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2024 Vol. 41, No. 11
Published: 2024-11-15
Urban Rail Construction
Engineering Economy and Management
Main Line: Engineering Geology and Subgrade
Information Technology
Main Line: Bridge Engineering
Main Line: Tunnel Engineering
Engineering Materials
Risk Management and Research
Main Line: Railway and Track
 
       Main Line: Engineering Geology and Subgrade
1 Study on the Disintegration Characteristics and Quantification of Red-bed Soft Rock under the Effect of Dry-wet Cycles in East Sichuan
HUANG Shiguang, ZHOU Xiancai, ZHANG Guodong, YAO Ruiting, LIU Mingyu, LING Sixiang, WU Xiyong
Research purposes: In response to the problems caused by the collapse of red bed soft rock subgrade along the railway, such as slurry, mud, and foundation settlement, the Jurassic red bed soft rock in the central and eastern Sichuan Basin was taken as the research object. Referring to the climate and environmental background conditions of the study area, an external disturbance resistance test was carried out under dry wet cycle conditions. Through quantitative analysis of multiple indicators of the disintegration process, the disintegration characteristics of red bed soft rock under dry wet cycle effects were explored, and the differences in the disintegration of red bed soft rock in different strata were clarified. The evolution law of disintegration rate with cyclic dry wet was identified.
Research conclusions: (1) The variation pattern of the content of disintegrated particles with the increase of dry-wet cycles in the disintegration resistance test can be divided into three stages: the rapid reduction stage of coarse particles, the stable stage of intermediate particles, and the continuous increase stage of fine particles. (2) There are significant differences in the particle content and disintegration of red bed soft rocks in different regions, with the order of disintegration strength being Neijiang> Suining> Dazhou. (3) The disintegration law of red-bed soft rock shows that as the number of dry-wet cycles increases, the disintegration resistance index, disintegration ratio, and standard basic entropy decrease continuously, while the small particle index increases continuously. As the number of wet-dry cycles increases, the disintegration rate decreases continuously, the content of large particles decreases, while the content of small particles continues to increase, and the disintegration gradually reaches stability. (4) The research results can provide a reference and theoretical basis for railway route selection and disaster prevention of red-layer soft rock subgrade.
2024 Vol. 41 (11): 1-6 [Abstract] ( 13 ) HTML (1 KB)  PDF  (778 KB)  ( 4 )
7 Calibration of Discrete Element Simulation Parameters of Shenyang Sand and Gravel Formation
HE Enguang, ZHAO Wenchao, QI Peng, ZHOU Peng
Research purposes: In the process of conducting discrete element-based simulation analysis of the interaction between shield machines and sandy cobblestones, there is a mismatch between the actual sandy cobblestone parameters and the simulation parameters of the discrete element method. To address this issue, it is necessary to conduct physical and simulation tests on the sandy cobblestones from the actual construction stratum of the Ganguan Station-Qiandaohu Street Station (referred to as Gan-Qian Section) section of Line 3 of the Shenyang Metro. By taking the angle of repose as the response value, Plackett-Burman and Box-Behnken experimental designs were carried out to calibrate the simulation parameters required for discrete element simulation analysis, providing a basis for the simulation analysis of the interaction between shield machines and sandy cobblestones.
Research conclusions: (1) Physical experiments measured the particle size distribution, the density of 1 719 kg/m3, and the accumulation angle of 38.68°. (2) Plackett-Burman experimental design, and screened out the factors that have a significant influence on the accumulation angle of sand gravel: sand gravel-sand gravel static friction coefficient, sand-gravel-sand gravel rolling friction coefficient, sandstone-shield machine rolling friction coefficient (3) Box-Behnken experimental design, establish a regression model between the accumulation angle and the significance factor, and the inverted optimal simulation parameters are: the static friction coefficient of sand pebble is 0.599, the rolling friction coefficient of sand pebble-sand pebble is 0.195, and the rolling friction coefficient of sand pebble-shield machine is 0.033. (4) The research results can be applied to the discrete element simulation analysis of shield tunneling machines.
