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Quick Search     Advanced Search MODERN TUNNELLING TECHNOLOGY   2024 Vol.61 Issue.6 Published 2024-12-25 1 Patterns and Distribution Characteristics of Shaft Construction Accidents in China (2003—2022) ZHANG Junwei1 YANG Zhe To investigate the development patterns of shaft construction accidents in China, this study statistically analyzed 106 shaft construction accidents that occurred from 2003 to 2022. Using line charts, bar charts, regional distribution maps, and pie charts, the study examined accident numbers, fatalities, and injuries to identify temporal distribution characteristics, spatial distribution features, and the classification characteristics of accidents by severity and type. Safety prevention and control measures for shaft construction were proposed based on the findings. Temporal distribution characteristics were analyzed by year, month, weekday, and time period, revealing distinct periodicity in the three indicators during the study period. June was identified as the peak month for accidents, with Thursdays being the most accident-prone weekday. Spatial distribution analysis showed that accidents predominantly occurred in central regions of China, followed by the northwest and southwest regions. Based on fatality counts, the severity of accidents was assessed, revealing that most accidents were categorized as minor, while fatalities from major and significant accidents accounted for approximately 84% of the total. The study classified shaft construction accidents into nine types, with the most common being personnel falling, falling objects, and shaft wall collapses. 2024 Vol. 61 (6): 1-8 [Abstract] ( 61 ) [HTML 1KB] [ PDF 3491KB] ( 349 ) 9 Non-Steady Cvisc Creep Model for Rock and Its Parameter Inversion Method WANG Yanyan1,2 SHEN Yusheng1,2 CHANG Mingyu1,2 PAN Xiaohai1,2 ZHANG Xinyang1,2 TENG Kongxian3 Rock creep under long-term stress may exhibit three stages: decay creep,steady-state creep, and accelerated creep. The Cvisc model in FLAC 3D software can effectively simulate the decay and steady-state creep stages of rocks but shows significant limitations in describing the accelerated creep stage. To address this, the viscosity coefficient of the Cvisc model was modified to create a non-steady version capable of capturing the characteristics of accelerated creep. A corresponding three-dimensional creep equation was derived.To obtain the creep parameters of the non-steady Cvisc model for surrounding rock, a BP-PSO algorithm-based neural network inversion model was established. This algorithm was validated using monitored vault settlement data from field tunnels. A comparative analysis of the vault settlement prediction performance of the non-steady Cvisc model and the original Cvisc model was conducted.The results demonstrate that the non-steady Cvisc model significantly outperforms the original model in fitting the accelerated creep stage, enabling a more accurate description of the entire creep process, including the accelerated stage. 2024 Vol. 61 (6): 9-20 [Abstract] ( 68 ) [HTML 1KB] [ PDF 4280KB] ( 229 ) 21 Study on the Movement Law of Rock Blocks inside the Cavity in Wedge Cut Blasting WU Guobin1，2 CHEN Bigang3 CHEN Zhihuo3 LIAO Dagang3 LOU Xiaoming1，2 ZENG Huaheng1，2 To study the movement law of rock blocks inside the wedge cut cavity in tunnel blasting and to determine the reasonable delay time for wedge cutting, a theoretical model of the rock block throwing process in wedge cut blasting was established based on reasonable assumptions. The time-history curves of rock block movement inside the wedge cut cavity under different design parameters were solved using the one-dimensional unsteady flow law and Newton's second law. The SPH-FEM coupled numerical simulation was used to verify the rationality of the derived movement law of rock blocks inside the cavity and the throwing process of the rock blocks to be blasted under different hole network parameters, as well as the throwing characteristics and movement law of rock blocks in the cavity. The results indicate that when the first wedge cut depth is 2.0 meters, the reasonable delay time for the second wedge cut hole in soft rocks, medium-hard rocks, and hard rocks is 32.68-35.66 ms, 33.10-36.45 ms, and 34.4-38.22 ms, respectively. The designed delay time for the "two-step" wedge cutting needs to be greater than the above-mentioned cavity formation time. 2024 Vol. 61 (6): 21-28 [Abstract] ( 63 ) [HTML 1KB] [ PDF 5679KB] ( 202 ) 29 A Novel Active Earth Pressure Distribution Model Based on the Critical Depth of Soil Arching Effect CAI Guangyuan In the process of solving active earth pressure behind retaining walls considering the soil arching effect, the soil arching effect does not act across the entire region but only starts to function after reaching a certain depth.Based on this concept, the critical depth at which the soil arching effect occurs is analyzed using the soil pressure theory considering the soil arching effect and the classical Coulomb earth pressure theory, and a novel active earth pressure model based on the critical depth of the soil arching effect is proposed. Numerical simulation methods are employed to validate the critical depth of the soil arching effect, and a sensitivity analysis is conducted on the parameters influencing the critical depth. Results indicate that the critical depth is significantly affected by the internal friction angle of the soil and the wall-soil friction angle. As the internal friction angle increases, the critical depth decreases, and the spatial extent of the soil arching effect increases. The height of the retaining wall has a minor influence on the critical depth. 