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Quick Search     Advanced Search MODERN TUNNELLING TECHNOLOGY   2023 Vol.60 Issue.2 Published 2023-04-25 1 A Review of Experimental and Theoretical Studies on the Slump of Conditioned Spoils of Earth Pressure Balance Shields LIU Tingyu1,2 WANG Shuying1,2,3 ZHONG Jiazheng1,2 During the tunnelling of earth pressure balance shields, it is often necessary to evaluate the physical and mechanical properties of the conditioned spoil so that the parameters can be adjusted in real-time to optimize the shield tunneling parameters and ensure safe and efficient construction. Due to different advantages, such as simple equipment, convenient operation and intuitive results, slump test has been widely used in the field to measure and determine the plastic fluidity of conditioned spoil. In terms of tests on the slump of conditioned spoil of earth pressure balance shields, this paper offers a detailed analysis of domestic and foreign test techniques for slumps and developments in theory and numerical calculation, from the following four perspectives: the suitable slump state indicators for conditioned spoil, influence factors and mechanism of conditioned spoil slump, rheological theory and numerical simulation of slump tests, This paper also summarizes gaps in existing researches, and puts forward a proposal for future research direction: to propose new evaluation indicators for spoil conditioning state based on the whole process of slump development; to investigate the impact laws of foam decay, chemical properties and mineral composition of the spoils on the slump and the inherent mechanisms; to improve the rheological theoretical model for describing the slumping behavior of conditioned spoil, and construct the mapping relationship between the slump and the rheological parameters; to investigate the relationship between the slump of conditioned spoil and flow behavior and rheological parameters under pressure. 2023 Vol. 60 (2): 1-13 [Abstract] ( 389 ) [HTML 1KB] [ PDF 3539KB] ( 1065 ) 14 Research and Application of TBM Key Construction Technologies for the Underground Tunnel Group of Pumped Storage Power Station YE Fumeng1 YU Qingzeng2 HE Fei2 ZHANG Xiao2 To address the various problems in excavation of the underground tunnels of pumped storage power sta? tions, such as long construction period, large construction difficulties, and high safety risk, this paper takes into account the types and characteristics of underground tunnels and puts forward three key technologies: large-diameter small-turning radius TBM, "Elf" TBM, and large-inclined shaft TBM. The study also develops three improved TBM equipment, which are applicable to the construction of traffic tunnels, drainage galleries, and water diversion inclined shafts respectively. In view of the short construction length of single power station and the large development scale of "power station groups", this paper carries out a study on the key technologies of intelligent TBM tunnelling. Based on a cloud computing platform and big data collection and analysis, this paper plans a construction platform system for the intelligent excavation of pumped storage power stations. The study applies large-diameter small-turning radius TBM equipped with vibration monitoring and TBM-SMART intelligent tunnelling system in the traffic tunnels of Funing Pumped Storage Power Station and realizes the analysis and sharing of the tunnelling data. It also applies the "Elf" TBM, which is equipped with ground remote control and the TBM-SMART intelligent tunnelling system and vibration monitoring technology, in the drainage galleries of several pumped storage power stations to realize the continuous construction of the "power station groups". 2023 Vol. 60 (2): 14-21 [Abstract] ( 404 ) [HTML 1KB] [ PDF 4189KB] ( 638 ) 22 Research on Virtual Joint Test Method of Shield Tunnels Based on Independent Cover Isogeometric Shell Model CHEN Jingxu CAI Yongchang To address the limitations of engineering analogy, physical tests, and numerical simulations in the bending stiffness acquisition and performance study of deep-buried, large-section, and irregular-shaped shield tunnel joints, this paper establishes a virtual joint test method and platform based on independent cover isogeometric shell models. The study discusses the key theories, algorithms and techniques to realize the virtual tests, analyzes the feasibility and advantages of virtual tests against physical tests, and uses virtual tests to analyze the joint bending resistance of a large-section deep-buried tunnel and its influencing factors. The results show that joint bending resistance curves that match physical tests can be obtained by inputting non-sensitive parameters in the virtual test platform, and the computation cost is only about 0.75% of the solid finite element model. Within the range of the study,the joint stiffness of large-section deep-buried tunnels is valued in the range of 2.98×105~2.57×106 kN·m/rad, and the joint stiffness decreases significantly with the increase of the deformation joint length of the segment. 2023 Vol. 60 (2): 22-27 [Abstract] ( 392 ) [HTML 1KB] [ PDF 2693KB] ( 557 ) 28 A Statistical Study on the Design Characteristics of Highway Tunnel Drainage Systems in Different Regional Environments LIU Yuyang1 SHENG Anhu1 LAI Hongpeng2 ZHUANG Chaohui3 WANG Hejun3 Whether the tunnel drainage system is working properly during the operation of a highway tunnel is directly relevant to the safety of the tunnel's support structure. To better understand the design characteristics and applicability of highway tunnel drainage systems in different regional environments in China, this paper collects the design samples of typical highway tunnel drainage systems from fourteen provinces and autonomous regions based on the characteristics of the climatic environment and geographic information in China, and conducts a comparative analysis of the design differences and characteristics of the drainage systems in different regional environments from three perspectives: the general drainage ways, local drainage design, and different structural combinations of the drainage systems. This paper also discusses the design of highway tunnel drainage systems and drainage model construction and optimization in carbonate areas. The results show that China's highway tunnel drainage systems can be categorized into three types: main drainage through the underground side culvert, main drainage through the central drainage trench, and main drainage through the underground side culvert + central drainage trench, with obvious regional characteristics. These different types of drainage systems are different in terms of their advantages, but similar in terms of their disadvantages. The drainage design in non-frozen areas is diversified, and the design of main drainage through underground side culvert is recommended for small drainage amounts, which would have a shorter drainage path and is easy for later maintenance, while the design of main drainage through underground side culvert+ central drainage trench can be used for large drainage amounts. Tunnel drainage systems in frozen areas are all of the main drainage through central drainage trench, of which, the inspection wells of the central drainage trench can be arranged with multiple layers of insulation materials to form a multi-layer internal cavity structure, which can effectively guarantee the temperature level of the water environment in the trench. By lowering the elevation of the transverse blind pipes in the longitudinal blind pipe inspection well, the existing mesh drainage model can be optimized into a series-parallel drainage model, which has a short drainage path and low probability of drainage system blockage, and can be automatically converted into the mesh drainage model when the drainage volume is large, thus ensuring the overall drainage capacity. 