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Quick Search     Advanced Search MODERN TUNNELLING TECHNOLOGY   2022 Vol.59 Issue.2 Published 2022-04-25 1 Study on the Support Structure Design of Spatially Small-spaced Four-tube Section of He′ao Tunnel XIAO Mingqing1,2 XU Chen1,2 ZHENG Qiang1,2 PENG Changsheng1,2 The quantified design of parameters and safety analysis of the support structure of a spatially smallspaced multi-tube tunnel are the major difficulties in the current design. In view of the design of the spatially smallspaced four-tube section of He′ao Tunnel on the Bao′an International Airport-He′ao Expressway of Shenzhen, the total safety factor method is adopted to conduct the research and comparison of excavation and support modes of four tubes, excavation sequences of various tubes and support parameters. The load-structure method specified in the tunnel design code, incremental method and ground-structure method are used to compare and calculate the safety coefficients of the support structure. The conclusions are as follows: (1) the design method of spatially small-spaced multi-tube tunnel is put forward based on the principle of total safety factor method; (2) according to the total safety factor method, the spatially small-spaced four-tube section of He'ao Tunnel shall adopt the excavation and support mode that "the secondary lining of the first tube should be fully completed before excavation of the next tunnel tube", and following the excavation sequence during construction: Tube 1 → Tube 2 →Tube 3 → Tube 4; and (3) the tunnel code specified load-structure method, incremental method and ground-structure method cannot get the total bearing safety coefficient of the structure, but it can reflect the safety of some support structure to some extent possible. 2022 Vol. 59 (2): 1-10 [Abstract] ( 376 ) [HTML 1KB] [ PDF 2744KB] ( 659 ) 11 Research and Application of the Safety Coefficient Method for the Middle Rock Pillar of Parallel Tunnels with Small Clear Distance WANG Mingnian1,2 YANG Henghong1,2 ZHANG Yiteng1,2 LIU Kerui1,2 YU Li1,2 The middle rock pillar is a key component for the stability control of the surrounding rocks in tunnels with small clear distance, and it is a major challenge in the engineering design and construction process to distinguish the safety of the middle rock pillar. This paper establishes the mechanical analysis model of parallel tunnels with small clear distance under Class IV surrounding rock conditions by analyzing the failure modes of the middle rock pillar under different surrounding rock grades and buried depths, and identifies the location of the fracture surface of the middle rock pillar. This paper divides the upper sliding block of the middle rock pillar into two cases according to the different shapes, derives the calculation formulas of the slip resistance, sliding force and safety coefficient of the upper sliding block of the middle rock pillar according to the principle of slope stability, the assumption of ultimate equilibrium and Protodyakonov′s compressive arch theory, so as to establish the safety coefficient meth? od to evaluate the safety of the middle rock pillar and verify it by introducing numerical simulations. The verified safety coefficient method is then applied to an actual tunnel project to evaluate the safety of the middle rock pillar,which concludes that the critical thickness for the tunnel middle rock pillar failure is 6 m. Middle rock pillar sections with thickness below 6 m are then reinforced using anchor bolts. 2022 Vol. 59 (2): 11-19 [Abstract] ( 419 ) [HTML 1KB] [ PDF 1925KB] ( 724 ) 20 Analysis on Spacing Optimization for Circumferential Blind Drainage Pipes of Tunnels in the Water-rich Area FU Helin1,2 AN Pengtao1,2 CHENG Guowen3 LI Jie1,2 YU Xiaohui3 CHEN Long1,2 As for the water inflow in water-rich tunnels, it follows the treatment principle that "priority is given to blocking, and waterproof and drainage are combined". The rationality of drainage system is a key factor of the safe construction and good operation of tunnels. First the tunnel drainage system is analyzed to reveal its working principle, and then the finite difference software FLAC 3D is adopted to carry out the 3D fluid-solid coupling simulation for different spacing conditions of circumferential blind drainage pipes in the water-rich fault zone of Hongtu extralong tunnel, and the seepage pressure, rock bolt stress and water inflow are analyzed to reveal the volume and distribution characteristics of the plastic zone. The study result shows that the pore water pressure on the support structure along the tunnel axis is roughly periodically distributed, with the period approximating to the longitudinal spacing between circumferential blind drainage pipes; increasing the density of circumferential blind drainage pipes, it could reduce the stress on the support structure and the volume of plastic zone and also increase the amount of tunnel drainage; with an increase in the spacing between circumferential blind drainage pipes, the plastic zone of grouting reinforcement ring first appears in the area where the surrounding rock is good and appears in the fault area at the latest; the reinforcement effect of anchor bolts in the fault area is poor, so the circumferential spacing between steel ribs can be reduced to improve the structural rigidity and make the axial stress on the grouting reinforcement ring more reasonable. After due consideration of various factors, it is recommended that regarding the studied tunnel project the spacing between circumferential blind drainage pipes in the fault area should be 3 m and the spacing in the areas near the fault should be 4 m. 2022 Vol. 59 (2): 20-27 [Abstract] ( 384 ) [HTML 1KB] [ PDF 3978KB] ( 691 ) 28 Study of the Impact of Single-and Double-tube Tunnel Systems on Rockburst in Deep-buried Extra-long Tunnelling LUO Chun1 ZHANG Zhiqiang1 LIN Dirui1 TANG Zelin2 Rockburst is one of the main disasters for tunnelling under high ground stress. Taking the rockburst sec? tion of Ping′an Tunnel with high ground stress, which is located on Chengdu-Lanzhou Railway, as the study object,this paper adopts combined methods of filed measurement, numerical analysis, and laboratory test, and with respect to rockburst development mechanism, energy density change and rockburst strength it comprehensively analyzes the impact of two construction schemes (single-tube double-track tunnel system and double-tube single-track tunnel system) on the rockburst in deep-buried extra-long tunnels with high ground stress. The study results show that the order relation of maximum energy density at various locations of the tunnel is Uside wall >Uhance >Utunnel face >Uvault, and rockburst easily occurs at the working face of the tunnel section to be excavated and both side walls of excavated and supported section; compared with vault, hance, side wall and other locations, more energy would be released at the tunnel face, and the stress release holes shall be reasonably installed in the process of excavation; the double-tube single-track tunnel system scheme can effectively reduce the rockburst intensity and the rockburst hazards, so as to better avoid the occurrence of rockburst. 