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Quick Search     Advanced Search MODERN TUNNELLING TECHNOLOGY   2021 Vol.58 Issue.3 Published 2021-06-25 1 2021 Vol. 58 (3): 1-5 [Abstract] ( 713 ) [HTML 1KB] [ PDF 1454KB] ( 1849 ) 6 Challenges and Prospects of Construction Technology for Extra-large Diameter Composite Shields ZHU Weibin1,2 ZHONG Changping3 MI Jinsheng1 HUANG Weiran4 Following the concept of "geology is the foundation, shield the key, and people (technology and manage? ment) the root" in shield tunnelling technology decision-making, risks in the process of the survey, design, shield selection and configuration, as well as construction are analyzed for extra-large diameter shields driving in composite strata, mainly including three typical rock groups of granite, limestone and clastic rock as the dominant matrix. And the relevant targeted solutions are put forward. It elaborates on the current status and challenges of the construction technology of extra-large diameter composite shields and makes an outlook on the future development of extra-large diameter composite shields in China, which is of significant guiding implications. 2021 Vol. 58 (3): 6-16 [Abstract] ( 702 ) [HTML 1KB] [ PDF 7193KB] ( 1177 ) 17 Dialectical Thinking on Solving Major Issues in Tunnelling MA Shiqiang The most prominent feature of tunnelling is that it is built underground and embedded in a certain geo? logical environment. The construction of a tunnel project, however, will inevitably break the balance of the original geological environment and eventually establish a new balance. Along the process, some major issues are bound to be faced, such as the stability of the surrounding rock, problems about the groundwater, selection of excavation methods and support forms, among others. This paper abstracts the ideas of solving these major issues and explores the solutions to these issues at the level of unity of opposites of materialistic dialectics and based on the principle of concrete analysis of specific problems, which enhances the wisdom and art of dealing with these major issues and enables them to be better applied to concrete project practices for verification. 2021 Vol. 58 (3): 17-22 [Abstract] ( 720 ) [HTML 1KB] [ PDF 622KB] ( 1460 ) 23 Influence of Tectonic Characteristics of Surrounding Rocks on Engineering Geology of Water Conveyance Tunnel in the Hanjiang-to-Weihe River Valley Water Diversion Project ZHANG Jie1 LI Wei1 LI Limin2 WAN Jiwei3 DING Weihua4 JIA Chao1 The water conveyance tunnel of the Hanjiang-to-Weihe River Valley Water Diversion Project, which crosses the Qinling Mountains, is a key section that affects the overall progress of the Project. The complex lithology and tectonic characteristics of the Qinling Orogenic Belt have a huge impact on the construction and maintenance of the water conveyance tunnel. An in-depth geological analysis of the tentonic characteristics of the tunnel surrounding rocks can provide an important geological basis for the construction of the Project. Based on field geological work, this paper combines microscopic observation of typical rock sample slices and rock mechanics tests to obtain the tectonic data and mechanical properties of the surrounding rocks in the South Qinling section. The South Qinling section can be divided into four lithological sections according to the macro and micro tectonic characteristics of the surrounding rocks: gneisses section of upper amphibolite facies, metamorphic rock section of lower amphibolite facies, epimetamorphic rock section and granite section. The deformed structure that affects and constrains the engi? neering characteristics of the surrounding rocks can be further divided into two categories: one is the surrounding rocks that develop brittle deformation, which are affected by the intracontinental tectonic evolution since the Middle Cenozoic with the brittle deformation extremely developed and have the most intuitionistic and obvious impact on the project construction. The other is the surrounding rocks with weak structural surfaces, which causes the mechanical properties of the whole rock mass to have significant anisotropy, and the relationship between the occurrence of weak structural surfaces and the orientation of principal stress governs the mechanical properties of the surrounding rocks. 2021 Vol. 58 (3): 23-32 [Abstract] ( 683 ) [HTML 1KB] [ PDF 8282KB] ( 888 ) 33 Study on the Tunnel Lining Cracking Patterns and Failure Ranges under Fire Scenarios HAN Xingbo1,2 ZHAO Weifeng1 Tunnel fires pose a threat to human life and have an impact on the structural safety of tunnels. First, this paper establishes a 3D temperature field of the fire smoke according to the actual fire conditions in a metro running tunnel. Then, the basic equations and solutions to the lining temperature field during the fire are derived by taking into consideration the thermal convection, heat conduction between the tunnel wall and heating smoke, the nonlinearity of heat transfer properties of the lining materials as well as the concrete spalling, The accuracy of the proposed method is verified by comparing with the test results. Furthermore, combined with the 3D temperature field obtained from the solution, the stress in the lining during the fire is solved by the finite element method under considering the lining material's thermodynamic properties as the non-linear functions to the temperature. Finally, the lining failure patterns and ranges are analyzed according to the elastic failure criterion and the triaxial stress conditions. The study results show that the lining failure is mainly caused by the compressive crushing of the inner concrete; after 2h of the fire, the compressive stress of the lining exceeds the compressive strength within the range of 16 m along the driving direction, 12 cm thickness of concrete and 112° from the vault to the sidewall; at the depth of main reinforcements of the lining segment, the concrete stress is less than the strength within 30 min; the failure pattern of the segment is mainly flake splitting; and the bolts have insufficient shear strength in the late stage of the fire, within the range of 37° at both sides of the vault. 