2023 Vol. 60 (2): 28-37 [Abstract] ( 357 ) [HTML 1KB] [ PDF 3653KB] ( 622 ) 38 Research on the Intelligent Comprehensive Evaluation of Coal Seam Impact Risk Based on the BP Neural Network Optimized by the Bat Algorithm ZHANG Kexue1,2,3,4,5,6 WU Yongwei1,3,6 HE Manchao2 CHEN Xuexi1,3,6 JIANG Yaodong4 LI Dong1,3,6 An intelligent comprehensive evaluation model of coal seam impact risk based on the BP neural network optimized by the Bat algorithm was established through in-depth analysis of the in-fluence of mining depth, property of top and bottom floors of coal seams, impact tendency, geological structure, mining technology and other factors on coal seam impact risks. The determined factors in-fluencing impact risks are classified by order of magnitude,and the Bat algorithm is employed to optimize the selection of the optimal weight and threshold value of the BP neural network, and the rating evaluation is performed for coal seam impact risks in terms of no-impact risk, weak impact risk, medium impact risk and strong impact risk. The intelligent comprehensive evaluation model of coal seam impact risk based on the BP neural network optimized by the Bat algorithm was used for in-stance validation of coal seams in a mine in Inner Mongolia and a face in Jiangsu Province, and the evaluation results were consistent with the results calculated by the synthetic index method, showing that this model could be used to evaluate coal seam impact risks. When this model is employed to evaluate coal seam impact risks, the random defects in the determination of weight and threshold value of the BP network structure can be overcome and the algorithm stability can be improved, so the evaluation results obtained are more reasonable. 2023 Vol. 60 (2): 38-46 [Abstract] ( 388 ) [HTML 1KB] [ PDF 1985KB] ( 680 ) 47 An Intelligent Inversion Study of In-situ Stress Field in Deep Buried Super-long Tunnels under Complex Geological Conditions REN Yang1,2 LI Tianbin1,2 ZHANG Jiaxin3 WANG Gangwei1,2 To improve the inversion accuracy and efficiency of in-situ stress in deep-buried super-long tunnels un? der complex geological conditions, an intelligent inversion method is developed based on tectonic analysis and RBF(radial basis function) neural network for deep-buried super-long tunnels under complex geological conditions. The main steps of this method are as follows: firstly, the regional geological conditions and tectonic analysis will be used to establish a 3D geological model of the tunnel engineering area, and the Heim hypothesis and Kinnick hypothesis will be applied to jointly determine the range of conditions for the tectonic stress boundary as the training samples for intelligent inversion. Then, the RBF neural network method will be used to obtain the optimal stress boundary conditions, which will be used for an inversion calculation of the in-situ stress. A deep-buried super-long tunnel in southwest China is chosen as the pilot project, in which the established intelligent inversion method for in-situ stress fields is applied in an actual scenario. In addition, the in-situ stress values obtained from the inversion calculation are fitted and compared with the actually measured values, which shows that the overall fitting error of the maximum principal stress inversion is about 10% and the fitting accuracy is close to 90%, indicating that the method is feasible and the inversion calculation results are reasonable. 2023 Vol. 60 (2): 47-53 [Abstract] ( 411 ) [HTML 1KB] [ PDF 2929KB] ( 529 ) 54 A Study on Neural Network Evaluation Model of Blasting Effect in Mountain Tunnel and Decision-making Method for Blasting Parameter Optimization LEI Mingfeng1 ZHANG Yunbo1 QIN Guifang2 SHI Yuanbo1 GONG Chenjie1,3 In view of the various problems faced by the blasting of mountain tunnels, such as overbreak and under? break and unsuitable muck block size, this paper analyzes the main influencing factors of these problems, and establishes the evaluation index system of tunnel blasting effect. Furthermore, the study establishes a neural network evaluation model for tunnel blasting effects with blasting block size and over- and under-break amount as the prediction target, puts forward an instance segmentation algorithm for the size of tunnel blasting muck blocks based on deep learning, and forms a decision-making method of blasting parameter optimization for mountain tunnels, which is applied to and verified by engineering application. The results show that (1) The size of muck blocks detected by the instance segmentation algorithm of tunnel blasting muck blocks based on deep learning has an error of less than 6.9% (confidence level is 95%) from the true value, realizing the rapid acquisition of the sample data for tunnel muck blocks; (2) The neural network evaluation model of tunnel blasting effect is trained by 148 sets of engineering sample data, after which it can better predict the size of blasting muck blocks and amount of overbreak; (3) The average linear overbreak in the test section after the optimization of the blasting parameters is about 10%, showing an over 50% reduction from the original plan, and the measured size of the muck blocks and amount of overbreak are in good agreement with the model predictions, with a deviation less than 20%. 