2022 Vol. 59 (2): 28-37 [Abstract] ( 399 ) [HTML 1KB] [ PDF 6124KB] ( 733 ) 38 Study of Standardized Pre-processing Method of TBM Tunnelling Data Wang Shuangjing1,2 Wang Yujie1 Li Xu3 Liu Lipeng1 Yin Tao1,2 During TBM construction process, massive data are collected through information technology, and the stan? dardized pre-processing of TBM data is a precondition for multiple studies. Thus, a standardized pre-processing method of TBM tunnelling data is put forward. Based on the big data generated in TBM tunnelling and the TBM rock-breaking characteristics, the basic tunnelling parameters (e.g. cutterhead rotation speed, advancing speed, cutterhead thrust, and cutterhead torque) are selected to analyze the data characteristics during TBM tunnelling. The judgement methods of starting points of idle stage, ascent stage, stable stage and descent stage during the process of cyclic tunnelling are proposed, and furthermore the standard deviation judgement method, mean value judgement method and histogram judgement method are put forward for the starting point of the stable stage, so as to meet the requirements for segmentation of real-time and non-real-time data. Finally, the standardized pre-processing of TBM data is conducted for two TBM tunnel projects to realize the standardization of big data during construction.The result shows that the proposed standardized pre-processing method can realize the effective segmentation of cyclic tunnelling data. The research results can be applied to the standardized data processing of many TBM tunnel projects to effectively create the database for machine learning. 2022 Vol. 59 (2): 38-44 [Abstract] ( 450 ) [HTML 1KB] [ PDF 2609KB] ( 620 ) 45 Radar Image Recognition of Tunnel Lining Cavity Fillings Based on SVM HENG Aichen1,2 ZHAO Haoran1,2 TAN Bingxin1,2 HUANG Feng1,2 HE Zhaoyi1 Cavities and fillings behind the tunnel lining have an important impact on the safety of the tunnel struc? ture, and it is crucial to carry out cavity detection and identification to realize the assessment of the structural safety and the treatment of defects. Firstly, this paper adopts a combination method of indoor tests and FDTD forward simulations to obtain the radar mapping data under the conditions of filling the cavity with air, water, dry and wet sand,and compares and analyzes the waveform patterns of different fillings. Then, this paper extracts and classifies the waveform features based on support vector machine (SVM) algorithm and establishes an artificial intelligence recognition method for cavity fillings. The results show that the six types of fillings behind the lining can be effectively distinguished by taking four statistics (the mean, variance, mean absolute deviation before Fourier transform and maximum amplitude value max (fft(X)) after Fourier transform) as the SVM identifying features; and the recognition accuracy is better when single propensity data is taken, where all the six substances ′ binary classification can reach an accuracy of over 90%. 2022 Vol. 59 (2): 45-52 [Abstract] ( 381 ) [HTML 1KB] [ PDF 4042KB] ( 1152 ) 53 Study on Modes and Calculation Method of Stress and Deformation of TunnelPortal Landslide Parallel System ZHAO Jin1 WEN Lina1 WU Honggang2,3,4 ZHOU Chici1 At present, the unified industry standard has not yet been issued in China for the design of tunnel-land? slide engineering. Particularly, there is a lack of corresponding calculation theories for tunnels at the portal-landslide section. Taking the tunnel-portal landslide in the parallel system as the research subject, this paper constructs the corresponding engineering geological model by summarizing the failure characteristics of the tunnel lining in the landslide sections. Considering the residual landslide thrust as the direct cause of the tunnel deformation and failure, the additional load acting on the tunnel structure is obtained by the load transfer mechanism, and the calculation formula for external load on tunnels is derived through superimposing the additional load and the surrounding rock pressure. Using the elastic foundation beam theory, the calculation method for the tunnel internal forces under the action of the landslide thrust is derived, and thus obtaining the modes and calculation theory of stress and defor? mation of the tunnel-portal landslide parallel system. Finally, the rationality of the proposed method is verified through model tests, showing that the method is consistent with actual projects, and providing references for the design of tunnels in portal landslide sections. 2022 Vol. 59 (2): 53-61 [Abstract] ( 305 ) [HTML 1KB] [ PDF 3269KB] ( 661 ) 62 The Impact of Spatial Variability of Soils on Shield Tunnelling JIN Xuemei1,2 HUANG Hongwei2 ZHANG Dongming2 To investigate the impact of spatial variability of soil strength parameters on the ground surface deforma? tion caused by shield tunnelling, the cohesion and internal friction angle are selected as the random variables, the random fields are discretized through the Karhunen-Loève expansion method, the soil parameters random fields are mapped respectively to FLAC 3D model elements by using the Matlab software, and analytical calculations are performed by using FLAC 3D software. The results show that the spatial variability of the soil strength parameters has a significant impact on ground surface deformation. Specifically, the impact of the scale of fluctuation in vertical direction is greater than that of the scale of fluctuation in horizontal direction, and the horizontal displacement of the ground surface is more affected than the ground surface settlement. Furthermore, when the scale of fluctuation in ver? tical direction is less than 1 times the tunnel diameter, the values of ground settlement obtained from multiple simulations conform to a normal distribution, allowing to estimate the exceeding probability or the specified limit of the ground surface settlement by deterministic analysis method. 