2024 Vol. 41 (11): 7-11 [Abstract] ( 8 ) HTML (1 KB)  PDF  (617 KB)  ( 1 )
12 Research on the Characteristics of Climate and Frozen Soil Changes along the Qinghai-Tibet Line under Heating Conditions
MIAO Xueyun, TANG Zhanfeng, MI Weijun, KONG Lingwei, CHENG Jia
Research purposes: The permafrost on the Qinghai-Tibet Railway is gradually degraded due to the global temperature rise, which brings many technical problems to railway safety operation and related railway construction in the plateau cold region. By collecting and analyzing the changes in temperature, precipitation, ground temperature, and frozen soil upper limit of meteorological stations along the Qinghai-Tibet Railway, the characteristics of climate and frozen soil changes along the Qinghai-Tibet Railway under the condition of temperature rise of the Qinghai-Tibet Railway are analyzed. The research results aim to provide theoretical support for the engineering maintenance and engineering construction in the plateau cold area under warming conditions.
Research conclusions: (1) In the past 20 years, the warming rate of the Qinghai-Tibet Plateau has reached 0.64 ℃/ 10 a, and the precipitation has increased at a rate of 16.8 mm/10 a. (2) The temperature along the Qinghai-Tibet Railway is influenced by altitude and dimensions, with an average temperature value of -5.9 ℃~-2.7 ℃. The annual average precipitation has shown an increasing trend from 1996 to 2022, an increase of 75~86 mm compared to 1976 to 1995. (3) The ground temperature in the permafrost region of the Qinghai-Tibet Railway in 2022 has increased by 0.06~0.21 ℃ compared to 2007, and the temperature at the north and south ends of the permafrost has increased by 0.04 ℃~0.17 ℃. The freezing index along the route ranges from 1.5 to 5.6. (4) The research results can provide theoretical support and technical reference for the construction of road projects in plateau cold areas and the disposal of existing engineering diseases.
2024 Vol. 41 (11): 12-16 [Abstract] ( 11 ) HTML (1 KB)  PDF  (1087 KB)  ( 1 )
       Main Line: Railway and Track
17 Influence of Mortar Void Length Considering Random Mechanical Parameters on Running Performance
FENG Yulin, XIE Yuhang, WEN Sheng, JIANG Lizhong, CHU Jinhui, ZHOU Wangbao
Research purposes: The mortar void disease of ballastless track directly affects the operating speed and running performance of high-speed railway line. Taking a six-span simply supported girder bridge-CRTS Ⅱ type ballastless track system and the CRH2C, CRH3 and CRH380A high-speed EMUs as the research object, the modal analysis of the ballastless track-bridge submodel is carried out based on ANSYS to obtain the overall mass, stiffness and damping matrix. Combined with HBMAT command and PYTHON language, the overall matrix is transformed into sparse matrix and imported into multi-body dynamics software together with node degree of freedom mapping file. Based on wheel-rail contact relationship, a dynamic model of track-bridge coupling system considering mortar void is finally established and verified. With the Chinese track spectrum as the initial irregularity, the track deformation caused by pier settlement based on the general representation model of bridge-rail developed by the author is the additional irregularity. Considering the randomness of fastener stiffness, mortar elastic modulus and pier settlement, the Box-Behnken method was used to design the test points based on Design-Expert software, coupled dynamics model calculation is carried out respectively to evaluate the running performance of CRH2C, CRH3 and CRH380A under different mortar void conditions and mechanical parameter randomness.
Research conclusions: (1) The established dynamics model of train-track-simply-supported beam bridge coupling system is in good agreement with the calculation results of the literature model. (2) Under the same mortar void condition, the influence on the safety index is CRH380A>CRH2C>CRH380A, and the influence on the comfort index is CRH2C>CRH3>CRH380A, the influence on the stability index of the three types of trains is basically the same. (3) After considering the randomness of parameters, the index values of safety, comfort and stability indexes are all fluctuate up and down, and the control limits of each index are upper and lower limits boundary values. Taking the upper limit boundary value as the control limit is safer and more reliable than not considering parameter randomness. (4) The research results can provide some reference for the design and checking calculation of high-speed railway simply supported girder bridge.
