20 October 2025, Volume 21 Issue 5
    

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  • Preliminary Study on the Development and Utilization of Underground Experimental Space in Beijing University Campus
    Huang Shiyao, Cheng Xiaoxi
    Chinese Journal of Underground Space and Engineering. 2025, 21(5): 1471-1481. https://doi.org/10.20174/j.JUSE.2025.05.01
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    Nowadays, when the country vigorously promotes "high-quality development", the requirements of laboratory environment in various disciplines in universities are gradually improving. In the context of "reducing the development" of Beijing's overall planning policy, the utilization of campus underground space has become one of the indispensable means for the development of universities in Beijing in recent years. Meanwhile, the strong anti-interference of the underground laboratory also shows important advantages. By investigating and analyzing the existing literature of cases of campus underground experimental space at home and abroad, several design principles of underground experimental buildings are summarized. On this basis, combined with the current situation of the location and the function of the peripheral existing buildings, planning and design on the surrounding underground space of the observatory, located in the western part of Tsinghua University campus has been done. Different schemes for the ground entrance form, plane function and streamline organization logic have also been compared, which is hoped to provide reference for the future development of the campus underground experimental space in Tsinghua University.
  • Evaluation and Optimization of Safety Resilience of Underground Public Space at Rail Transit Station
    Wang Qingjun, Wu Liang
    Chinese Journal of Underground Space and Engineering. 2025, 21(5): 1482-1494. https://doi.org/10.20174/j.JUSE.2025.05.02
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    The rapid expansion of urban rail transit networks has established the subway as a crucial mode of transportation for urban dwellers. Recent public safety incidents, like the 9/15 London subway bombing and the 7/20 Zhengzhou rainstorm disaster, as an important part of the rail transit network have highlighted the significant impact of rail transit station underground public spaces on citizen safety. This study adopts the "simulation-evaluation-identification-optimization" research approach. Initially, through a literature review, a resilience evaluation system for the safety of rail transit station underground public spaces will be established. Subsequently, three commercial rail transit stations in Dalian will be chosen. On-site investigations will be conducted to gather spatial layout characteristics and peak-hour passenger flow details. Using Anylogic software, the operation and evacuation status of underground public spaces at each station during peak hours will be simulated, and essential data will be collected. Thirdly, the safety resilience of each station will be assessed based on simulation experiment results. Weaknesses in the safety resilience of rail transit station underground public spaces will be identified, and optimization solutions will be proposed through specialized research. Finally, a construction strategy for enhancing the safety resilience of rail transit station underground public spaces will be summarized.
  • Triple-shear Finite Deformation Elasto-plastic Constitutive Model for Unsaturated Clay
    Hu Xiaorong, Lu Xiang, Wang Pan
    Chinese Journal of Underground Space and Engineering. 2025, 21(5): 1495-1504. https://doi.org/10.20174/j.JUSE.2025.05.03
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    The generalized effective stress variable method for unsaturated soils was applied to the triple-shear strength criterion to obtain the generalized effective stress triple-shear strength criterion for unsaturated soils. Based on this criterion, the three-shear destructive stress ratio and the new yield surface equation under the generalized effective variable method were derived. Subsequently, by introducing the S-R decomposition theorem within the framework of finite deformation elastoplastic theory, a three-shear finite deformation elastoplastic constitutive model suitable for normally consolidated unsaturated cohesive soils was established. Comparison between the established constitutive model and the conventional triaxial test of unsaturated soil shows that the simulation results of the finite deformation constitutive model are in good agreement with the test points, which verifies the feasibility of this constitutive model for finite deformation elastoplastic analysis of geotechnical materials. Comparison between the established constitutive model and the infinitesimal strain constitutive model shows that the calculation results of the established constitutive model are more accurate than the calculation results of the infinitesimal strain constitutive model under the same conditions of initial compaction, net confining pressure and matrix suction. The numerical simulation results of the true triaxial consolidation and drainage test show that, all other conditions being equal, the deviatoric stress and volumetric deformation of the soil body is positively correlated with the influence coefficient of the intermediate principal stress.
  • Study on the Creep Model of Sandstone Considering Hardening and Damage Effects
    Lu Mingxing, Yang Bin, Tian Shuai, Pan Jinbao
    Chinese Journal of Underground Space and Engineering. 2025, 21(5): 1505-1513. https://doi.org/10.20174/j.JUSE.2025.05.04
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    In order to study the influence of the combined action ofthe hardening effect and damage effect on the creep characteristics of rock, based on the Nishihara model, the hardening function which can reflect the yield strength strengthening with time and the damage variable which can reflect the deterioration of mechanical properties in the process of rock creep are introduced. The mechanism of hardening and damage in the three stages of instantaneous strain and creep deformation is analyzed, and the creep model of sandstone considering the hardening effect and damage effect is established. Finally, the rationality and correctness of the model are verified by comparing the model curve with the test curve. The results show that: The creep model curve of sandstone with hardening and damage effects shows a high degree of agreement with the test curve, and the correlation coefficient is over 0.90. Compared with the degree of agreement between the Nishihara model and the test curve, the constructed model curve can not only describe the creep curve containing accelerated creep more accurately, and it can also well describe the variation of decay creep and stable creep. Therefore, the established model comprehensively reflects the combined influence mechanism of the hardening effect and damage effect of rock in the whole process of creep deformation.
  • Macro-Meso Fracture Mechanical Mechanisms of Creep in Brittle Rocks after High-Temperature Heat Treatment
    Li Xiaozhao, Chai Bocong, Qi Chengzhi, Shao Zhushan
    Chinese Journal of Underground Space and Engineering. 2025, 21(5): 1514-1524. https://doi.org/10.20174/j.JUSE.2025.05.05
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    The creep behavior of brittle rocks after high-temperature heat treatment holds significant implications for the advancement of deep subsurface resource utilization. The long-term creep mechanical responses of rocks post-heat treatment may manifest diverse tendencies amid varying confining pressures accompanying temperature escalation; However, the underlying causalities remain obscured and the research focusing on the macro-meso mechanical mechanism is scant. Based on a microcrack crack propagation model, five temperature-dependent microcrack model parameters deduced via independent experiments, including initial crack damage (D0), fracture toughness (KIC), crack extension stress corrosion index (n), characteristic crack propagation rate (v), and initial crack friction coefficient (μ), are introduced. A macro-meso fracture mechanics model for creep behavior of brittle rock after high-temperature heat treatment has been established. The stress-strain constitutive relationship of rock under the influence of heat treatment temperature is also obtained, which provides an important basis for the selection of stress states of creep deformation mechanism. The influences of temperatures and confining pressures on parameters such as rock initiation stress, peak strength, long-term strength, and creep failure time are studied. Empirical validation substantiates the rationale of the model. Particular emphasis is vested in delineating the impact of confining pressure on the creep fracture attributes of rocks, as temperature undergoes variations. This emphasis arises from the divergent trends characterizing the evolution of the initial crack friction coefficient with temperature fluctuation. The research findings analyze the short-term and long-term mechanical characteristics of heat-treated brittle rocks from a meso-mechanical perspective. This offers a clearer and more profound understanding of the mechanical mechanisms underlying the behavior of heat-treated brittle rocks.