2022 Vol. 59 (2): 62-70 [Abstract] ( 380 ) [HTML 1KB] [ PDF 5906KB] ( 617 ) 71 Study on Characteristics of Water Pressure on Tunnel Single-layer Lining Structure LI Wei1 LI Qing2 YANG Dan3 There have been substantial research results on the material properties and structural stress state of tun? nel single-layer lining. However, limited studies have been done on the distribution characteristics of water pressure. In view of this, taking the single-layer shotcrete lining structure and composite sandwich lining structure as the research subjects, this paper deduces the water pressure calculation formula to analyze the pattern of how different factors, such as permeability coefficient of the shotcrete layer and thickness of the single-layer lining, affect the water pressure, based on the seepage continuity equation and Darcy′s law. The results show that: (1) when carrying out the design of single-layer linings, measures should be taken to reduce the permeability coefficient of the surrounding rock, such as surrounding rock grouting, and necessary drainage measures shall also be taken, without too much emphasis placed on the seepage resistance of the outer shotcrete layer, so as to reduce the water pressure of the single-layer lining structure; (2) the thickness of the single-layer lining should be minimized as much as possi? ble, with the recommended thickness not exceeding 40 cm, under the premise that it meets the role of surrounding rock load and self-weight load; (3) the inner-layer thickness of the composite sandwich structure should be less than 4/5 of the thickness of the outer layer. 2022 Vol. 59 (2): 71-77 [Abstract] ( 430 ) [HTML 1KB] [ PDF 1504KB] ( 745 ) 78 Inversion Analysis on the Joint Stiffness of Shield Tunnel Segments Based on Genetic Algorithm XUE Guangqiao1,2 CHENG Yan3,4 LIU Xiaodi3,4 LIU Xingen3,4 ZHANG Yi1,2 The beam-spring model is widely used in the calculation of segment lining structure. As for the joint stiff? ness there are mainly the model test method and the empirical method, of which the former is time-consuming and costly, while the latter is inevitably subjective to a certain extent. In view of this, this paper develops an inversion analysis program for the displacement of shield tunnel segment structure based on genetic algorithm by using C++ programming language. By inverse calculation examples of elastic modulus, the error between the inversion value and the theoretical value is 1.4%, verifying the feasibility of the algorithm and program. Using the program, the inversed joint stiffness values are compared with the segment joint stiffness values in actual design cases, the inversion calculation results show that the inversion error of the rotational stiffness of the circumferential segment joint is 2.6% under positive bending moment, and 4.3% under the condition of negative bending moment. 2022 Vol. 59 (2): 78-85 [Abstract] ( 384 ) [HTML 1KB] [ PDF 2348KB] ( 489 ) 86 Study on Dynamic Response and Long-term Settlement of Water-saturated Weathered Soft Rocks at the Base of Subway Tunnels SHI Yufeng1,2 CAO Chengwei1,2 TAN Yifan3 XU Changjie1,2,4 ZHANG Lichen5 HUANG Yong5 In order to investigate the dynamic response and long-term settlement of water-saturated weathered soft rocks at the base of subway tunnels under the cyclic loading of trains, this paper takes argillaceous siltstones with different degrees of weathering at the tunnel base of the Nanchang Metro as the research subject to carry out indoor dynamic triaxial tests. The paper proposes a mathematical model of cumulative plastic strain of fully-and moderately weathered argillaceous siltstones considering the number of loading, the dynamic stress ratio and the deviatoric stress ratio etc., and conducts a dynamic response analysis through dynamic finite element software. The results show that in combined strata with different degrees of weathering, the vertical influence ranges of dynamic stress and acceleration caused by the train loading are 16.0 m and 7.0 m respectively when the subway tunnel base is located in fully weathered soft rocks, and 11.0 m and 6.0 m respectively when located in moderately weathered soft rocks; also,the peak values of the dynamic stress and the acceleration in fully weathered soft rocks are both greater than those in moderately weathered soft rocks; furthermore, combined with the mathematical model of cumulative plastic strain,the predicted cumulative settlements of the tunnel base located in fully- and moderately weathered soft rocks are 25.68 mm and 17.98 mm, respectively, when the subway has been in operation for 100 years and the train is running at a speed of 110 km/h; and the variation in train running speed has less impact on the long-term settlement of the weathered soft rocks at the base of the tunnel. 2022 Vol. 59 (2): 86-95 [Abstract] ( 434 ) [HTML 1KB] [ PDF 4308KB] ( 758 ) 96 Study of Dynamic Response and Fatigue Damage of High-speed Railway Tunnels under the Impact Load of Aircraft Landing IU Kai1 WU Zaixin2 YANG Jizhong3 GUAN Haoyu4,5 In order to deal with the problems of dynamic response and fatigue damage of the lining structure of oper? ational high-speed railway tunnels under the impact load of aircraft landing, the finite element analysis method is employed to study the dynamic response and fatigue damage law of tunnels based on the tunnel on the ChengduZigong high-speed railway passing under the East Runway 2 of Tianfu International Airport. The results show that the maximum dynamic load appears at 0.05 s after rough landing of a Boeing 747-400, with the value of about 500kN; in a single rough landing condition, the tunnel vault would be subjected to maximum displacement and stress,and the maximum peak of displacement is 1.58 mm, the maximum peak of tensile stress is 437.79 kPa, the maximum peak of compressive stress is 556.24 kPa, with no plastic damage in the lining structure; under