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2022 Vol. 39, No. 7 Published: 2022-07-15

Terminal,Station yard and Building Main Line:Railway and Rail Main Line:Bridge Engineering Main Line:Tunnel Engineering Main Line:Engineering Survey and Design Blast Technology Risk Management and Research

Main Line:Engineering Survey and Design

	1	Research on the Progress of Dynamic Response of Pile-soil Composite Foundation under Train Load
		WU Honggang, GUAN Wei
		Research purposes: Under the train load, pile-soil composite foundation will produce dynamic action, and even cause strength failure or overall deformation and destruction, which seriously threaten the safety of train operation. Therefore, it is urgent to study the dynamic characteristics of pile-soil composite foundation under train load, which is of great significance to effectively improve the stability of railway subgrade and ensure the safety of high-speed train. This paper analyzes the reinforcement mechanism and failure mode of pile-soil composite foundation, summarizes the research status of domestic and foreign scholars on the dynamic response of pile-soil composite foundation under different dynamic loads and the dynamic response law of several commonly used different pile type composite foundation under train loads. On this basis, it points out the shortcomings of current research and puts forward the research problems that need to be paid more attention in the future. Research conclusions: (1) Although the dynamic response of pile-soil composite foundation under different dynamic loads presents different characteristics, the response of pile body is greater than that of soil body under dynamic loads, which is consistent with the action mechanism of pile-soil composite foundation, whether under static or dynamic loads, piles bear most of the load. Therefore, the research on the dynamic response of pile-soil composite foundation should focus on the response of piles, but the influence of soil between piles should not be ignored. (2) Pile materials, shape of pile, pile cap, thickness of mattress layer, modulus of composite soil and other factors will influence the dynamic characteristics of pile-soil composite foundation, and the dynamic response characteristics of pile-soil composite foundation under train load are also related to the speed of the train, train load, cycle times and so on. It is generally believed that the rigid pile composite foundation has good seismic performance, and gravel or gravel mats exhibit good isolation. (3) The soil vibration response of pile-soil composite foundation composed of different pile types under train loads attenuates along the depth direction, but the pile body amplifies in a certain part. Therefore, the dynamic characteristics of pile should be considered when designing composite foundation of different pile types. (4) The research conclusion can provide a theoretical basis for the optimal design of railway pile-soil composite foundation.
		2022 Vol. 39 (7): 1-11 [Abstract] ( 3068 ) HTML (1 KB) PDF (650 KB) ( 2040 )

	12	Research on the Meso-structure Evolution of Cinder Improved Soil under Freeze-thaw Cycles
		REN Kun, WANG Haitao
		Research purposes: In order to study the effect of freeze-thaw cycles on the micro-structure of cinder improved soil (CIS), CT scanning tests and triaxial tests of CIS under different freeze-thaw conditions were carried out, and the pore development laws and elastic modulus evolution laws of CIS under different freeze-thaw cycles, freezing temperature and initial moisture content were obtained. The development law of each area was analyzed through the zoning observation of the sample section. The relationship between meso-structure evolution and elastic modulus was established. Research conclusions: (1) With the increase of freeze-thaw cycles, the area of high-density zones decreased gradually, the area of medium-density and low-density zones increased gradually, and the area of pore zone basically remained unchanged. The first five freeze-thaw cycles had a great influence on the structure of CIS. (2) With the decrease of freezing temperature, the area of high-density zones decreased slightly, and the area of medium-density and low-density zones increased slightly, but the change degree is not significant. The area of pore zone remained basically the same. The change of high-density, medium-density and low-density zones were more sensitive in the range of -5℃ ~-15℃. (3) With the increase of moisture content, the area of high-density zones decreased gradually, the area of medium-density and low-density zones increased, and the area of pore zone also increased to a certain extent, and the development of each zone showed an accelerated trend. Under the condition of single factor, the number of freeze-thaw cycles had the greatest influence on the sample, followed by the initial moisture content of the sample, and the freezing temperature had the least influence. (4) The damage evolution model established according to the freeze-thaw damage factor had a certain accuracy, and can better reflect the relationship between meso-structure evolution and elastic modulus under freeze-thaw, which can provide a reference for the prevention and control of subgrade frost damage in cold region.
		2022 Vol. 39 (7): 12-17 [Abstract] ( 2875 ) HTML (1 KB) PDF (1208 KB) ( 1889 )