2021 Vol. 58 (3): 33-42 [Abstract] ( 689 ) [HTML 1KB] [ PDF 4850KB] ( 810 ) 43 DSR-Cloud Model Based Evaluation of Construction Safety of Tunnels with High Geotemperature GAO Lei BAO Xueying LI Aichun With respect to the construction safety of tunnels with high geotemperature, this paper attempts to estab? lish an appropriate and effective evaluation system for a comprehensive evaluation. Firstly, it uses the DSR model to establish an evaluation index system of environment driving force - measurement state - measure response; Secondly,it determines the indicator weights by using the variable weight theory; Thirdly, it obtains the numerical eigenvalues of the integrated cloud model and generates the contours through the cloud model theory, and then determines the evaluation levels by combining the calculated maximum membership degrees; Finally, it applies this evaluation method to the engineering case for verification. The results obtained from the engineering case show that its safety state is slightly worse than medium, and the indicators leading to the decrease of the safety level are screened and picked out. The results show that the indicator system developed by the DSR model is comprehensive and relevant;the variable weight theory makes the indicator weights objective and realistic; the use of the cloud model dissolves the fuzzy and random characteristics of qualitative concepts in the evaluation process and makes the evaluation re? sults more reasonable and effective. 2021 Vol. 58 (3): 43-51 [Abstract] ( 650 ) [HTML 1KB] [ PDF 2437KB] ( 1253 ) 52 A 3D GPR Imaging Technique of Tunnel Cavities Based on the Half-space Scanning Measurement Mode DENG Haiming1 YANG Xi2 LI Zhishan3 LEI Hongxian4 TANG Kan1 FAN Mingwai2 ZHANG Hantao2 As an efficient and non-destructive geophysical detection tool, ground penetrating radar (GPR) is wide? ly used in the detection of tunnel geological hazards, especially tunnel cavities. Due to the constraints of environmental conditions, the current GPR measurement methods used in tunnelling are mostly based on 2D reflection profiles,which results in the problem of large limitations on the spatial detection range. In order to improve the spatial detection range of GPR as much as possible without increasing the workload or reducing the efficiency of data acquisition,this paper proposes a detection mode based on half-space scanning measurement, by which it achieves the omnibearing 3D imaging within 30 m range of the half-space area of the tunnel face by the inversion of 3D data volume.The proposed method is verified by 3D FDTD numerical simulation analysis based on CPML absorbing boundary conditions and by spectral analysis on the received signals. The method is applied to the detection of cavities in the right tube of Ying'erling tunnel of Rongcheng-Wuhai Expressway in Hebei Province, successfully detecting the cavity hazards at the top of the tunnel from K103+607 to K103+567. In addition, the 3D GPR detection results are cross-validated with the 3D seismic geology prediction results, with good consistency. 2021 Vol. 58 (3): 52-59 [Abstract] ( 723 ) [HTML 1KB] [ PDF 3489KB] ( 1167 ) 60 Implementation and Application of Tension-Shear Fracture of Anchor Bolts in FLAC3D HE Lili Large deformations in tunnel surrounding rocks can easily lead to tension, shear, and tension-shear frac? ture of the anchor bolts. In view of this, this paper modifies the mechanical behaviors of the PILE structure unit based on the FLAC3D software and establishes a numerical simulation model for fracturing of PILE unit through the secondary development of FISH language. On such basis, it analyzes the mechanical behaviors of the fracture failure of anchor bolts in the anchorage system of the layered rock mass. The results show that: (1) the calculation results obtained by modifying the PILE unit are in good agreement with the indoor test results and can better reflect the mechanical behaviors of tension, shear and tension-shear fracture of the anchor bolts; (2) in the case of anchor bolt fracture in the layered rock mass, the maximum tensile force to which the tensile fractured anchor bolt is subjected reaches its ultimate tensile value before anchor bolt fracture; the maximum tensile and shear forces of tension-shear fractured anchor bolts are less than the corresponding ultimate tensile and shear values before fracture; and (3) for tension-shear fractured anchor bolts, if the shear fracture of the anchor bolts is not taken into consideration, it would exaggerate the support effect of the anchor bolts; while for tensile fractured anchor bolts, not considering the effect of shear fracture has a limited impact on the support effect of the anchor bolts. 2021 Vol. 58 (3): 60-69 [Abstract] ( 660 ) [HTML 1KB] [ PDF 4127KB] ( 1101 ) 70 Study on the Influence of Environmental Factors on the Brightness Value L20(S) outside Highway Tunnel ZHANG Xiaojian1 LIANG Bo1,2 ZHONG Shengming1,3 Brightness L20(S) outside a tunnel, as the basic parameter of lighting at entrance section of a highway tunnel, affects the lighting design of the transition section, and its value is subject to the combined action of various factors. Many factors affect the measurement of brightness outside a tunnel. This paper studies the influence of each factor on the brightness L20(S) value outside the tunnel based on three factors, i.e. the sky exposure rate outside the tunnel, the form of the tunnel portal and the color of the pavement surface outside the tunnel. Through investigating highway tunnels within the main city of Chongqing, corresponding tunnels which meet the requirements are selected as the research objects. In combination with theoretical analysis and field test verification, the influence law of each index parameter on the brightness L20(S) outside the tunnel is obtained and the indices of brightness outside a highway tunnel are put forward based on field brightness test method. The study results show that: (1) the recommended value of the brightness L20(S) outside a tunnel in autumn and winter should be at least one time and above the actual measured brightness value; (2) the patterns of the values of pavement brightness are consistent with that of the RGB values; and (3) the brightness outside a tunnel with end-wall type portal is smaller than that with bamboo-truncated type portal. 