the long-term rough landing of airplanes, the parts and degree of structural damage increase with an increase in the number of cycles, the most serious damage condition occurs in the vault followed by side walls, and the fatigue life of the tunnel lining is about 25 a. 2022 Vol. 59 (2): 96-102 [Abstract] ( 400 ) [HTML 1KB] [ PDF 3166KB] ( 572 ) 103 Analaysis of Deformation and Its Control Measures for Large-diameter Shield Tunnels Passing under Building Complexes SUN Shuangchi1,2 SHEN Yi1 ZHOU Zhiyan2 ZHOU Long1 ZHU Hehua1 The excavation construction of large-diameter shield tunnels would cause disturbance to the soils, result? ing in ground settlement or heave, and thus bringing serious threats to the structural safety of the building complexes above. Based on a large-diameter shield tunnel passing under a dense group of building complexes in an old neighborhood, this paper first calculates the settlement deformation of the houses on key sections through 2D finite element software, and then compares the calculation results with those through 3D finite element software to analyze the applicability of the two calculation methods. Subsequently, on the basis of the 3D model, it studies the effects of different initial load release rates on the ground surface and house deformation caused by the shield tunnel construction. Finally, by using the theoretical ground settlement data calculated by the Peck formula, it sorts out the internal correlation among the initial load release rate, the ground settlement, and the ground loss rate, and puts forward relevant measures to control deformation. The research results show that the smaller the initial load release rate is, the smaller the ground surface and house settlement as well as corresponding ground loss will be. In terms of ground deformation control, the reduction of the load release rate is equivalent to decreasing the ground loss rate, and the decreasing amounts of initial load release rate, ground settlement, and ground loss rate are in a linear correlation. 2022 Vol. 59 (2): 103-110 [Abstract] ( 419 ) [HTML 1KB] [ PDF 3030KB] ( 752 ) 111 Spatial Effect of Support Dismantling through Alternate Bay Construction Method in Shallow-buried Large-span Tunnels in Soft and Weak Strata GAO Xin WANG Wenjuan LI Qingfei FENG Shijie WU Qi For a mined large-span tunnel constructed through the double side drift method in soft, weak, broken and water-rich strata, the alternate bay construction is completely dependent on the "shed support effect" of the initial support to maintain the stability of the large-span structure after support dismantling, which is often in the dilemma of small support-dismantling step, high risk, low efficiency and high cost, and if an improper support-dismantling scheme is taken, safety accidents such as the collapse will be easily induced. To address this problem, this paper takes the Cuobuling Station of Qingdao Metro Line 4 as the engineering background and applies the combination of theoretical analysis and numerical calculation to demonstrate that the "spatial shed support effect" of the initial support after support dismantling is mainly composed of the "transverse arching effect" and the "longitudinal beam effect", both of which help maintain the safety and stability of the large-span structure. Also, this paper determines reasonable, safe, efficient and fast support-dismantling zone partition length and compart zone partition length, which are L=9 m and S=18 m respectively and have successfully passed the verification of on-site construction. The results show that the support-dismantling scheme of "comparting two partitions and dismantling one partition, constructing inside first and then portal" is practical and feasible for subsequent projects. 2022 Vol. 59 (2): 111-121 [Abstract] ( 316 ) [HTML 1KB] [ PDF 6585KB] ( 595 ) 122 Optimization and Application of the Treatment Schemes for Water Inrush in a Water-rich Tunnel in Fault Zones ZHANG Fujun1 HU Jun2,3 DUAN Yu4 ZHU Caihui4 Based on the Gaoloushan Highway Tunnel on Wudu-Jiuzhaigou Expressway as an example, this paper carries out a numerical analysis to investigate the treatment issues of water inrush in the tunnel governed by fault racture zones. Based on the FLAC 3D finite difference method and the principle of fluid-solid coupling analysis,this paper investigates the influence of different treatment methods on tunnel water inrush and stability of surrounding rocks, such as drainage, grouting, and combination of drainage and grouting. The results show that: (1) when a serious water inrush of Grade A or B occurs in a water-rich tunnel passing through fault zones, it should take the treatment measures combining the drainage through drainage tunnels with stopping water by grouting. Specifically, the drainage tunnels should be set near the fault, with a relative distance of 0.75 (D+l) to the tunnel, while the thickness and relative permeability coefficient of the grouting ring should be controlled within 7 m and 10 respectively. This can not only reduce the amount of water inrush but also ensure the stability of surrounding rocks; (2) for a tunnel with a Grade C water inrush, it could adopt the grouting measure with the grouting thickness no less than 3 m and the relative permeability coefficient no less than 20; (3) for a tunnel with a water inrush of Grade D or below, it could take conventional measures such as pumping and discharge 2022 Vol. 59 (2): 122-131 [Abstract] ( 429 ) [HTML 1KB] [ PDF 4553KB] ( 734 ) 132 Application of the Middle Partition Wall Made of the Steel Corrugated Plate in Inclined Ventilation Shafts of Extra-long Highway Tunnels ZHAO Wei1,2 ZHANG Ke1,2 GUO Chun1,2 As a mature technology, the middle partition wall made of the concrete is generally used for pilot head? ings with the purpose of ventilation. However, it comes with various shortcomings, such as rough surface, complex technics and uncontrolled construction progress, making it difficult to be applied to tunnel projects with complex air ducts. Taking the No. 1 inclined shaft of East Tianshan Tunnel as the background, this paper proposes an energysaving and fully-assembled construction technology for the partition wall made of the steel corrugated plate, and verifies its application feasibility in a single-tube four-duct inclined ventilation shaft through numerical simulation and theoretical calculation. The results show that using the partition wall made of the corrugated steel plate, it increases the effective ventilation sectional area of the inclined shaft and reduces the sectional wind speed by about 5.3%, while also significantly reducing the on-way ventilation resistance along the inclined shaft, which is only about 17% of the ventilation resistance of the existing concrete partition wall scheme. Also, the vault deformation and structure stress of the secondary concrete lining are far below the limits regarding the structural safety. This technology overcomes the shortcomings of traditional partition wall made of reinforced concrete, and improves the tunnel construction environment while meeting the requirements for tunnel ventilation and disaster prevention. Furthermore, the construction time can be shortened to one-third of the existing scheme. 