2024 Vol. 61 (6): 29-34 [Abstract] ( 67 ) [HTML 1KB] [ PDF 2498KB] ( 194 ) 35 Study on Structural Damage Characteristics of Tunnels Crossing Active Faults Based on Layered Dislocation Theory HUI Qiang1 GAO Feng1,2 TAN Xukai1 YOU Dongmei1 To investigate the damage characteristics of tunnel structures under fault dislocation, a model for tunnels crossing faults was developed based on layered dislocation theory and a concrete incremental elasto-plastic damage model. The damage characteristics of lining structures under different conditions were analyzed, and the model's accuracy was verified using actual engineering cases. The results indicate that: Composite linings struggle to resist large-scale dislocation. For the case study tunnel, the composite lining structure at the fault failed under moderateto-strong seismic events with a magnitude of Mw=5.0~5.2; With changes in the fault dislocation angle, the tensile and compressive damage zones of the lining structure shift correspondingly. Tensile damage zones align with the direction of fault dislocation, while compressive damage zones are perpendicular to the dislocation direction; Strikeslip dislocation causes more severe damage to lining structures compared to dip-slip dislocation; With increasing burial depth, the damage zones of the lining structure gradually concentrate near the fault and the haunches of the lining. 2024 Vol. 61 (6): 35-44 [Abstract] ( 82 ) [HTML 1KB] [ PDF 5099KB] ( 223 ) 45 Study on the Impact Zoning and Fortification Range of Tunnel Structures Crossing Strike-slip Faults KUANG Liang1 SU Wei1 TAO Weiming1 TIAN Siming2 SHEN Yusheng3 LI Xu2 WANG Huiwu1 To address the issue of impact zoning and fortification range for tunnels crossing strike-slip faults, a tunnel in a high-altitude and high-intensity area with active faults was studied. Using finite difference numerical simulation, the strain, deformation, and internal force characteristics of tunnel structures under strike-slip fault dislocation were analyzed. Impact zones and corresponding zoning were proposed, and a physical model test of the tunnel was conducted to validate the fault dislocation failure mechanisms and structural response characteristics. The impact scope and patterns induced by fault dislocation were determined. The results indicate that under strike-slip fault dislocation, the tunnel primarily undergoes horizontal compressive deformation at the arch haunch. As fault dislocation increases, deformation continues to grow, but the rate of growth decreases. The impact zones are divided into three categories: primary impact zone, secondary impact zone, and stable zone. The primary impact zone includes ranges of 1.4D on the fixed fault wall, 2.1D on the active fault wall, and the entire fault zone (where D is the tunnel span). The secondary impact zone on the active fault wall ranges from 2.1D to 6.3D, while other areas fall into the stable zone. Maximum shear stress is concentrated in the fault dislocation-affected zone, which requires enhanced fault dislocation-resisting design. The fault zone exhibits a stepwise decrease in displacement due to the joint displacement of the active wall, with the interface between the upper and lower walls and fault serving as the main sliding surface. Relative dislocation within the fault zone is minimal, and the tunnel structure's affected range includes the fault zone interior, 0.7D on the upper wall, and 1.5D on the lower wall. 2024 Vol. 61 (6): 45-54 [Abstract] ( 69 ) [HTML 1KB] [ PDF 6295KB] ( 283 ) 55 Calculation of Frost Heave Force and Analysis of Frost Heave Mechanism Induced by Water Accumulation in Voids behind Tunnel Lining in Cold-regions XU Peng1 YANG Ruisong1 WU Yimin2 This study investigates the issues of lining cracking and spalling caused by frost heave of accumulated water in voids behind lining in cold-region tunnels. Theoretical research on the calculation of frost heave force of accumulated water in voids behind tunnel lining was conducted. By introducing a frost heave force calculation model that accounts for drainage conditions, the freezing process of accumulated water in circular wedge-shaped voids under temperature fluctuations was analyzed, and the mechanism of frost heave force formation was revealed. The results show that the frost heave force increases with the height of the void but changes insignificantly with the void length. For voids outside the waterproof layer, the drainage coefficient is 0, and no frost heave force is generated during freezing.For voids inside the waterproof layer, when the drainage channel freezes first (drainage coefficient=1), the closer the drainage channel is to the bottom of the void, the larger the drainage coefficient and the bigger the frost heave force in the void. Freezing of water in the void begins at the thinnest edge and progresses toward thicker regions of the void. Under daily cyclic temperature fluctuations, the melting process of ice in the void is homology to the freezing process, that is ,the phenomenon of freezing and thrawing first. Under daily periodic fluctuations, the freeze-thaw and water recharge-freeze processes in voids inside the waterproof layer lead to a gradual increase in frost heave force. 2024 Vol. 61 (6): 55-63 [Abstract] ( 63 ) [HTML 1KB] [ PDF 3383KB] ( 182 ) 64 Analysis of the Suitability of Different Anchor Bolt Support Systems for Rockburst Mitigation and Optimization of Anchor Bolt Parameters ZHANG Chengyou1 WANG Bo1 DU Zehao1 GAO Junhan1 TAN Lihao2 To evaluate the support effectiveness of active rockboltanchor bolt-based active support systems in rock? burst-prone tunnels, a case study was conducted based on the Jiulingshan Tunnel. The secondary stress on tunnel walls and rock strength were obtained using the stress relief method and point load test. A comparative analysis of the suitability of rockburst prediction criteria was carried out, along with inversion of the initial stress field of the tunnel. Based on these results, the rockburst suppression mitigation effects of active and passive support systems were compared from the perspectives of stress and energy. Additionally, the key parameters of active support systems under varying different rockburst gradelevels were explored. The findings indicate the followingthat: (1) Compared to passive support, the active support system can significantly reduces the maximum value of σθ /Rb around the tunnel the maximum stress around the tunnel and suppresses the intensity of rockburst intensityoccurrences. The"energy absorption and release" effect of the active support system is more pronounced, aligning better with the principles of rockburst mitigation; (2) Increasing rockbolt anchor bolt strength and decreasing rockanchor bolt spacing both can improve the performance of the active support systems in mitigating rockburst; (3) For medium and intense rockburst scenarios, enhancing rockbolt anchor bolt strength proves to be more effective and economical than reducing rockbolt anchor bolt spacing. 