2024 Vol. 41 (11): 17-23 [Abstract] ( 9 ) HTML (1 KB)  PDF  (952 KB)  ( 3 )
24 Effect of Longitudinal Resistance of Line on Seismic Response of Bridge-track-catenary System
YAN Bin, YU Limei, LI Zhe
Research purposes: To investigate the seismic response characteristics of the bridge-track-catenary system under different longitudinal resistances, a sophisticated simulation model was established, taking the example of a 7× 32 m double-track simply supported box girder installation. The influence of longitudinal resistance on the seismic response of each component in the system was explored, the response characteristics of different components under various seismic waves were analyzed, and the impact of the catenary structure on the track-bridge system was also revealed.
Research conclusions: (1) The longitudinal resistance significantly affected the stress on steel rails and the longitudinal deformation of fasteners. Moreover, the implementation of a ballastless track system notably reduced the deformation of fasteners at the piers while increasing the stress on rails at both ends of the bridge piers. Under the action of El-Centro seismic wave, the longitudinal deformation of fasteners under longitudinal resistance of ballastless rail fasteners is 16.7% and 15.0% lower than that under ballasted track and small resistance fasteners respectively. (2) The seismic response of the catenary structure and the bridge structure showed minor sensitivity to longitudinal resistance. (3) Under different longitudinal resistances, the impact of El-Centro wave on the bridge structure and track structure was greater than that of the Taft wave. Specifically, under the El-Centro seismic wave, the bridge stress was 9.6% higher for smaller fastenings and 7.4% higher for the ballast track compared to the ballastless track. (4) The presence of the catenary structure influenced the overall stiffness of the system. Considering the catenary, the bridge stress and the bottom shear force of the bridge piers significantly increased. It is recommended that during the design of high-speed railway bridges in seismic regions, the influence of the catenary structure should be taken into account. (5) The research results can provide reference for the seismic design of the track structure on the bridge.
2024 Vol. 41 (11): 24-29 [Abstract] ( 9 ) HTML (1 KB)  PDF  (726 KB)  ( 1 )
30 Difference of Chord Offsets Method's Serviceability Analysis for Track Irregularities Representation
WEI Hui, YANG Fei, ZHU Hongtao, XIE Zhifeng, CAO Juanhua
Research purposes: In the process of importing High-speed railway ( HSR ) construction technology, the difference of chord offsets (DoCOs) method was introduced in China Railway for representing profile/alignment irregularities. Nevertheless, there are some controversies about DoCOs’ effects on track state evaluation and maintenance operation instruction, so DoCOs’ serviceability in track maintenance should be ascertained. To address the underlying mechanism of this issue, this paper starts with the correlation between DoCOs and car body acceleration and evaluates DoCOs’ reflection capability about vehicle dynamic response using correlation coefficient and normalized mutual information. Then in view of DoCOs’ state space description, discusses track deformation representing capability of DoCOs and addresses the instruction capability for maintenance operation, which employed track deformation state-space representation and observability analysis. On this basis, compares track irregularities representing the capability of mid-chord offset (MCO) and difference of chord offsets.
Research conclusions: (1) There is a weak correlation between 5 m/30 m or 150 m/300 m DoCOs and car body accelerations, and no evidence indicates that a nonlinear mapping structure exists. (2) Since the state space of 5 m/ 30 m or150 m/ 300 m DoCOs is not complete observable, it is difficult to instruct the maintenance from DoCOs. (3) MCO’s unobservable states are quite a few compared with DoCOs’ in the track deformation state-space representing, and it could be complete observable taking some supplementary observations, moreover, MCOs are strongly correlated with car body accelerations, all these characteristics are more propitious to evaluate the track states and instruct the maintenance operation. (4) These conclusions illuminate the serviceability problem of DoCOs existing in HSR track evaluation and maintenance and could present a theoretical foundation for selecting representation indices for track irregularities.
2024 Vol. 41 (11): 30-35 [Abstract] ( 8 ) HTML (1 KB)  PDF  (790 KB)  ( 2 )
       Main Line: Bridge Engineering
36 Research on Negative Moment Bending Behavior of UHPC Layer on Frame Bridge Joints
QIU Junfeng, ZHANG Jie, ZHANG Yang, YU Junjie
Research purposes: In order to investigate the mechanical performance of UHPC layer in the negative moment zone of small span continuous frame bridges, the crack resistance ability, rotation ability and ultimate bearing capacity of the joint were investigated by using the real bridge scaling model. Based on ABAQUS finite element software, the numerical simulation and parameter analysis of the test model were carried out to explore the effects of key parameters such as UHPC layer length, thickness and reinforcement ratio on mechanical performance of the negative moment joints of the frame bridges.