2022 Vol. 59 (2): 132-140 [Abstract] ( 435 ) [HTML 1KB] [ PDF 3476KB] ( 558 ) 141 Study on the Performance of Paper Fiber Based Modified Permeable Mortars in Tunnelling JIANG Yajun1 YU Liangmin1 WANG Cuijuan2 WANG Yongchao2 WANG Huqun In order to develop a type of mortar that is suitable for leveling of the tunnel initial support surface and has certain permeability, paper fibers are added to mortar samples to modify the performance. The degradation principle of paper fibers is analyzed, and paper fibers with different dosages are added to mortar samples, with the aim to test and analyze basic performance indicators (e.g. bulk density, water absorption and compressive strength) and microstructure. It can be seen from the test result that paper fibers have degradable property in an alkaline environment; paper fibers can increase the water absorption of ordinary mortar samples by 2～3 times and also contribute to a reduction in the bulk density and compressive strength of mortar samples; and there is a negative correlation between water absorption and compressive strength after linear fitting is performed for the water absorption and compressive strength of mortar samples. The study results show that it is feasible to improve the water permeability of mortars by using paper fibers, but the impact of the addition dosage of paper fibers on other performances of mortars needs to be studied further. 2022 Vol. 59 (2): 141-149 [Abstract] ( 391 ) [HTML 1KB] [ PDF 3252KB] ( 484 ) 150 Numerical Simulation and Field Experiment of the Blasting Technology with Water Bags in Notched Holes LI Ningjie1,2 ZHANG Xuefu1,2 ZHOU Jie1,2 CHU Bo1,2 MENG Lianghua1,2 In order to improve the effect of smooth blasting in tunnelling, this paper proposes the blasting technology with water bags in notched holes. It also analyzes the blasting effect based on the rock damage induced by radial decoupling charge and spaced charge, the blasting efficiency in radial and axial directions, the radial pressure on the hole wall and mark rate of perimeter holes at site, the rock fragmentation, and the overbreak and underbreak of the tunnel. The results show that: (1) The change of radial decoupling coefficient has an effect on the axial and radial blasting effects, and the change of spaced charge coefficient only has an effect on the axial and inter-hole blasting effects; (2) when Kd=1.25, rock damage is concentrated in zones between the explosive holes, and axial rock damage zones are relatively small; when Kd =1.75, excessive water bags would induce an energy dissipation, and the rock damage zones are smaller; and (3) the blasting technology with water bags in notched holes can produce smooth tunnel contour profile, with more finely broken rock mucks, and the optimal charging factors are Kr= 1.5 and Kd=1.5. 2022 Vol. 59 (2): 150-158 [Abstract] ( 510 ) [HTML 1KB] [ PDF 3827KB] ( 547 ) 159 Experimental Study and Numerical Simulation of Crystallization-induced Blockage in Drainage Pipes in Karst Tunnels CHENG Yongchun1 ZENG Xiangji1 WANG Zhenjia1 WANG Dong1 YANG Yun2 WU Yongjing3 DONG Ping3, 4 In order to realize the accurate description, early warning and control of the blockage process of the tun? nel drainage system in the karst area, the laboratory test on blockage in the drainage pipe system is carried out at the 1∶1 scale, and the variation law of the crystal precipitation is discussed under the conditions of field hydrodynamics,hydrochemistry and wetting-drying cycle. The numerical model of crystallization-induced blockage in tunnel drainage pipes in karst areas is constructed considering the coupled driving process of hydrodynamic force and dissolution-precipitation reaction of carbonate components, and is verified combined with the laboratory test data. The simulation results show that the error between the simulated values and the experimental observation values is gradually decreased as time goes by, and the determination coefficient of fitting (R2) reaches 0.67 at about 15 d, proving that the numerical model can predict the crystallization process in the tunnel drainage pipes in a relatively long time scale. The proposed model can provide theoretical guidance for the prevention and control of blockage in the tunneldrainage system, and further guarantee the early identification and safety assessment of geological hazards of karst tunnels. 2022 Vol. 59 (2): 159-166 [Abstract] ( 419 ) [HTML 1KB] [ PDF 2769KB] ( 656 ) 167 On Discrimination Method and Treatment Measures for Overall Soil-carrying Effect of Shallow-buried Rectangular Pipe Jacking Projects ZHEN Liang1 ZHANG Xianyu2,3 LI Xiaojun2,3 Friction exists between shallow-buried rectangular pipe jacking machine, pipes and soils, and when the machine has no drag reduction or anti-soil-carrying device, the substantial friction between the machine and soils will induce an overall soil-carrying effect. This paper introduces a discrimination method of overall soil-carrying effect considering the friction difference between machine (pipe) and soils. Taking the test section of the rectangular pipe jacking project between Luxiang Road and Qilianshan Road in Shanghai as the background, it carries out an analysis of the overall soil-carrying effect based on measured data, and introduces the relevant treatment measures.The results show that the method has successfully predicted the overall soil-carrying failure occurring in the test section, where the calculated critical machine (pipe)-soil