2024 Vol. 61 (6): 64-73 [Abstract] ( 95 ) [HTML 1KB] [ PDF 4518KB] ( 259 ) 74 Study on the Temperature Prediction Formula and Application in Urban Utility Tunnels PENG Zi1,2 WEN Meng3 CHEN Yuan4 DENG Yu5 GUO Chun1,2 The temperature inside urban utility tunnels is a critical factor affecting their safe operation. To address the challenges of predicting tunnel interior temperature, a temperature prediction formula for utility tunnels is developed based on heat transfer theory. Firstly, the thermal equilibrium equation of the tunnel interior is derived by analyzing the heat transfer process between the tunnel and the surrounding soil. Secondly, a parameterized prediction formula for tunnel interior temperature is established by introducing a fitting formula for the temperature difference between the tunnel air and wall surfaces. Finally, the results of the prediction formula are compared with measured data and numerical simulation results.The study results demonstrate that the proposed temperature prediction formula has reasonable accuracy. Compared to measured data, the average error for air temperature is 1.57%, and for wall surface temperature, it is 12.14%. When compared with numerical simulation results, the temperature difference remains within 1.8°C.The formula is applied to analyze the temperature of a utility tunnel in Chengdu. Results indicate no risk of condensation from August to November, as the atmospheric temperature is lower than the wall surface temperature, requiring only basic ventilation. However, during February to May, condensation risk is high due to atmospheric temperatures exceeding wall surface temperatures. In this period, in addition to basic ventilation, an increased airflow rate is necessary to mitigate condensation. 2024 Vol. 61 (6): 74-81 [Abstract] ( 72 ) [HTML 1KB] [ PDF 3940KB] ( 203 ) 82 Mix Proportion Design of Similar Materials for Tunnel Surrounding Rocks Based on GA-BP Neural Network ZHANG Xinyang1, 2 SHEN Yusheng1, 2 CHANG Mingyu1, 2 WANG Haokang1, 2 PAN Xiaohai1, 2 WANG Yanyan1, 2 To control and optimize the physical and mechanical parameters of surrounding rock similar materials in tunnel model experiments, a GA-BP neural network algorithm was developed for parameter prediction. The neural network structure comprises a three-node input layer, a seven-node hidden layer, and a three-node output layer.The Genetic Algorithm (GA) was employed to optimize the weights and thresholds of the BP neural network. The input parameters included the content of river sand, fly ash, and motor oil, while the output parameters included density, cohesion, and internal friction angle. Using measured data as samples, the model's performance was thoroughly evaluated by comparing the mean square error, absolute error, and relative error of the BP neural network before and after GA optimization. Based on the analysis, a mix proportion design method for surrounding rock similar materials under a given similarity ratio was established.The results indicate that the GA-BP neural network algorithm can effectively fit and predict the physical and mechanical parameters of surrounding rock similar materials. Compared to the traditional BP neural network, the GA-BP neural network achieves lower prediction errors and higher accuracy. The prediction model based on the GA-BP neural network can quickly and accurately determine the range of raw material mix ratios under a given similarity ratio, significantly reducing the number of repeated experiments. 2024 Vol. 61 (6): 82-91 [Abstract] ( 70 ) [HTML 1KB] [ PDF 6928KB] ( 241 ) 92 Deformation Prediction and Control for Shield Tunnelling Passing under Existing Tunnels Based on BO-Adam-Bi-LSTM ZHANG Mingshu1 YAO Chen1 WU Xianguo2 CHEN Hongyu3 FENG Zongbao2 YANG Sai2 To address deformation and safety control issues induced by shield tunnelling passing under existing tun? nels, a deep learning-based prediction model was designed to capture deformation development patterns. A Bi-directional Long Short-Term Memory network (Bi-LSTM) was optimized using the Adam algorithm, with parameter tuning performed via Bayesian Optimization (BO), forming the BO-Adam-Bi-LSTM model for deformation predic? tion of shield tunnelling passing under existing tunnels. The model's prediction results were compared with other neural network models, and SHAP was used to enhance interpretability and identify key construction parameters.Results show that the BO-Adam-Bi-LSTM model achieves high prediction accuracy, with R2 values of 0.935 and 0.924, RMSE values of 0.504 and 0.903, and MAE values of 0.415 and 0.824 for the test sets. SHAP analysis reveals that shield chamber pressure has a significant impact on the prediction of horizontal deformation in existing tunnels.By adjusting a few key parameters with high contributions to the model predictions, tunnel deformation values can be effectively controlled within the warning range. 2024 Vol. 61 (6): 92-99 [Abstract] ( 62 ) [HTML 1KB] [ PDF 3187KB] ( 202 ) 100 Prediction of Blasting Vibration Parameters in Urban Tunnels Based on Feature Dimensionality Reduction and Deep Learning GAO Fuzhong To achieve precise prediction of vibrations induced by blasting construction, an optimized GRU deep learning model is proposed based on the t-SNE feature dimensionality reduction algorithm and the BWO algorithm.Using blasting vibration monitoring data from the shallow-buried land section of the Xiamen Haicang tunnel, six parameters—rock uniaxial compressive strength, rock mass integrity coefficient, distance from blasting source, explosive consumption, auxiliary hole spacing, and peripheral hole spacing—were selected as input variables. The key blasting vibration parameters, including blasting vibration velocity and blasting dominant frequency, were set as output variables to validate the predictive accuracy of the model. Comparative analysis was conducted with traditional machine learning models, including SVR and BPNN algorithms. Results show that the t-SNE-BWO-GRU deep learning model achieves an average R2 value of 0.976 0, an average MAPE value of 5.70%, a RMSE of 0.019 3 for blasting vibration velocity, and a RMSE of 2.214 0 for blasting dominant frequency, demonstrating high accuracy in predicting blasting vibration parameters. 