[an error occurred while processing this directive]

Home | About Journal |  Editorial Board |   |  Instruction |  Subscription |  Advertisement |   |  Download |  中文  Office Online   Search     Adv Search

·Online Submission ·Manuscript Tracking ·Peer Review ·Editor Work ·Office Work ·Editor-in-chief  Journal Online ·Forthcoming Articles ·Current Issue ·Next Issue ·Archive ·Advanced Search ·Read Articles ·Download Articles ·Email Alert ·  Download · More>>

Quick Search     Advanced Search MODERN TUNNELLING TECHNOLOGY   2023 Vol.60 Issue.4 Published 2023-08-25 1 For the Harmony between Tunnelling and Geological Body ——Discussion on Focused Hot Issues in Conventional Tunnelling WANG Jianyu With the construction concept innovation in conventional tunnelling changing from“passive supporting” to“active controlling”, some focused hot issues such as monitoring measurement, ground improvement, integration of the double-shell lining and structural design models are discussed in this paper. Meanwhile, in response to the tunnelling challenges in two specific geological environments namely the squeezing ground with high initial stress and high waterhead groundwater, treatment measures of“rock bolting+constant reaction support”and“rock grouting+lining drainage”can be used respectively.That is to say, for the large amount release (of stress or hydraulic potential) induced by excavation, only the “yieldingc principle”instead of the“resistance principle”is feasible to realize the harmony between tunnelling and geological body. 2023 Vol. 60 (4): 1-5 [Abstract] ( 194 ) [HTML 1KB] [ PDF 604KB] ( 1376 ) 6 Analysis of Gas Leakage Model and Influencing Factors of Shield Tunnel Segment Joint XIAO Mingqing1,2 TANG Yuheng3 CHEN Junwei1,2 ZHANG Chaoyong3,4 In a tunnel that is excavated through a stratum containing methane, the differences in the physical proper? ties of gas and liquid will result in different leakage characteristics, so it is necessary to investigate gas leakage mechanism at segment joints. First, from the perspective of leakage path, the segment joint gas leakage model is built, to derive the segment joint gas leakage rate formula. Then, the gasket numerical simulation model is built to analyze how gasket roughness and external air pressure will affect gas tightness. Finally, the multiple linear regression analysis of the simulation data is conducted to analyze the sensitivity of the factors, and the method for reducing segment joint gas leakage is proposed. As the results suggest, reducing the roughness will significantly inhibit gas leakage; when roughness is greater than 0.8 μm, the gas leakage rate increases significantly; with production cost considered, it is recommended to keep the gasket roughness within the range of 0.4~0.8 μm; as the external air pressure increases, the average contact stress between the contact surfaces does not increase continuously, and the height of leakage path does not change significantly as the positive pressure increases; the factors that affect gas leakage rate are roughness, external air pressure, dislocation, opening and hardness in descending order in terms of their degree of influence. 2023 Vol. 60 (4): 6-13 [Abstract] ( 188 ) [HTML 1KB] [ PDF 2466KB] ( 608 ) 14 Calculation Method for Safe Thickness of Water Insulation Rock in Tunnelling Based on Timoshenko Beam Theory ZHENG Xiaoyue1,3 SHI Chenghua1,2,3 WANG Zuxian1,3 YU Guoliang4 ZHENG Keyue1,3 Considering the bending effect and the shear effect of the water insulation rock mass around the tunnel under the pressure of the mud water in the karst cavity, an analytical calculation model of the safe thickness of the water insulation rock of the tunnel is established based on the Timoshenko beam theory, the calculation method of the minimum safe thickness is derived as per the flexural strength criterion and the shear strength criterion, and the influencing factors of the analytical model for the safe thickness of the water insulation rock are systematically analyzed based on project cases. The results indicate that the diameter of the karst cavity has the most significant impact on the minimum safe thickness of the water insulation rock. The minimum safe thickness of the water insulation rock increases with the rise of tunnel burial depth, cavity diameter, and cavity water pressure. With the increase of tunnel burial depth and water pressure in the karst cavity, the water insulation rock is more prone to bending failure compared with shear failure. As the azimuth angle of the karst cavity increases, the minimum safe thickness of the water insulation rock first decreases and then increases, the rate of reduction first increases and then slows down, the maximum safe thickness value occurs when the karst cavity is located at the top of the tunnel, and there is the minimum safe thickness value when the karst cavity is located at the bottom of the tunnel. Compared with existing researches,it is found that the calculation method for the minimum safe thickness of water insulation rock, in which the impact of both bending and shear effects of rock beam is considered, can more effectively reflect the deformation characteristics of rock beams between the karst cavity and the tunnel, and is of good practicality. 2023 Vol. 60 (4): 14-22 [Abstract] ( 177 ) [HTML 1KB] [ PDF 2730KB] ( 494 ) 23 Calculation of Damage Range of Tunnel Surrounding Rock and Analysis of Influencing Factors under Single-hole Blasting LI Tao WANG Linfeng LI Song ZHANG Jixu TANG Ning In order to solve the inaccurate calculation problem of damage range from tunnel blasting, a calculation method of tunnel surrounding rock damage range under single-hole blasting is proposed based on the D-P criterion and fracture mechanics principle. Based on the relevant project, the damage range of tunnel surrounding rock is calculated under the action of single-hole blasting. The results show that the calculated radius of the crushing zone is 242 mm, which is within the range of measured values; the radius of Fissure Zone Ⅰ is slightly larger than that of the crushing zone, and the radius of Fissure Zone Ⅱ is 1 473 mm, slightly larger than the range of measured values.The calculated results are close to the results of the finite element simulation; The crushing zone of surrounding rock under the action of single-hole blasting is formed at 130 μs, Fissure Zone Ⅰ formed at 220 μs, and the fissure within the Fissure Zone Ⅰ expands at 220-820 μs, so as to form Fissure Zone Ⅱ at 820 μs; The attenuation rates of the vibration velocity in X and Y directions within Fissure Zone Ⅱ and the crushing zone increase with the growth of the distance to the blasting center, respectively; Under the action of single-hole blasting, the main control factors for the radii of the crushing zone and Fissure Zone Ⅰ and the radius of Fissure Zone Ⅱ are the explosive blasting velocity D and Poisson's ratio μ, respectively. 