friction coefficient is 0.35, the predicted maximum jacking path at the time of failure is 31.05 m (actually 34 m), and the lateral influence range of the overall soil-carrying effect occurring in the pipe jacking is approximately equal to the sum of the overburden depth and the equivalent radius of the section. Also, the influence range of heaving is about 3.0L (L is the head length), and the ground deformation shifts from heaving to settlement when the working face passes through 3.0L 2022 Vol. 59 (2): 167-171 [Abstract] ( 364 ) [HTML 1KB] [ PDF 1732KB] ( 491 ) 172 On Settlement Control in Large-diameter EPB Shield Tunnelling under Civil Housing Complex in Upper-soft and Lower-hard Strata ZHANG Bangchao1 LIU Hongliang2 LEI Fengguo2 PENG Guanghuo2 The shield tunnelling of Guangzhou Metro Line 18 is faced to such characteristics as complex ground dis? tribution, large strength differences between soft and hard rocks, and dense residential building complex located above the tunnel. In view of this, it is intended to address two major problems in actual construction, i.e. settling the reasonable tunnelling parameters and controlling the settlement deformation of buildings on the ground surface through a series of active measures, such as grouting reinforcement, on-site dynamic monitoring, and optimization of tunnelling parameters. The results show that: (1) in this type of soft and hard rock interbedded strata, tunnelling parameters (such as torque and thrust) would fluctuate greatly when the cutterhead passes through the geological boundary of different strata, and the total thrust would be in a fine correlation with the torque, where it is appropriate to control the tunnelling parameters at certain values, i.e. the thrust at 30 000～35 000 kN, the torque at 4 500～6 000kN·m, and the advancing speed at 35～45 mm/min; (2) the proposed technological process of multi-section sealing and advanced grouting in the tunnel can lift the ground surface by 3～5 mm within the scope of 18 m in front of the cutterhead, with maximum lifting value of 9.02 mm, while it can also mitigate the settlement tendency of the soil mass induced by shield driving and subsequent consolidation and stabilization; (3) temporary shield stoppage caused by tool wear, large fluctuation in tunnelling parameters, and the jamming of the screw conveyor can cause the daily settlement rate of the buildings on the surface to exceed 3 mm/d. The adoption of advanced grouting in tunnel and the clay shock method ahead of the preset machine stop point can effectively alleviate the settlement tendency and control the daily settlement rate below 2 mm/d during the hyperbaric intervention of the earth chamber; (4) the settlement of the surface buildings near the left and right tunnel axes can be basically divided into three phases of slight heave—large settlement—gradual stabilization, with maximum settlement of -21.38 mm and -22.49 mm respectivly, being less than the control values. 2022 Vol. 59 (2): 172-181 [Abstract] ( 387 ) [HTML 1KB] [ PDF 5671KB] ( 617 ) 182 Study of the Settlement Control of Deformation Joints of Tunnels Passing Closely under the Existing Station LIANG Erbin The newly-built tunnel passing closely under the existing station will inevitably lead to settlement of the existing station, and especially deformation joints are prone to differential settlement. Based on the Suzhoujie Station of Beijing Subway Line 16 passing closely under the existing Line 10, this paper analyzes the overall settlement of the existing station and the differential settlement at deformation joints through a combination of field measurement and numerical simulation. The study results show that installing jacks significantly prevents the settlement of the existing station, after installation of jacks the settlement of the existing station is reduced by about 58%, and the jacking force of the jack shall be controlled between 180-450 t; the impact of construction on the single-deck station structure side at deformation joints is greater than that on the double-deck station structure side, the stress on the socket is gradually increased with the excavation of the lower tunnel, and reduced after installation of jacks, indicating that the jack can effectively reduce the tensile stress of the existing station and maintain the safety of the existing station; with the action of the jacking force of jacks, the settlement curve of the existing station presents a stepwise change at the jack installation points, while the upper ground surface settlement is relatively uniform. 2022 Vol. 59 (2): 182-191 [Abstract] ( 358 ) [HTML 1KB] [ PDF 5906KB] ( 521 ) 192 Key Technologies in the Design of the Xiangyang Hanjiang Immersed Tube Tunnel WANG Yong XU Guoping LI Yong LIU Minghu REN Yaopu XU Yu FAN Zhe Based on the engineering design practice of the Xiangyang Hanjiang Immersed Tube Tunnel, and in view of the tunnel characteristics, such as strong scouring, deep and thick highly-permeable ground and high requirement for flood control, this paper investigates the various aspects in terms of the tunnel design, including the horizontal-and longitudinal layout of the tunnel, the tunnel element structure and water-stopping structure of the joints, the type and structure of the dry dock, foundation and backfilling of the immersed tube tunnel, final closure joint structure and water-stopping structure of the connection ends. The results show that: (1) for the inland river immersed tube tunnel, the arrangement scheme of long-distance dual-axis dry dock is adopted, and the support and water isolation problems of the deep foundation in highly permeable strata are solved through a combination of technologies,such as lattice underground diaphragm wall, ultra-deep closed curtain, underground diaphragm wall with prestressed anchor cables and concrete sealing bottom; (2) the full-face continuous casting technology is used to prefabricate monolithic elements, and the independently developed water stop profiles are first used for the element joints;(3) for the inland river immersed tube tunnel, a high-precision floating leveling barge is used for pre-paving the peb? ble foundation, and the anti-scouring solution is provided for the top of the elements in strong scouring areas; (4) the land final joint without independent thrust structure is used, and at the connection end the support structure composed of large diameter interlocked steel pipe piles and outside water-stopping wall as well as the secondary waterstopping structure composed of piece-by piece hoisted double-wall steel cofferdam are installed according the project demand. 