, and the obtained law conforms to engineering practices. The new method provides an alternative route for obtaining rapid and accurate solutions of noncircular tunnel excavation problems taking grouting circle into account. The results are expected to provide a reference for numerical computation of noncircular tunnels taking grouting circle into account.
  • Theoretical Model and Field Test of Pressure Distribution of Constant Pressure Group-hole Grouting Slurry
    WANG Hong-bo, ZHANG Qing-song, LIU Ren-tai, LIU Ya-nan, LIU Yan-kai, JIANG Peng
    China Journal of Highway and Transport. 2018, 31(10): 266-273.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    The long-term operation safety of tunnel is seriously threatened by the water leakage of primary supports. The grouting inhomogeneity which could trigger destructions of arch bottom and poor effects of vault is the crucial issue for the water leakage treatment. A novel group-hole grouting theory aiming at multi-hole was put forwards in view of the existing defects such as facility waste and complicated process in the aspect of water leakage treatment. Besides, a constant pressure group-hole grouting device was developed, and accordingly several grouting holes could be performed simultaneously at the same pressure only with one grouting pump. Furthermore, the slurry diffusion law was analyzed and the pressure equation was derived in view of the slurry gravity. At the same time, the variation of grouting pressure along with tunnel section angle was obtained via the derived pressure equation. Last but not least, the field tests on the grouting behind tunnel primary supports was conducted and the relationship between the actual grouting pressure and the tunnel section angle was investigated. After comparing theoretical results and experimental results, a series of proposals for grouting design were introduced from the perspective of grouting principles, engineering characteristics and treatment effects. The results show that not only the engineering efficiency but the treatment homogeneity could be greatly improved by the group-hole grouting device. In addition, there is good consistency between the theoretical results taking slurry gravity into consideration and the field results. The pressure of group-hole grouting showing an obvious elliptical distribution is symmetrical with the tunnel section angle and the pressure at arch bottom is 2.3 times of that at vault. Nevertheless, there is a giant difference between the pressure calculated by the traditional theory without respect to slurry gravity and the field pressure, which is presented from -43% to 33%. Hence, the slurry gravity should be pay enough attention in the process of grouting design, which may provide a reference for the grouting theory and process of the water leakage of tunnel primary supports.
  • Test of Grout Diffusion of Shield Tunnel Backfill Grouting in Sandy Strata
    CAI De-guo, YE Fei, CAO Kai, YANG Peng-bo, XIONG Wei
    China Journal of Highway and Transport. 2018, 31(10): 274-283.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Grout diffusion of shield tunnel backfill grouting was investigated based on an analysis conducted for the construction phase. The experimental design included a test model box, grouting system, grout preparation system, and testing and data processing system. The properties of the grout were tested, and three kinds of sand strata with different gradations (in different fractal dimensions) were grouted using three different fluids based on model tests:Newtonian, Bingham, and power-law fluids. The regularity of variations in the grout flow velocity, soil density, and water content during the backfill grouting period were analyzed based on the test results. Combined with theoretical calculations, the regularity of variations in the grout filling ratio (λ), over-excavation coefficient and grout compression coefficient (λ1+λ2), grout loss coefficient (λ3), grout permeability coefficient, and compaction coefficient (m) in the soil were analyzed. The results show that the water cement ratio significantly influences the grout flow speed and diffusion time in the process of grouting, and the impact of the fractal dimension of the sand sample on the injectable time of the formation is pronounced. The grout filling ratio is related to the water cement ratio, and the grout loss coefficient is positively correlated with the water cement ratio. There is minor change in the over-excavation coefficient and grout compression coefficient values for the different sands. The grout permeability coefficient and compaction coefficient in soil are negatively correlated with the fractal dimension of the sand sample. After grouting with the three different fluids, the density of the surrounding soil is inversely proportional to the depth of the grouting hole. The rate of change of this density decreases and tends to have a low discreteness in the longitudinal direction. The water content of the surrounding soil is directly proportional to the depth of the grouting hole. The rate of change of this water content decreases and tends to be constant in longitudinal direction.