2023 Vol. 60 (2): 54-61 [Abstract] ( 391 ) [HTML 1KB] [ PDF 4199KB] ( 517 ) 62 Study on Construction of Remote Automatic Monitoring and Early Warning System for Tunnel and Underground Works Yu Jian Based on Python programming language and big data, an automatic monitoring and early warning system is constructed, which can realize such functions as works monitoring, comprehensive early warning, visualization, parameter inversion, and real-time dynamic analysis etc. This automatic monitoring and early warning system can monitor in real time the pressure, displacement, and seepage water pressure of rock and soil mass during the construction process, automatically acquire monitoring data for remote wireless transmission, automatically store the data in a database, and use an Internet cloud platform for data sharing. The monitoring data can be used by the IA-BP algorithm module and the early warning and prediction module. The IA-BP intelligent algorithm performs inversion and intelligent prediction analysis on the monitoring data in the database, and makes comprehensive comparison and analysis between single threshold algorithm and IA-BP intelligent algorithm, thus achieving the purpose of early warning and prediction for engineering disasters. 2023 Vol. 60 (2): 62-72 [Abstract] ( 335 ) [HTML 1KB] [ PDF 6526KB] ( 619 ) 73 A Study on the Rock-breaking Mechanism of Disc Cutters on Cone Cutterhead of Full-face Tunnel Boring Machines NING Xiangke1 GENG Qi2 LU Zhiyong2 YU Qingzeng1 To reveal the rock-breaking mechanism of disc cutters on cone cuttehead of full-face tunnel boring ma? chines (TBM) and verify the influence pattern of the installation arrangement of the disc cutters on the rock-breaking effect, this paper constructs a numerical model of disc cutters on cone cutterhead based on the particle discrete element method, carries out experiments for verification, and conducts a numerical simulation study of the rock-breaking process of disc cutters on cone cutterhead "flat-conical" transition area, based on the analysis of the multi-stage suspension cutting and rock breaking mode of the cone cutterhead. The results show that the rock-breaking of the disc cutters in the conical area is in nature the free-face supported rock-breaking, with the breaking effect jointly influenced by the conical angle of the cutter head, the cutter spacing, and the cutter inclination angle. To improve the rock-breaking efficiency of the cutters, it is advisable to increase the conical angle of the cutter head, reduce the spacing between the cutters in the conical area, and raise the installed angle of the cutters to achieve the "erect in? stallation of oblique cutters" in the conical area. For extremely hard granite with a compressive strength of 180 MPa,the study suggests that the conical angle of the cutter head should be 25°, with the spacing between the cutters in the conical area no more than 70 mm, and the installed inclination of the cutters close to the conical angle of the cutter head. 2023 Vol. 60 (2): 73-83 [Abstract] ( 370 ) [HTML 1KB] [ PDF 6854KB] ( 895 ) 84 A Numerical Simulation Study on the Mucking Mechanism of TBM Two-stage Spiral Cutterhead GENG Qi1 ZHANG Xingyu1 HE Fei2 QI Zhichong2 WANG Xuebin1 YE Min1 ZHANG Daqing3 To address the lack of reasonable structural solutions and optimized design methods for the mucking of two-stage cutterhead of existing full-face rock tunnel boring machines (TBMs), this study constructs a numerical model using the particle discrete element method to simulate the mucking process of two-stage cutterhead of TBMs,so as to verify the reliability of the numerical model through scaled mucking tests. Numerical simulations are carried out to investigate the influence of various factors, including mucking outlet arrangement and size, spiral form and pitch, diameter ratio of primary/secondary cutterheads, and cutterhead rotation speed, on the performance of mucking. The results show that the spiral structure is an effective structural solution for mucking of TBM two-stage cutterhead, and the impact degree of each factor on the integrated mucking performance of two-stage cutterhead is, in descending order, cutterhead roation speed > length of back outlet of the primary-stage cutterhead > rear spiral pitch.For a two-stage spiral cutterhead with a tunnelling diameter of 8 m, the optimal structural form and parameters are recommended to be: the face and back muck outlets are in the same position with front and rear spirals, and specifically, the rear spiral pitch should be 0.85 m, the back muck outlet of the primary-stage cutterhead should be 0.9 m long, the diameter ratio of the primary/secondary-stage cutterhead should be no more than 0.55, and the cutterhead rotation speed should not exceed 6 r/min. 2023 Vol. 60 (2): 84-93 [Abstract] ( 375 ) [HTML 1KB] [ PDF 6469KB] ( 790 ) 94 A Study on Reduction Coefficient of External Hydraulic Pressure at the Lining of Diversion Tunnel in Saturated Q2 Loess Stratum ZHU Caihui1,2 YING Li2 YANG Qiqiang2 LI Yubo3 The value of the reduction coefficient of external hydraulic pressure has a great impact on the design of the lining structure of hydraulic tunnels. This paper is based on the case of a water diversion tunnel crossing Q2 loess stratum and investigates the saturated permeability characteristics of in-situ and remodeled Q2 loess through indoor tests and in-situ pumping tests. Also, the study comparatively investigates the changing pattern of the reduction coefficient of external hydraulic pressure on the lining under different five factors: stratigraphic conditions, limited discharge rate, tunnel size, groundwater level, and thickness of the ground grouting ring, through a model test and according to the principle of flow-solid coupling analysis of the FLAC 3D program. The results show that the increase in the limited discharge rate of the tunnel and the thickness of the grouted reinforcement ring will significantly reduce the reduction coefficient of external hydraulic pressure at the lining, and the increase in the permeability coefficient of the ground will cause an increasing trend that follows a logarithmic function for the reduction coefficient of external hydraulic pressure. Also, as the equivalent radius of the tunnel increases, the reduction coefficient of the external hydraulic pressure decreases before an increase, while the groundwater level has an insignificant effect on the reduction coefficient of the external hydraulic pressure. For this project, it is recommended to take the value of 0.57~0.71 for the reduction coefficient of the external hydraulic pressure. 