2023 Vol. 60 (4): 23-32 [Abstract] ( 163 ) [HTML 1KB] [ PDF 2360KB] ( 456 ) 33 Study on the Influence of Internal Water Pressure on the Composite Lining Structure of Water Conveyance Shield Tunnels MENG Qinghui1 FENG Kun1 YANG Guodong1 HE Xiao2 YANG Zhao2 HUANG Qingfu3 GAO Chong1,4 In view of the influence of internal water pressure on the mechanical characteristics of the composite lining structure of the shield tunnel, and in combination with the Longquan Inverted Siphon Tunnel of the Central Yunnan Water Diversion Project, the shell-spring model of the composite lining is improved, and the mechanical behaviors of the double-layer lining structure under the internal water pressure are analyzed. The results show that the bending moment of the segment structure is less affected by internal water pressure, while the axial force of the segment and the flexural rigidity of the longitudinal joint decrease with the increase of internal water pressure; The axial force and the bending moment of the secondary lining are greatly affected by internal water pressure; The internal water pressure has a significant effect on the flexural rigidity of the joint with a larger bending moment, with a maximum decrease of 47.97% in the flexural rigidity of the joint; Under external soil and water loads, the deformation of the segment shows a trend of vertical convergence and horizontal expansion. After filled with water, the overall downward displacement of the lining structure leads to its further vertical convergence. Under the action of internal water pressure, the force between the segment lining and the secondary lining is mainly radial compression. When the longitudinal joint of the segment is subjected to a positive bending moment, the compressive stress significantly increases.When subjected to a negative bending moment, the radial interaction force is zero, and there is a separation trend between layers. 2023 Vol. 60 (4): 33-42 [Abstract] ( 162 ) [HTML 1KB] [ PDF 5305KB] ( 407 ) 43 A Case Study on Adjacent Impact Zoning and Control Measures for New Double-line Shield Tunnel Undercrossing Existing Tunnel FAN Wenhao1,2 XIE Shenghao1,2 ZHOU Feicong1,2 WANG Zhijie1,2 ZHANG Kai3 LUO Yunjian3 In order to explore the impact of new undercrossing tunnel on the existing tunnel structure under differ? ent adjacent degrees, based on the Chengdu Subway Line 30 undercrossing the existing Jinxiu Tunnel on ChengduZigong High Speed Railway, the expression for adjacent impact degree is proposed by the theoretical research method, and the impact zoning control standard is determined by the structural displacement discrimination criteria. Numerical simulation and regression analysis methods are used to quantify and zone the adjacent impact range of the undercrossing construction, and targeted control measures are proposed for different impact zoning. The results show that the maximum settlement of existing tunnel segments is negatively correlated with the net distance between the newly-built tunnel and the existing tunnel, as well as the separation distance between left and right lines of the newly-built tunnel. A "gate" type protection structure is proposed for construction in the strong impact zone, which can reduce the maximum settlement of existing tunnel segments by 77.10%. For construction in weak impact zones,grouting reinforcement is proposed behind new tunnel segment walls, which can reduce the maximum settlement of existing tunnel segments by 56.86%. The monitoring results indicate that reasonable construction control measures can effectively control the displacement of the existing tunnel structure, and control the maximum settlement of the existing tunnel segment within the warning value of 6 mm. 2023 Vol. 60 (4): 43-57 [Abstract] ( 164 ) [HTML 1KB] [ PDF 8584KB] ( 494 ) 58 Study on TBM Tunnelling Parameters Under Ultra-small-radius Turning Conditions Based on Field Data XIE Miao WANG Haonan LI Siyao TIAN Bo LIU Yafeng ZHANG Hongyu In order to study the variation law of TBM tunnelling parameters under ultra-small-radius turning condi? tions, the TBM-driven drainage gallery project of Jinyun Pumped Storage Power Station in Zhejiang Province is taken as an example for analysis. The TBM turning process is analyzed to find out that the adjustment amount of the shield is the main factor affecting the minimum turning radius of TBM. The forces on the disc cutters during rock breaking are analyzed to obtain the mechanism of interaction between the forces and various parameters. On the basis of on-site actual tunnelling data, the relationship among the penetration, thrust and torque of the TBM cutterhead under different rock uniaxial compressive strengths, rock mass integrity coefficients, and included angles between joint strike and tunnelling direction are analyzed. The analysis results show that under ultra-small-radius tunnelling conditions, the penetration increases logarithmically with the increase of thrust, and the torque increases exponentially with the increase of penetration, the increase rates being closely related to rock parameters. In addition,a prediction model for tunnelling parameters and rock parameters is established to carry out multiple groups of actual predictions for projects. The prediction results have an average relative error of less than 10%, indicating a high prediction accuracy of the prediction model. 