Research conclusions: (1) The UHPC layer of frame bridge joint has a high cracking stress (6.56 MPa). In the normal use stage, the UHPC layer effectively inhibits the formation and development of cracks in the negative bending moment zone, and improves the overall cracking resistance of the structure. (2) Increasing the reinforcement ratio of UHPC layer can effectively improve the flexural bearing capacity of frame bridge joints, but will reduce the cracking resistance of UHPC surface layer. (3) The crack resistance and load bearing capacity of frame bridge joint increases with the increase of UHPC layer thickness. (4) On the premise that both the UHPC layer and the UHPC-NC interface have good crack resistance, it is the most economical to set the UHPC layer between the zero points of the negative bending moment of frame bridge. (5) The research results put forward a high performance joint design method for the negative moment zone of small span continuous frame bridge, which can provide an effective reference for similar bridge design.
2024 Vol. 41 (11): 36-41 [Abstract] ( 8 ) HTML (1 KB)  PDF  (952 KB)  ( 1 )
42 Experimental Study on Vibration and Noise of Continuous Composite Box Girder of Railway Bridge
GU Yiwei, WEN Wangqing, NIE Xin, ZENG Jiahua, JIANG Yuexin
Research purposes: To study the vibration and noise response of steel-concrete continuous composite beam bridges under railway heavy loads, a railway steel-concrete continuous composite beam bridge with a span of (40+50+40) m on a certain passenger dedicated line was used as the engineering background to conduct on-site testing of structural vibration and noise. The valid data for 16 trains of different formations under operating conditions has been recorded, with train speeds ranging from 160 to 210 km/h. Based on the valid data, the characteristics of vibration and noise of railway composite beam bridges were analyzed and discussed. This research can provide data reference for the research and engineering application of acoustic and vibration response of railway composite structure bridges.
Research conclusions: (1)The results showed that the dominant frequency range of vehicle-induced vibration of the composite bridge was 30 to 2 000 Hz, the peak frequency of vertical vibration of the bridge appeared at 100 Hz, and the peak frequency of transverse vibration of the bridge appeared at 63 Hz. (2) The dominant frequency range of A-weighted sound pressure level at each field point in the test was 63 to 1 250 Hz. (3) The local vibration response of the steel web in the steel-concrete composite bridge was prominent, and the acceleration effective value can reach 6 to 10 m/s2, significantly higher than the vertical and transverse vibration of the bridge. (4) The noise pressure level of the railway boundary field point can reach 75 to 78 dB(A). (5) The research results can provide measured data support for railway steel-concrete composite beam bridge engineering and research.
2024 Vol. 41 (11): 42-46 [Abstract] ( 7 ) HTML (1 KB)  PDF  (930 KB)  ( 1 )
47 Study on the Flexural Performance of Old Hollow Slab Beams Strengthened with Textile Reinforced Concrete
YIN Shiping, XING Aojie, SU Xun, YANG Yuhou, FENG Jian, LI Litao
Research purposes: To verify the feasibility of applying textile reinforced concrete (TRC) to bridge strengthening, this paper investigates the flexural performance of TRC strengthening old hollow slab beams based on four-point bending tests in the field to address the problems of inadequate load carrying capacity and large deflection of in-service reinforced concrete (RC) bridge main beams.
Research conclusions: (1) The specimens mainly suffer from the failure modes of fracture of the textile, relative slip of the textile and the matrix, local debonding and interlaminar peeling, and the load carrying capacity is increased by 9.09%~30.3% by TRC reinforcement. (2) TRC reinforcement reduces the deflection of hollow slab beams by 8.4% to 26.8%, effectively improving their stiffness and limiting the development of cracks, but reducing ductility by 13.8% to 31.9%. (3) The optimum textile lap length obtained from this test is 400 mm. (4) The load carrying capacity of TRC reinforced hollow slab beams is calculated, and the theoretical value is in good agreement with the test value. (5) The research results have certain guiding significance for the application of TRC in the strengthening of bridge projects.