2022 Vol. 59 (2): 192-199 [Abstract] ( 372 ) [HTML 1KB] [ PDF 5901KB] ( 581 ) 200 Key Design Technologies for Mechanized Construction of Railway Tunnels by Drilling and Blasting Method CHEN Guodong1 GAN Mufei2 LIU Ke2 As a technical method, the mechanized construction of D&B tunnels, which is based on the matching of high-efficiency large-scale machinery in full process, is intended to solve various construction problems of long and large mountain tunnels in complex mountainous areas with the goal of safety, quality, efficiency and economy. This paper discusses the two key challenges faced by mechanized construction of tunnels by drilling and blasting method,i.e. safety control of the tunnel face and deformation control of the tunnel body from the perspective of the design,and summarizes the key design technologies for mechanized construction of tunnels by drilling and blasting method,including the full-face mechanized construction technology in various geological conditions, the assessment method of tunnel face stability, the active advance support technology of tunnel face, the "quantified" accurate design technology of active advance support, the active support technology with low prestressed anchor bolts, the active support technology with early high-strength shotcrete, the fast-closing technology of primary support ring, and the calcula? tion method for deformation pressure of surrounding rocks, which can provide technical supports for the promotion and application of mechanized construction method in D&B tunnels. 2022 Vol. 59 (2): 200-209 [Abstract] ( 440 ) [HTML 1KB] [ PDF 4948KB] ( 866 ) 210 Optimization and Application of the Construction Scheme for Large-section Tunnels in Water-rich and Weakly Cemented Strata WANG Huaizheng1 SONG Zhanping1,2 ZHANG Xuewen3 TIAN Xiaoxu1,2 PAN Hongwei4 In water-rich and weakly cemented strata, tunnel construction is very likely to induce the collapse of the surrounding rocks or serious large deformation of the support structure. This paper puts forward the lower double pilot tunnel construction method applicable for water-rich sandstone strata condition, based on the main tunnel construction of the 3# inclined shaft of the Taoshuping Tunnel on the Lanzhou-Chongqing Passenger Dedicated Line.Meanwhile, it adopts an integrated dewatering scheme of vacuum light well point + water collection well for advanced dewatering of the tunnel to reduce the construction difficulties. Using numerical analysis and on-site monitoring method, it analyzes and evaluates the reasonableness and effectiveness of the construction scheme. The results show that when the lower double pilot tunnel construction method is used, the vault settlement and clearance convergence are 50 mm and 32 mm respectively, while the maximum contact pressure on the support structure is 135.3 kPa, and the deformation and stress of the support structure are both within the acceptable range with the tunnel structure being safe and stable. The lower double pilot tunnel construction method has been successfully applied to the Taoshuping Tunnel, providing references for the construction of extra-large section tunnels in water-rich and weakly cemented strata or soft rock strata. 2022 Vol. 59 (2): 210-219 [Abstract] ( 457 ) [HTML 1KB] [ PDF 5660KB] ( 491 ) 220 Construction and Safety Control of New Metro Tunnels Passing under Existing Operational Metro Lines in Close Proximity FENG Huijun The running tunnel between Qingdao North Station and Cankou Station of the new Qingdao Metro Line 8 passes under the existing operational Metro Line 3 in close proximity, with the distance between the initial support of new metro tunnel and the bottom floor structure of Line 3 being only 0.4 m, which is extremely challenging for construction without affecting the normal operation of the existing Metro Line 3. By constructing a 3D finite element model, this paper simulates the full construction process of the new running tunnel passing under the operational existing line. And relevant targeted measures are prepared: using non-blasting mechanical excavation to reduce vibration; strengthening advance support and fast-closing support ring to control settlement; and automatic monitoring structural deformation of Line 3 to provide rapid feedback and guide on-site construction. Through on-site technical and safety control means, the maximum settlement of the tunnel structure of Line 3 during the underpass construction was only 2.11 mm, and the maximum settlement of the track bed was only 1.55 mm, which satisfied the requirements for settlement control without affecting the safe operation of Metro Line 3 during the construction period. The relevant engineering experience can provide a reference for design and construction of similar tunnel works passing under existing operational metro tunnels with small clearance, small angle and long distance. 2022 Vol. 59 (2): 220-226 [Abstract] ( 458 ) [HTML 1KB] [ PDF 3762KB] ( 715 ) 227 The Concept and Practice of Treatment for Damage in Railway Tunnel Linings Caused by High-pressure Karst Water ZHANG Peng1 WANG Lichuan2, 3 LI Linyi3 YAO Yong1 ZHANG Xuemin3 ZHENG Bo4 LIU Maobing5 In recent years, railway tunnels in karst areas have frequently suffered flooding after high-intensity rain? fall, which seriously affects the safety of tunnel operation and the order of transportation, and even interrupts the traffic. Based on the water hazard case in the Yuanbaoshan Tunnel on the Zhijin-Bijie Railway Line, this paper explores the causes of lining damage in terms of geology, rainfall, and the design and construction of water hazard sections, and puts forward the treatment technology for tunnel water hazards with the core concept of "making full use of existing structures and employing open drainage methods in key sections". Besides, this paper simulates and analyzes the formation of hazards and the treatment effect through numerical simulation. The results show that the subjective causes for the damage in tunnel linings include an insufficient understanding of the water-bearing formations at the geological investigation stage, the