2023 Vol. 60 (4): 58-66 [Abstract] ( 144 ) [HTML 1KB] [ PDF 4990KB] ( 384 ) 67 Study on a Deep Learning-based Model for Detecting Apparent Defects in Shield Tunnel Lining WU Gang1 LUO Wei2, 3 WANG Xiaolong1 ZHU Jingjing1 JIA Fei2, 3 XUE Yadong2, 3 In this paper, a detection model for many apparent defects of shield tunnel lining based on deep learning modular design is proposed to quickly and accurately identify defects such as water seepage, cracking, falling blocks, and mud & sand leaking on the surface of shield tunnel lining. The model is divided into four modules: data loading, network structure, loss function and post-processing, training and evaluation. Combining the detection principle and data set characteristics of SSD (Single Shot MultiBox Detector) and YOOv4 (You Only Look Once), it is proposed to comprehensively evaluate the matching degree between the prior boxes of the model and this dataset by using two indicators: fitness and maximum possible recall rate. Based on the distribution of defect labeling boxes of the dataset, the K-means method is used to cluster and obtain a set of prior boxes with the highest matching degree.The structure of the SSD model is optimized by considering the structural characteristics of the YOLOv4 model. The results show that the optimized model has a detection accuracy of 0.623, which is nearly 70% higher than that of the original SSD model (0.373). The detection speed has been increased from 40 FPS to 50 FPS, fully proving the rationality of the optimized model. 2023 Vol. 60 (4): 67-75 [Abstract] ( 156 ) [HTML 1KB] [ PDF 4755KB] ( 527 ) 76 Detection Method for Blockage of Tunnel Drainage Holes Based on U-Net++ Network WANG Yaodong DU Yaohui GAO Yue In order to improve the recognition efficiency of tunnel drainage hole images based on traditional image detection, the artificial intelligence semantic segmentation method of the U-Net++ neural network model is used to process the blockage images of tunnel drainage holes, and the evaluation indicators of siltation degree are introduced to accurately classify drainage holes with different degrees of siltation. The results show that the loss curve of the proposed method shows a good convergence trend, and the accuracy on both the training and validation sets shows a stable improvement trend. It outperforms other commonly used image segmentation methods in terms of accuracy, recall rate and F1 score, reaching 96%, 95% and 95%, respectively. This model also performs well in terms of IoU and Dice coefficients, reaching 91% and 95% respectively. Furthermore, the model has certain adaptability to changes in lighting and different noise environments, and still performs well in different scenarios. The proposed intelligent recognition method based on U-Net++ neural network has shown high levels in terms of accuracy, robustness and adaptability, providing an effective solution for the detection of blockage of tunnel drainage holes. 2023 Vol. 60 (4): 76-85 [Abstract] ( 126 ) [HTML 1KB] [ PDF 5409KB] ( 384 ) 86 Study on Action Mechanism of Double-layer Support for the Parallel Adit of Tunnels in Extremely-squeezed Surrounding Rocks WANG Guan Based on the Yuelongmen Tunnel on the Chengdu-Lanzhou Railway, a combined method of field moni? toring and finite element calculation is used to explore the causes for the primary support failure and the action mechanism of secondary support in the parallel adit of tunnels in extremely-squeezed surrounding rocks. Firstly, according to the deformation monitoring data of the adit, the deformation characteristics of the adit and the restraining effects of different measures on deformation are analyzed. Then, on the basis of the Rock Mass Rating (RMR) method,reasonable physical and mechanical parameters of the surrounding rock are selected, and the deformation and the stress of the adit support are calculated using elastic-plastic finite element analysis, and the action mechanism of the double-layer support is discussed. The study shows that measures such as adding bolts and grouting reinforcement can slow down the deformation rate of the tunnel, but the control effect on the accumulated deformation of the tunnel is not significant. The application of the secondary support can change the stress state of the primary support,increase the bearing capacity of the primary support by about 12%~14%, and can effectively control the deformation of surrounding rock. 2023 Vol. 60 (4): 86-94 [Abstract] ( 186 ) [HTML 1KB] [ PDF 5119KB] ( 373 ) 95 Mechanical Response Analysis for Tunnel Structure Considering the Interaction of Fault Dislocation and Seismic Motion ZHAO Daneng1 WANG Yi2 REN Zhihua3 In this study, for an expressway tunnel project crossing the secondary fault of the Xiaojiang active area, a finite element model of tunnel dislocation-seismic motion response is established based on the wave theory and the numerical analysis method and taking into consideration the interaction between surrounding rock, structure and fault. The model is used to study the mechanical response characteristics of the tunnel support structure system under different seismic intensities on the basis of the existing reverse fault dislocation, and further analyze the influence law of the width of the fault fracture zone, fault dip and the quality of hanging-wall and footwall rock mass on the structural mechanical response. The results show that under the action of reverse fault dislocation-seismic motion, the lining structure damage first appears at the wall foot in the fault fracture zone, and the stress and the displacement of the lining wall foot change greatly, and the damage is more serious. Under the identical dislocation and seismic intensity, the distribution range of severe damage at the wall foot is 2-4 times those of other typical parts,and the wall foot and the fault fracture zone are the most unfavorable parts for fortification. As the seismic intensity increases, the width of the fault zone decreases, the dip of the fault increases, and the quality difference between hanging-wall and footwall of rock mass and the surrounding rock in the fractured area increases. The degree of lining damage and distribution range significantly increase, and the stress concentration is intensified. The fluctuation of stress amplitude rises, and the residual stress after the earthquake and the displacement abrupt change of the fault dislocation surface become more obvious. 