2021 Vol. 58 (3): 70-78 [Abstract] ( 785 ) [HTML 1KB] [ PDF 3480KB] ( 1010 ) 79 Solutions to the Spherical Cavity Grouting Pressure in Circular Tunnels Based on the Generalized SMP Strength Criterion ZHANG Chang′an1 QI Xiangcheng2 Based on the generalized spatially mobilized plane (SMP) strength criterion, which reasonably considers the effect of intermediate principal stress on soil mass strength, this paper theoretically analyzes the spherical cavity compaction grouting process, establishes the generalized SMP strength criterion based solutions to the grouting pressure in circular tunnels, and verifies it by comparing with the measured values in the literature. At the same time, in combination with existing solutions based on MC strength criterion in the literature, this paper analyzes the characteristics of the influence of soil strength parameters on the grouting pressure. The results show that the grouting pressure based on the generalized SMP strength criterion is higher than that in the literature based on MC strength criterion, and is more conducive to setting the actual range of spherical cavity grouting pressure in engineering; the effect of strength parameters of soil mass on grouting pressure is significant, and the effect of cohesion is more significant than that of internal friction angle. 2021 Vol. 58 (3): 79-83 [Abstract] ( 732 ) [HTML 1KB] [ PDF 1044KB] ( 1165 ) 84 DEM Analysis on Soil Arching Effect of Unloading Structure of High-Filled Open Cut Tunnels YAO Yuxiang1 LI Sheng1 MA Li1 WANG Changdan2 ZUO Di3 The concentration of soil pressure on the tunnel roof caused by the stiffness difference between the highfilled open cut tunnel and the soil masses will often lead to the longitudinal cracking of the roof, which will lead to the occurrence of engineering accidents. This paper establishes a numerical model for the unloading structure of open cut tunnels through the Mesoscopic Particle Flow Code in 2D (PFC2D) software, and studies the effects of different load reduction measures on soil arching effect at the mesoscopic level of vertical soil pressure, vertical particle displacement, inter-particle contact force chain, and porosity, etc. At the same time, taking the working condition Y7 (EPS plate + geogrid + concrete column) as the benchmark, this paper also takes into consideration the EPS plates of different densities and thicknesses for parametric analysis. The research results show that the load reduction measures above the tunnel roof can effectively reduce the soil pressure on the roof, and the load reduction effects of different load reduction measures are arranged from strong to weak as follows: EPS plate + geogrid + concrete column > EPS plate + geogrid > EPS plate > low compacted soil + geogrid + concrete column > low compacted soil + geogrid > low compacted soil. Among them, setting concrete columns on the side slopes of the original open cut tunnel can strengthen both the soil arching effect and the tensile membrane effect, so that most of the filling soil load can be transferred to the concrete columns and thus reduce the soil pressure on the top and side of the open cut tunnel. The development of soil arching effect is related to the change of porosity of the soil at the top of the tunnel.The porosity increases before decreasing with the increase of the density and thickness of the EPS plates, and it reaches the maximum value when the density of the EPS plate ρ=15 kg/m3 and thickness T=15 cm, while the soil arching effect is the strongest and the load distribution at the top of the open cut tunnel is the least. 2021 Vol. 58 (3): 84-93 [Abstract] ( 649 ) [HTML 1KB] [ PDF 4802KB] ( 1246 ) 94 Research on the Calculation Method of Vertical Soil Pressure on High-Filled Open Cut Tunnels Based on Multi-factor Coupling HAN Guoqiang1 ZHOU Peng1 LI Sheng1 HE Chuan2 MA Li1 On the basis of the traditional calculation theory of soil pressure, this paper modifies the traditional cal? culation formula of soil pressure by defining related influence coefficients such as the tunnel width, section type, filling property, slope angle/ trench width, and proposes a calculating formula for the vertical soil pressure on the top of a high-filled open cut tunnel under considering these four influence coefficients. Firstly, the uneven soil pressures are transformed into uniformly distributed loads through the equivalent load method, the mathematical expression of the regression curve of vertical soil pressure on the top of the high-filled open cut tunnel is determined through the mathematical regression method and numerical simulation method, and the change law of the influence coefficients with H/W (the ratio of filling height to tunnel width) is analyzed, obtaining the influence degree and trend of the influence coefficients on the vertical soil pressure on the top of the high-filled open cut tunnel, so as to determine the calculating formula for the vertical soil pressure on the top of the tunnel. Then the established formula is verified by selecting two design conditions of railway open cut tunnels, and the results show that the average relative error between the calculation results by the proposed formula and the numerical simulation results is 1.68%, which verifies the correctness of the formula. 