2024 Vol. 41 (11): 47-53 [Abstract] ( 12 ) HTML (1 KB)  PDF  (2015 KB)  ( 4 )
54 Calculation of Bearing Capacity of Cast-in-place Piles in Collapsible Loess Site Based on Immersion Environment
ZHANG Yanjie, TIAN Wang, WANG Xu, YANG Shaojun, JIANG Daijun
Research purposes: When the pile foundation of a railway bridge passes through a large-thickness collapsible loess site, the current specification calculates the negative friction resistance according to the limit value under the most unfavorable state, which leads to the length of the pile body is too long, resulting in a lot of waste of engineering investment. This paper proposed the concept and classification of a site immersion environment. Considering the topography and landforms, focusing on the analysis of the immersion conditions and degree of the site, the flooding environment of the site is divided into four states: complete immersion environment, long-term immersion environment, short-term immersion environment, and comprehensive treatment measures environment. For different immersion environments, when calculating the negative friction resistance, the lower limit depth of the collapsible soil layer is considered to be reduced.
Research conclusions: (1) In terms of evaluation of collapsible loess with large thicknesses, the current specification is suitable for industrial and civil construction projects with thin collapsible soil layers, but not for railway projects with large-thickness collapsible soil layers. (2)For a complete immersion environment, negative skin friction is calculated according to the recommended method of current specifications. For a long-term immersion environment, the calculated depth of collapsible soil layer around piles can be considered 10~15 m. For a short-term immersion environment, the calculated depth of collapsible soil layer around piles can be considered as 5~10 m. (3) For comprehensive foundation treatment in large-thickness collapsible loess sites, negative skin friction can be ignored, which can shorten pile length, reduce construction difficulty, and save investment. (4) The research results can provide a reference for pile foundation engineering design in collapsible loess regions.
2024 Vol. 41 (11): 54-58 [Abstract] ( 9 ) HTML (1 KB)  PDF  (369 KB)  ( 2 )
       Main Line: Tunnel Engineering
59 Analysis of Influencing Factors of Rockburst Tendency of Deep Buried TBM Tunnel with High Ground Stress
GAO Xinqiang, YANG Tengjie, DAI Shangkun, FAN Haobo, ZHU Zhengguo, ZHAO Jingbo
Research purposes: Rockburst disasters are most prominent in the construction of deep-buried high-ground stress hard rock tunnels, and the clear influence of the main factors affecting the occurrence of rockbursts is of great significance for the prediction and prevention of rockburst disasters. This paper takes a new mountain TBM tunnel in southwest China as the engineering background, based on the summary analysis of the conditions of rock explosion, based on the FLAC3D software to establish a numerical model of the TBM tunnel boring, analyze the impact of the ground stress and the strength of the surrounding rock on the propensity to rock explosion; and then use the game combination of empowerment-gray correlation analysis to determine the degree of influence of different factors on the propensity to rock eruption.
Research conclusions:(1) High energy storage brittle rock mass, sufficient energy source, and engineering excavation unloading are the conditions for the occurrence of tunnel rockburst. (2) Rockburst propensity increases gradually with the increase in depth of burial. Lateral pressure coefficient <1.0, the side wall of the largest rock explosion tendency; lateral pressure coefficient >1.0, the arch (arch bottom) at the largest rock explosion tendency. With the increase in lateral pressure coefficient, the arch and arch shoulder rock explosion propensity gradually increased, and the side wall rock explosion propensity gradually decreased. (3) The rockburst tendency increases slightly with an increase in cohesion. When the internal friction angle is small, the rockburst tendency increases with the increase of the internal friction angle, but the larger the internal friction angle, the smaller the influence on the rockburst tendency. (4) The degree of influence of different factors on the rockburst propensity is burial depth > internal friction angle > lateral pressure coefficient > cohesion. (5) The results of this study can provide support for the determination of influencing factors of rockburst prediction in high-ground stress tunnels and also provide a reference for the prevention and control of rockburst disasters.
2024 Vol. 41 (11): 59-65 [Abstract] ( 7 ) HTML (1 KB)  PDF  (644 KB)  ( 2 )
66 Research on Peck Formula for Sedimentary Strata of Kunming Lake
RUAN Yongfen, QIU Long, HUAI Yigao, WU Long, ZHENG Tianyong, QIAO Wenjian
Research purposes: The Peck formula is one of the important methods for studying tunnel surface settlement. Its prediction results are mainly affected by parameters such as settlement groove width i and formation loss rate η, and due to the strong regional characteristics of each parameter, the parameter values vary greatly in different regions. Therefore, this paper takes the double line shield tunnel in the sedimentary strata of Kunming Lake as the research object, explores the variation rules and value distribution of each parameter, and finally obtains a surface settlement prediction formula for the double line tunnel applicable to the region, filling the research gap in China.