2023 Vol. 60 (4): 95-105 [Abstract] ( 167 ) [HTML 1KB] [ PDF 5020KB] ( 370 ) 106 Study on Seismic Response Characteristics of Immersed Tube Tunnels with Longitudinal Limit Device WANG Mingjun1 LIANG Qizhi1 HUANG Yongbin2 LI Yadong2 YANG Chunshan3 Based on the Ruyifang Immersed Tube Tunnel Project in Guangzhou, the finite element software ABAQUS and the improved response displacement method are used to establish an integrated multiple mass-beamspring model of immersed tube tunnel with flexible joints by considering longitudinal limit devices. The model is used to analyze the 3D seismic dynamic response of the immersed tube tunnel as a whole and key sections under seismic action, study the dynamic response characteristics and damage distribution at the maximum stress section of the tunnel, and explore the stability of key cross-sections of the immersed tube tunnel. The results indicate that under seismic action, uneven soil layers will increase internal forces of the tunnel and cause certain damage to the tunnel structure; the damage is mainly distributed at the junction of the side wall and the bottom plate, as well as in the middle of top and bottom plates. The cracks here develop from outside to inside, while the inner side cracks in the middle of the traffic tube develop from inside to outside; The damage condition of the maximum stress section of the tunnel reflects that the tunnel still has a large safety margin, but close attention should still be paid to the reinforce? ment of key weak places. 2023 Vol. 60 (4): 106-115 [Abstract] ( 153 ) [HTML 1KB] [ PDF 5423KB] ( 344 ) 116 Study on Deformation Characteristics of Tunnel Inverts in Mudstone Considering Rheological Effects ZHANG Chonghui LIANG Qingguo SUN Weiyu YUE Jianping ZHANG Xingchen In this paper, to explore the influence of mudstone rheological effect on the long-term stress deformation law of tunnel structures, the Burgers model is used for rheological numerical calculation. The calculation results are compared and discussed with long-term monitoring data of tunnels in similar situations at home and abroad to verify its rationality and correctness. The results show that under the rheological effect, the surrounding rock shows a trend of overall inward "flow" deformation during operation stage, the base uplift is the most obvious, and the deformation of the invert presents a "jujube pit" shape with a large middle and two small ends. The displacement of the invert and the filling layer shows an increasing trend over time, and remains basically stable after 50 years. The filling layer is in a tensile state, and the maximum principal stress in each part continues to increase over time, reaching a peak at 1/4 of the tunnel diameter away from the arch floor, and approaching the tensile strength of C25 concrete. In the practical project, the characteristics of invert floor heave are characterized by long time effect and difficulty in convergence. Therefore, when designing and constructing tunnels in mudstone, it is necessary to consider their rheological characteristics and their impact on the long-term deformation and stress of the tunnel structure. 2023 Vol. 60 (4): 116-127 [Abstract] ( 136 ) [HTML 1KB] [ PDF 5980KB] ( 393 ) 128 Study on the Influence of Bolt Failure on Bending Strength of Longitudinal Joint of Shield Tunnel Segments QI Meilin FENG Kun GUO Wenqi LU Xuanyi HE Chuan The purpose of this paper is to investigate the bending strength of shield tunnel segment joints after bolt failure or when bolts cannot be installed under special conditions. Based on the Jinan Yellow River Tunnel, a threedimensional refined numerical calculation model for large diameter shield tunnel segment joints with/without bolts is established based on ABAQUS, to analyze the opening angle of joint surface, bending stiffness of segment joint,the variation of bolt stress with the internal force of the joint and the law of joint compression damage when the segment joint is subjected to positive bending moment and negative moment with/without bolted connection. The results indicate that: (1) The influence of bolt failure on the opening angle of the joint is mainly reflected in the latter half of the joint stress state, and the greater the axial force on the joint, the weaker the influence of bolts on the opening angle of the joint. (2) The bending stiffness of the joint is smaller without bolted connection, and the decrease in the bending stiffness of the joint under the negative bending moment is smaller than that under the positive bending mo? ment. (3) The bending moment at which the bolt yields under the negative bending moment is greater than the yielding bending moment under the positive bending moment; and the greater the axial force on the joint, the greater the corresponding bending moment value when the bolt yields. (4) Under the high axial load, the compression damage of shield tunnel segments is almost unaffected by bolts. 2023 Vol. 60 (4): 128-137 [Abstract] ( 211 ) [HTML 1KB] [ PDF 4424KB] ( 398 ) 138 Study on Action Mechanism of Double-layer Support for the Parallel Adit of Tunnels in Extremely-squeezed Surrounding Rocks WANG Guan Based on the Yuelongmen Tunnel on the Chengdu-Lanzhou Railway, a combined method of field moni? toring and finite element calculation is used to explore the causes for the primary support failure and the action mechanism of secondary support in the parallel adit of tunnels in extremely-squeezed surrounding rocks. Firstly, according to the deformation monitoring data of the adit, the deformation characteristics of the adit and the restraining effects of different measures on deformation are analyzed. Then, on the basis of the Rock Mass Rating (RMR) method,reasonable physical and mechanical parameters of the surrounding rock are selected, and the deformation and the stress of the adit support are calculated using elastic-plastic finite element analysis, and the action mechanism of the double-layer support is discussed. The study shows that measures such as adding bolts and grouting reinforcement can slow down the deformation rate of the tunnel, but