2024 Vol. 61 (6): 100-110 [Abstract] ( 62 ) [HTML 1KB] [ PDF 5631KB] ( 229 ) 111 Numerical Study on the Response of Rectangular Open Cut Tunnels with Loess Backfills to the Rockfall Impact SUN Zhongqiu ZHU Ming JIA FeiYang XU Yifei The impact dynamic load transmission process in rectangular open tunnels subjected to falling rocks is highly complex. Considering the discrete characteristics of backfilled soils, a numerical model was established using the discrete element method (DEM) to simulate the impact process of falling rocks. The study investigates the effects of backfilled soil compactions, backfill thicknesses, and rock impact angle on the impact response characteristics of the open tunnel structure under different rockfall heights. The results indicate that: (1) The thickness of loess backfills has minimal effect on the impact force, while higher compaction results in greater impact forces; (2) When the vertical impact energy is the same, the impact angle of falling rocks has little influence on the impact load experienced by the structure, with vertical impacts representing the most unfavorable condition under the same total impact energy;(3) When the backfill thickness is small, its cushioning performance is insufficient, and the impact load on the tun? nel roof is significantly higher compared to conditions with thicker backfills; (4) When the vertical impact energy is ≤1.63 MJ, increasing the backfill thickness beyond 1.5 m does not significantly reduce the impact load on the tunnel roof, as the additional static load of the backfills outweighs the reduction in impact load. The optimal backfill thickness is related to the falling rock impact energy; for vertical impact energy ≤1.63 MJ, a backfill thickness of no less than 1.0 m is recommended. 2024 Vol. 61 (6): 111-117 [Abstract] ( 65 ) [HTML 1KB] [ PDF 3466KB] ( 201 ) 118 Analysis of the Support Effect of Micro Steel Pipe Pile-Anchor Bolt at Tunnel Portal Slope Based on the Incremental Method XU Xiaojing1,2 SONG Zhanping1,2,3 TIAN Xiaoxu1,2 DING Libo? SUN Yinhao? ZHAO Junbo1,2 The combined support system of micro steel pipe pile and anchor bolt, due to its advantages such as con? venient construction, simple structure, and flexible layout, is widely used in landslide remediation and foundation pit protection projects, but its application in tunnel portal slopes is less common. Based on the Georgia No. 1 Tunnel project, the incremental method is used to conduct a numerical simulation study of the support effect of the micro steel pipe pile-anchor bolt system at tunnel portal slopes, and the simulation results are analyzed in conjunction with field monitoring data. The research results show that the incremental method considering the construction process is more reasonable for simulating the micro steel pipe pile-anchor bolt support system. After the pile breaking construction, the maximum displacement of the slope is 10.20 mm, the maximum axial force of the anchor bolt is 339.42 kN, which is less than the design axial force of the anchor bolt of 420.14 kN. The maximum lateral displacement of the selected characteristic pile is 9.90 mm, and the maximum bending moment is 31.26 kN·m, which is lower than the design bending moment value of 84.80 kN·m. The actual monitoring results of the vertical displacement of the slope and the numerical simulation results both show a "V" shaped distribution and the data are consistent. The crown settlements of the left and right tunnels are 11.11 mm and 8.01 mm, respectively, and the horizontal displacements are 2.33 mm and 1.30 mm, respectively. The micro steel pipe pile-anchor bolt support system has been sucessfully applied to the Georgia No. 1 Tunnel project, ensuring the construction safety of the tunnel portal section. 2024 Vol. 61 (6): 118-128 [Abstract] ( 68 ) [HTML 1KB] [ PDF 6472KB] ( 197 ) 129 Study on Shear Mechanical Performances of Circumferential Mortise and Tenon Joints with Oblique Bolts in Shield Tunnelling QIU Wei1 ZENG Qingcheng1 OUYANG Jian1 MU Haixing2 GUO Wenqi2 FENG Kun2 HU Dawei3 To investigate the shear mechanical performances and shear failure mechanisms of circumferential mor? tise and tenon joints with oblique bolts in super-large diameter shield tunnels, a study was conducted based on the Haizhu Bay Tunnel project in Guangzhou. A three-dimensional refined numerical model of circumferential segment joints was developed using a concrete plastic damage constitutive model. The deformation behavior, bolt stress, mortise and tenon reinforcement stress, and structural damage of the circumferential joints were analyzed under varying shear states and longitudinal forces. The results indicate that: The deformation of circumferential segment joints exhibits distinct phases under both forward and reverse shear conditions, comprising four stages. The shear stiffness of circumferential joints under forward shear state is higher than that under reverse shear state; The effect of longitudinal force on enhancing the shear stiffness of the circumferential segment joints is primarily observed in the first de? formation stage; Under forward shear state, bolt deformation is dominated by tension, whereas under reverse shear state, shear deformation prevails. Bolts quickly reach yielding once in contact with the bolt holes,respecially under reverse shear condition, where the contribution of bolts to shear stiffness is limited; Mortise and tenon reinforcement improves structural ductility and prevents brittle failure; Concrete damage at the contact points of bolt holes and mortise and tenon joints is characterized by compressive crushing. Compared to bolts, mortise and tenon features significantly enhance the shear stiffness and bearing capacity of the circumferential segment joints. 2024 Vol. 61 (6): 129-138 [Abstract] ( 66 ) [HTML 1KB] [ PDF 7050KB] ( 189 ) 139 Study on Settlement Patterns of the CFG Pile-reinforced High-speed Railway Subgrade Caused by Parallel Shield Tunnelling WU Beiyu1 XIE Weiping2 LIN Xingtao1,3,4 GAO Chen2 SU Dong1,3,4 CHEN Xiangsheng1,3,4 Focusing on the shield tunnelling of the Xi′an Metro Line 1 beneath the Xuzhou-Lanzhou High-speed Railway, this study performs a statistical analysis of the monitored track settlement data before and after the tunnelling. A refined three-dimensional finite element model of parallel shield tunnelling crossing under a high-speed railway subgrade is established using Plaxis-3D software. The numerical model′s validity is verified through comparison with field measurements. Based on the model, the settlement transfer mechanism of the track-subgradeCFG pile-soil-shield tunnel system induced by shield tunnelling is analyzed, and the stress and deformation behaviors of CFG piles are investigated. Research results indicate that when the shield tunnel completely passes through the railway subgrade, a 50 m long surface settlement trough forms, with a double-peak distribution curve. The bottom of CFG piles becomes loose after shield tunnelling beneath the railway subgrade, resulting in an effective pile length of 75% of the original length. The range of loosening in CFG piles in the horizontal and longitudinal sections of this project is determined as (-12.6 m, 12.6 m) by studying CFG piles at different positions. 