2021 Vol. 58 (3): 94-99 [Abstract] ( 581 ) [HTML 1KB] [ PDF 1755KB] ( 1114 ) 100 Simulation Study on Seismic Response Laws and Seismic Mitigation Measures of Tunnels under Fault Dislocation GAN Xingqiu1 XU Feng1 WANG Xiaowei1 LI Pei1 PENG Shuquan2 QI Binxi2 FAN Ling2 WANG Fan2 Taking the No.2 tunnel of the Lot 3 of the Phase I project of Nariobi-Malaba Railway as the background, this paper uses the ANSYS software to conduct numerical modeling for the simulation study of the seismic response and seismic mitigation measures of tunnels under fault dislocation and seismic action. The results show that the seismic response of the tunnel sidewalls is the most obvious both under the action of fault dislocation in the vertical direction and the seismic action in the horizontal direction; fault dislocation leads to stress redistribution in the tunnel under the effect of gravity as well as seismic action, where the principle stress extreme value, X-displacement extreme value and maximum acceleration increase obviously, with the largest increase in acceleration; the seismic response of the tunnel under fault dislocation and seismic action decreases obviously with increasing of damping ratio of the shock mitigation layers, and a shock mitigation layer with larger damping ratio can effectively reduce the extent of increase in the stress, displacement and acceleration induced by the seismic response of the tunnel due to fault dislocation; sand-rubber mixture and gravel-rubber mixture, in combination with geocell reinforcement, are potentially suitable seismic mitigation materials for tunnels. 2021 Vol. 58 (3): 100-106 [Abstract] ( 669 ) [HTML 1KB] [ PDF 3364KB] ( 983 ) 107 Study on the Influence of the Spatial Combination Relationship of Structural Planes on the Stability of Tunnel Surrounding Rocks YUAN Bin1 XU Fanxian2 LIAO Huan3 ZHONG Yutian3 LUO Gang3 The deformation and failure of tunnel surrounding rocks are closely related to various factors, including the rock strength, the spatial combination relationship of the structural planes, the groundwater and geostress etc. In order to study the influence of the spatial combination relationship of structural planes on the stability of tunnel surrounding rocks, this paper is based on the geological conditions of the Xiangjiawan tunnel on Zhengzhou-Chongqing High-speed Railway, and uses the UDEC discrete element software to numerically simulate the stability of the surrounding rock under full face excavation, with the focus on the influence of the spatial combination relationship of two groups of structural planes on the shear slip of the structural planes as well as the plastic failure and displacement of the surrounding rocks. According to the deformation differences of the surrounding rocks after excavation(intact, falling and collapse), the paper conducts qualitative statistics to obtain a statistical table of the influence of the spatial combination of structural planes on the stability of tunnel excavation and proposes corresponding con? struction suggestions. The study shows that the deformation failure of the tunnel surrounding rocks mainly occurs in the spatial combination of condition where the distance between structural planes is less than 1.5 m, the dip angle of J1 is 45°~75° and J2 103°~133°. 2021 Vol. 58 (3): 107-114 [Abstract] ( 600 ) [HTML 1KB] [ PDF 5690KB] ( 1028 ) 115 Theoretical Analysis of the Stability of Tunnel Face under Pipe Roof Presupport AN Yonglin1 LI Jiahao1 OUYANG Pengbo2 LIU Wenjuan1 SU Guangming3 ZHOU Jian3 In order to investigate the stability of the tunnel face under pipe roof support, this paper takes into con? sideration the stress characteristics of the pipe roof, establishes a Winkler foundation model for the pipe roof, and applies the foundation reaction force on the upper part of the tunnel face in the model. Meanwhile, based on the rigid limit equilibrium theory, this paper derives the calculation formula of the safety coefficients for the stability of the tunnel face. Finally, taking the No. 3 transverse adit of Badong tunnel as the engineering background, this paper analyzes the stability of the tunnel face with and without the pipe roof, and discusses the effect law of each parameter on the deflection of the pipe roof and the stability of the tunnel face. The results show that the maximum deflection of the pipe roof and the displacement near the tunnel face will decrease and the safety factor for the stability of the tun? nel face will increase, as the diameter of the pipe roof increases, the displacement of the support at the end of the pipe roof decreases, the advance per round and the height of excavation bench decrease, and the internal friction angle and cohesion of the surrounding rock increase; shorter advance length has more obvious effect on improving the stability of the tunnel face under better surrounding rock conditions, lower excavation heights and smaller pipe roof support displacements; as the tunnel buried depth increases, the safety factor for the stability of the tunnel face first decreases before it increases, and then remains constant. This is related to the calculation formula for the surrounding rock pressure specified in the code, for a shallow buried tunnel, the larger the buried depth, the larger the load; for a tunnel located between the deep buried depth and shallow buried depth, due to the existence of the confining effect from both sides of the surrounding rocks, the surrounding rock pressure will decrease when the buried depth increases; for a deep buried tunnel, the load will remain constant due to the collapse arch effect. 