underestimation of water hazard risks posed by high-intensity rainfall during construction, and the unimproved waterproof and drainage system in the design alteration, while the objective reasons include the development of karst near the tunnel section that passes through the stratum, the strong connectivity of water conduits, and the high-intensity rainfall in a certain period of time on the tunnel site. As for the simulation results, they show that the increase of external water pressure caused by the sudden rise in groundwater level after rainstorm significantly increases the internal force of linings, and eventually leads to a much lower safety factor of sidewall linings and large scale damage, which is in consistency with the characteristics of the actual on-site damage. After on-site emergency treatment, the tunnel structure has become stable and even encountering unprecedentedly heavy rainfall twice, the tunnel has still remained in a good condition. Since then, no water hazards and other disasters have occurred, which proves that the treatment plan is valid. 2022 Vol. 59 (2): 227-241 [Abstract] ( 347 ) [HTML 1KB] [ PDF 8002KB] ( 492 ) 242 Cause Analysis of Persistent Heaving of Tunnel Floors in Red-bed Mudstone with Complex Geo-stress YUAN Wei1 LU Junfu2 LIU Jinsong1 WU Junmeng1 In order to investigate the characteristics and causes of persistent heaving of tunnel floor in red-bed mud? stone with complex geo-stress, taking a specific tunnel as the research subject, this paper carries out a statistic analysis on the deformation characteristics of the tunnel floor heaving through various methods such as long-term deformation monitoring, groundwater level monitoring, and surrounding rock displacement monitoring at the tunnel bottom. And it studies the respective factors that may lead to tunnel floor heaving through the combined assistance of different approaches such as analysis of drilling core samples, geo-stress test, surrounding rock swelling force test,rock creep test and numerical simulation analysis. The results show that governed by the near-horizontal bedded mudstone and complex geo-stress, some sections of the tunnel display three features, i.e. "non-convergence" of the floor heaving time, "uncontinued" of floor heave sections, and "uneven" of heaving degree. The occurrence of the tunnel surrounding rocks is nearly horizontal, with a lithology of silty mudstone, so it is a soft rock that does not meet the classification criteria for swelling rock, with medium-low creep characteristics, and the geo-stress field at the tunnel site is mainly horizontal tectonic stress, with the horizontal stress between 9.5 ~ 13.73 MPa. As the tunnel is excavated, the local stress concentration leads to surrounding rock creep, and when the creep generates excessive deformation pressure, the parts of the inverted arch would enter into a plastic state, and thus inducing the tunnel floor heave. 2022 Vol. 59 (2): 242-250 [Abstract] ( 410 ) [HTML 1KB] [ PDF 4191KB] ( 691 ) 251 Research and Application of New Spherical Tungsten Carbide Cutting Tools in Guiyang Metro Shield Tunnelling in Karst Strata ZHANG Longguan1,2 ZHU Xiaohai2 TUO Hongtao2 WANG Liangdong2 TAN Jiang2 WANG Wei3 In the shield tunnelling of Guiyang Rail Transit Line 3, the used ordinary cutting tools were prone to ab? normal wear of cutting tools and falling-off of cutter rings, such as polygonal wear, eccentric wear, and cutting-edge chipping . To improve the capacity of anti-abrasion and impact resistance of disc cutter rings, and increase the overall life of the cutting tools, this paper proposes to use spherical tungsten carbide cutting tools to replace ordinary tools, and introduces the laser cladding welding process and macroscopic wear inspection process. By application of new spherical tungsten carbide cutting tools in actual construction, it is found that the spherical tungsten carbide cutting tool is of better wear resistance with the average wear of 0.002 55 mm/linear meter, while the average wear of the ordinary cutting tool is 0.016 55 mm/linear meter. In the tunnelling of Ring 338-736, the maximum wear of the new spherical tungsten carbide cutting tools is 0.015 mm/linear meter, without cutting-edge chipping or abnormalities in the disc cutter bearings and seals. It has effectively resolved the problems of ordinary cutting tools such as easy and uneven wear and provides reference for the selection of shield cutting tools in the geological conditions of karst strata. 2022 Vol. 59 (2): 251-257 [Abstract] ( 306 ) [HTML 1KB] [ PDF 3220KB] ( 515 ) 258 Study of Thermal Insulation Effects of Off-wall Corrugated Steel Plate Liner Applied in Tunnels in the Seasonally Frozen Region CUI Guangyao1 JIANG Mengxin1 WANG Daoyuan2,3 WANG Xuelai1 In order to prevent and control frozen damage that frequently occurs in tunnels in the seasonably frozen region, a new thermal insulation liner composed of off-wall corrugated steel plates is developed, which is characterized by easy construction, reliable waterproof performance, resistance to concrete chipping, an increase in the service life of polyurethane and so on. Numerical simulation is performed to study the temperature field of the tunnels installed with thermal insulation liner composed of off-wall corrugated steel plates in the seasonably frozen region and its thermal insulation effect. The results show that the installation of the new thermal insulation liner composed of off-wall corrugated steel plates in tunnels in the seasonably frozen region can prevent the impact of cold air on the lining structure, the area of surrounding rocks with positive temperature is increased, and the tunnel frost line moves forward from the surrounding rock position at 0.48 m away from the lining to the thermal insulation liner, effectively preventing the occurrence of frozen damage of tunnels in the seasonably frozen region; the thermal insulation effect of wall-mounted polyurethane thermal insulation layer of tunnels in the seasonably frozen region is 89.90%~96.43%, and the thermal insulation effect of new thermal insulation liner composed of off-wall corrugated steel plates is 101.94%~107.14%, with better thermal insulation effect than that of the former. 2022 Vol. 59 (2): 258-263 [Abstract] ( 419 ) [HTML 1KB] [ PDF 2932KB] ( 571 )

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