  • Freezing Deformation Law and Mechanical Response of Frost-Shrinkage Surrounding Rock in Cold Region Tunnels
    Chen Wei, Cao Shanpeng, Xia Caichu, Guo Kuo, Guo Bihuai
    Chinese Journal of Underground Space and Engineering. 2025, 21(5): 1525-1533. https://doi.org/10.20174/j.JUSE.2025.05.06
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    To investigate the freezing pressure in tunnels subjected to the frost deformation of frost-shrinkage surrounding rock and lining in cold regions, laboratory tests were conducted to determine the frost deformation behavior of water-saturated rocks and their frost-shrinkage linear strain at various temperatures. The elastic solution for frost-shrinkage pressure of the surrounding rock was derived analytically. Case analysis and numerical comparison validation were performed, and the control variable method was used to analyze the effects of different parameters. The research shows that: Water-saturated tuff and sandstone exhibit overall frost-shrinkage deformation under different freezing temperature conditions. Notably, water-saturated sandstone demonstrates some frost-heave recovery during the freezing and shrinking process, with porosity being the key factor influencing this recovery. The results of theoretical calculations and numerical simulations for surrounding rock pressure in cold region tunnels in various types of rock and under low-temperature concrete frost deformation are consistent, demonstrating the reliability of the theoretical solution. The frost-shrinkage surrounding rock pressure in cold region tunnels increases exponentially with the maximum freezing depth of the surrounding rock and increases linearly with the increase of the frost-shrinkage linear strain of the surrounding rock and the ratio of the elastic modulus of the frozen rock to the unfrozen rock. The proposed frost-shrinkage surrounding rock pressure solution in cold regions of tunnels can provide certain theoretical guidance for the frost resistance design of similar tunnels in cold regions.
  • Study on Damage Model of Polypropylene Fiber Recycled Concrete with Different Mix Proportions
    Yang Xin, Zhou Daowen, Liu Xinrong
    Chinese Journal of Underground Space and Engineering. 2025, 21(5): 1534-1543. https://doi.org/10.20174/j.JUSE.2025.05.07
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    In order to study the effect of different mix proportions on the compressive strength of polypropylene fiber reinforced recycled concrete, 30 sets of specimens with coarse aggregate particle sizes of 5~10 mm and 10~20 mm at 4∶6, 5∶5, and 6∶4 were designed and conducted. Through uniaxial compression tests, the stress-strain curves, elastic modulus, peak strength, and other parameters of each set of specimens were obtained. The test results show that: As the coarse aggregate particle size decreases, the peak stress shows an overall downward trend; Polypropylene coarse fibers have the best strengthening effect on the elastic modulus, and the mixing of coarse and fine polypropylene fibers has the best strengthening effect on the peak stress of recycled concrete. A statistical damage constitutive model for polypropylene fiber reinforced recycled concrete was established, and it was found that the specimen with a ratio of 5∶5 for coarse aggregates of 5~10 mm and 10~20 mm exhibits the most severe damage, and the mixture of coarse and fine fibers had the best inhibitory effect on damage. Finally, support vector machine regression was used to predict the post peak strain of recycled concrete. The study show that using a linear kernel function and using the post peak compressive machine strain as the input variable had the best prediction effect.
  • Study on Heating-Damage-Cracking Regularity of Microwave Irradiation of Hard Basalt
    Chen Denghong, Shi Wei, Wang Zhipeng, Wang Chaojia, Yuan Yongqiang
    Chinese Journal of Underground Space and Engineering. 2025, 21(5): 1544-1553. https://doi.org/10.20174/j.JUSE.2025.05.08
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    Wave velocity and uniaxial compressive tests were performed on basalt specimens before and after microwave radiation. The correlation mechanism between heating, damage, and cracking in microwave-irradiated rocks was investigated by combining scanning electron microscope tests with macro- and microfracture analysis. The results show that: Under 1.4 kW microwave irradiation, the two ends of the specimen heated up rapidly at first, followed by slower heating in the middle, resulting in a bimodal temperature distribution with higher temperatures at the ends and lower temperatures in the center. After microwave heating, the longitudinal wave velocity of the specimen gradually decreased with increasing radiation time. Both the damage factor and strength loss coefficient increased progressively with radiation time. The inflection point for the damage factor in wave velocity occurred between 160 and 180 seconds, and the inflection point for the strength loss coefficient was between 160 and 200 seconds. After the “inflection point”, the damage factor reached a plateau and no longer exhibited significant changes with continued radiation. The inhomogeneous temperature distribution within the specimen—due to the microwave heating—induced microcracks, and crack expansion occurred in three stages: crack initiation (0~160 s), crack expansion stage (160~240 s), and collapse and damage stage (after 300 s). The most significant crack expansion occurred during the steep increase in both the damage factor of wave velocity and the strength loss coefficient. The findings of this study can provide valuable insights and references for microwave radiation effects on hard rocks under similar conditions.
  • Cracks Evolution and Mechanical Properties of Granite with Random Damage under Freeze-Thaw Action
    Zhu Shijie, Qi Changqing, Bian Xinyu, Deng Fuqi
    Chinese Journal of Underground Space and Engineering. 2025, 21(5): 1554-1564. https://doi.org/10.20174/j.JUSE.2025.05.09
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    Freeze-thaw cracking is considered to be one of the main reasons for the failure of low permeability hard rock in the high cold area, repeated freezing-thawing will lead to increased damage and intensity weakening of rock mass. Granite samples with random damage were obtained through temperature impact test, and cyclic freeze-thaw tests were carried out. CT and nuclear magnetic resonance tests were used to study the evolution process of microscopic cracks in granite during freeze-thaw cycle, and uniaxial compression tests were used to study the weakening law of its mechanical properties. The results show that: The damage of granite under the action of freeze-thaw cycle is mainly caused by the expansion and connectivity of the initial fissure, and the porosity and the proportion of macropores increase gradually with the freeze-thaw cycle. It is difficult to form long and large freeze-thaw fissures due to the mutual influence and restriction of the initial fissures distributed randomly, and the fissures are mainly distributed in irregular network. With the progress of freeze-thaw cycle, the permeability of rock increases gradually and the saturation wave velocity presents a unimodal curve form of first increasing and then decreasing. The degradation of rock strength follows the form of exponential function, and the degradation relationship between strength value and elastic modulus value of rocks with different initial damage degree is similar under the condition of long-term freeze-thaw weathering, and may eventually tend to the same level. The research results have important reference values for the long-term mechanical properties evaluation and engineering stability evaluation of crystal rocks in cold regions.
  • Research on the Microscopic and Hydraulic Characteristics of Bentonite Modified Loess under Drying-Wetting Cycles Effect
    Xu Jian, Liu Yonghao, Li Yanfeng, Wang Ruitao, Wang Zefeng
    Chinese Journal of Underground Space and Engineering. 2025, 21(5): 1565-1575. https://doi.org/10.20174/j.JUSE.2025.05.10
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    Bentonite modified loess has the potential to serve as a clay liner layer in landfills, but the drying-wetting cycles can cause changes in the permeability and mechanical properties of the bentonite modified loess cushion layer, leading to leakage or instability damage in landfills, posing a threat to the long-term stability of the modified loess cushion layer. Taking plain loess and bentonite modified loess as research objects, experiments were conducted under different drying-wetting cycles, including scanning electron microscopy, mercury intrusion, flexible wall permeability, and uniaxial compression. The effects of dry-wet cycles on the microstructure, anti-seepage performance, and mechanical properties of modified loess were comprehensively analyzed at macro, micro, and nano scales, and the deterioration mechanism of modified loess under drying-wetting cycles was explored. The results show that: Bentonite can be used for loess solidification mainly due to the filling effect and water absorption and expansion characteristics of montmorillonite particles. The pore distribution of plain loess under different drying-wetting cycles is a three peak pore structure, while the pore distribution of modified loess is a bimodal pore structure; The permeability coefficient of plain loess continues to increase with the increase of drying-wetting cycles, while the permeability coefficient of modified loess tends to stabilize after five drying-wetting cycles; The uniaxial compression strength of both plain loess and bentonite modified loess tend to reach a stable value after five dry-wet cycles. Under different drying-wetting cycles, the uniaxial compressive strength of modified loess is higher than that of plain loess.