2021 Vol. 58 (3): 115-122 [Abstract] ( 756 ) [HTML 1KB] [ PDF 2997KB] ( 1125 ) 123 Study on Damage Behaviors of Tunnel Secondary Lining under Rheological Load CHENG Gang1 WANG Jun2 The rheological effect of soft and weak surrounding rocks can easily lead to the cracking of tunnel sec? ondary lining, affecting the safety and durability of the structure. In view of this, this paper takes the Dujiashan tunnel on Guangyuan-Gansu Expressway as an example and establishes a numerical calculation model based on Weibull damage distribution to investigate the damage evolution behaviors of the secondary lining under rheological load. The results show that: (1) if the secondary lining is in good contact with the surrounding rock, the lining cracking area is distributed near the arch waist, arch foot, as well as the top and bottom of the arch respectively when the lateral pressure coefficients are λ=0.5,1 and 2; (2) the cavity has a great impact on the lining cracking area and the order of the occurrence of the cracking, that is, the cracking is first induced in the concrete near the cavity, and the concrete at that specific location will all produce quite serious damage; and (3) the influence of the geostress on the damage patterns of the secondary lining with cavities can be divided into two kinds: the impact on the order of the occurrence of the damage location, but not on the final damage pattern of the structure, or the impact on both the order of the damage occurrence and the final damage pattern of the structure. 2021 Vol. 58 (3): 123-129 [Abstract] ( 639 ) [HTML 1KB] [ PDF 3872KB] ( 1158 ) 130 Study on the Stress Characteristics of the Mid-pillar in the Expansion of an Existing Tunnel into a Double-arch Tunnel JIA Yanling1,2,3 ZHOU Shaowen2,3 WANG Gang2,3 ZHOU Weizheng2,3 YANG Kunguang2,3 As the core structural component of double-arch tunnels, the force condition of the mid-pillar is not only related to the safety of the tunnel structure during construction but also directly affects the long-term safety and stability of the tunnel structure during operation. This paper takes the expansion of an existing single-tube tunnel into a double-arch tunnel as an example and carries out the model test and numerical simulation to study the stress characteristics of the mid-pillar during the construction. The construction plan is excavating the right tube (first tube) followed by the left tube (second tube). The results of the model test show that after completion of the expansion construction, the left side of the curved top surface of the mid-pillar is under tension while the right side is under compression; the left and right sides of the shoulder of the mid-pillar are both under tension, and the tensile stress on the right side is 2.86 times that on the left side; the left and right sides of the waist of the mid-pillar are both under compression, and the compressive stress on the right side is 1.32 times that on the left side, which are basically consistent with the numerical simulation results; the compressive stress at the toe of the left side of the mid-pillar is greater than that of the right side, and the mid-pillar is subject to bias pressure toward the left side of the tube. The horizontal displacement of the mid-pillar moves firstly to the side of the second tube then to the side of the first tube, and finally to the side of the second tube. 2021 Vol. 58 (3): 130-138 [Abstract] ( 635 ) [HTML 1KB] [ PDF 5239KB] ( 1166 ) 139 Analysis of the Mechanical Response in the Construction of Large-Span Mined Metro Stations by the Arch-Cover Method ZHANG Zilong1 JIANG Annan1 YU Hai2 WANG Feng2 Based on the large-span shallow mined Shikui Road Station of Dalian Metro Line 5, this paper uses the FLAC3D finite difference software for 3D numerical modeling, conducts a detailed analysis of the changes of ground settlement, lining and surrounding rock stress during the construction with the arch-cover method, proposes corresponding construction measures according to the characteristics of the mechanical response of each construction stage, and optimizes the reasonable excavation spacing of the pilot tunnel with large section. Finally, the results are compared with the actual monitoring data. The results show that the excavation of the main pilot tunnel with large section is the main factor leading to the ground settlement, which basically remains stable after the completion of the construction of the secondary lining at the vault; the excavation of the single-sided pilot tunnel has an obvious asymmetrical loading effect, and it should strictly follow the construction sequence of "the side first before the middle";the removal of the temporary support and the middle diaphragm has a significant impact on the initial support and surrounding rock stress, and measures such as segmented removal, cross removal and bolt installation instead of support can be taken to ensure the stability of the structure; the excavation spacing of the main pilot tunnel with large section has an obvious impact on the ground settlement, and the reasonable spacing should be controlled within the range of 20~35 m. The numerical calculation results are in good agreement with the field monitoring data, which can provide references for similar engineering practices. 2021 Vol. 58 (3): 139-146 [Abstract] ( 581 ) [HTML 1KB] [ PDF 4324KB] ( 790 ) 147 Study on the Optimization of Air Duct Outlet Position of Forced Ventilation in Plateau Spiral Tunnels GAO Feng1 TANG Yuchen2 ZHANG Gensi3 LIU Lin3 To study the flow field characteristics of the forced ventilation in plateau spiral tunnels and the influ? ence of the layout parameters of air duct outlet position on the tunnel construction ventilation effect, this paper studies the flow field characteristics near the tunnel face based on the Wolonggou No.1 tunnel project, by using the Fluent software and taking into consideration two kinds of longitudinal gradients, three kinds of air duct diameters and seven kinds of air duct outlet distances and other factors. The results show that if the air duct outlet in forced ventilation is too close or too far away from the working face, it is not conducive to the ventilation efficiency, and the optimal air duct outlet positions for Wolonggou No.1 tunnel are obtained regarding different longitudinal gradients and different duct layout diameters, which are applied to the tunnel practice, and the reliability of the results is verified by field tests. 