2024 Vol. 61 (6): 139-147 [Abstract] ( 68 ) [HTML 1KB] [ PDF 5399KB] ( 198 ) 148 Deformation Distribution Characteristics and Control Measures of Large-section Rectangular Pipe Jacking Over-crossing Metro Tunnels XUE Qingsong Using the Suzhou Chengbei Road utility tunnel project as the case study, numerical simulations were con? ducted to investigate the deformation patterns of metro tunnels induced by the construction of a large-section rectangular pipe jacking over-crossing the tunnels, focusing on tunnel uplift and surface settlement. The results indicate that pipe jacking construction reduces the load above the metro tunnels, leading to an imbalance in soil and water pressure. After applying anti-uplift counterweights inside the jacking pipe, the uplift of the right-line tunnel decreased by 28.0%, and that of the left-line tunnel decreased by 35.5%, effectively controlling the uplift deformation of the metro tunnels. Additionally, the horizontal displacement of the right-line tunnel was reduced by 61.6%, and that of the left-line tunnel was reduced by 55.9%, significantly mitigating tunnel horizontal displacement. The counterweights also reduced the maximum positive bending moment at the tunnel crown and the maximum negative bending moment at the haunches by 33.1% and 32.9%, respectively. Although surface settlement increased by approximately 1 mm, the impact is considered minor. 2024 Vol. 61 (6): 148-161 [Abstract] ( 64 ) [HTML 1KB] [ PDF 11117KB] ( 244 ) 162 Study on Drainage Schemes for Karst Tunnels Based on Hydraulic Pressure Characteristics ZHAO Dongping1, 2 HE Qi1 DU Qing3 ZHANG Wen3 The water pressure on the lining of in-service karst tunnels is closely related to the drainage design scheme. Based on the Zhongliangshan Tunnel on the Chongqing-Kunming High-Speed Railway, three improved drainage schemes were designed on the basis of the general drainage design scheme for mountain tunnels. Treating the karst strata as equivalent homogeneous seepage strata, a three-dimensional numerical simulation was conducted to analyze the water pressure distribution patterns on tunnel lining under the three schemes. Field measurements of water pressure were also performed. The results reveal the following: (1) For weakly developed karst tunnels, under normal drainage conditions, water pressure at the crown and haunch of the tunnel lining can be significantly reduced, but the sidewall, wall-foot, and invert arch still bear substantial water pressure; (2) Along the longitudinal direction of the tunnel, the water pressure on all measuring lines of the lining exhibits an "M"-shaped distribution,with the lowest pressure at the circumferential drainage pipes and higher pressure between two circumferential drainage blind pipes; (3) In terms of reducing water pressure on the invert arch, the scheme with a bottomed central drainage ditch is the most effective, followed by the scheme with additional dense drainage holes in the invert arch, while the scheme with only circumferential drainage blind pipes in the invert arch performs the worst; (4) Considering both water pressure reduction effectiveness and construction quality, it is recommended that the weakly developed karst sections of the Zhongliangshan Tunnel adopt a scheme with circumferential drainage blind pipes in the invert arch and additional drainage holes in the invert arch and wall-foot; (5) Monitoring results of water pressure on invert arch show significant fluctuations influenced by surface rainfall. The measured water pressure and distribution on invert arch closely match the numerical simulation results, validating the effectiveness of the recommended drainage scheme. 2024 Vol. 61 (6): 162-717 [Abstract] ( 68 ) [HTML 1KB] [ PDF 7820KB] ( 208 ) 172 Study on Gradation Characteristics and Arching Effect of Talus in Southwest China CHEN Zhimin WANG Hong CHEN Jun ZHAI Wenhao WANG Duobin LI Wenhao CAI Yunchen To explore the arching effect and arch height evolution law of the rock skeleton in talus surrounding the tunnel, a sleeve test and theoretical analysis were used to analyze the influence of gradation, water content, and filled soil content on the arching effect of the skeleton-type talus. The relationship between the maximum distance ? from the tunnel crown to the natural equilibrium arch of the surrounding rock and the horizontal calculation distance of the arch axis was derived. The study shows that the stress transmission path of the talus is not uniformly distributed and is directly related to the constraints. The effectiveness of reducing the ground arch height among the three factors(grading, water content, and filled soil content) is as follows: increasing water content > increasing filled soil content > increasing gradation uniformity. The relationship between the maximum distance ? from the tunnel crown to the natural equilibrium arch of the surrounding rock and the horizontal calculation distance of the arch axis is a quadratic function, being consistent with the sleeve test results. The quadratic term represents the stress equilibrium condition, and ? is positively correlated with the interlocking strength of the talus, influenced by the relative grain size and compaction degree of the rock blocks. 