  • Dry-Wet Durability of Solidified Sludge under Capillary Immersion Mode
    He Jun, Zhu Yuanjun, Long Sihao, Luo Shiru, Li Wenjing
    Chinese Journal of Underground Space and Engineering. 2025, 21(5): 1576-1584. https://doi.org/10.20174/j.JUSE.2025.05.11
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    Using soda residue (SR)-ground granulated blast furnace slag (GGBS)-carbide slag (CS) and cement as solidifiers of sludge, the dry-wet durability of solidified sludge under capillary immersion and full immersion in seawater are conducted, and the influence laws and mechanisms of different immersion methods on the durability of solidified silt under seawater erosion environment are investigated. The results show that: SR-GGBS-CS solidified sludge shows better dry-wet durability than cement solidified sludge when cement dosage equals GGBS dosage. Generally, the samples in full immersion mode are damage severely, and show a high mass loss rate and low unconfined compressive strength. However, the strength of the sample in capillary immersion mode is lower than that in full immersion mode when the solidifier dosage and dry-wet cycles increase. The corrosive ions rising with the capillary water cause salt crystallization and the formation of Thaumasite, which deepens the inhomogeneity and damage for the samples under the coupling effects of multiple dry-wet cycles and seawater. Therefore, the adverse effect of capillary immersion on the dry-wet durability of solidified sludge gradually exceeds that of full immersion, and the zone above groundwater is the weakest.
  • Experimental Study on the Shear Mechanical Properties of Regular Tooth-Shaped Rock-Like Material Joints
    Guo Baohua, Cheng Shengjin, Li Yizhe, Sun Jiehao, Chen Yan
    Chinese Journal of Underground Space and Engineering. 2025, 21(5): 1585-1593. https://doi.org/10.20174/j.JUSE.2025.05.12
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    In order to study the shear mechanical properties of regular tooth-shaped joints, the RDS-200 rock joint shear test system was used to conduct direct shear tests on regular tooth-shaped rock-like material joints with 5 types of undulating angles under various normal stress. The results show that: (1) The shear stress-shear displacement curves of regular tooth-shaped joints with different undulating angles generally have compaction stage, approximate straight line stage, pre-peak yield stage, post-peak softening stage and residual stage, there are three modes of slip wear failure, slope gnawing failure and serrated complete shear failure in the shear failure of tooth-shaped joints. (2) Based on the concept of effective undulating angle, an empirical formula for the peak shear strength of regular tooth-shaped joints is proposed, with an average relative error of only 2.9%. (3) As the tooth-shaped asperity undulation angle increases, the peak shear strength, pre-peak shear stiffness, debris quality, and the proportion of shear failure area of the rock joints all increase overall. The research conclusion has certain reference significance for the engineering design and protection of regular tooth-shaped jointed rock masses.
  • Experimental Study on Long-Term Mechanical Properties of Red Sandstone under Hydrochemical Effect
    Liu Taogen, Li Ling, Wang Wei
    Chinese Journal of Underground Space and Engineering. 2025, 21(5): 1594-1604. https://doi.org/10.20174/j.JUSE.2025.05.13
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    Serious environmental pollution exacerbates the extent of water-rock interaction. The physical and mechanical properties as well as microstructure of engineering rock mass are changed due to the water-rock interaction, having a significant effect on the long-term stability of rock engineering. Creep characteristic of rock plays an important role in analyzing and evaluating the long-term stability of rock mass engineering. In order to investigate the creep mechanical behavior and hydrochemical corrosion mechanism of red sandstone under water-rock interaction, the red sandstone from Taoyuan hydropower station in Hunan province was taken as the research object, and then a series of triaxial compression creep tests were performed on the red sandstone after immersing into salt solutions with different ion concentrations and pH values. The results show that: The water-rock chemical corrosion damage of red sandstone is closely correlated to the ion concentration and pH value of salt solution. The stronger the acid-base property and the higher the ion concentration are, the greater the secondary porosity and the bigger the volumetric expansion deformation is. Meanwhile, the creep deformation and instantaneous deformation increase. Nevertheless, the long-term strength shows a decreasing tendency when the ion concentration increases or the pH value decreases. The sensitivity of red sandstone to chemical solution is as follows: acidic salt solution > alkaline salt solution > neutral salt solution > distill water. The curves of axial steady-state creep strain rate versus deviatoric stress all exhibit a “S”-shaped characteristic. The relationship of axial steady-state creep strain rate with deviatoric pressure can be well described by an exponential function. Based on the experimental results, the hydrochemical corrosion mechanism on creep behavior of red sandstone is preliminarily discussed.
  • Experimental Study on Strain Rockburst Characteristics of Metamorphic Sandstone in Deep Buried Tunnel
    Jiang Hu, Jiang Ming, Sun Xiaoming, Miao Chengyu, Zhang Yong
    Chinese Journal of Underground Space and Engineering. 2025, 21(5): 1605-1612. https://doi.org/10.20174/j.JUSE.2025.05.14
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    Rock burst is a geological hazard that frequently occurs in deep underground engineering and has become a significant problem during the construction of deeply buried tunnels. Using the Gaoloushan Tunnel as the research background, we utilized a self-developed experimental system for simulating deep rock burst processes to conduct strain rock burst experiments. These experiments were conducted under varying stress paths to replicate both hysteresis and instantaneous rock burst phenomena. The experiment involved analyzing the infrared thermal imaging and acoustic emission characteristics of the entire strain rock burst process. The results indicate that: The rock burst sample experiences a quiet period, crack propagation period, particle ejection period, and rock burst occurrence period from the initial loading to the point of rock burst failure under various stress paths. The temperature in the area of failure rapidly increases during rock burst, and particle ejection often accompanies the highest temperature. In addition, energy is generated throughout the loading process until the sample ultimately fails. The amplitude and peak frequency of acoustic emission are comparable between delayed and instantaneous rockburst samples, and the cumulative energy of acoustic emission is relatively high.
  • Experimental Study on Creep Deformation of High-Temperature Frozen Soil Based on Microscopic Pores
    Guo Huanming, Zhang Hu, Liu Feng, Chou Yaling, Zheng Bo
    Chinese Journal of Underground Space and Engineering. 2025, 21(5): 1613-1620. https://doi.org/10.20174/j.JUSE.2025.05.15
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    The high-temperature frozen soil is prone to creep deformation under long-term load. In order to explore the influence of its internal pore structure on the creep deformation of high-temperature frozen soil, static triaxial creep tests under different temperatures, dry densities and axial stresses were carried out on the high-temperature frozen soil. At the same time, CT scanning and pore extraction were carried out on the air-dried triaxial samples after the creep test. The results show that: Avizo was used to conduct 3D modeling and pore extraction on CT scan images. After conducting pore equivalence analysis on the extracted pores using three different methods, it was found that sphere equivalent error was the smallest. Therefore, sphere equivalent was selected for microscopic pore analysis, and the pores were divided into four categories: 0~200 μm, 200~500 μm, 500~1 000 μm and >1 000 μm. Under the given test conditions, the pore size of the sample is mainly distributed in the range of 200~500 μm, and the creep deformation is positively correlated with the number of pores with the pore size >500 μm. The creep deformation increases with the increase of temperature, the decrease of dry density and the increase of axial stress, and the temperature, dry density and axial stress all have significant effects on the creep deformation and the number of pores with pore size >500 μm. The number of pores with pore size >500μm increases with increasing temperature, decreasing dry density and increasing axial stress.