2021 Vol. 58 (3): 147-153 [Abstract] ( 499 ) [HTML 1KB] [ PDF 3323KB] ( 1103 ) 154 Study on the Hydrodynamic Characteristics of the Coupling System of Submerged Floating Tunnel Tubes and Anchor Cables under Wave Action ZOU Pengxu1，2 LIU Mengyuan1，2 CHEN Liangzhi1， Submerged floating tunnel (SFT) is a new type of sea-crossing transportation channel. This paper uses the CFD method to study the dynamic response characteristics of the coupling system of submerged floating tunnel tubes and anchor cables under wave action, and analyze the impacts of different factors, such as submersion depth,buoyance-weight ratio (BWR), inclined mooring angle (IMA), anchor cable stiffness, arrangement pattern of anchor cable system and pre-tension distribution of anchor cable system and wave parameters, on the hydrodynamic characteristics of SFT. The results show that the motion response of the SFT decreases with the increase of submersion depth and increases with the increase of wave height and IMA; there is a reasonable range of values for BWR and the vertical stiffness of the anchor cable to meet the requirements for structural stability; the pre-tension distribution of the anchor cable system is not a critical factor affecting the hydrodynamic properties of SFT; it should avoid the arrangement pattern where only inclined anchor cables are located in the plane and the resonance phenomenon where the SFT- anchor cable coupling system is under specific wave periods. 2021 Vol. 58 (3): 154-162 [Abstract] ( 567 ) [HTML 1KB] [ PDF 6371KB] ( 1238 ) 163 Study on the Mechanical Properties of Frozen Fractured Sandstone YUE Peng In order to derive the influence patterns of confining pressure, fracture dip angle and freezing tempera? ture on the mechanical properties of the sandstone, this paper uses the triaxial compression test method and theoretical analysis method to study the changing characteristics of the strength, internal friction angle and cohesion of sandstones without fracture and fractured sandstones with dip angles of 0°, 15°, 30° and 45° at frozen temperatures of -5 ℃, -10 ℃ and -15 ℃ under different confining pressures. The results show that the strengths of fracture-free and fractured sandstones increase nonlinearly with decreasing of freezing temperature, decrease nearly linearly with decreasing of confining pressure, and decrease with increasing of fracture dip angle; the cohesions decrease with the increase of the freezing temperature, and both the internal friction angle and cohesion have the tendency to decrease first and then increase with the increase of the fracture dip angle; and the internal friction angles of fracture-free sandstone and fractured sandstone with 0° and 15° dip angles all decrease with the increase of the freezing tempera? ture, the internal friction angle of fractured sandstone with 30° dip angle increases first before decreasing with the decrease of the freezing temperature, and the internal friction angle of fractured sandstone with 45° dip angle decreases first before increasing with the decrease of the freezing temperature. 2021 Vol. 58 (3): 163-168 [Abstract] ( 500 ) [HTML 1KB] [ PDF 2456KB] ( 984 ) 169 Experimental Study on the Precision Evaluation and Error Correction of 3D Laser Scanners FANG Jianghua1,2 JIANG Pingwei2 WANG Qiusheng1 ZHANG Gong The 3D laser scanning technology has provided a new solution for the monitoring of settlements and de? formations in metro tunnels under complex conditions by acquiring the 3D coordinates of target objects in a fast and highly precision way. This paper combines the factors affecting the precision of scanner points at the construction site and designs a quasi-level experiment of scanning errors using the orthogonal experimental method, which takes no or any vehicle running load conditions, different horizontal ranges and different measurement environment conditions as the factor levels. By analyzing the variance, contribution rate and the indicator-factor level, the influence degree of each factor on scanning errors is obtained. Based on the analysis of the experiment results, it establishes two error correction models by using the baseline comparison model and in conjunction with the actual monitoring requirements of project engineering. The results show that horizontal ranging and vehicle running load are significant factors affecting scanner errors. Combined with the established error correction model, the systemic correlation between the corrected point errors and the scanner ranging is significantly reduced, and the point coordinates meet the precision requirements for later point cloud splicing and monitoring points in the specifications, which provides a theoretical basis for the application of 3D laser scanning technology in the monitoring of settlements and deformations of metro tunnels. 2021 Vol. 58 (3): 169-175 [Abstract] ( 606 ) [HTML 1KB] [ PDF 2048KB] ( 1645 ) 176 Study on the Effect of Foam Agent on the Main Tunnelling Parameters of Earth Pressure Balanced Shields ZHANG Xun1 HE Xiongfei2,3 In order to achieve fast and efficient excavation of earth pressure balanced shield, the influencing fac? tors of the main tunnelling parameters of the shield are researched and the intrinsic relationship between the foam agent parameters and shield tunnelling parameters is analyzed based on the shield construction of the Wetland Park station -Wuyuanwan station running tunnel of Xiamen Metro Line 2, Lot 3. Through lab proportioning tests of four foam agents and in combination with field tests, the effects of foam agent concentration, gas-liquid ratio and foam injection ratio on the internal friction angle and bulk density of the improved soils are studied. The results show that when the concentration of the foam agent increases