2023 Vol. 60 (2): 94-102 [Abstract] ( 395 ) [HTML 1KB] [ PDF 3324KB] ( 547 ) 103 A Study on the Bearing Characteristics of Composite Concrete-filled Steel Tube Support Structure in Tunnels SUN Huibin1 ZHANG Jianli2 YANG Huixiang1 YANG Hui2 WANG Lei3 WEI Jun2 LIN Weinan3 To investigate the deformation and failure characteristics and bearing mechanism of composite concretefilled steel tube support structure, pure bending indoor tests and refined numerical simulation are carried out for support structures, taking into account the arch frame-concrete bond-slip characteristics on the basis of typical failure mode of support structures. An in-depth analysis is conducted on the mechanical response of the specimens under the action of bending moment, so as to clarify the impact pattern of different parameters, such as arch frame installation position, shotcrete strength, steel mesh diameter and protective layer thickness, on the structural bearing capacity. The results show that the concrete-filled steel tube specimens without steel mesh (SRCS-FW) are weaker in strength, the concrete cracks rapidly and then slips with the arch frame, while the concrete-filled steel tube specimens with double-layer steel mesh (SRCS-FS) are better in terms of deformation effect and display better bearing characteristics later. Besides, the SRCS-FS specimen has a higher strength of critical slip failure and its ultimate bending moment is 40.9% higher than that of the SRCS-FW specimen. Furthermore, the synergistic effect of the arch frame, the steel mesh and the concrete is significant in the elastic deformation phase of the component. The tensile force of the specimen in the cracking phase is mainly shared by the tensile-side steel mesh and the arch frame, while the pressure is shared by the arch frame and the concrete under compression. It is suggested that the parameter design for the support structure should take into account its load-bearing performance, economy and engineering experience, and construction convenience. 2023 Vol. 60 (2): 103-114 [Abstract] ( 334 ) [HTML 1KB] [ PDF 6223KB] ( 822 ) 115 A Study on the Stability of Surrounding Rocks in Construction of Undercrossing Tunnels with Super-large Section Based on Radial Displacement Release Rate of Surrounding Rocks YAN Bo1 ZHANG Junru2 ZHANG Xinjin1 PENG Lei1 Ning Bo1 Based on the Liuyuan Tunnel Project on Huanggang-Huangmei High-speed Railway, numerical simula? tion and field measurement methods are adopted to analyze the stability law of surrounding rocks in construction of undercrossing tunnels by full-face construction method and micro-bench construction method, in which the radial displacement release ratio of surrounding rock is used as an indicator for comparison. The results show that the construction of the new tunnel crossing under the air-raid shelter section by micro-bench construction method has outstanding advantages over the full-face construction method in controlling the radial displacement release rate, plastic zone distribution and stability safety factor of the surrounding rocks. The radial displacement release rate and stability safety factor of the surrounding rocks are 46.13% and 2.13 respectively under the micro-bench construction method, and 78.08% and 1.99 respectively under the full-face construction method. The stability of surrounding rocks in construction of undercrossing tunnels is relatively good when the bench length is 3 m. The monitoring data shows that, under the micro-bench construction method, the deformation in the tunnel meets the specified requirements and the deformation values are in good agreement with the simulation results, which further verifies the reliability of the simulation results. 2023 Vol. 60 (2): 115-124 [Abstract] ( 397 ) [HTML 1KB] [ PDF 4152KB] ( 482 ) 125 Impact Zoning and Dynamic Response to Blasting Vibration in Adjacent Tunnel under Hard Rock Strata LIU Jiaming1 ZHANG Junru1 WANG Zhiyong1 JING Yawen1 JIANG Manlin1 TAN Yumei1 CHEN Kegang2 To investigate how the blasting of overlapped tunnels affects adjacent existing tunnels in hard rock strata, a study is carried out on the impact zoning of the blasting vibration and dynamic response of new tunnels based on the "frequency-velocity" criterion specified in China′ s standards for blasting vibrations, with the new Damaoshan No.1 Tunnel and the existing Xinliutang No.1 Tunnel on Fuzhou-Xiamen Passenger Dedicated Line as the study case. First, the calculation parameters are obtained through triaxial tests and the Hoek-Brown criterion. Second, the blasting vibration pattern of new tunnels under different cases is studied and the impact zoning of the blasting vibration is obtained. Finally, a 3D finite element model is established to investigate the dynamic response pattern of the existing tunnel when the new tunnel is being blasted directly below the existing tunnel. The results show that: (1) the impact of the project′ s blast vibration can be zoned through the maximum vibration attenuation curve on the blast face and it can be determined that the existing tunnel is in the weak impact zone; (2) The impact range of blasting in the up and down directions is greater than that in the left and right directions, and the total impact zones of blasting vibration can be obtained for single-track railway tunnels under hard rock strata; (3) The impact range of blasting on the existing tunnel above the unexcavated section is greater than that on the excavated section, and because of media reflection, the attenuation of the vibration speed of the existing tunnel above the excavated section is slow; (4)the correctness of the numerical simulation is verified with the field monitoring results, and it is found that the deformation and stress of the existing tunnel structure both meet the requirements for impact control. 2023 Vol. 60 (2): 125-137 [Abstract] ( 381 ) [HTML 1KB] [ PDF 7686KB] ( 545 ) 138 A Study on Impact of Soft Soil Stratum Reinforcement on the Attitude Regulation of Shield Machine and Stratum Deformation SU Dong1,2,3 TAN Yijun1 SHEN Xiang1,2,3 HUANG Changfu4 CHEN Xiangsheng1,2,3 Based on the large-diameter shield tunnel project in soft soil strata in Hengqin District of Zhuhai City, this paper establishes a numerical simulation and analysis model for large-diameter shield tunnelling in unreinforced and pre-reinforced strata, and investigates the relationship between the deflection moment and pitch angle of the shield machine as well as the impact of the changes in the machine′s attitude on the deformation of the strata by changing the load distribution of the thrust system to apply the deflection moment. The results show that the gravitational eccentric moment that causes the initial "bow" of the shield machine is 261 MN·m, and the deflection moment required to level the attitude under the condition of pre-reinforced strata is about 21 MN·m, which is 81.1% smaller than the condition of un-reinforced strata (111 MN·m). Under the condition of pre-reinforced strata, for every 100 MN·m increase in the positive deflection moment, the pitch angle of the shield machine will increase by about 0.015°, which is 84.2% smaller than the condition of un-reinforcement (0.095°). Also, under the condition of identical negative deflection moment, the absolute value of pitch angle after pre-reinforcement is more than 85.0% smaller than the un-reinforced case. Pre-reinforcement of the strata results in a reduction of over 95.0% in both the maximum uplift and maximum settlement of the ground surface. 