  • Experimental Study on the Enlarged Head Pumping and Drainage Model of Static Drilling Rooted Pile
    Yu Shan, Deng Yuebao, Hu Shuhao, Zheng Rongyue, Zhang Rihong
    Chinese Journal of Underground Space and Engineering. 2025, 21(5): 1621-1628. https://doi.org/10.20174/j.JUSE.2025.05.16
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    Static drilling and rooted pile is a green and environmentally friendly pile foundation construction method, which is mainly composed of PHC pipe pile and cement soil around the pile, and the expansion head treatment is added near the pile end. In order to accelerate and enhance the solidification of cement soil at the head of static drilling pile and further enhance the bearing capacity of pile foundation, the technology of vertical drainage channel and vacuum negative pressure drainage at the expanding head of pile end is proposed. Model tests were carried out to compare the bearing capacity of static drilling pile and static drilling pile with extended head pumping and drainage. The test results show that: The vacuum negative pressure drainage can accelerate the hardening of soil-cement around the enlarged head pile and make it reach the final strength earlier than the traditional static drilling pile. Vacuum negative pressure drainage consolidation strengthens the soil around the pile and the soil at the end of the pile to a certain extent. The ultimate bearing capacity of the enlarged head drainage pile at 28 days of pile formation is about 59% higher than that of the ordinary pile.
  • Uplift Field Prototype Tests and Mechanical Characteristic Study of Root Pile Foundation
    Duan Jun, Xie Qiang, Xiang Chengming, Peng Yuan, Fu Xiang
    Chinese Journal of Underground Space and Engineering. 2025, 21(5): 1629-1635. https://doi.org/10.20174/j.JUSE.2025.05.17
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    To address the challenges faced by transmission line tower foundation projects in complex mountainous environments, a root pile foundation composed of a short pile and three inclined anchor rods evenly distributed around the pile is proposed, aiming to enhance the uplift resistance of the pile foundation. Through field prototype testing, the vertical displacement of the pile top, anchor rod axial force, failure modes, and load distribution coefficient of the root pile foundation under uplift load were investigated. The results show that: The uplift load-displacement curve of the root pile foundation can be divided into three stages, including initial elastic straight line stage, elastoplastic curve transition stage, and the linear failure stage. In the early loading stage, the load-bearing capacity of the anchor rods is not significantly demonstrated, but as the load increases, the axial force of the anchor rods continues to grow. The ultimate uplift bearing capacity of the root pile foundation increased by 29.41% compared to that of the short pile foundation, indicating that the inclined anchor rods significantly improved the load-bearing capacity of the root pile foundation. Additionally, radial and circumferential cracks formed around the root pile foundation, with the main cracks concentrated in the area where the inclined anchor rods were arranged, presenting a radial distribution. This is because the anchor rods compress the soil and rock mass upwards, causing tensile failure in the upper soil and rock mass, and ultimately leading to the failure of the anchor rod structure due to tensile damage. Analyzing the bearing mechanism of the root pile foundation, the load distribution coefficient between short piles and inclined anchor rods can be used to characterize the bearing characteristics of the root pile foundation, and both components working together to bear the load. During the test, the load distribution coefficient of the inclined anchor rods gradually increased from a low level in the early loading stage to 48%, effectively dispersing and transferring the load. The research findings can provide a theoretical basis for the design and optimization of transmission line tower foundations in complex mountainous environments.
  • Study on Unidirectional Freezing Test and Numerical Simulation of Sandy Loam in Tianjin Area
    Wang Shoujie, Ren Tielun, Ding Jianwen, Jiao Xueyang, Liu Xueyuan
    Chinese Journal of Underground Space and Engineering. 2025, 21(5): 1636-1645. https://doi.org/10.20174/j.JUSE.2025.05.18
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    A closed-system unidirectional freezing experiment is conducted on the sandy silt found at the entrance and exit portal of the shield tunnel in Tianjin Metro. The test aims to investigate the temperature variation and frost heave deformation characteristics of frozen specimens under different freezing temperatures and moisture contents. Additionally, a numerical simulation of the unidirectional freezing process of sandy silt is performed using ANSYS finite element software. The test results indicate that: The higher initial moisture content in the soil, the longer duration of the stable freezing stage, and the initial freezing temperature of sandy silt increase with the increase of soil moisture content. Under the closed unidirectional freezing condition, the frost heave of the soil significantly grows with the increase of moisture content, while the influence of lower freezing temperatures on the final frost heave is relatively small. The simulated temperature variation trend corresponds well with the laboratory test results, except for an obvious mutation from the stable freezing stage to the slow cooling stage. As the freezing time progresses, the vertical frost heave increases at different depths within the soil. A more significant vertical displacement can be observed closer to the upper surface soil layer. After freezing for 500 minutes, the vertical frost heave displacement at different positions of the soil is linearly related to its depth.
  • Study on the Mix Ratio of Fluidized Soil Based on Bored Cast-in-Place Pile Treatment in Karst Areas
    Zheng Kexi, Zhang Ruida, Li Bing, Gong Weiming
    Chinese Journal of Underground Space and Engineering. 2025, 21(5): 1646-1653. https://doi.org/10.20174/j.JUSE.2025.05.19
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    There are problems such as excessive diffusion range and waste of materials when traditional fluidized soil is used in bored cast-in-place pile projects in karst areas. It is proposed to solve this problem by adding admixtures to shorten the initial setting time. Considering different admixtures, such as early strength agents, rapid setting agents and water reducing agents, the improvement effect of various admixtures on the initial setting time of fluidized soil is studied through laboratory tests first. Then, the appropriate admixture is preliminarily determined, and its influence on the fluidity and strength of fluidized soil is studied. Finally, the fluidized soil mix ratio suitable for bored cast-in-place pile treatment in karst areas is proposed. The results show that: The addition of sodium sulfate and water reducing agents can significantly shorten the initial setting time of fluidized soil, with water reducing agents having a better effect, while other early strength and rapid setting agents have significantly lower coagulation-promoting effects than sodium sulfate and water reducing agents. Although sodium sulfate can promote coagulation, the strength of the fluidized soil mixed with sodium sulfate will be slightly lower than that of the fluidized soil without sodium sulfate when the age reaches 14 and 28 days. For the fluidity and strength of fluidized soil, the addition of a water reducer is beneficial, while the addition of sodium sulfate has certain negative effects, but the impact is relatively small. Taking into account both performance and cost factors, it is recommended that the fluidized soil used in bored pile projects in karst areas should be a mixture of 10% cement, 6% water reducer, and 3% sodium sulfate.
  • Research on the Mechanical Properties of C100 Ultra-High Strength Double Layer Reinforced PRC Pipe Pile
    Qi Yuliang, Tang Mengxiong, Huang Keke, Zhao Qian, Liang Weijian
    Chinese Journal of Underground Space and Engineering. 2025, 21(5): 1654-1661. https://doi.org/10.20174/j.JUSE.2025.05.20
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    Full-scale model bending performance tests and finite element modeling analysis were conducted on C100 double-layer reinforced pipe piles to meet the high bending bearing capacity requirements of certain special engineering projects. The results show that: The cracking moment and ultimate bending moment of the prepared C100 double-layer reinforced PRC pipe pile reach 1648.66kN·m and 4 025.10 kN·m, respectively. Compared with the PRC I-1000 C-type pile with higher bending performance among the existing standard pipe pile products, the bending performance of C100 double-layer reinforced PRC pipe pile improve significantly. The failure form of pipe piles is manifested as the steel bars in the tension zone yielding first, and the concrete in the tension zone exits the work after cracks appear. Then, the concrete cracks in the tension zone rapidly develop and expand to a ductile failure of 1.5 mm. The theoretical calculation values of cracking bending moment and ultimate bending moment are slightly smaller than the test results, and the finite element computing results are in good agreement with the test results. The applicability of normative formulas and finite element analysis to large diameter double layer reinforced C100PRC pipe piles is verified.