the control effect on the accumulated deformation of the tunnel is not significant. The application of the secondary support can change the stress state of the primary support,increase the bearing capacity of the primary support by about 12%~14%, and can effectively control the deformation of surrounding rock. 2023 Vol. 60 (4): 138-146 [Abstract] ( 143 ) [HTML 1KB] [ PDF 6162KB] ( 365 ) 147 Analysis of the Optimal Penetration of Disc Cutter in Rock Breaking Based on Characteristic Particle Size ZHAI Shufang1,2 DU Hongkun1 YUE Qichao1 WU Fan3 GONG Qiuming4 Based on the mechanical rock breaking platform of Beijing University of Technology, the linear cutting test is performed with disc cutters on the composite rock mass composed of mudstone and green sandstone, to explore the relationship between the rock debris features and the penetration after rock breaking with disc cutters. During the test, six sets of different penetrations (1.0 mm, 3.0 mm, 5.0 mm, 7.0 mm, 9.0 mm and 11.0 mm) are set to collect the rock debris generated from rock breaking with the disc cutters at different penetrations. The Rosin-Rammler function is used to analyze the rock debris data, and the characteristic particle size theory is used to analyze the optimal penetration during rock breaking with the disc cutters. Furthermore, a method based on the characteristic particle size theory is proposed to determine the optimal penetration. Through comparative analysis, it was found that the optimal penetration obtained using the characteristic particle size theory is consistent with the optimal penetration obtained through specific energy, which verifies the effectiveness of the proposed method; and this method is more direct and convenient. 2023 Vol. 60 (4): 147-152 [Abstract] ( 119 ) [HTML 1KB] [ PDF 1699KB] ( 345 ) 153 Study on Vibration Characterization Parameters of TBM Rock-breaking Cutterhead LIU Dongxin1 XIAO Yuhang2 ZHOU Xiaoxiong3 GONG Qiuming1 LIU Junhao1 During the TBM rock breaking process, it is inevitable to generate strong vibration on the cutterhead. The vibration response of the cutterhead is the result of the interaction between rock and TBM, and it can serve as an important basis for rock mass identification and tunnelling parameter optimization. It is particularly important to obtain the information contained in this multi-source vibration signal of the cutterhead. Based on the TBM tunnelling test data, the influence of time on the distribution of vibration features is analyzed, a random forest model of multi-dimensional vibration features and tunnelling parameters is constructed, and the vibration features that can respond sensitively to changes in tunnelling parameters are screened through its feature importance evaluation function. The research results indicate that on-site vibration monitoring duration should reach at least one rotation period of the cutterhead, during which the distribution of various vibration characteristics tends to be stable. Peak factor and frequency standard deviation are the features that can best respond to changes in thrust and rotation speed, and can be used as key features for studying the relationship between vibration signal and change in tunnelling parameters. 2023 Vol. 60 (4): 153-162 [Abstract] ( 133 ) [HTML 1KB] [ PDF 4642KB] ( 438 ) 163 Study on Steel Fiber Reinforced Concrete Test and Uniaxial Tensile Constitutive Model ZHOU Jiamei1 CUI Kaiqi1 FENG Tianwei1, 2 LI Ruihan1 YUE Feixiang1 XUE Zhibin1 The load-crack width curve of steel fiber reinforced concrete components is obtained from the single point loading test on the notched beam, and a flexural-tensile constitutive model is established based on this curve.The uniaxial tensile constitutive model of steel fiber reinforced concrete is proposed by modifying the conversion relationship between flexural-tensile strength and tensile strength of hooked steel fiber reinforced concrete. At the same time, finite element numerical simulation is used to obtain the failure mode, damage evolution law, and loaddeflection curve of steel fiber reinforced concrete under the action of this model. In combination with the results of the compression and bending test, the toughening and strengthening mechanism of hooked steel fiber reinforced concrete is analyzed. The study shows that when the notched steel fiber reinforced concrete beam is damaged, most of the steel fibers is pulled off and the hooks at the ends are pulled to be straight. Hooked steel fiber has a secondary strengthening effect on the flexural tensile strength of concrete components. By taking 25 kg/m3 as the benchmark,when the steel fiber content increases by 5 kg/m3, 10 kg/m3 and 15 kg/m3, the secondary peaks in the flexural-tensile strength are increased by 20.4%, 28.57% and 12.04%, respectively. In terms of failure mode and damage evolution, the hooked steel fiber reinforced concrete exhibits the characteristics of steel fiber being straightened and many cracks, small spacing and length, respectively, which shows its higher toughness. Compared with ordinary concrete,the load-deflection curve of the hooked steel fiber reinforced concrete shows a fiber reinforced section after the elastic section, intuitively demonstrating higher strength and toughness of the hooked steel fiber reinforced concrete.The numerical simulation results of the model are highly consistent with the test results, verifying the reliability of the model. 