  • Mechanical Properties of Fractured Rock Mass with Consideration of Grouting Reinforcement（in English）
    LIU Ren-tai, ZHENG Zhuo, LI Shu-cai, YANG Hong-lu
    China Journal of Highway and Transport. 2018, 31(10): 284-291.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Based on the results of a theoretical analysis, a mechanical model was proposed for a fractured rock mass with consideration of grouting reinforcement. A uniaxial compressive test was conducted to analyze the influence of various factors, such as the volume of block proportion (VBP), crushing degree, roughness of the boundary, and cohesive force of the grout material, on the compressive strength of the rock mass. The results reveal that during the failure process, the internal blocks maintain their integrity, and the fracture mainly occurs on the boundary between the blocks and grouting material or in the interior of the grouting material. However, when the VBP is high, a failure surface cannot be generated at once owing to discontinuities in the internal blocks, and a shear failure is observed. For an ungrouted fractured rock mass, the compressive strength decreases as the VBP increases, and the dispersion degree of the test data is large. After grouting reinforcement, the compressive strength increases as the VBP increases and displays a clear linear dependence. The compressive strength decreases as the number of rock blocks increases, and the linear dependence is not obvious. Furthermore, the compressive strength increases as the cohesive force of the grouting material increases, and decreases as the fracture density increases. The overall strength of the rock mass is the result of a coupling effect between the fracture density and cohesive force. Based on the theoretical model and experiment data, a formula that considers the influence of the block amount, fracture degree, interface roughness, and cohesive force of the grouting material was proposed to calculate the compressive strength of the reinforced fractured rock. The accuracy of the formula was evaluated by comparing calculated values with test values.
  • Failure Modes of Floor Heave in Large Section Tunnel Invert
    DU Ming-qing, ZHANG Ding-li, WANG Xu-chun, GUAN Xiao-ming, ZENG Ke-han, ZHOU Qiu-shuang
    China Journal of Highway and Transport. 2018, 31(10): 292-301,358.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    An invert is an important part of a tunnel, and the deformation of the tunnel invert is a key factor that affects track regularity and is closely related to the safety of tunnel operations. To determine the failure modes of floor heave in a large section tunnel invert and its mechanism, model tests and extended finite element method analyses were conducted for different loading methods. The surrounding rock pressure was divided into three components for analysis:dominant forces in the bottom, dominant forces in the flank, and simultaneous dominant forces in the bottom and flank. This guaranteed the reliability of the loading mode in the model test. The results show that the basic failure modes of floor heave of the invert in the large section tunnel are of the U-W, U-LJ, and U-H crack types. The U-W crack type is mainly characterized by bending failure in the middle span. The bottom is subjected to a large supporting force that leads to uplift deformation, and the sides of the tunnel are connected to the lining, which has an inhibition effect on the uplift deformation, eventually leading to the U-W crack type. In the U-LJ crack type, the large section tunnel invert receives a large horizontal axial force, which leads to shearing failure of the tunnel invert. The U-H crack type generally emerges when the tunnel invert is subjected to simultaneous bottom and side loading; the connection between the tunnel invert and side wall is broken by the shearing and cannot effectively transmit axial force, thus causing the tunnel invert and side wall to eventually disengage. It is found that the center of the tunnel invert and the connection between the invert and side wall are the weak portions of the invert. Furthermore, the accuracies of the basic failure modes are verified by comparisons of the calculated results with those from the extended finite element analyses. The research results in this study can provide a theoretical basis for the design and construction of tunnel inverts and may be of great significance to ensure the safety of tunnel operations.
  • Laboratory Tests on Reasonable Grouting Final Pressure of Water-rich Sand Layer
    JIANG Peng, ZHANG Qing-song, LIU Ren-tai, LIU Ya-nan, ZHANG Lian-zhen
    China Journal of Highway and Transport. 2018, 31(10): 302-310.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    In the grouting reinforcement project of water-rich sand layer, the compaction effect of the grout vein on sand layer controls the stability and stability-time of the strengthened working face. The final grouting pressure is a key parameter that determines compaction. A reasonable grouting final pressure can help achieve the best grouting effect while reducing the amount of grouting and surface uplift deformation. The cohesive soil sand layer in Qingdao area was selected as the typical stratum in this study. One-dimensional drainage consolidation compression was used to simulate the process of compacting the sand layer. The changing rules between the permeability coefficient and stability-time with respect to consolidation pressure were studied using the test device, which was specifically designed for determining the permeability coefficient and stable length. Based on the theory of natural equilibrium arch by Przewalskii, the stability of the sand layer under different consolidation pressure conditions was verified. The results of the study show that when the consolidation pressure exceeds 800 kPa, the influence of any increase in the consolidation pressure on the permeability coefficient and stable length of the sand layer is insignificant. For the section of the standard single-hole subway tunnel in Qingdao area, when the consolidation pressure exceeds 700 kPa, the shear strength of the compacted sand layer is guaranteed to meet the excavation self-stability requirements. Therefore, 800 kPa is comprehensively determined as the reasonable grouting final pressure of such water-rich sand layers in the Qingdao area. The research results were applied to the consolidation of water-rich sandstones in the Ling-Huang interval undercut tunnel of Qingdao Metro Line 13, which verifies the accuracy of these theoretical results. This work is thus significant in terms of the theoretical research and practical engineering applications that may help control water-rich sand disasters in shallow buried tunnels.