  • Study on Surrounding Rock Classification during Double Shield TBM Tunneling
    Zhang Shishu, Zhao Xiaoping, Zhong Guo, Ran Congyan, Hu Jinshan
    Chinese Journal of Underground Space and Engineering. 2025, 21(5): 1662-1669. https://doi.org/10.20174/j.JUSE.2025.05.21
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    Rock mass classification plays a key role in the tunnel design and excavation. Being limited to an enclosed area, the tradition rock classification method is difficult to adapt to double-shield TBM excavation. Based on the whole process of double-shield TBM excavation of tunnels in areas with complex geological conditions, this paper proposes a comprehensive classification method (DT) of surrounding rock suitable for double-shield TBM construction conditions. The results show that: (1) Content of schistose muck, penetration ratio and seismic wave velocity of rock mass are the three main characterization factors of surrounding rock quality during double-shield TBM constructing; (2) The three main factors have a good correlation on surrounding rock classification; (3) Compared with the traditional HC method, DT classification method can comprehensively reflect the quality of the surrounding rock mass within 3% error. (4) According to the three main factors can be obtain with the characteristics of convenient, real-time, objective and quantization during double-shield TBM constructing, the surrounding rock classification by DT method is more meticulous in the same tunnel section.
  • Calculation of Non-uniform Deformation of Segmented Pipe Gallery under Silt Soil Base
    Liu Yong, Chai Shaoqiang, Wang Fulai, Xin Jian, Zou Kunyi
    Chinese Journal of Underground Space and Engineering. 2025, 21(5): 1670-1676. https://doi.org/10.20174/j.JUSE.2025.05.22
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    Aiming at the settlement and deformation problem of segmental pipe gallery under lock loading, based on the theory of Winkler elastic foundation beam, a pipe gallery settlement analysis model is established, and the deformation law of long pipe gallery structure on silt ground is analyzed by combining with the simulation model of "pipe culvert + natural foundation", so as to put forward a correction model for the calculation of uneven settlement of segmental pipe culvert. The results shows that: Under the action of uneven load, the loaded box body of pipe culvert experiences the most settlement, and the neighboring boxes produce uneven settlement, causing the settlement difference of the structural joints of the box body. The settlement amount and the settlement difference increase with the increase of uneven load. The pipe culvert settlement analysis model based on elastic foundation beam can only be used for elastic foundation, and the modified pipe culvert uneven settlement analysis model can evaluate the pipe culvert settlement and the settlement difference of structural joints under the large deformation pulverized ground foundation; Combined with the control indexes of pipe culvert settlement in coastal pulverized ground foundation, the permissible load of the pipe culvert overlay load is determined. The overlying load of pipe culvert should not be greater than 65.4 kPa, and the uneven load between pipe culverts should not be greater than 59.6 kPa. The results can provide technical support for the settlement prediction and safety control of thin pipe culverts in soft soil areas.
  • Study on the Bearing Characteristics of Diaphragm Walls of Deep and Long Foundation Pit under the Confined Water Level Fluctuation
    Zhang Minchao, Liu Xinrong, Wu Shaoming
    Chinese Journal of Underground Space and Engineering. 2025, 21(5): 1677-1684. https://doi.org/10.20174/j.JUSE.2025.05.23
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    For the deep and long foundation pit affected by confined water, based on the foundation pit of the second expressway of Guangzhou New Bai-Yun international airport, the study on the bearing characteristics of diaphragm walls under different confined water levels was carried out. First, the monitoring data of the foundation pit under low-pressure water levels were analyzed. Then, simulation results from Midas GTS/NX were compared with the monitoring data, and the numerical method was also used to analyze the effect of 3 m, 6 m, 10 m confined water level after foundation pit excavation on the horizontal displacement along wall depth, the surface settlement and the axial forces of supporting. The results show that: (1) The horizontal displacement along wall depth significantly increases, and the maximum value is located near the bottom of the foundation pit. (2) The surface settlement appears to be a “grooving” shape, which increases first and then decreases, with the increase of outer distance from the diaphragm wall. The maximum settlement appears at 0.67 times the excavation depth of the foundation pit. As the confined water level rises, surface subsidence increases significantly. (3) The axial forces of the first supporting gradually decrease, and the axial forces of second and the third supporting significantly increase with the increase of confined water level. The research results provide the basis for the design and construction of the deep and long foundation pit affected by the high confined water level in coastal areas.
  • Analysis of Plane Attitude Control of Shield Tunneling Machine in Small Radius Curve Section
    Huang Dawei, Yu Jue, Xu Changjie, Chen Houhong, Chen Kai
    Chinese Journal of Underground Space and Engineering. 2025, 21(5): 1685-1693. https://doi.org/10.20174/j.JUSE.2025.05.24
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    It is difficult to control the plane posture of shield tunneling machines during construction on small radius curved sections. In actual construction, construction person mainly determine the main parameters based on experience, and there is currently no relevant theoretical basis. This article analyzes the plane posture of shield tunneling machines and proposes a reasonable plane state for shield tunneling machines, that is, the cutter head of the shield tunneling machine passes through curved sections close to the outer boundary; When obtaining a reasonable plane posture of the shield tunneling machine, the relationship between the inner and outer jack travel of the shield tunneling machine can be obtained. During construction, as long as the pushing amount of the inner jack is controlled, the pushing amount of the outer jack can be obtained; A reasonable calculation method for the maximum over excavation amount of the shield machine under different top pushing amounts in the plane state of the shield machine is obtained; It is proposed to only perform over excavation on the inner side of the curve, without over excavation on both the upper and lower sides, and a calculation method for the extension of the over excavation knife at different angle positions is obtained. The results have laid the theoretical foundation for intelligent control of shield tunneling posture in curved sections.
  • Research on Dynamic Selection Technology for Universal Segment Construction of Shield Tunnels
    Yao Yinbing, Hu Qiubin, Zhang Haitao, Wang Junke
    Chinese Journal of Underground Space and Engineering. 2025, 21(5): 1694-1701. https://doi.org/10.20174/j.JUSE.2025.05.25
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    Universal segments are a widely used type of tunnel lining segments in shield tunneling. During construction, different assembly positions are selected to ensure that the assembled segments match the attitude of the shield machine, and that the segments at the tail of the shield are not squeezed during the tunneling process. In order to realize automatic selection of segment assembly points in the construction process and improve the quality of segment assembly, a dynamic selection method of general type segment assembly points was proposed. The spatial geometric relationship between the driving attitude of the shield machine and the attitude of the segment is solved by using the driving parameters of the shield machine. With the change of the shield tail clearance as the optimization control objective, the influence of the direction deviation between the shield tail plane and the end surface of the segment, the stroke difference of the propulsion cylinder and the point position of the segment assembly on the shield tail clearance is considered, and the optimization function of the dynamic selection point of the segment assembly is established. It can solve the difficult problem of segment point selection during shield construction. Taking the Jiangxinzhou Tunnel project in Nanjing as an example, MATLAB software was used to edit the optimization algorithm of segment point selection, and the predicted gap of the shield tail was in good agreement with the measured results, which effectively verified the feasibility of the method. Compared with the manual experience method, the gap deviation of shield tail is smaller after the point selection, which is conducive to improving the quality of segment assembly.