2023 Vol. 60 (4): 163-171 [Abstract] ( 134 ) [HTML 1KB] [ PDF 3290KB] ( 342 ) 172 Study on Occurrence Characteristics and Risk Prevention Measures of Gas in Non-coal Strata in Zhegushan Tunnel on Wenchuan-Maerkang Expressway LIU Jiamin1 YANG Feng2 LI Xiaohong2 MA Hongsheng2 Carbonaceous phyllite is a kind of metamorphic rock widely distributed in Southwestern China. Multiple abnormal gas emission accidents have occurred in the tunnel excavatrion through the carbonaceous phyllite stratum,seriously threatening the safety of construction personnel and causing a sharp increase in construction cost. Based on the Zhegushan Tunnel on the Wenchuan-Maerkang Expressway, the carbonaceous phyllite stratum is tested and analyzed in respect of the gas composition, carbon isotope test, rock mass maturity and adsorption capacity, and gas pressure. The results show that the carbonaceous phyllite is in the mature-highly mature stage and has the ability to generate organic hydrocarbons. The maximum gas adsorption capacity of the rock mass is 0.59-0.73 mmol/g, with low gas adsorption amount and underdeveloped migration channels. The safety risk caused by gas desorption is not high. In areas with complex geological structures, the gas distribution in the carbonaceous phyllite stratum is uneven, and a large amount of pressurized gas accumulates locally, resulting in a high hazard degree. During construction, the measures shall be taken to mainly prevent gas outburst accidents caused by gases in the areas with complex geological structures and air bags formed by high-pressure enclosed rock mass. 2023 Vol. 60 (4): 172-177 [Abstract] ( 142 ) [HTML 1KB] [ PDF 2640KB] ( 414 ) 178 Study on Risk Level Classification Method and Control Measures for Railway Tunnel Floor Heave ZHAO Wanqiang1 LU Junfu2 TANG Yin1 ZHENG Changqing1 In recent years, the invert floor heave problem in high-speed railway tunnels has become prominent, which has seriously affected the running speed and safety of trains on the ballastless track. In order to accurately and quantitatively evaluate the risk level of railway tunnel floor heave, a study is conducted on the classification of risk levels and control measures for railway tunnel floor heave during the design and operation stages through investigation and analysis of floor heave deformation of some railway tunnels in China and in combination with the unascertained measure theory and the improved analytic hierarchy process. The research results indicate that, considering these factors such as geological environment, tunnel structural characteristics and floor heave characteristics, a risk level classification indicator system of floor heave including 5 Level I indicators and 11 Level II indicators is determined in the tunnel design stage; another risk level classification indicator system of floor heave including 6 Level I indicators and 15 Level II indicators is determined in the tunnel operation stage; According to the risk degree of rail? way tunnel floor heave defects, the risk levels of railway tunnel floor heave are divided into Level I, II, III and IV.The risk level evaluation method and process of railway tunnel floor heave are established based on the risk level of tunnel floor heave and the influence law of each indicator on floor heave; corresponding integrated control measures are prepared for the floor heave risk levels of railway tunnels during the design and operation stages. 2023 Vol. 60 (4): 178-187 [Abstract] ( 165 ) [HTML 1KB] [ PDF 4033KB] ( 413 ) 188 Study on Major Engineering Geological Problems of Yuelongmen Tunnel in Mountain Areas Under Complex Strong Earthquake Conditions YUAN Chuanbao1 LU Jinlin1 TAO Yujing1 SONG Zhang1 LIU Guoqiang2 In order to solve the construction problems of the Yuelongmen Tunnel on the Chengdu-Lanzhou Railway, in-depth research is carried out in terms of formation background, cause mechanism, characteristic laws and prevention countermeasures of major engineering problems such as active fault, karst water inflow, harmful gases, large deformation and high ground temperature. The results show that the regional geological characteristics of the complex western mountainous area with strong earthquakes, where the Yuelongmen Tunnel is located, are remarkable, and the regional geological research and test effort should be strengthened. During construction in active fault areas, tunnel body should be verified to understand the nature of the fault and the differences between the renovations of hanging wall and footwall. To solve complex geological problems, it is necessary to strengthen regional geological evolution analysis, divide geological environmental units, and form a regional engineering geological concept. 2023 Vol. 60 (4): 188-195 [Abstract] ( 206 ) [HTML 1KB] [ PDF 3733KB] ( 347 ) 196 Study on Cross Section Optimization in Plateau Railway Tunnels Constructed by Drill and Blast Method LI Xu1,3 WANG Huiwu2 TAO Weiming1,3 CAO Yu2 WU Jian4 In this paper, the factors affecting the cross section of the plateau railway tunnel constructed by drill and blast method are analyzed, and emphasis is laid on tunnel cross section optimization from three influencing factors:aerodynamic effect, OCS suspension and underrail structure layout. Analysis and research show that there is room for optimization of tunnel cross section at high-altitude areas in terms of aerodynamic effects. The suspension type and the suspension height of OCS have a significant impact on the height of the tunnel cross section, while the layout of grooves mainly affects the width direction of the tunnel cross section. By combining with different altitude spans,an optimization plan for tunnel cross section is proposed based on altitude classification, and the research results can provide reference for the design of cross sections in similar high-altitude railway tunnel projects. 2023 Vol. 60 (4): 196-203 [Abstract] ( 127 ) [HTML 1KB] [ PDF 2889KB] ( 376 ) 204 Construction Design for Super-large Section Tunnels in Fault Zone with High Geotress CHEN Xiwu1 QING Weichen1 LIU Guoqiang2 The excavation area of the transition section of combined and separate construction in the Shiziyuan Tunnel is 345 m2, and this transition section passes through Wangjiaping No.1 fault with high geostress. In order to solve construction problems faced by super-large section tunnel crossing the fault zone with high geostress, such as primary support deformation and secondary lining cracking, a combination of numerical simulation and engineering analogy is used based on geological conditions to compare and select the tunnel section form, determine structural support parameters, and propose a new construction method. Practice shows that this construction method can solve problems such as difficulty in tunnel construction and difficulty in controlling deformation. 