  • Time-dependent Behavior for Coupling Model of Pre-stressed Bolt and Rock Mass
    WANG Gang, HAN Wei, LIU Chuan-zheng, WANG Ke, LUAN Heng-jie
    China Journal of Highway and Transport. 2018, 31(10): 311-319.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    To reveal the time-dependent behavior of pre-stressed bolt and rock mass, the elastic solutions of the coupling model under a distributed force model were acquired. The rheological model of the bolt and rock mass were selected based on the material properties and scale effect. A one-dimensional Kelvin model was selected for the bolt, and a three-dimensional Burgers model was used for the rock mass to solve the analytic solutions in the Laplace space. Then, the viscoelastic solutions of the coupling model can be acquired by the inverse variation of the Laplace space. The influences of pre-stress and viscous parameters on the stress or displacement fields of the rock mass and the axial force were discussed. The numerical simulation was performed based on the theoretical model and the secondary development of numerical simulation software FLAC3D. The comparison and analysis show that the analytical solutions are in good agreement with numerical solutions, which verifies the correctness of the analytical solutions. The results show that with the increase in time, the support force gradually decreases at the excavation surface in the tunnel. In addition, the pre-stress and rock mass viscosity parameters strongly affect the bolt support effect. There is a significant positive correlation between support effect and bolt pre-stress. The change in rock mass displacement shows a significant time correlation. In addition, there is a negative correlation between the rock mass displacement and bolt pre-stress. The research shows that when the bolt pre-stress is too large, the rock mass displacement is no longer significantly reduced. Thus, it can be seen that the pre-stress applied to the bolt should not be too large. In addition, the early support effect is mainly affected by the viscosity coefficient of the first creep stage in the Burgers model of rock mass. However, the later support effect is mainly affected by the viscosity coefficient of the second creep stage. The greater the viscosity coefficient, the better the later support effect. Furthermore, the rheological state of the bolt is independent of the viscosity coefficient of the rock mass.
  • Research and Application of Fabricated Confined Concrete Construction System for Large Cross Section Tunnel
    SUN Hui-bin, LI Shu-cai, WANG Qi, ZHOU Lei-sheng, JIANG Bei, ZHANG Xiao, XU Shuo, ZHANG Hao-jie
    China Journal of Highway and Transport. 2018, 31(10): 320-327.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    This study was conducted to solve the difficulty of controlling the soft surrounding rock of a large section tunnel and the problem of low efficiency and poor safety during the construction process. Based on the research achievements of the confined concrete arch support, a series of intelligent installation equipment, fabricated confined concrete arches (FCC arches), and corresponding supporting devices was developed, and the FCC system of a large section tunnel was formed. A mechanical simulation test of the machine assembly construction process of the FCC arch was carried out. The deformation and stress of the arch in the construction process were monitored in real time, the mechanical characteristics of the construction process of the arch were clearly defined, and the strengthening measures, including the anti-bending plate in the shoulder area, were put forward. The field experiments on the mechanized construction of fabricated confined concrete support were carried out, and the characteristics and laws of the convergence and deformation of the surrounding rock, the contact pressure of the surrounding rock and the initial support, and the internal force distribution of the arch were determined. The results showed that under the combined influence of self-weight and mechanical construction of the FCC arch, the deformation value in the shoulder area of the arch, which is the key part of the stress and deformation, suddenly changes, and the stress concentration situation is obvious; there is no obvious deformation in the process of the installation of the reinforced FCC arch. In the field test section, the eccentric compression phenomenon was obvious. The deformation and stress of the upper stage surrounding rock exhibit three stages of fluctuating growth, with the most intense fluctuation in the vault and shoulder area; the stress of the arch was characterized by "bigger on the upside and smaller on the downside", and the maximum stress value appeared on the outside of the vault, followed by the left arch shoulder position. The mechanized construction could effectively control the deformation of surrounding rock of the large section tunnel, improve the effectiveness and fabrication level, and guarantee security and reliability of the construction process, which can provide a reference for similar projects.