2023 Vol. 60 (2): 138-148 [Abstract] ( 387 ) [HTML 1KB] [ PDF 5484KB] ( 575 ) 149 Study on the Deformation Control of Non-barrier Launching of Large Diameter Double-mode Shields at Shallow Depth WEI Lifeng1 TIAN Yang1 ZHU Muyuan1 ZOU Kunmi2 FANG Yong1 To investigate the deformation control strategy during the non-barrier launching of large-diameter dou? ble-mode shields at the shallow depth conditions, a study is conducted based on the shield-driven running tunnel section of the Zirui Tunnel on the new Chengdu-Pujiang Railway. A visual numerical model is established by using the FLAC3D software and taking into account field monitoring data and construction parameters to simulate the whole process of the non-barrier launching of a double-mode shield, and to study how the numerical characteristics of the cutterhead thrust applied when the cutterhead is cutting the retaining piles at the tunnel portal will affect the soil displacement behind the piles. The application feasibility of the traditional reinforcement theory and its improved methods under non-barrier launching are verified by comparing the displacement control effects at different reinforcement ranges. The results show that: (1) There is a stratigraphic variability in the influence of the numerical characteristics of the cutterhead thrust on the soil displacement behind the piles. Specifically, the effect in cohesive strata is significantly greater than that of non-cohesive strata such as gravel and sandy pebble strata; (2) The effect of the cutterhead thrust gradient on the soil displacement behind the piles is significantly greater than the numerical value of the thrust, regardless of the stratum types; (3) The traditional reinforcement theory and its improved methods are still applicable under the non-barrier launching, where the theoretical calculation value of the transverse reinforcement width is relatively conservative, and the length of the longitudinal reinforcement can basically meet the requirements for soil stability; (4) The choice of the location for the shift of the shield mode at the launching section has a significant impact on the surface vertical displacement caused by the subsequent construction, and the study suggests that this location shall be chosen within or near the boundary of the reinforced area. 2023 Vol. 60 (2): 149-158 [Abstract] ( 348 ) [HTML 1KB] [ PDF 4712KB] ( 652 ) 159 Prediction Methods for Segment Uplift in Large-diameter Shield Tunnels Based on Double Elastic Foundation Beams ZHANG Jianyong1 LI Mingyu2,3 CHEN Jian3,4 YU Liucheng2 LI Yixiang1 YANG Gongbiao3,4 WANG Yue2,3 Based on the double elastic foundation beam theory, the modified longitudinal equivalent continuous model, and the grout circumferential filling theory, this study constructs a segment uplift prediction model taking into account the time-variability of uplift force with further consideration of the impact of superposition effect of shield construction steps, grout pressure distribution and the shield machine weight. The impact of two calculation methods of the equivalent formation resistance coefficient in uncoagulated grouting areas on the prediction results is also discussed. The results show that the modified double elastic foundation beam calculation method put forward by the study can better reflect the anti-floating effect of the surrounding soil layers on the segments, and when the subgrade reaction coefficient of the uncoagulated grouting areas is obtained by averaging the subgrade reaction coefficients of the shield tail area and the coagulated grouting area, the calculation results are closer to the actual measured results. 2023 Vol. 60 (2): 159-167 [Abstract] ( 417 ) [HTML 1KB] [ PDF 2976KB] ( 502 ) 168 A Study on Disturbance Pattern of Asymmetric Synchronous Grouting on Ground during Large Diameter Shield Tunnelling ZHENG Shuang1,2 LIU Chao3 ZHU Delin3 LIU Hai3 JIA Xinjuan1 To investigate the disturbance pattern of asymmetric synchronous grouting on the ground during the con? struction process of large-diameter shield tunnel, this paper simulates the synchronous grouting process at the shield tail through the finite element method based on the construction of super large diameter slurry balance shield at the launching section of the south bank of Qianjiang Tunnel, and compares the simulated data with the field monitoring data for analysis. Based on the existing analytical solution, the study realizes the non-uniform distribution pattern of synchronous grouting pressure of the finite element model through secondary development, which can fully reflect the non-symmetric grouting case. In the simulation, it considers the effects of asymmetric grouting pressure ratio, grouting rate, and distribution pattern of grouting defects (i.e., positions of local grouting pressure deficiencies)on the ground disturbance. The study shows that asymmetric grouting pressures can result in the irregular shape of settlement trough, with the side with higher grouting pressures being prone to ground surface uplift, and the asymmetric grouting pressure and stratum loss rate show a negative linear correlation. As the grouting rate increases, the settlement value of deep soils will also increase, and this trend will be more pronounced as the depth increases. The distribution pattern of different grouting deficiencies has different degrees of impact on ground settlement. Particularly, the pressure from the top grouting hole has a greater influence on the extent of ground settlement, while the pressure of the waist grouting hole has a greater impact on the width coefficient of the ground settlement trough, and the pressure from the bottom grouting hole has a relatively small influence on ground settlement. 2023 Vol. 60 (2): 168-177 [Abstract] ( 410 ) [HTML 1KB] [ PDF 5293KB] ( 495 ) 178 A Study on Optimization of Reinforcement Scheme for Adjacent Construction of Super-large Rectangular Pipe Jacking Shield Tunnel in Soft Ground CUI Guangyao1 MA Jianfei2 NING Maoquan3,4 TANG Zaixing3,4 LIU Shunshui3,4 TIAN Yuhang1 In order to ensure the safety of the adjacent construction of the super-large rectangular pipe jacking shield tunnel in the soft ground, taking a rectangular pipe jacking shield tunnel adjacently passing under the existing high-speed railway as a study case, the effects of different construction and reinforcement schemes of the superlarge rectangular pipe jacking shield tunnel adjacent to the high-speed railway section are studied. The results show that when advanced grouting is adopted, the active instability displacement can be reduced by 25.64%, the passive instability displacement can be reduced by 17.65%, and the track settlement can be reduced by 30.38% for the excavation face. And when the manually excavated pile + D-shaped steel auxiliary beam are adopted, the active instability displacement can be reduced by 51.28%, the passive instability displacement can be reduced by 29.41%, and the track settlement can be reduced by 42.31% for the excavation face. Field monitoring shows that the maximum settlement of the track after reinforcement by the manually excavated pile + D-shaped steel auxiliary beam is only 1.65 mm. The super-large rectangular pipe jacking shield tunnel has successfully passed under the existing highspeed railway. The manually excavated pile + D-shaped steel auxiliary beam ensure the adjacent construction safety of the super-large rectangular pipe jacking shield tunnel and the normal operation of the high-speed railway. 