2023 Vol. 60 (4): 204-212 [Abstract] ( 153 ) [HTML 1KB] [ PDF 8181KB] ( 381 ) 213 Study on the Structural Design for Tunnels Undercrossing Airport Section in High-speed Railway Throat Area under a Complex Environment SONG Yi1,2 The purpose of this paper is to determine the structural design method for tunnels undercrossing the air? port terminal section in high-speed railway throat area under a complex environment. Based on the tunnel project undercrossing the GTC and the T2 terminal of the Yaoqiang International Airport, which is on the Jinan connection line of the Tianjin-Weifang High Speed Railway, the structural form, structural stress, pile foundation layout, tunnel settlement and deformation control and structural strengthening measures for the tunnel are studied, so as to propose the straight wall, flat top and circular arch structure form, the long-span straight wall tie-arch structure form, the uniform layout pattern of pile foundation and the structural measures of the overall vertical and horizontal hidden beams plus locally reinforced ring beams, and to analyze the above-mentioned structural forms. The results show that the use of straight wall, flat top and circular arch structure and the large span straight wall tie-arch structure in the undercrossing tunnel can meet the load-bearing requirements. The deviation between the two-dimensional calculation result of complex cross-section tunnel structures and the three-dimensional calculation result is only 14%. During design, reinforcement can be made based on the two-dimensional calculation result and verified based on the three-dimensional calculation result. The uniform layout scheme of pile foundation is more beneficial to controlling deformation and settlement of the tunnel structure, and the measures of setting vertical and horizontal hidden beams can improve rigidity and stability of the tunnel structure. 2023 Vol. 60 (4): 213-221 [Abstract] ( 145 ) [HTML 1KB] [ PDF 4003KB] ( 382 ) 222 Study on Ventilation Technology for Long-distance TBM Construction in Railway Tunnels DUO Shengjun With the increase of the ventilation length, the ventilation resistance along the tunnel and the air leakage rate of the air pipe gradually increase, resulting in a harsh construction environment in TBM tunnelling, seriously endangering the safety of personnel during construction. In view of this, various research methods such as on-site measurement, data investigation and theoretical analysis are used to clarify the ventilation control standards for long-distance TBM construction in railway tunnels, which cover multiple indicators such as air supply volume, ventilation speed and sanitary safety, etc. When the ventilation length exceeds the dead-end ventilation limit distance of single fan, it is recommended to use the dead-end forced ventilation or combined ventilation scheme with an increase in the number of fans, and provide corresponding method for dividing the scheme phases. Appropriate improvement measures are developed based on potential issues that may arise during the three phases of combined ventilation. Based on the construction of the Zhongtianshan Super-long Tunnel Project, a combined ventilation scheme during tunnel construction is determined. The specific fan design is given through theoretical calculations of air volume and ventilation resistance. According to the field test results of ventilation speed, air temperature and harmful gases in the three phases of combined ventilation, it is recommended to optimize the ventilation effect by taking measures such as repairing air pipes and improving the TBM ventilation system. 2023 Vol. 60 (4): 222-228 [Abstract] ( 189 ) [HTML 1KB] [ PDF 2852KB] ( 399 ) 229 Analysis on Causes of Large Deformation in the Deep-buried Mountain Ridge Section of Yuelongmen Tunnel on Chengdu-Lanzhou Railway TAO Yujing1 YUAN Chuanbao1 WANG Maojing1 SONG Zhang1 LIU Guoqiang2 The middle parallel pilot tunnel of the Yuelongmen Tunnel on the Chengdu-Lanzhou Railway encoun? tered severe deformation in the deep-buried mountain ridge section. After effective support measures were taken,the deformation tended to be stabilized. After excavation and breakthrough of the left line main tunnel in the corresponding deformation section of the pilot tunnel, severe deformation occurred again in the pilot tunnel and the left line main tunnel. On this basis, this paper systematically introduces the geological environment of the tunnel site area,regional geostress condition, deformation characteristics of surrounding rock during construction, and the process of identifying large deformation in site construction. The analysis shows that the large deformation in this section is caused by the weak and broken rock mass in the high geostress environment. In this special geological environment,the tunnel group effect is significant, and the large deformation is closely related to the included angle between the rock strata strike and the tunnel axis, and the included angle between the maximum horizontal principal stress direc? tion of the geostress and the tunnel axis. The problem of large deformation is solved by backfilling the middle pilot tunnel, constructing a new outside pilot tunnel with a larger spacing between pilot tunnel and main tunnel. 2023 Vol. 60 (4): 229-236 [Abstract] ( 144 ) [HTML 1KB] [ PDF 4311KB] ( 442 ) 237 Study on Tunnel Face Collapse and Corresponding Treatment Measures in Shield Tunnelling in Silty-fine Sand Layer LI Zifeng1 DUAN Baoliang2 When the slurry shield machine is used for excavation in the silty-fine sand layer, it is easy to cause problems such as the collapse of tunnel face, difficulty in cutterhead releasing, and difficulty in recovery of advance.Taking the construction of the Heyan Road River Crossing Tunnel in Nanjing as an example, by analyzing the collapse process of tunnel face in the silty-fine sand layer, specifically focusing on such aspects as the control of slurry chamber pressure, slurry performance adjustment, and tunnelling parameter control, the cutterhead releasing method for the extra-large diameter shield machine is studied and the engineering experience of effectively controlling the risk of tunnel face collapse and quickly restoring to the normal working condition is summarized. At the same time, based on the principle of bubble chamber pressure balance and the changes in tunnelling parameters, the following conclusions are drawn: (1) Before the collapse of tunnel face in the silty-fine sand layer, the tunnelling parameters of the slurry shield machine vary most significantly in the discharged slurry density and water pressure at cutting face. Multiple abnormal increases in the discharged slurry density and unstable water pressure at cutting face can serve as accident signs. (2) After the collapse of the tunnel face, the principle of "low rotation speed, large penetration and many times of short-time stops" should be followed to resume tunnelling. 