Research conclusions: (1) Due to the influence of the right line leading, the fitting degree of the Peck formula on the left line has decreased. (2) i is directly proportional to the tunnel depth z and can be characterized by the settlement groove width coefficient k. Its correlation with the weighted compression modulus E is weak. (3) η is positively correlated with z, negatively correlated with grouting rate g, and has little regularity with E. (4) The double line tunnel surface settlement prediction formula takes the leading tunnel k1 [0.23,0.68], η1 [0.31%, 1.66%], and the following tunnel k2 [0.21,0.58], η2 [0.31%, 1.79%]. (5) The rationality of the formula was verified by the measured data of a certain line, and the predicted results were basically consistent with the actual settlement, both located between the upper and lower limits. At the same time, based on the maximum settlement of the upper limit curve, it can be roughly judged whether the predicted settlement value exceeds the engineering warning, which can provide reference for safe construction of similar tunnels.
2024 Vol. 41 (11): 66-73 [Abstract] ( 9 ) HTML (1 KB)  PDF  (1554 KB)  ( 2 )
74 Intensification Effect of Aerodynamic Load in Lining Cracks of High-speed Railway Tunnel
YANG Weichao, HE Hong, ZHAO Lun, LIU Yikang, DENG E
Research purposes: Frequent falling blocks in high-speed rail tunnels can cause serious economic losses and even casualties. The intensification effect of high-speed train aerodynamic load in the crack may be an important reason for the crack expansion and eventually the formation of falling block. In order to prevent falling block accidents in high-speed railway tunnels and strengthen tunnel disease control, the intensification effect of aerodynamic load in lining cracks should be studied. In this study, based on Fluent software, finite volume method (FVM) and Pressure-Based solver are used to simulate the aerodynamic pressure in crack space by unsteady viscous k-ε turbulence model considering the compressibility of air. Using this model, the temporal and spatial characteristics of the aerodynamic loads of circumferential, inclined and longitudinal cracks are discussed. The spectrum characteristics of aerodynamic pressures are analyzed, and the effects of crack length, width, depth and vehicle speed on the aerodynamic loads of crack surface are analyzed.
Research conclusions: (1) The pressure wave enters the circumferential crack space instantaneously, and the pressure wave enters the inclined and longitudinal crack space procedurally. (2) The peak value of circumferential crack pressure is 5.32 times of the input pressure. The peak pressure values of inclined and longitudinal crack are only 79.5% and 64.9% of the corresponding values of circumferential crack, respectively. (3) The PSD of the aerodynamic pressure of the circumferential crack is 4.04 and 1.54 times higher than the value of longitudinal and inclined cracks on average. (4) The crack length and width have limited influence on the peak pressure of crack surface. The crack depth and the peak pressure meet the linear function relation, and the speed and the peak pressure meet the power function relation of 2.303 3. (5) The research findings can provide references for the design of high-speed rail tunnels, and the assessment and repair of cracks within the tunnels.
2024 Vol. 41 (11): 74-82 [Abstract] ( 10 ) HTML (1 KB)  PDF  (3138 KB)  ( 1 )
83 Research on the Key Green Elements of "Tunnel - Environment" in Mountain Railway
YAN Linjun, CHEN Huixin, BAO Xueying, GUO Haidong, LI Yajuan
Research purposes: The complex geological conditions and fragile environment in mountainous areas make the construction of railway tunnels arduous in terms of environmental protection, soil and water conservation, etc. It is imperative to reduce the disturbance of tunnel construction to the regional environment and balance the relationship between tunnel construction and environmental stability. To clarify the key nodes of green coordinated development of "tunnel-environment" and formulate targeted strategies to reduce the adverse impact of tunnel construction on the regional environment, an analysis method of key green elements of "tunnel-environment" in mountain railway based on a multi-layer coupling network model is proposed.