  • Study on the Influence and Mechanism of the Tooth Layers Number on the Compressive Bearing Performance of Tooth Piles
    Du Peng, Liu Xiaoling, Li Guangfan, Fu Yujia
    Chinese Journal of Underground Space and Engineering. 2025, 21(5): 1702-1709. https://doi.org/10.20174/j.JUSE.2025.05.26
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    In order to solve the pile bearing problem of poor foundation, a new type of tooth pile with small modified cross-section is proposed. Five types of tooth piles with different tooth spacing were designed, and numerical simulation study of tooth pile-soil interaction under layered foundation was carried out on an actual project by using ABAQUS, which revealed the influence law of tooth layers number on vertical bearing capacity of tooth piles, and analyzed the mechanism of the tooth structure on the soil around the piles. The results show that: Tooth piles can significantly increase the lateral resistance and reduce the pile top settlement compared with smooth piles. When the tooth spacing is equal to one times the pile diameter, the bearing capacity of tooth piles is the most economical. The increase in the tooth structure delays the softening of the lateral resistance, expands the influence range of the soil around the pile, effectively transfers the upper load to the soil around the pile, fully exerts the shear resistance of the soil around the pile, thereby increasing the bearing capacity of the tooth pile by increasing the lateral resistance. The innovative introduction roughness concept and the quantitative standard of roughness are proposed, which can lay the foundation for the subsequent development of theoretical calculations. The research results can provide a theoretical basis for the design and construction of tooth piles.
  • Study on the Influence of Earth Pressure Balance Shield Construction on Cutterhead Mud Cake in Composite Stratum
    Zhong Xiaochun, Liu Shuangquan, Huang Siyuan
    Chinese Journal of Underground Space and Engineering. 2025, 21(5): 1710-1719. https://doi.org/10.20174/j.JUSE.2025.05.27
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    Due to the high mud content in the mudstone strata, the mud cake is easy to occur in earth pressure balance shield excavation. Through the improved direct shear apparatus, the interface tangential adhesion strength test was carried out on the mudstone slag sample considering the influence of temperature, and the growth law of adhesion strength was discussed. The influence of cutterhead on soil extrusion and interface adhesion strength of excavation face under different shield tunneling parameters is analyzed. Combined with the shear strength of mudstone, the analysis model of the occurrence conditions of the cutterhead mud cake and the influence of shield tunneling parameters on the cutterhead mud cake are proposed. According to the analysis model, the critical penetration of mud cake during EPB shield tunneling is obtained. The results show that: The shear strength and adhesion strength of clay are used as indicators to establish a judgment model for the risk of mud cake formation on the cutterhead, which has certain rationality; The adhesion strength of clay increases linearly with the increase of penetration, the decrease of opening rate and the increase of buried depth; For Nanjing Metro Line 6, the critical penetration of shield tunneling should be controlled below 1.9 cm/r. The research results can provide construction guidance for the prevention of mud cake in EPB shield.
  • Numerical Simulation Study of Double-Line Shield through Cutting Group Piles
    Ye Xiaowei, Gao Sijia, Liu Zhixiong, Song Yuejun, Lu Cirong
    Chinese Journal of Underground Space and Engineering. 2025, 21(5): 1720-1728. https://doi.org/10.20174/j.JUSE.2025.05.28
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    The case of direct cutting of obstacle piles by shield tunneling frequently appears in the project, and it is very important to study the construction impact of shield cutting piles to ensure the quality and safety of tunnels and existing structures. Relying on the Shaoxing Metro Line 2 crossing underground passage pile group project, the finite element numerical simulation method is used to analyze the influence of the double-line shield tunnel cutting pile group on the formation and existing structure, and the influence of MJS reinforcement range on the deformation of the existing structure is explored. The results show that: The lower residual pile floats up after the shield is cut, and the upper residual pile and the rest of the pile foundation have obvious settlement. The truncated pile foundation has obvious tensile stress, with a maximum tensile stress of 1.23MPa. The MJS reinforcement can reduce the channel settlement and the lateral deformation of the pile foundation caused by shield excavation. With the increase of MJS reinforcement range, the channel settlement decreases significantly. Among them, the channel settlement is reduced by more than 38% after the MJS reinforcement under the tunnel, and the channel settlement is reduced by more than 48% after the MJS reinforcement around the tunnel.
  • Study on the Stiffness Efficiency and Bending Moment Transferring Coefficient of the Hexagonal Tunnel
    Zhang Hongwei, Cheng Xuesong, Guo Lin
    Chinese Journal of Underground Space and Engineering. 2025, 21(5): 1729-1739. https://doi.org/10.20174/j.JUSE.2025.05.29
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    The hexagonal tunnel has the advantages of better deformation and mechanical performance, and the space utilization ratio is better than that of the circular tunnel. But it's still a lack of research on the performance comparison and corresponding design parameters under different types of assembly forms. In order to explorer the performances of the transverse effective rigidity ratio of the hexagonal tunnel, stagger-jointed, straight-jointed and uniform models are investigated based on model tests and similarity theories. The experiment results are verified by numerical simulation. On this basis, numerical models are used to further study the bending moment distribution of the three models, and the bending moment transferring coefficient of stagger-jointed structure is calculated. The results show that: The transverse effective rigidity ratio is between 0.85 and 0.89 under stagger-jointed condition, and significantly better than that between 0.62 and 0.68 under straight-jointed condition. The bending moment distribution and bending moment transferring coefficient of staggered joint structure change periodically. The bending moment transferring coefficient is between 0.18 and 0.36. The results can be used as a reference for the design of hexagonal tunnel.
  • Deterioration Damage Characteristics of Rhyolite under Cyclic Immersion of Hydrochemical Solutions
    Wang Huaqiang, Zhong Yupei, Niu Fusheng, Liu Yao, Chen Wei
    Chinese Journal of Underground Space and Engineering. 2025, 21(5): 1740-1751. https://doi.org/10.20174/j.JUSE.2025.05.30
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    The tunnel surrounding rock in water-rich regions is subjected to long-term chemical corrosion and cyclical water immersion erosion. In order to investigate the damage mechanisms of chemical corrosion and cyclical water immersion on rock masses, a 60-day cyclical water immersion test was conducted on sandstone specimens under simulated water chemistry environments with different pH values (7, 5, 3) and flow velocities (0, 300, 900 mm·s-1). The degradation and damage mechanisms of rock mechanical parameters were analyzed through triaxial compression tests and techniques such as scanning electron microscopy, digital image correlation, and XRD diffraction experiments. The results reveal that: (1) Lower pH values and higher flow velocities in the chemical solution are associated with greater microstructural damage, porosity increase, attenuation of elastic wave velocity, internal friction angle reduction, and cohesive strength decline in the sandstone specimens. (2) In the triaxial compression tests, the failure mode of the sandstone specimens under pH=7 environment is mainly shear slip failure, while under pH=5 and 3 environments, columnar splitting failure is prominent. The globally distributed strain fields and localized deformation bands coincided with the location of failure, with higher flow velocities corresponding to larger strain values in the specimens. (3) During the initial stage of water immersion testing, the mass loss factor and degradation rate of elastic wave velocity decreased gradually over time. (4) Under constant flow velocity, the peak strength and maximum volumetric strain of sandstone increased with increasing confining pressure, while under constant confining pressure, they decreased with higher flow velocities.