2024 Vol. 61 (6): 172-181 [Abstract] ( 76 ) [HTML 1KB] [ PDF 3941KB] ( 205 ) 182 Study on the Deterioration Mechanism of Subway Shield Tunnel Structure Based on the Full-scale Test WEI Gang1,2 XU Tianbao3 FENG Feifan4 MU Zhiyuan3 ZHANG Zhiguo5 To investigate the differences in the deterioration behaviors of subway shield tunnels under various loading conditions, the full-scale test was conducted to comparatively analyze the evolution patterns of segment deterioration under different load scenarios, summarizing the characteristics of shield tunnel structural deterioration. The results indicate that the primary impact of loading and unloading states on shield tunnel segments is the disruption of force equilibrium and alteration of constraint conditions, thereby changing the evolution process of deterioration.The convergence deformation and stress variations of segments exhibit entirely opposite trends under symmetric loading and unloading. In the final stage of asymmetric unloading, the maximum positive and negative convergences of segments occur at 90° and 180°, respectively, with bolt stress undergoing multiple polarizations. Concrete cracks concentrate near the bottom of the arch crown, distributed at a 45° angle. In the final stage of asymmetric surcharge loading, the maximum positive and negative convergences are located at 90° and 30°, respectively. Bolt stress follows a linear pattern, and concrete cracks first appear at the arch haunch corners and are distributed at a 180° angle. 2024 Vol. 61 (6): 182-190 [Abstract] ( 69 ) [HTML 1KB] [ PDF 6093KB] ( 217 ) 191 Study on Surface Vibration Velocity Characteristics and Settlement Patterns Induced by Tunnel Blasting Construction LI Junhong1,2,3 SHEN Jun1,2,3 BAO Xiaohua1,2,3 CHEN Xiangsheng1,2,3 XU Zhihao1,2,3 XIE Hailin4 To investigate the correlation between surface settlement patterns and tunnel blasting vibrations, a case study was conducted on the eastern tunnel of the Zhuhai Xingye Express Line (north section). Real-time monitoring and analysis were performed on the vibration velocity and frequency induced by tunnel blasting excavation. Additionally, tunnel structural reliability analysis was conducted using Copula theory. The results show that within different horizontal distance ranges from the blast center, vertical (Z) vibration velocities at monitoring points exceed radial(X) and tangential (Y) vibration velocities, while the frequency remains relatively stable. The maximum uplift and settlement occur on the left line of the tunnel, and monitoring points located between the left and right tunnel lines exhibit significant settlement variations, necessitating focused attention during construction. The Frank Copula function is recommended for constructing dependence models for tunnel structural reliability analysis, while the Clayton Copula is unsuitable for modeling surface settlement. In practical engineering, the optimal Copula function should be selected based on specific data characteristics to accurately represent parameter dependency relationships. 2024 Vol. 61 (6): 191-199 [Abstract] ( 69 ) [HTML 1KB] [ PDF 5730KB] ( 236 ) 200 Experimental Study on the Influence Zoning on Existing Pile Foundations Induced by Tunnelling YANG Wendong1 WU Yang1 WANG Zhide1 WU Haigang1,2 LI Gen1 To investigate the impact on the mechanical effects and deformation of existing pile foundations due to subway tunnel excavation, a combined approach of theoretical analysis and model test was adopted. The study analyzed tunnel excavation-induced soil disturbances, stress characteristics of existing pile foundations, and the interaction between tunnels and piles. The results reveal that: (1) The disturbance deformation region caused by tunnel excavation is primarily concentrated within four times the tunnel diameter on both sides of the tunnel axis. The disturbance degree of the surrounding soil increases as excavation progresses, and the additional bending moment of the pile foundation exhibits an "S" shape at different excavation stages. (2) The closer the distance between the tunnel and the pile foundation, the greater the disturbance to the pile foundation. As the tunnel depth increases, strain disturbances in the pile foundation decrease while deformation disturbances increase. (3) Based on the single pile disturbance degree theory, the excavation influence range between the tunnel and pile foundation was classified, and corresponding reinforcement measures were proposed for different influence zones. 2024 Vol. 61 (6): 200-208 [Abstract] ( 77 ) [HTML 1KB] [ PDF 4497KB] ( 193 ) 209 Study on the Performance Degradation of Concrete Under Freeze-thaw Cycles Based on Mesoscopic Mechanical Models WANG Xun1,2 ZHANG Kangjian3 GUO Jinlong1,2 WEI Ronghua3 ZHANG Zhiqiang3 To clarify the influence of mesoscopic characteristics on the structural performance degradation of con? crete under freeze-thaw conditions, a three-dimensional mesoscopic mechanical model of concrete under different freeze-thaw levels was developed using ABAQUS secondary development, combined with freeze-thaw cycles and uniaxial compression test results. The mechanical performance of concrete with varying aggregate characteristics was analyzed using peak stress and peak strain as evaluation metrics. The findings are as follows: (1) During compression, cracks in the concrete initiate around the aggregates, primarily appearing in the mortar and interfacial layers.Diagonal surface cracks form in the early stages of loading, while microcracks appear in the central internal region.As compression displacement increases, the length and width of cracks grow, and diagonal cracks rapidly extend into through-cracks, causing structural failure; (2) As freeze-thaw damage intensifies, the damage distribution in concrete becomes more extensive, and crack width and length increase; (3) With increasing freeze-thaw cycles, larger aggregate gradation and particle size result in a greater rate of change in peak stress and a smaller rate of change in peak strain. Conversely, higher aggregate content leads to smaller rates of change in both peak stress and peak strain; (4) Optimizing aggregate gradation, increasing aggregate content, and reducing aggregate particle size improve freeze-thaw resistance and compressive strength of concrete, while aggregate shape has no significant impact. 