Research conclusions: (1) Based on clarifying the interaction relationship of the "tunnel-environment" in mountain railway, build an element system that includes tunnel green, interface, and environmental elements. Using the multi-layer coupling network model, each element is abstracted as the node of the network at different levels, and the organic relationship of each node in and between the network layers is established, which can establish the basis for the quantitative expression of the interaction relationship of the "tunnel-environment". (2) Taking a railway tunnel engineering in a mountainous area as an example, the network node importance assessment method is used to identify seven key green elements: tunnel section size, tunnel excavation length, tunnel blasting mode, tunnel ventilation mode, tunnel lining waterproof design, tunnel grouting and water plugging, tunnel ventilation equipment layout, which should be optimized and controlled. (3) The research results are in line with the engineering practice, and verify the applicability of the model, which can provide a basis for determining the key points to reduce the stress effect of railway tunnel construction in mountainous areas on the regional environment.
2024 Vol. 41 (11): 83-89 [Abstract] ( 7 ) HTML (1 KB)  PDF  (1203 KB)  ( 1 )
       Information Technology
90 Application of Convolutional Neural Networks in Intelligent Recognition of Fault Fracture Zones
SUN Keguo, JIA Jinglong, JIANG Bing, XIONG Zhi, ZHOU Yulong
Research purposes: The fracture zone is one of the most common geological anomalies in tunnel construction, which is prone to gushing water and mud, landslides and other geological disasters. To help solve the problems of relying on experience and low accuracy of traditional geological prediction interpretation, an intelligent identification algorithm of tunnel fault fracture zone based on Convolutional Neural Network (CNN) was proposed to assist professionals in identifying fault fracture zone quickly and effectively.
Research conclusions:（1）Based on the geological background and standardized forecast picture data set, the YOLOv5 deep learning framework was adopted, the BoTNet module was introduced, and the self-attention mechanism was combined to form an intelligent identification algorithm for fault fracture zone (New_YOLOv5), which can realize the intelligent identification of its location, scale and other elements.（2）Compared with the traditional YOLOv5 algorithm, the optimized algorithm has a higher accuracy in identifying undesirable geologic bodies, with the growth rates of mAP as well as mAPmax values of 13.68% and 9.96%, respectively, where the highest mAP value can reach 84.79%.（3）To a certain extent, the research results can promote the further improvement of the interpretation level of the results of the over-advance prediction of tunnel fault fracture zones, and realize the technological progress from "experience-based, varying quality" to "intelligent identification, fast and effective", which can provide favorable technical support for the intelligent construction of tunnels, and has a good prospect of engineering application.
2024 Vol. 41 (11): 90-95 [Abstract] ( 5 ) HTML (1 KB)  PDF  (2075 KB)  ( 1 )
       Urban Rail Construction
96 Study on Seismic Performance of Subway Station with Tenon Column End Joints
XIONG Zhongming, QIAN Hao, CHEN Xuan, TIAN Penggang, NIU Jianhui, XIE Zhixun
Research purposes: To improve the deformation capacity and construction efficiency of center columns in assembled subway stations, a mortise-and-tenon prefabricated column end connection was proposed. In this paper, ABAQUS finite element software was used to analyze the damage mode, force mechanism and seismic performance of prefabricated column end connections, and to compare the difference in dynamic response between assembled subway stations with mortise-and-tenon prefabricated column end connections and cast-in-place subway stations under seismic action.
Research conclusions: (1) The tenon-bolt column end joints have better load carrying capacity, deformation capacity, and energy dissipation capacity, and better seismic performance. (2) Compared with cast-in-place subway stations, the structural interstory displacement angle of the assembled subway station with tenon-bolt column end joints increases slightly, but the tensile damages of the center columns and the connection of the top base plate with the side walls are smaller. (3) The design of tenon-bolt joints effectively enhances the center columns and the connection of top base plate with side walls by releasing some of the column bottom constraints, which effectively improves the safety of the center column and enhances the collapse resistance of the structure. (4) The results of this paper have reference value for the application and promotion of dry prefabricated column end connections in subway stations.