  • Prediction of Foundation Settlement of Transmission Line Tower Due to Sheild Tunnels Excavation
    Zhang Jun, Zeng Chuanfeng, Liang Jianming, Lin Peiyuan, Ma Baosong
    Chinese Journal of Underground Space and Engineering. 2025, 21(5): 1752-1762. https://doi.org/10.20174/j.JUSE.2025.05.31
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    Tunnel boring is a common construction method for urban subway tunnel excavation. However, the tunnel boring process can easily induce ground and nearby building foundation deformations. Electrical transmission towers are crucial infrastructure for urban power supply, and when tunnel boring approaches these towers, an assessment of induced tower foundation settlement should be carried out. The finite element method is a powerful tool for conducting such assessments. However, due to the complexity of the geology and construction conditions, in regions lacking engineering experience and field data, finite element predictions often exhibit significant errors and are challenging to correct. In light of these challenges, this paper proposes a correction method for the finite element prediction model of tower foundation settlement near shield tunnel excavation based on the principle of similarity between ground and foundation settlement in the same finite element model. This method first utilizes pre-measured ground settlement data to determine the expression for its finite element model factor and then introduces it as a correction term into the tower foundation settlement prediction model. The empirical constants in the correction term are updated in real-time using actual tower foundation settlement data obtained during the tunnel boring process, leading to dynamic adjustments and improved accuracy in the prediction model. Using a shield tunnel project in Foshan, Guangdong as an example, this paper validates the superiority and practical value of the proposed method. The research indicates that: Without correction, the finite element model of the tower foundation overestimated its settlement by approximately 30%, with moderate accuracy and variability in predictions. Additionally, the predicted tower inclination based on settlement data did not align with the measured values. After applying the calibration method proposed in this paper, the overall accuracy of the tower foundation finite element model became unbiased, with reduced variability. The inclination of the tower, calculated based on the calibrated settlement data, exhibited high congruence with the measured values and consistent trends.
  • Opening-Closing Prediction of Immersed Tube Tunnel Joints Based on SSA-LSTM-WNN
    Li Shuliang, Li Ke, Guo Hongyan, Chen Jianzhong
    Chinese Journal of Underground Space and Engineering. 2025, 21(5): 1763-1770. https://doi.org/10.20174/j.JUSE.2025.05.32
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    The prediction of joint opening-closing deformations helps improve the operational safety of immersed tunnel systems. Addressing issues such as the poor accuracy and limited applicability of existing models, a novel method for predicting the joint opening-closing deformations of immersed tunnels is proposed. Firstly, the Sparrow Search Algorithm (SSA) is used to adaptively optimize the hyperparameters of the Long Short-Term Memory (LSTM) network, constructing an SSA-LSTM model to achieve feature learning and preliminary prediction of the deformation information. Based on this, the Ljung-Box (LB) test is employed to analyze the residual sequences, and a Wavelet Neural Network (WNN) is introduced to further extract effective information from the residual sequences, obtaining corrected values for the residual sequences. Finally, the prediction results from the SSA-LSTM model and the corrected residual sequence results are superimposed and reconstructed to obtain the predicted values of the joint opening-closing deformations. The proposed method is validated based on the immersed tube tunnel project of the Hong Kong-Zhuhai-Macao Bridge. The results show that: The proposed model exhibits excellent overall prediction performance, effectively mining useful information from the deformation sequences and having an advantage in considering the local features of the deformation sequences. The final prediction achieve an R2 of 0.999 4, RMSE of 0.007 2 mm, and MAE of 0.006 6 mm, which are higher in accuracy and stability compared to LSTM, SSA-LSTM, and traditional SVR, BP, and XGBoost models. This method can serve as a means to deeply explore the development and variation patterns of joint opening-closing deformations.
  • Prediction Method of Tunnel Lining Strain in High Cold Regions Based on Deep Learning
    Che Bowen, Bao Weixing, Lu Hanqing, Pan Zhenhua, Yin Yan
    Chinese Journal of Underground Space and Engineering. 2025, 21(5): 1771-1783. https://doi.org/10.20174/j.JUSE.2025.05.33
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    The service environment in which the lining structure of tunnels in high cold regions was usually harsh and susceptible to the coupling effects of various extreme factors, leading to different forms of cracks in the lining concrete and posing significant safety hazards to the entire tunnel structure. Therefore, monitoring and predicting the cracking behavior of tunnel lining structures in high cold regions has important engineering significance, so, a multi-factor coupling prediction model for tunnel lining strain in cold regions based on deep learning is proposed. Firstly, a CNN-Bilstm-Transformer (CBLT) multi-factor coupling prediction model was developed based on the LSTM model, using a high cold region tunnel of Xinjiang as a supporting project. Then, based on a large amount of on-site monitoring data, CBLT was trained and tested to explore the influence of different input features on the model's predictive performance, and the predictive performance between CBLT and different models was compared and analyzed. The research results indicate that: With the improvement of input features, the predictive performance of CBLT gradually improves; the average RMSE, MAE and MAPE on the test set were only 2.61 με, 2.22 με and 1.24%, R2 can reach 0.815; the predictive performance of CBLT is better than RNN, LSTM, CNN-Bilstm and Bilstm-Transformer. The application of CBLT in predicting lining cracking behavior in practical engineering could achieve high accuracy. The research results can provide scientific guidance for the analysis of cracking behavior of tunnel lining in high cold regions and the prevention of frost damage.
  • Prediction of Rockburst Intensity Level Based on Comprehensive Weighting-Set Pair Analysis
    Yin Xiong, Guo Qifeng, Fang Minghua, Zhang Ying, Yan Jingxuan
    Chinese Journal of Underground Space and Engineering. 2025, 21(5): 1784-1792. https://doi.org/10.20174/j.JUSE.2025.05.34
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    In response to the unreasonable preference coefficients of different weighting methods in the comprehensive weighting method and the problem of misjudgment in the maximum membership criterion, the rock brittleness coefficient σc/σt, rock mass stress characteristic coefficient σθ/σt, elastic energy index Wet, and rock integrity coefficient Kv are comprehensively selected as prediction indicators. By introducing a distance function to determine the preference coefficient of the improved Analytic Hierarchy Process and the Coefficient of Variation method, and combining the indicator set to obtain the comprehensive connectivity function. Finally, the maximum membership principle and confidence criterion are used for the comprehensive evaluation of rockburst intensity levels, and an improved rockburst intensity level prediction model based on comprehensive weighting and set pair analysis is established. Through the verification of 17 typical rockburst cases at home and abroad and actual engineering cases, it is shown that the proposed model has high accuracy and good practical application effects, which has certain engineering guidance significance.