by 1%, the internal friction angle of the soils decreases by about 2.43°; the influence degree of each parameter of foam on the cutterhead torque is foam concentration > foam flow rate > expansion rate, and the influence degree on shield thrust is foam concentration > expansion rate > foam flow rate, with foam concentration having the greatest influence on both tunnelling parameters. When the parameters of the foam system are changed to improve the tunnelling condition, it is preferred to select the foam concentration,which has a significant linear relationship with the tunneling parameters, so as to control the shield thrust and cutterhead torque to a reasonable range, to ensure the safe and smooth tunnelling of the shield. For each 1% increase in foam concentration during the construction of the project, the average reduction in shield thrust is about 1,710 kN and that in cutterhead torque is about 316 kN?m. 2021 Vol. 58 (3): 176-181 [Abstract] ( 592 ) [HTML 1KB] [ PDF 1367KB] ( 977 ) 182 Experimental Study on the Soil Conditioning in EPB Shield Tunnelling in the Shijiazhuang Sandy Soil Stratum WANG Leilei1 YIN Lijun1 GONG Qiuming1 LI Rui2 WU Fan1 BAN Chao1 Sandy soil is a typical mechanical unstable stratum with poor flow behaviors. When an earth pressure balance shield drives in the sandy soil stratum, it is prone to abnormal wear of the cutterhead and cutters, increase of torque and thrust of the cutterhead, failure and collapse of the working face, blow-out and other problems. In regards to this, taking a certain running tunnel section of Phase 2, Shijiazhuang Metro Line 1 as an example, where the earth pressure balance shield driving in the sandy soil stratum, it first conducts lab tests on soil conditioner, slump and mixing, and then applies the test results to the construction site, finally analyzes the construction parameters after soil conditioning. The results show that the performance of the soil conditioner is better when the foam concentration is 6% and the slurry concentration is 16%, meeting the requirements of shield construction; the best soil conditioning option is the slurry injection ratio of 8% and foam injection ratio of 60%, with the slump in the range of 100- 200 mm, as well as small stirring torque and low fluctuation; within a certain range, with the increase of the foam injection ratio, the indices of torque penetration, screw conveyor torque and soil pressure fluctuation in the soil chamber during tunnelling will be reduced, which is conducive to shield construction, but the foam injection should not be excessive. 2021 Vol. 58 (3): 182-189 [Abstract] ( 621 ) [HTML 1KB] [ PDF 3366KB] ( 1049 ) 190 Monitoring and Analysis of Riverway Conditions during the Construction and Operation of River-Crossing Metro Tunnels HU Chaoyang1,2,3 WANG Lele2,3 HUANG Meiqiong2,3 LIANG Yue2,3 WANG Xinqiang2,3 HE Chengnong2,3 River-crossing metro tunnels are faced with risks such as leakage and abnormal deformation of the river? bed. Therefore, riverway monitoring during the construction and operation period is essential to ensure the safety of river-crossing tunnels. Taking the river-crossing tunnel of Fuzhou Metro Line 1 as an example, this paper introduces the riverway monitoring work such as underwater environment perception, riverbed topography survey and water flow pattern observation during the shield construction, including monitoring results and early warning analysis, and analyzes the changes of riverbed erosion and deposition in the river-crossing tunnel section during 2009-2018 based on the actual measurement data. The results show that based on the monitored riverway conditions, two alerts regarding water leakage hazards during the shield construction have been issued timely, achieving good monitoring effects; since 2009, the riverbed within the cross-section of the river-crossing tunnel is in a small alternate state of erosion and deposition between years, with the deepest elevation point at -16.06 m in 2018, a gap of only 2.51 m compared to the -18.57 m used for the river-crossing tunnel design. It is recommended that engineering measures such as riverbed protection and branching diversion etc. should be taken, the riverbed safety monitoring mechanism should be established for the river-crossing tunnel section, and emergency protection measures should be prepared to ensure the metro operation safety. 2021 Vol. 58 (3): 190-195 [Abstract] ( 581 ) [HTML 1KB] [ PDF 3840KB] ( 1231 ) 196 Study on the Deformation Failure Laws and Support Measures for Tunnels in Layered Phyllite ZI Xiaoyu1 SHEN Yusheng1 ZHU Shuangyan1 LUO Ningning2 YANG Jiaqi1 CAO Bangjun1 The phyllite rocks are interbedded and severely weathered, with weak and developed structural surfaces. Tunnel construction in similarly layered rocks will result in large deformations in the surrounding rocks, seriously endangering the safety of tunnelling. Taking the Yangjiaping tunnel on Chengdu-Lanzhou Railway as an example and based on FLAC3D, this paper establishes a macroscopic bedding distribution model to study the deformation failure laws and support measures of tunnels in layered phyllite rocks. The research results show that the normal displacements of the rocks are obliquely distributed in an "X" shape around the tunnel, and the displacement peaks are situated at the tunnel vault and the sidewalls; the tangential displacements of the rocks are distributed in a "butterfly" pattern at a cross 45°direction of the tunnel, while the displacement peaks are located in the arch shoulders and arch foots of the tunnel, with obvious asymmetry displacement distribution; the surrounding rocks near the tunnel sidewalls mainly show tensile failure between bedding surfaces, while those near the tunnel arch mainly show dislocation slip failure between bedding surfaces. Based on the above analysis results, this paper puts forward optimizaion measures for the on-site support parameters and carries out monitoring of tunnel deformation and support stress.On-site monitoring results show that after adjustment of the support parameters, it shows an obvious control effect on the deformation of the surrounding rocks, effectively improving the asymmetric stress condition of the tunnel. 