2023 Vol. 60 (2): 178-184 [Abstract] ( 367 ) [HTML 1KB] [ PDF 4346KB] ( 597 ) 185 Quantitative Deviation Correction Technologies for Subway Shield Tunnels in Operation through Compaction Grouting WU Ze1 GU Fulin2 FU Yanbin3 To address the problem of deviations in subway shield tunnels in operation caused by surrounding con? struction projects, this paper puts forward a quantitative grouting correction method. Through the theoretical study and finite element analysis of the compaction grouting process, the study focuses on the deviation correction mechanism of compaction grouting on the shield tunnel, obtains the key parameters, and establishes the theoretical model and calculation formulae for the vertical and horizontal displacements of the shield tunnel under the action of grouting. The analysis results show that the compaction grouting in the strata can effectively correct the displacement and deformation that have occurred in subway shield tunnels in operation, which can be simulated by using the volume strain method for compaction grouting. The tunnel displacement can be calculated by the layered summation method, and the main control factors of the correction effect are the grouting distance, grouting pressure, and grouting range. By comparing the results of field tests and calculation formulae, the theoretical model put forward by this paper is proved reasonable with credible conclusions. 2023 Vol. 60 (2): 185-193 [Abstract] ( 353 ) [HTML 1KB] [ PDF 3380KB] ( 579 ) 194 A Study on Control Size of Blast Muck for Vertical Shaft Construction Using the Raise-boring Method LI Yao1 DONG Xing1 CAO Xiaoyong2 XU Ping2 To address the problem of muck-induced blockage in the construction of vertical shafts through the raiseboring method, this paper uses the 3D discrete element simulation method to simulate the muck-dropping process in vertical shafts and pilot shafts. The results show that when the muck diameter is larger than 0.2 m, it is easy for the muck to block the shaft (v=0), and when the muck diameter is smaller than 0.2 m, the muck above the pilot shaft can be smoothly discharged to the pilot shaft, with part of the muck accumulated at the bottom of the shaft. Also, if the diameter of the pilot shaft increases from 1.5 m to 3 m, it can effectively expand the arching range of the muck in the shaft, speed up the muck-dropping speed in the shaft, reduce the probability of arching and blockage (v≈0), and improve the muck falling rate, while the pilot shaft encounters muck blockages several times, reducing the muck falling rate. When the muck size is larger than 0.3 m, it is easy for the muck to cause the blockage of the pilot shaft if the shaft diameter is 1.5 m. In a long pilot shaft, large-size muck with higher velocity will still block the pilot shaft under the arching effect. 2023 Vol. 60 (2): 194-202 [Abstract] ( 380 ) [HTML 1KB] [ PDF 4742KB] ( 603 ) 203 High-precision Discrete Simulation Method of Floating Dusts Based on Two-stage Solution and Its Application SANG Conghui1,2 QIAO Liwei1,2 WANG Lieni3 YUAN Wenchao4 ZHAO Yanfa5 To solve the dynamic simulation of the space-time evolution characteristics of floating dusts in a tunnel after the blasting, this study introduces a numerical approximation model to fit the initial emission of floating dusts.On this basis, the study proposes a two-stage discrete numerical simulation method to solve the problem of subjective assignment and accurate solution according to the actual working conditions of the tunnel. Taking a tunnel under construction in Guizhou as the background, the study calculates in a two-stage solution the dynamic space-time concentration field of floating dusts by using the discrete mode of finite element Ansys-Fluent software. In the first stage, the dispersion of floating dusts on the concentration gradient under the condition of static wind is simulated,and in the second stage the diffusion of floating dusts with the flow under the condition of mechanical ventilation is simulated. The results show that the maximum error between the simulated data and measured data at sampling points along the range within the ventilation test cycle is 13.67%, and the figure at random sampling points is 12.39%. Also, the study uses the two-stage simulation solution to dynamically simulate the floating dusts in two other tunnels under construction with air duct vault layout and bench method excavation, and the error at random sampling points is all controlled within 11%. The relevant data show that the two-stage simulation solution method is largely applicable and can effectively guarantee a low error in the simulation data under different cases, and the method can be used as a new high-precision simulation application method for the dynamic evolution of floating dusts after tunnel face blasting. 2023 Vol. 60 (2): 203-211 [Abstract] ( 349 ) [HTML 1KB] [ PDF 3503KB] ( 493 ) 212 A Study on Diffusion Characteristics and Crossflow Mechanism of Pollutants at the Portals of Highway Tunnel Group ZHU Kai1,2 YANG Wenjing1 ZHANG Qionghua3 LIU Bin4 WANG Qiang1 ZHANG Xin5 WU Ke2,6,7 With the increase in highway tunnel groups with multiple tunnel portals in close proximity, there has been a more and more prominent problem of pollutants gathering and cross-impact between tunnel portals. However, parameters in extant studies are of a narrow range and there is a lack of systematic analyses of the crossflow mechanism of tunnel pollutants. The study uses CFD simulation and scale model test to investigate the process of pollutant diffusion at the portals of highway tunnel group, and analyzes the flow field characteristics of pollutant diffusion and the changing pattern of crossflow ratio at the tunnel portals with 20~320 m spacing. The impact range of upstream jet and downstream suction are also taken into account, a pollutant crossflow model is constructed, and an empirical formula of crossflow ratio is obtained applicable for engineering calculation. The results show that: (1) The diffusion of tunnel pollutants is affected by the joint action of jet development at the upstream tunnel portal and suction at the downstream tunnel. The diffusion of upstream tunnel pollutants is in line with the 3D wall jet theory, and the wind speed, expansion range, and decay rate of pollutant concentration of each section at the portal section are similar and satisfy the standard for similarity in terms of distribution. The length of the downstream convergence section is short and the suction does not change the morphology of the upstream jet. (2) The crossflow of tunnel pollutants is affected by the joint action of the structural parameter L/D (tunnel portal spacing/tunnel hydraulic diameter) and the operational parameter vup/vdown (upstream and downstream wind speed ratio), both of which act independently of each other on the crossflow. As L/D increases, the crossflow ratio φs and the crossflow concentration ratio φc decrease together. When vup/vdown increases, φs first stays constant before decreasing gradually, while φc first increases before stabilizing. This pattern is not affected by the form of the tunnel section. (3) The empirical formula the study constructs for the crossflow ratio is in line with extant studies and has a wider scope of application. 