  • Numerical Study on Seismic Wave Field of Shaft Boring Machine in Rock Layer Interface with Different Dip Angles
    Guo Zhidong, Li Guang, Zhu Hechao, Hu Shichao, Liu Xiangyu
    Chinese Journal of Underground Space and Engineering. 2025, 21(5): 1793-1801. https://doi.org/10.20174/j.JUSE.2025.05.35
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    Shaft boring machine is the development direction and trend of comprehensive mechanized shaft sinking. Advanced geological exploration based on the seismic wave field of the rock-breaking source of the shaft boring machine is an effective method to ensure the construction safety of the shaft boring machine. In order to study the seismic wave field characteristics of rock-breaking source of shaft boring machine, taking the rock stratum interface of common geological conditions as an example, the geological model of rock stratum interface with different dip angles is established by using the full wave field numerical simulation software Tesseral. The continuous random signal is used as the rock-breaking source for forward calculation, and the seismic wave field of the rock-breaking source of the shaft boring machine is obtained. Taking the strata without interface as the reference group, the direct wave in the seismic wave field is removed, and the reflected wave, diffraction wave, etc., are obtained in the seismic wave field. The time domain characteristics of the reflected wave are analyzed, and the frequency domain characteristics of the reflected wave at the interface of each rock layer are compared through wavelet packets. The results show that: The dominant frequency of the reflected wave in the seismic wave field at the interface of different dip strata is in the range of 50~200 Hz, and the component and dominant frequency of multiple waves are relatively complex, which are distributed within 600 Hz. With the increase of the dip angle of the rock stratum interface, the smaller the propagation distance of the wave, the earlier the arrival time of the reflected wave, and the greater the amplitude. The energy of each dip angle is concentrated between 70~125 Hz. As the dip angle of the rock stratum interface increases, the energy value of the reflected wave at each dip angle increases, while the energy proportion of the low-frequency component decreases. The main frequency of the seismic source has a relatively small impact on the time-domain and frequency-domain characteristics of the reflected waves at the interfaces of various rock layers. The geological conditions have a significant impact on the time-domain and frequency-domain characteristics of the reflected waves at the rock layer interface. The maximum amplitude and energy of the reflected waves in the upper soft and lower hard geological conditions are much greater than those in the upper hard and lower soft geological conditions. The energy proportion of the low frequency band of the reflected waves in the upper soft and lower hard geological conditions is relatively small. The research results provide a reference for the theoretical understanding of the seismic wave field of the rock-breaking source of the shaft boring machine.
  • Study on the Mechanical Characteristics of Blind Tube Clogging and Water Pressure Distribution in Linings of High Water Content Railway Tunnels
    Liu Jianhong
    Chinese Journal of Underground Space and Engineering. 2025, 21(5): 1802-1814. https://doi.org/10.20174/j.JUSE.2025.05.36
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    In water-rich geological formations, the crystallization blockage of drainage blind pipes in railway tunnels can lead to water leakage in tunnel linings and even severely impact tunnel structural safety. Laboratory model tests are conducted to investigate the crystallization patterns in drainage pipes under different flow rates. Additionally, three-dimensional numerical models are employed to analyze the water pressure distribution behind tunnel linings and the evolution of drainage volume in water-rich mountain railway tunnels equipped with different waterproof and drainage systems. The impact of the spacing between circumferential blind pipes on tunnel drainage capacity and the water pressure exerted on the lining is also explored. The results indicate that:(1) As the flow rate within the drainage pipes increases, so does the amount of crystallization within the pipes, suggesting that drainage volume is one of the primary factors influencing pipe blockage. (2) Compared to the semi-encapsulated waterproofing system, the fully encapsulated waterproofing system results in a more uniform distribution of water pressure on the lining at the arch crown and arch soles, which is more beneficial for the structural stress. (3) The water pressure distribution on the lining is closely related to the spacing between circumferential blind pipes, highlighting the critical importance of selecting an appropriate blind pipe spacing to meet lining safety requirements and ecological emission limitations. (4) Blockage in blind pipes leads to an increase in water pressure on the lining on both sides of the pipes, with the water pressure growth rate at the arch crown being greater than that at the arch soles. Special attention should be given to the arch crown area when monitoring the water pressure behind the tunnel lining. This study provides theoretical support for the design of waterproofing and drainage systems in railway tunnels located in water-rich geological formations.
  • Risk Identification and Reinforcement Strategy for Tunnel Excavation in Clay Altered Rock
    Du Libing, Lin Peng, Chen Tao, Xia Yong, Liu Yuanguang
    Chinese Journal of Underground Space and Engineering. 2025, 21(5): 1815-1824. https://doi.org/10.20174/j.JUSE.2025.05.37
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    The excavation of tunnels in clay-altered rocks, formed through long-term geological and hydrothermal interactions, often results in disasters. It is challenging to identify and prevent these disasters during the excavation in clay-altered rock. To address these challenges, this study first analyzes 12 typical tunnel cases in clay-altered rock. The results reveal that clay-altered rocks can be classified into three types: vein-type, full-section-type, and pocket-type. Collapse incidents are prone in vein-type altered rock. Excavation in full-section-type rock exhibits substantial deformation of soft rock, easily leading to tunnel blockage caused by catastrophic collapse. The pocket-type is prone to large collapses and may encounter water and mud/rock inrush disasters when groundwater is abundant. Subsequently, methods for risk identification of the three types of altered rocks are proposed. Risk identification for vein-type rocks is based on the width, density, and angle with the tunnel axis of the alteration zone. The Global Altered Index (GAI) is proposed from the thorough hydration products of surrounding rocks and is used for risk identification of full-section-type rock. Risk identification for pocket-type rocks relate the filling material in pocket-like rock cavities. Clay-altered rock zones serve as excellent water transportation channels and water storage zones. Risks are exacerbated by the hydro-mechanical coupling mechanism in altered rock. Advanced geophysical exploration combined with borehole exploration can effectively prevent excavation risks. Proactive drainage, strong support, and closely following the second lining are essential for the smooth excavation process. The research results provide a scientific basis and technical support for the identification and prevention of risks associated with tunnel excavation in clay-altered and weathered rock formations.
  • Exploring the Construction of a Composite Risk Prevention and Control System Framework for Underground Space Digitalization
    Ni Hewei, Zhang Tong, Ma Wen, Wang Shouzhong
    Chinese Journal of Underground Space and Engineering. 2025, 21(5): 1825-1836. https://doi.org/10.20174/j.JUSE.2025.05.38
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    Accidents such as underground space fires, floods, equipment failures, and environmental pollution occur suddenly and rapidly, making evacuation and rescue difficult. The task of risk prevention is arduous. Therefore, it is of great significance to use digital means to carry out comprehensive risk prevention and control in underground spaces. Regarding the comprehensive risks of multiple disasters in underground spaces, this article takes the digital twin technology system as the framework, adopts multiple technologies such as intelligent video monitoring, cloud edge computing and storage, intelligent simulation and deduction, and collaborates to build a real-time, accurate and comprehensive situation awareness, early warning of sudden accidents, multi-party collaborative response, and visual emergency guidance digital composite risk prevention and control system. It realizes the transformation from "end of the line disaster relief" to "front-end disaster prevention and control" and from "single disaster prevention and control" to "disaster recovery and control", comprehensively improving the digital level of the integrated system of composite risk prevention and control, and providing strong support for the emergency response of sudden disasters and accidents in underground spaces.
  • Research Advances in Propagation Regularities and Control Technologies of Air Blast Waves Induced by Tunnel Drilling and Blasting
    Yan Shuohao, Fan Yong, Leng Zhendong, Yang Guangdong, Zhou Tao
    Chinese Journal of Underground Space and Engineering. 2025, 21(5): 1837. https://doi.org/10.20174/j.JUSE.2025.05.39
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    The air shock wave generated by tunnel blasting will not only endanger the safety of workers and construction machinery in the tunnel, but also affect the stability of surrounding rock and lining structure. Reasonable control of the generation and propagation of air shock wave is important to ensure the safety of tunnel blasting construction. This article summarizes the research progress on the propagation regularities, harmful effects, prediction methods, and control measures of air shock waves in tunnel blasting in recent years, focusing on the propagation law and control technology of tunnel drilling and blasting shock waves. Several representative air shock wave overpressure prediction formulas were selected, the prediction accuracy of different formulas under different blasting conditions was calculated, and the applicable conditions of different formulas were analyzed. The research trend of tunnel air shock wave is prospected from the aspects of tunnel air shock wave overpressure prediction method, air shock wave evolution law research and air shock wave active prevention and control device.
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