2023 Vol. 60 (4): 237-245 [Abstract] ( 304 ) [HTML 1KB] [ PDF 4377KB] ( 374 ) 246 Study on the Growth Mechanism of Calcium Carbonate Crystal of Karst Water on the Tunnel Concrete Substrate LI Wei1 JIANG Yajun2 LIU Shijun2 WANG Cuijuan3 XIAO Huarong4 CUI Hengtao2 A large number of crystals on the tunnel concrete substrate in the karst area will greatly increase the maintenance cost of the tunnel. Combined with theoretical analysis and test simulation methods, the process and principle of crystal formation and attachment on the tunnel concrete substrate were analyzed through observation of the changes in the microstructure of crystals on the surface and section of mortar blocks. The results showed that the growth process of calcium carbonate crystals on the concrete substrate could be split into 3 stages: initial stage, middle stage and later stage of calcium carbonate crystallization. At the initial stage, the concrete surface reduced the surface energy barrier at the time of nucleation, creating conducive conditions of heterogeneous nucleation for the nucleation of calcium carbonate crystals; at the middle stage, a great number of bonds were formed and a large amount of energy was released in uneven positions (holes, recesses, etc.) on the concrete surface, which was conducive to the stable growth of crystal nucleus, and crystals were more inclined to nucleate and adhere; after a transitional layer was formed on the concrete surface at the later stage, the calcium carbonate crystallization process was closer to homogeneous nucleation, and in this case, the solidification of crystal particles on the transitional layer accelerated and these particles were firmly bonded to the substrate.. 2023 Vol. 60 (4): 246-253 [Abstract] ( 159 ) [HTML 1KB] [ PDF 5399KB] ( 411 ) 254 Experimental Study on Prevention and Treatment of Tunnel Leakage with Rapid Setting Permeable Crystallographic Grouts ZHENG Kunlong1,2 WANG Jianyun2 LINGHU Yan1 YANG Xiaohua3 DING Yate1 CHEN Kun1 WANG Zhifeng3 In this study, in order to improve the integrated performance of permeable crystallographic grouts and study its grouting effect when used to prevent tunnel leakage, through mechanism analysis and preparation of rapid setting grouts, tunnel pre-grouting model tests in the fault fracture zone are designed, three model tests in three cases are carried out: no grouting, pre-grouting with cement grouts, and pre-grouting with rapid setting permeable crystallo graphic grout. A comparative analysis is conducted in terms of the water leakage in the tunnel, grout diffusion condition and performance of consolidated grouts, to get integrated evaluation of the grouting effect of the grouts. The results show that: (1) When calcium chloride is used together with the Penetron ADMIX, their effects do not decrease by each other, and the integrated performance of the rapid setting grout with a proportion of mcement:mPA∶mCaCl 2∶m water=1∶0.04∶0.03∶1 is better. (2) In Case 1, the maximum water leakage occurs when excavated to around 30 cm, with about 385.3 L/h, and the thickness of the inrush prevention layer is about 12 cm; In Case 2, the maximum water leakage occurs when excavated to around 37 cm, with about 53.5 L/h, and the thickness of the inrush prevention layer is about 5 cm; In Case 3, there is only a small amount of water seepage when excavated to the fault. (3) The diffusion radius of both types of grouts within the fault is 23 cm, and the diffusion range is similar. However, the compressive strength of the consolidated new type grouts is greater than that of the consolidated cement grouts, and its permeability coefficient is much smaller than that of the cement grouts. The study shows that pre-grouting with cement grouts can reduce the water leakage in the tunnel, but its anti-leakage effect is limited; the rapid setting permeable crystallographic grout has a high consolidation rate and low permeability coefficient, effectively preventing tunnel leakage under the same conditions, and the grouting effect is better than that of cement grouts. 2023 Vol. 60 (4): 254-263 [Abstract] ( 151 ) [HTML 1KB] [ PDF 4557KB] ( 374 ) 264 Influence and Action Mechanism of Residual Admixture on the Flocculation and Separation Characteristics of Waste Slurry in Shield Tunnels LIU Zhitao1,2 WU Silin1,2,3 SUN Xiaohui3,4 ZHOU Aizhao1,2 The action mechanism of admixtures on flocculation and separation characteristics of waste slurry in slur? ry shield construction is still unclear. To figure out this, waste slurry with different gradients of bentonite and CMC(Carboxymethyl cellulose sodium) are prepared, so as to study the influence of residual admixtures on the flocculation and separation characteristics of waste slurry and the action mechanism. Research shows that the presence of bentonite and CMC deteriorates the dewatering effect of slurry, and increases the specific filtration resistance by 1~2 orders of magnitude; Bentonite and CMC affect the water form of soil particles by changing their electrical characteristics and by adsorption and bridging, deteriorating the dehydration effect; Polyaluminium chloride (PAC), which has the function of electrical neutralization and compressing polymer molecular chains, has achieved better results in waste slurry treatment. Based on the research results, the countermeasure for the preparation of shield slurry and the treatment of waste slurry is proposed. 2023 Vol. 60 (4): 264- [Abstract] ( 195 ) [HTML 1KB] [ PDF 3909KB] ( 353 )

More>>   · · More>>

Copyright © 2011  Editorial By MODERN TUNNELLING TECHNOLOGY Supported by:Beijing Magtech Co.ltd  Email:support@magtech.com.cn