2023 Vol. 60 (2): 212-222 [Abstract] ( 307 ) [HTML 1KB] [ PDF 4592KB] ( 543 ) 223 Effect of Glass Dust on the Resistance of Concrete to Calcium Corrosion under Contact Corrosion Conditions JIANG Yajun1 ZHENG Yi1 YU Liangmin1 CUI Hengtao1 CAO Danyang2 The precipitation of calcium ions from concrete is one of the main causes that will lead to crystallization in tunnel drainage systems. To study the effect of glass dust on the resistance of concrete to calcium corrosion under contact corrosion conditions, this study prepares some concrete test specimens and cement mortar test specimens by replacing 0%, 10%, 15% and 20% of the cement with equal mass of glass dust to carry out deionized water immersion tests to detect the calcium ion concentration. X-ray diffractometer and scanning electron microscope are used to analyze and study the type, content, microscopic morphology and element composition of the hydrated products of the test specimens. The results show that glass dust can reduce the content of calcium hydroxide (CH) and the precipitation of calcium ions in the hydrated products of the cement mortars, and the best effect is achieved when 10% of glass dust is mixed. When the corrosion lasts 28 d, the microstructure of the cement mortars mixed with glass dust is improved compared with that of cement mortars without any glass dust, but the volcanic ash activity of the glass dust has not yet been fully brought into play. 2023 Vol. 60 (2): 223-229 [Abstract] ( 359 ) [HTML 1KB] [ PDF 3628KB] ( 461 ) 230 An Experimental Study on the Active Regulation of Filling Pressure in Shield Receiving Steel Sleeve YUAN Jie1 QI Jiarui2 XIAO Xiang1 LI Zanxin1 YU Lixin1 PAN Yiheng2 The control of the pressure balance between the fillers in the steel sleeve and the ground is the key to en? suring the project's safety during receiving the shield with the steel sleeve in subway tunnelling. To realize the active regulation of the filling pressure in the steel sleeve, this study improves the fixed cover of a conventional steel sleeve to a piston cover that can slide freely along the longitudinal direction of the sleeve, and puts forward the corresponding methods for hydraulic pressure regulation and mechanical pressure regulation. The steel sleeve model is designed according to the 1∶5 ratio, and model tests are carried out for different working conditions, such as water injection with pressure increase, water release with pressure decrease, mechanical pressure increase under low levels of internal pressure, mechanical pressure increase and decrease under high levels of internal pressure, so as to study the variation pattern and influence mechanism of the filling pressure with the external hydraulic pressure and mechanical thrust, as well as the variation pattern of the jack counterforce and steel sleeve deformation. The results show that the filling pressure inside the steel sleeve varies linearly and proportionally to the external hydraulic pressure during hydraulic pressure regulation. Specifically, the increase of the mechanical pressure at lower filling pressures (≤0.15 MPa) shows multi-segment characteristics where the filling pressure changes to the variations in the jack pressure, while under the condition of high filling pressure (>0.15 MPa), the filling pressure varies steadily with the regulation process of the mechanical pressure. Both methods can achieve controlled active regulation of the filling pressure in the steel sleeve, and shall be chosen flexibly according to the characteristics of the regulation method,the construction ability, and the regulation's technical requirements. 2023 Vol. 60 (2): 230-237 [Abstract] ( 361 ) [HTML 1KB] [ PDF 3656KB] ( 620 ) 238 Cleaning Test for Highway Tunnel Cameras Based on High-pressure Water Jet and Robotic Arms WANG Chao1,2 YANG Yusheng1,2 ZHANG Jun1,2 BIAN Yanni3 YE Min1,2 LIU Xiaona3 To address the problem of low efficiency and potential safety hazards in the cleaning of highway tunnel cameras at height, this study proposes a high-pressure water jet method to clean the lens surfaces of the cameras, and designs a cleaning device with six-degree freedom. The composition of the contaminants is analyzed using the Fourier transform infrared spectrometer (FTIR) based on the contaminants on the surface of the tunnel cameras. To achieve a good combination of parameters for the cleaning process, 70 camera samples are collected in the tunnels around the Yuhua Palace in Shaanxi Province, and a cleaning parameters optimization test is carried out through the single factor variable method. Then, the images are processed through the method of "graying + sharpening + binarization", so as to investigate the impact of the cleaning pressure (0.5~2 MPa), the cleaning spacing (0.3~1.5 m), and cleaning time (0.2~2 s) on the cleaning efficiency. The test results show that the main components of the contaminants on the shell surface of the tunnel cameras are carbon black and PAHs, while those on the lens surface are mainly particulate fugitive dust.The better combination of parameters for the cleaning process is as follows: cleaning pressure 0.5 MPa, cleaning spacing 1 m, and cleaning time 0.4 s (clean twice with an interval of 0.2 s). In this combination of parameters, the clean?ing efficiency is over 99%. 