2024 Vol. 41 (11): 96-103 [Abstract] ( 14 ) HTML (1 KB)  PDF  (1629 KB)  ( 2 )
       Engineering Materials
104 Study on Freeze-thaw Properties of Calcium Sulfate Whisker Concrete
LIU Minghui, JIA Siyi, WANG Xiaoqing, XU Zhou
Research purposes: In northern China, concrete structures not only face freeze-thaw cycles but also suffer from abrasion caused by sediment and gravel during flood seasons, leading to significant durability degradation. Adding high-strength, high-modulus fibers can effectively improve durability. This study investigated the concrete used in a high-speed railway bridge in northern China. By incorporating calcium sulfate whisker (CSW), freeze-thaw and abrasion tests were conducted on C40 and C60 CSWC, and the effects on durability were analyzed.
Research conclusions: (1) Incorporating CSW significantly improved the freeze-thaw and mechanical properties of CSWC. (2) The optimal surface performance under freeze-thaw and abrasion occurred with 5 kg/m³ of CSW. (3) A plastic microstrain-based freeze-thaw damage model was established to predict frost resistance durability. (4) The research results can provide a theoretical basis for the improvement of concrete durability, and have guiding significance for the practical application of CSWC in cold regions of northern China.
2024 Vol. 41 (11): 104-111 [Abstract] ( 11 ) HTML (1 KB)  PDF  (1010 KB)  ( 1 )
       Risk Management and Research
112 Safety Risk Evaluation of Substructure Construction of Deep Valley Long-span Bridges
CHEN Shitong, MENG Xiangyu, LI Linhao
Research purposes: As the center of gravity of railroad construction gradually shifts to the southwest region, deep valley long-span bridges are widely used in complex and dangerous areas. Aiming at the problems of many potential risk factors and limited accuracy of traditional assessment methods for deep valley span bridges, we take a deep valley span bridge in Southwest China as the research object, establish a risk identification and optimization system based on the Delphi method (DELPHI) versus the work-risk decomposition method (WBS-RBS) and carry out the risk assessment research based on the fuzzy hierarchical analysis method (FAHP) coupled with the results of the risk matrix method (LS) to improve the accuracy and rationality of the evaluation results from both risk identification and assessment.
Research conclusions: (1) The WBS-RBS is optimized by DELPHI, which can comprehensively and accurately identify potential risk sources, and the RBS risk decomposition structure system is determined based on the optimized 206 RBM identification results. (2) Adopting three-value coupling calculation to derive the risk degree to identify the significant risk sources can avoid the influence of single-value chance on the assessment results, and identify seven major risk sources, such as equipment quality defects, personnel working without safety measures, and equipment fixing connection is not secure. (3) In addition to the seven major risk sources, in order to improve the rigor of the assessment process, the unreasonable preparation of the construction program and flooding as a single-value risk source still need to be focused on. (4) The research in this paper can provide theoretical support and methodological reference for the safety risk evaluation of deep valley long-span bridges.
2024 Vol. 41 (11): 112-117 [Abstract] ( 8 ) HTML (1 KB)  PDF  (1733 KB)  ( 1 )
       Engineering Economy and Management
118 Research on Intelligent Control of Subway Construction Investment Based on Big Data
DUAN Xiaochen, YANG Jing, WANG Hui, WANG Dan
Research purposes: Due to the complexity, sequence, space and openness of investment consumption factors in subway construction projects, the existing fixed investment control mode has far failed to meet the requirements of investment randomness and nonlinear evolution, and it is urgent to reform the subway investment control management mode. Therefore, this paper comprehensively uses BIM, Python technology, fuzzy mathematics, BP neural network, acquired value theory and PDCA cycle method to build an intelligent prediction and control method for subway construction investment.
Research conclusions: (1) The basic database of subway construction investment is established, and the cause and countermeasure database of subway project investment is constructed. (2) Using SPSS factor analysis, rough set theory, fuzzy mathematics combined with BP neural network, the overall construction objective of the whole line is obtained. (3) Integrated PDCA cycle and acquired value theory carry out dynamic investment optimization control for key control projects, significantly improving the overall management efficiency and level of the project. (4) The computer aided intelligent control software for subway construction investment was established and applied in Chengdu subway construction example. (5) The research results can provide a feasible plan for the investment control of the entire subway line construction.
2024 Vol. 41 (11): 118-123 [Abstract] ( 7 ) HTML (1 KB)  PDF  (502 KB)  ( 1 )
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