2024 Vol. 61 (6): 209-218 [Abstract] ( 67 ) [HTML 1KB] [ PDF 9197KB] ( 223 ) 219 Testing and Analysis of Natural Ventilation in No. 1-2 Shaft in the Tianshan Shengli Tunnel CHEN Jianxun1 WANG Heqi1, 2 JIA Haiyang1 LIU Weiwei1 LUO Yanbin1 ZHAO Zhiqiang1 HUANG Dengxia2 To investigate the natural ventilation characteristics of deep and large shafts in ultra-long tunnels at high altitudes, this study focused on No. 1-2 Shaft of the Tianshan Shengli Tunnel on the Urumqi-Yuli Highway. Fixed meteorological and wind speed monitoring stations were established at the shaft base and mouth to conduct longterm monitoring of wind speed, wind direction, air temperature, and atmospheric pressure. The relationships between natural wind parameters (wind speed, wind direction) and air temperature, air pressure under different seasonal and temperature conditions were analyzed. Using fluid dynamics and tunnel ventilation network theories, the primary factors influencing natural wind speed and direction in the shaft were calculated and analyzed. The results show that during the construction phase of the Tianshan Shengli Tunnel, No.1-2 shaft primarily exhibit an exhaust ventilation mode under natural ventilation conditions. The natural wind in the shaft is closely related to meteorological conditions inside and outside the tunnel. Abrupt temperature changes could reverse wind direction. In spring, summer, and autumn, natural wind speeds at the shaft mouth show an increasing trend, with higher frequency and amplitude of fluctuations. On a daily basis, natural wind speeds in different time periods exhibit varying positive or negative correlations with air temperature and pressure. The wind speed at the shaft mouth is more sensitive to temperature changes, with average wind speed higher than 3.32 m/s on cloudy days compared to sunny days. During spring and summer, the effective exhaust speed in the shafts fails to meet tunnel ventilation requirements for pollutant removal, suggesting the need for jet fans to assist ventilation during construction. In contrast, the effective exhaust speed in autumn is sufficient for pollutant removal, allowing for the shutdown of ventilation fans to conserve energy. The thermal potential difference inside and outside the tunnel plays a decisive role in change in wind speed and direction. When the tunnel temperature exceeds external temperatures, the directions of thermal potential difference and hyperstatic pressure difference are aligned, increasing the shaft exhaust wind speed. Moreover, when the temperature difference inside and outside the tunnel is greater, the thermal potential difference between the shaft base and shaft mouth, as well as the exhaust wind speed inside the shaft, are greater, and the natural ventilation effect is more significant. 2024 Vol. 61 (6): 219-23 [Abstract] ( 64 ) [HTML 1KB] [ PDF 8048KB] ( 222 ) 231 The Impact of Light Source Brightness and Color Temperature on Driving Safety at Tunnel Entrance Section under Different Visibility Conditions LIN Zhi1 HU Yongbo1 WU Yifei2 ZHAO Yao2 YU Chongchong1 SUN Xinyang1 ZHAO Yingci2 Current highway tunnel lighting standards use brightness as the design indicator, neglecting the effects of visibility and color temperature on driving safety at tunnel entrance section. However, the visibility and color temperature can impact driving safety and visual perception. To address this, the study considers the interaction effects of different visibility levels, light source color temperatures, and brightness on driving safety. A physical experiment was designed and conducted using reaction time as a measure of driving safety. The results indicate: (1) Visibility and color temperature affect reaction time to varying degrees; (2) Under high visibility, increasing light source brightness can reduce reaction time, with a maximum decrease of about 20%. Under low visibility, the effect of increasing brightness diminishes, and excessively high brightness may cause a white wall effect, prolonging reaction time; (3)The influence of visibility on reaction time is significant at different color temperatures. Under low visibility, a low color temperature of 3 000 K is recommended. 2024 Vol. 61 (6): 231-239 [Abstract] ( 74 ) [HTML 1KB] [ PDF 3671KB] ( 176 ) 240 Structural Health Assessment of TBM Water Diversion Tunnels Based on the AHP-Matter-Element Extension-Variable Weight Theoretical Model ZHANG Yina1 CHEN Lei2,3 HOU Ge2 ZHI Baoping1 LIU He2 To ensure the safe construction and operation of water diversion tunnels, a TBM water diversion tunnel project was used as the research case. Utilizing field monitoring data, a comprehensive structural health evaluation method based on the Analytical Hierarchy Process (AHP)-Matter-Element Extension-Variable Weight Theory was proposed, considering structural response, durability, and external factors. The influence of AHP and the AHP-MatterElement Extension-Variable Weight Theory on the weights, nearness degrees of various evaluation indicators, and health grades was explored, identifying key indicators affecting the structural health of the water diversion tunnel.Research results show that the variable weights adjust dynamically with indicator values, enabling real-time and accurate tunnel health status evaluation. The computed grade characteristic values for the tunnel structure by the two methods are 1.589 and 1.695, respectively, corresponding to the basic safety status of grade B. Apart from concrete strength and grout properties, the variable weight values and grade characteristic values of other indicators increase with their respective values. Segment settlement, segment opening, segment misalignment, and segment cracking are identified as the most sensitive indicators of TBM water diversion tunnel health status. The proposed AHP-MatterElement Extension-Variable Weight Theory method can provide precise health status evaluation for water diversion tunnel structures. 2024 Vol. 61 (6): 240-250 [Abstract] ( 65 ) [HTML 1KB] [ PDF 4570KB] ( 194 ) 251 Vibration Reduction Technology and Safety Control Standards for Multi-arch Tunnels without Middle Walls MENG Desheng1,2 PENG Xiaodong3 YANG Guanghua3 The existing lining and supporting structure of the first excavated tunnel in multi-arch tunnels without middle walls are prone to damage and failure due to blasting in the subsequent excavated tunnel. To address this issue, this study, based on the Mengxing—Lvchun Expressway Tunnel Project in Yunnan, analyzes the vibration response and damage distribution of the lining in the first excavated tunnel through field vibration monitoring and blasting damage simulation of the tunnel support structure. The vibration reduction effects of measures such as reserving isolation rock columns and laying foam concrete layers are evaluated. Reasonable thicknesses for isolation columns and the optimal positions of vibration reduction layers are determined, and a reliable