2023 Vol. 60 (2): 238-246 [Abstract] ( 349 ) [HTML 1KB] [ PDF 3763KB] ( 566 ) 247 A Full-scale Experimental Study on the Fire Characteristics of Dual-source Tunnel Fire GUO Chao1,2 YAN Zhiguo1,2 LI Wei1,2 ZHOU Xifang3 Vehicle collisions, flames and high-temperature smoke inside tunnels will generate factors for thermal ra? diation and thermal convection that can easily lead to dual-source or multi-source fire accidents, posing serious threats to the safety of people in the tunnel. To investigate the development characteristics of dual-source fires in tunnels under the condition of longitudinal ventilation, an on-site full-scale fire test is carried out based on the Beiheng Passageway in central urban Shanghai, which includes a total of five sets of fire tests using two sets of diesel pool fires. By changing the ignition time and spacing of the dual fire sources, it is focused on analyzing the characteristics of key parameters in the whole development process of chain-type dual-source fires and parallel-type dualsource fires with different source spacings, including flame deflection angle, heat release rate, vertical and longitudinal smoke temperature, and carbon monoxide concentration. The results show that due to different ignition time, the chain-type fires are not synchronized in development for the dual sources, and the heat release rate of the dualsource fires shows the development pattern of one growing and the other decaying, indicating a significant competi? tive combustion mechanism. For chain-type dual-source fires with a source spacing of 2 m, the flame deflection angle of the downstream fire source remains greater than that of the upstream fire source during different phases of development. For parallel-type dual-source fires with a source spacing of 5 m, 10 m and 20 m, the flame deflection angles of the duel-source fires are more or less consistent. In contrast to crown smoke temperature measurement schemes in extant full-scale tunnel fire tests, this study adopts Fiber Bragg Grating temperature sensors with a spacing of 1 m to measure the smoke temperature at the tunnel crown. For dual-source fires with different source spacings, there are multiple temperature peaks in the longitudinal distribution curve of smoke temperature on the crown.Whether the temperature peak is caused by thermal radiation or thermal convection, the temperature peak corresponding to the downstream fire source stays greater than that corresponding to the upstream fire source. As the source spacing increases, the maximum smoke temperature at the crown corresponding to the dual-source fire will gradually decrease. The distribution characteristics of smoke temperature at the downstream crown for both dualsource and single-source fires satisfy the exponential decay law. 2023 Vol. 60 (2): 247-259 [Abstract] ( 379 ) [HTML 1KB] [ PDF 6582KB] ( 578 ) 260 A Study on the Detection and Evaluation of the Technical Condition of Fire Damage in Shield Tunnels DU Yongxiao1,2,3 SUN Xiaoli1,2,4 YANG Jun1,2,4 ZHANG Yansen1,2 The detection and evaluation of the technical condition of fire damage is the basis for the maintenance and reinforcement of shield tunnels and their safe use. This paper establishes a comprehensive evaluation method that follows a phased and in-depth process of site investigation, testing program development, detailed testing and damage assessment and analysis, with the objective to achieve the effective detection and evaluation of the technical condition of post-fire damage in shield tunnels. A case study is carried out on a shield-driven running tunnel with a focus on the inspection method and process, inspection result analysis, grading system and treatment recommendations. The results show that the action of fire will lead to a reduction in the presumptive strength of the concrete. The carbonization depth of all the segments is between 0 and 2.0 mm, and the inspection of the shield tunnel segments by the ultrasonic phased array method has found that the action of fire has less effect on the internal compactness of the segments. The study further grades the shield tunnel by section and puts forward corresponding recommendations for treatments. 2023 Vol. 60 (2): 260-270 [Abstract] ( 354 ) [HTML 1KB] [ PDF 4831KB] ( 502 ) 271 A Model Test Study on the Catastrophic Occurrence of Water Inrush on the Tunnel Face in Sand-slate Interbedded Strata XU Peng1,2 PENG Peng1,2 JU Guoquan3 ZHAO Wanqiang3 ZHANG Zhiqiang1,2 To investigate the catastrophic mechanism and pattern of water inrush in tunnels in sand-slate strata, this paper takes the Xinping Tunnel on China-Laos Railway as the study case, and through model tests, reproduces the catastrophic occurrence and evolution process of the water inrush in the progressive failure of slate aquifuge, so as to analyze the changing pattern of the stress-strain characteristics of surrounding rocks, seepage pressure and flow rate with the decreasing thickness of the aquifuge. The results show that: (1) The water inrush in the sand slate strata would experience three stages: seepage, inrush and attenuation, which is essentially a gradual evolution process where, under the action of excavation unloading and stress and seepage coupling, fractures in the weak parts of the aquifuge gradually expand and break through until inrush channels are formed and the stability of the aquifuge loses gradually; (2) The stress-strain curve of the surrounding rocks and the relationship between the seepage pressure and flow show significant precursor and stage characteristics, and their changing patterns reflect the breeding, development and evolution process of the disaster; (3) A sudden change point exists in the changing process of the seepage pressure and flow rate, and this sudden change point can be seen as the characteristic point of degradation in the water-blocking capacity of the aquifuge. The aquifuge thickness reflected by this point can be seen as the critical safety thickness of the aquifuge. 2023 Vol. 60 (2): 271-281 [Abstract] ( 375 ) [HTML 1KB] [ PDF 6630KB] ( 540 ) 282 An Experimental Study on the Application of Spray-applied Polyurea Membrane in Remediation of Tunnel Lining Spalling WANG Song1 YANG Changyu2 XU Xingwu1 LI Chuanfu1 WANG Jushan1 YUAN Xun2 WANG Fang2CHEN Ang2 YANG Yi1 WANG Hui1 GUO Jijun1 GUAN Qiang3 WANG Fuhai3 LIU Qiang1SUN Cheng4 ZHANG Yongqin4 In view of the shortcomings of the traditional remediation process of spalling failures, such as complex construction process, high labor intensity, slow construction speed, low efficiency, and high cost etc., this paper proposes to use spray-applied polyurea membrane to remediate spalling failures of tunnel lining. The study carries out a theoretical analysis of the spalling block weight and aerodynamic load accommodated by the spray-applied polyurea membrane and establishes an on-site tunnel lining model for an actual measurement test, with a focus on the bonding strength and tensile strength of the spray-applied polyurea membrane. The test shows that the spray-applied polyurea membrane with a thickness of 5 mm does not break in tension under the joint action of the weight of the test blocks and the aerodynamic effect with a load of about 14 t, and is able to support the spalling of the lining.During the loading process, the spray-applied membrane peels within a certain range around the test blocks, indicating that the bonding strength between the spray-applied polyurea membrane and the concrete surface of the tunnel lining within the peeling range gradually decreases. It is recommended to take different measures to prevent the spalling of the tunnel vault lining, such as increasing the bonding strength between the spray-applied membrane and concrete or raising the thickness of the spray-applied membrane. 2023 Vol. 60 (2): 282-292 [Abstract] ( 313 ) [HTML 1KB] [ PDF 5395KB] ( 576 )

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