  • Dynamic Fracturing Diffusion Law Considering the Influence of Multiple Sequence Grouting in Argillaceous Fault
    LI Peng, ZHANG Qing-song, WANG Qian, DONG Kun, LI Shu-cai, ZHANG Xiao
    China Journal of Highway and Transport. 2018, 31(10): 328-338.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    The grouting method is an effective method to reinforce argillaceous fault in tunnel engineering. By using the theoretical derivation and model test methods, this study aims to realize the calculation of pressure and splitting path width of multiple sequence grouting in argillaceous fault, also to reveal the dynamic influence law among them. In this way, the development of scientific and controllable grouting can be promoted. In the engineering of fracturing grouting for argillaceous fault, establishing a reasonable ε-p curve model of soil was the basis of the calculation of grouting design parameters (pressure, splitting path width). The grouting process had the characteristic of multiple sequences and the pre-sequence grouting reinforcement effect could make the soil ε-p curve model with dynamic character, and then the slurry split diffusion model also had the dynamic performance. On the basis of initial soil compression, the pre-consolidation pressure p and the recompression soil characteristic compression modulus E's1-2 were regarded as the characterization parameter, and put forward the order sequence was applicable to the grouting in the soil recompression deformation ε-p curve model and its parameter solving method, and then the recompression soil slurry split diffusion model was established. Compared with the initial compression soil slurry split diffusion model, the calculated value of the split path width was reduced by up to 26.59% under the working condition, slurry drive pressure to enhance the value of the maximum increase of up to 269%, which proved that the necessity of the first sequence grouting was considered. The model test of identification of "three tube four order" fracturing grouting test was carried out. Comparison of the results of the first order and the second order test show that the maximum and average injection pressure can increase by 96.4% and 104.8%, respectively, while they become 5.45% and 20.16% in the second order and the third order test. Furthermore, the average width of the post grouting split path was reduced by 58.2%-69.3% compared to the first order, which fully proved that the correctness of the theoretical results. The changes of soil pressure and the three-dimensional distribution of the slurry splitting path also can be monitored by the experiment.
  • New Protective Structure for Shallow-buried Bias Tunnel at Portal Section and Its Simplified Calculation Method
    DONG Jian-hua, XIE Yong-bin, LI Jian-jun, KOU Hai-jun, ZHAO Yong-da
    China Journal of Highway and Transport. 2018, 31(10): 339-349.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    To address the problems of easy collapse and excessive displacement of the support structures of shallow-buried bias tunnels during construction of an existing tunnel section, a new protective structure for the shallow-buried bias tunnel at the portal section was proposed. The advantages of anti-slide piles, anchor cables, and pipe sheds were considered and utilized for the cross-construction. The simplified analysis model of the protective structure under terrain bias was established, and the internal force and displacement of the protective structure under terrain bias were solved using the M method. Then, the internal force and displacement of the structure under the combined action of terrain and construction bias were corrected and obtained by the deformation coordination condition. Combined with the example model, the internal force and displacement distributions of the new protective structure were analyzed. The reliability of the simplified calculation method was thus verified by comparing the calculation results and the ADINA simulation results, which provides a theoretical basis for the analysis and design of similar new structures.
  • Dynamic Model Test on Anchoring Effect of Prestressed Anchor Cables
    JIA Xiao-yun, ZHU Yong-quan, JIA Chao
    China Journal of Highway and Transport. 2018, 31(10): 350-358.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    In order to determine the influence of train vibration load on the prestress loss of anchor cables and the subsidence and horizontal displacement of the pile-taking the deep foundation pit pile-anchor retaining structure in the open-cut section of the Shijiazhuang six line-tunnel as engineering background-the materials of the soil-pile anchor system were determined in model tests based on the similarity relation. According to the vibration characteristics of the train load, model test with continuous vibration for 162 days (similarity) after foundation excavation was carried out. The law of prestress loss in anchor cables, the subsidence and horizontal displacement of the pile under different vibration frequencies, and the effect of anchor depth on prestress loss were analyzed when vibration frequencies were 8.282, 13.801, 20.704 Hz. Test results reveal that the prestress loss of anchor cables and the subsidence and horizontal displacement of the pile greatly increased with the increase of vibration frequency. The average loss rate of prestressed anchor cable is 2% when driving for 28 days (prototype) continuously at the speed of 120 km·h-1. The average loss rate increases to 8% and 23% when driving for 53 days (prototype) continuously at the speed of 200 km·h-1 and 300 km·h-1, respectively. The prestress loss of anchor cables in the anchorage section decreased along the anchorage depth of the anchor cables; the prestress is almost zero at the bottom of the anchorage section. The dynamic model test result reveals the effect of traveling speed on the prestress of anchor cables and the subsidence and horizontal displacement of the pile. The prestress loss of anchor cables under the train load is known according to the dynamic model test, which can reference for the design and construction of anchor cables in deep and large foundation pits near railways.
News More>>
Download More>>
Links More>>
New Media
  • Wechat Account
  • WeChat video Account
Visited
    Total Visits:    Today:    Online:
Copyright © China Journal of Highway and Transport, All Rights Reserved.
Tel: 029-82334387　
E-mail：zgglxb@163.com
Powered by Beijing Magtech Co. Ltd,.