2021 Vol. 58 (3): 196-204 [Abstract] ( 615 ) [HTML 1KB] [ PDF 4939KB] ( 1050 ) 205 Study on the Reasonable Excavation Option of "Tunnel First before Shaft" for an Running Tunnel of Xi′an Metro Line 9 ZHU Caihui1 LAN Kaijiang1 DUAN Yu1 HE Hong2 DENG Guohua1,2 The difficulty for the "tunnel first before shaft" construction method is the construction of the cross pas? sage of the air shaft through the existing shield tunnel segments. It′ s extremely important to choose the appropriate number of excavation benches, bench spacing and breaking method of the segments for the stability of the excavation face, the safety of the adjacent shield tunnel segments and the control of the ground settlement. This paper takes a running tunnel of Xi′an Metro Line 9 as the engineering background, establishes a 3D finite element model for the construction method of "tunnel first before shaft", and carries out tracking simulation of shield tunnelling process and inverse analysis of ground parameters based on the measured ground settlement. The results show that it is quite reasonable to adopt the bench construction method with reserved core soil to excavate the cross passage, in which the number of excavation benches is recommended to be 4 and the bench spacing is recommended to be 3 m. When the cross passage is excavated through the existing shield tunnel segments, the segments on both sides of the junction with the cross passage should be broken first before the segments in the middle, and the joint bolts between the segments in the affected area should be loosened before breaking the segments, so as to reduce the longitudinal and circumferential failures of the segments. 2021 Vol. 58 (3): 205-215 [Abstract] ( 658 ) [HTML 1KB] [ PDF 6967KB] ( 1132 ) 216 On the Causes and the Control Measures of the Tunnel Inverted Arch Heaving in Water-rich Coal Measure Strata WAN Zheng1 ZHANG Xuemin1 FENG Han1 OU Xuefeng2 ZHOU Xianshun1 When a tunnel in Guizhou passed through the coal measure strata with high water pressure during con? struction, it encountered the problem of the inverted arch heaving. This paper analyzes the causes of the tunnel inverted arch heaving through on-site observation and monitoring of the lining structure deformation, combined with numerical simulation. The results show that the rock softening at the base and high water pressure are the two main factors for the heaving of the tunnel inverted arch, and the former has a greater impact on the safety of the inverted arch structure. Combined with the engineering characteristics and the causes of the disease, comprehensive remediation measures are taken at the site, such as installing additional discharge holes at sidewalls, horizontal and vertical drain pipes to strengthen the drainage system and reduce the water pressure, installing perforated grouting pipes at the arch foot to strengthen the bedrock at the base and replacing the arch structure, etc., achieving good remediation results. 2021 Vol. 58 (3): 216-222 [Abstract] ( 581 ) [HTML 1KB] [ PDF 2915KB] ( 1102 ) 223 Analysis on Water Inrush in Shield Tunnels under Buildings and Corresponding Countermeasures LIU Daosheng1,2 As for the Shadi tunnel on the Guangzhou-Foshan Intercity Railway Ring Line, a water inrush event sud? denly occurred at the tunnel face when the shield passed under the Yongfeng Textile Buildings, resulting in the over-limit of settlement and deformation of the Yongfeng Textile 1# Building above the tunnel. In order to ensure the subsequent tunnel construction and the safety of the above-ground buildings, supplementary survey and hydrological test are carried out timely, by which the causes of the water inrush in the tunnel are identified. While strengthening the monitoring of the ground surface, treatment measures are carried out, such as grouting reinforcement of the deformed building foundation and grouting of the deep rock fissures for water blocking. For the difficult sections without surface grouting conditions, the treatment measures are taken, such as grouting and filling into the chamber, driving under maintaining the pressure. With those measures the water inrush at the tunnel face is effectively reduced, the settlement and deformation of the buildings are controlled, ensuring the shield safely passing through the high-risk Yongfeng Textile Buildings. 2021 Vol. 58 (3): 223-228 [Abstract] ( 488 ) [HTML 1KB] [ PDF 3589KB] ( 771 ) 229 Study on the Impact of the Capacity Expansion and Renovation Project of the Chengdu-Chongqing Expressway on Xinshuangbei Tunnel LIU Hebing In order to ease the traffic congestion in the Zhongliangshan tunnel section of the Chengdu-Chongqing Expressway, the particular section is to be expanded and renovated to increase its capacity. The cutting section to be widened is located above the Xinshuangbei tunnel of the Chongqing-Guiyang Railway, and the clearance distance between the bottom of the protection piles and the tunnel arch is only 4.3 m. In order to evaluate the impact of the cutting construction on the railway tunnel, this paper adopts the numerical analysis method to simulate the various construction steps of the renovated expressway above the railway tunnel, calculates the internal force and deformation of the railway tunnel at each construction stage, demonstrates the feasibility of the construction plan of the renovated expressway above the existing tunnel with small clearance distance, and prepares relevant protection measures, providing a basis for the review and smooth implementation of the plan. 2021 Vol. 58 (3): 229-234 [Abstract] ( 582 ) [HTML 1KB] [ PDF 3509KB] ( 753 )

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