safety control standard for blasting in multi-arch tunnels is proposed. The results show that: (1) Increasing the thickness of the isolation rock column in the excavation area can effectively reduce the lining vibration and damage. Considering subsequent secondary blasting for the reserved rock column, it is recommended to retain a 1 m wide rock column. (2) Placing the vibration reduction layer outside the initial support can significantly reduce the lining vibration. However, to minimize lining damage and enhance the overall tunnel stability, it is recommended to place the foam concrete vibration reduction layer outside the secondary lining of the first excavated tunnel. (3) The safety control standard for blasting in multi-arch tunnels is that the peak particle velocity (PPV) at the arch waist on the blasting side of the first excavated tunnel should not exceed 25 cm/s. 2024 Vol. 61 (6): 251-260 [Abstract] ( 71 ) [HTML 1KB] [ PDF 4242KB] ( 196 ) 261 Dynamic Risk Assessment of Water Inrush and Mud Burst in Tunnels Based on Fuzzy Two-dimensional Cloud Probability Model DING Wanqin1 LIU Yuan2 WANG Wendong1 ZHOU Yunxin3 LI Haibing2 RUI Yi4 The groundwater environment during tunnel construction is highly dynamic, making it challenging to fully capture the uncertainties of tunnel construction risks under complex multidimensional geological conditions using a one-dimensional cloud model. To address this, a dynamic evaluation model for water inrush and mud burst risks in tunnels is proposed, combining a two-dimensional cloud model with fuzzy mathematics theory and probabilistic algorithms. The model evaluates risks from two dimensions: severity of consequences and likelihood of occurrence. A fuzzy mathematics normal distribution membership function is used to quantify and transform the traditional risk matrix. Deviation degree is introduced to replace membership degree, further improving the two-dimensional cloud model. Multi-source data acquisition and expert system are used to generate cloud droplets, whose distribution reflects risk uncertainty and quantifies risk probabilities. This approach enables the determination of risk levels and early warning states. Engineering application results demonstrate that this method dynamically updates risk environment information as tunnel construction progresses and provides real-time assessments of water and mud inrush risks. 2024 Vol. 61 (6): 261-268 [Abstract] ( 79 ) [HTML 1KB] [ PDF 3790KB] ( 171 ) 269 Construction Methods of Longitudinal Synchronous Grouting for Tunnel Crown Secondary Lining Voids WANG Lichuan1,2 GE Lihui3 WANG Haiyan2 KONG Chao4 LI Qingbin1 WANG Yuntao3 LIU Yufei1 Conventional void prevention technologies for the crown of secondary tunnel linings struggle to signifi? cantly reduce void formation and often result in layering between cast-in-place concrete and grouts. To address these issues, a study was conducted based on the Qu'ao Tunnel on the Lanzhou-Hezuo Railway. Using numerical simulation, the impact of crown voids and asynchronous grouting on the stress behaviors of the lining structure was analyzed. A longitudinal synchronous grouting technology for the crown of secondary linings was proposed, and its effectiveness was verified through field applications and cross- detection using various specifications of ground-penetrating radar. The findings are as follows: (1) Compared to a dense state, crown voids and asynchronous grouting increase the minimum principal stress of the crown by 86% and 39%, respectively. This indicates that crown voids pose the greatest safety risk to secondary linings, and layering between grouts and concrete is also a weak point in the structure. Grouting must be synchronized with concrete casting to ensure the integrity of secondary lining; (2)The proposed longitudinal synchronous grouting technology involves arranging grouting pipes with vent openings along the longitudinal direction within the inner edge of the waterproof board at the crown. Grouting is performed immediately after concrete placement and compaction, eliminating blind spots in radial grouting and avoiding cavities or density defects. This also eliminates the composite beam effect in the lining structure and enhances its overall load-bearing capacity; (3) The construction method for longitudinal synchronous grouting is simple to operate and significantly reduces costs compared to radial grouting with mold. 2024 Vol. 61 (6): 269-277 [Abstract] ( 83 ) [HTML 1KB] [ PDF 5200KB] ( 266 ) 278 Research on the Active-control Press-in Prefabricated Shaft Construction Method Applied in the Central Urban Areas with Water-rich Soft Soils ZHU Yanfei1 BI Xiangli2 PAN Weiqiang1 GUO Yan1 GUAN Panfeng3 To meet the construction demands of deep and large shafts in water-rich soft soil strata and address chal? lenges such as dense surrounding buildings, limited construction sites, and stringent environmental protection requirements in the central urban area, a novel active-control press-in prefabricated shaft construction method was developed. This method integrates the "underwater excavation and press-in sinking" features of the SOCS method and the "shaft segment prefabrication and suspended sinking" characteristics of the VSM method with the key technologies of pipe-jacking, including "thick slurry injection and borehole pressure retention. " The method employs the "press-in and lifting" dual-mode system for stable sinking of the prefabricated assembled shaft segment, utilizes a multi-degree-of-freedom robotic arm with a specialized cutter suction head for fully automated underwater soil excavation, and reduces shaft wall friction resistance by synchronously injecting thixotropic-static slurry. Furthermore, a comprehensive visualized intelligent control system integrates excavation conditions, sinking parameters, shaft posture, and environmental monitoring to achieve precise, micro-disturbance sinking of shaft structure in water-rich soft soil strata in the central urban area. This method was applied to the Xingle Road Escape Shaft project on the western extension of Shanghai Metro Line 13, achieving favorable results. The maximum average deep horizontal displacement of the soil was 5.10 mm, and the maximum average surface settlement was 4.81 mm. 2024 Vol. 61 (6): 278-285 [Abstract] ( 74 ) [HTML 1KB] [ PDF 5377KB] ( 253 )

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