	18	Research on the Reinforcement Effect of Cement-soil Mixing Pile on Collapsible Loess Foundation
		JIA Jianqing, ZHAO Yangyang, JIA Chao, XIN Chengping, ZHANG Bangxin
		Research purposes: To determine the reinforcement effect of cement-soil mixing pile on collapsible loess foundation, taking one section located at Taiyuan-Jiaozuo high speed railway engineering as an example, firstly, physical and mechanical properties of the loess were tested, the collapsibility indexes and grades were determined, and mechanical characteristics and change law were also analyzed. Then the reinforcement plans and the parameters of tested piles were designed, and the pile quality was tested by core pulling test. Thirdly, the characteristic value of bearing capacity of composite foundation reinforced by cement-soil mixing pile with different parameters were all studied using bearing capacity test of composite foundation as well as numerical simulation method. Finally, the test subgrade was paved on the foundation reinforced by cement-soil mixing pile, and the settlement laws were determined by means of field monitoring, theoretical calculation and numerical simulation. Research conclusions: (1) The quality of the three kinds of water-cement ratio test piles was great and the unconfined extrusion strength was 1.6 MPa, 1.8 MPa and 2.0 MPa respectively which were larger than 1.0 MPa, and the water-cement ratio in this foundation construction is 0.5. (2) The characteristic value of bearing capacity of single pile composite foundation from field monitoring was 261~266 kPa, and they were 282.87 kPa and 209 kPa respectively obtained from theoretical calculation and numerical simulation. (3) The field monitoring subsidence, theoretical calculation subsidence and numerical simulation subsidence were 21.17 mm, 31.25 mm and 26.14 mm, respectively. All of these indicated that the strength of composite foundation could meet requirement of engineering design. (4) The research results can provide reference for the design of reinforcement scheme on soft foundation of high speed railway.
		2022 Vol. 39 (7): 18-24 [Abstract] ( 2342 ) HTML (1 KB) PDF (1590 KB) ( 1940 )

	25	Research on the Application Effect of Intelligent Micro Infiltration and Moistening Technology in the High Speed Railway Subgrade
		ZHAO Yonghu, MI Weijun, MIAO Xueyun, HAN Kan, ZHANG Xiaobo, SUN Mengke
		Research purposes: Taking effective measures to prevent and control the threat of desertification environment to the operation safety of high-speed railway line is one of the major railway engineering problems to be studied. Based on the background of desertification in Ningxia areas, the application effect of intelligent micro infiltration and moistening technology in desertification controlling of high-speed railway subgrade was objectively evaluated, which provided scientific basis for ecological environment protection engineering construction along high-speed railway in desertification areas. Research conclusions: (1) As an innovative technology, the intelligent micro infiltration and moistening technology has been successfully applied to the field of soil and water conservation and sand controlling of high-speed railway subgrade slope, which is a new technology and method of sand controlling along the high-speed railway in desertification areas. (2) The intelligent micro infiltration and moistening technology can obviously improve the moisture and nutrient conditions of subgrade slope soil, and provide the necessary basic environment for vegetation growth at the same time. (3) Compared with the ordinary maintenance conditions, the survival rate, density, coverage and plant height of vegetation on the embankment slope of the micro infiltration and maintenance section have been greatly improved, which can not only achieve the ecological and environmental protection purpose of sand controlling, but also play a good landscape effect. (4) The research results can provide a reference for sand controlling and ecological protection along the high-speed railway subgrade in desertification areas.
		2022 Vol. 39 (7): 25-29 [Abstract] ( 2715 ) HTML (1 KB) PDF (672 KB) ( 1938 )

Main Line:Railway and Rail

	30	Comparative Research on the Railway Track Quality Index in Different Countries
		WANG Yingjie, CHU Hang, SHI Jin, ZHANG Yuxiao, KANG Yanbo
		Research purposes: Track quality index has been widely used in railways maintenance in the world, which is an important index to evaluate the status of track irregularity. The calculation methods of the track quality index of China, United Kingdom, United States, Japan, Canada, India and Poland are introduced, and the characteristics, similarities and differences of the track quality indexes of these countries are compared. With some track measured data, the sensitiveness of track quality index on local fluctuation and single irregularity defect is performed. Research conclusions: (1) The standard deviation is chosen as the basic statistical indicator of track irregularity in most of the countries, and there is a little difference for the track quality index calculation methods in different countries. (2) Compared with the other methods, Chinese TQI index, Polish J index and American TRI index can capture the track irregularity local fluctuation, which have strong sensitivity to local fluctuation. (3) For comprehensive track quality index, Chinese TQI index and Polish J index can reflect the effect caused by single irregularity defect, which have strong sensitivity to geometry defect. (4) The research conclusions are of great significance for guiding railway maintenance and improving quality criteria.
		2022 Vol. 39 (7): 30-35 [Abstract] ( 4010 ) HTML (1 KB) PDF (528 KB) ( 2034 )

	36	Running Performance Analysis of High-speed Railway Trains under Different Track Irregularity Spectrum Excitation
		HE Binbin, FENG Lei, FENG Yulin, ZHOU Wangbao, LIU Xiang
		Research purposes: Taking the high-speed railway line of a three-span continuous beam bridge with a main span of 48 m+80 m+48 m, two simply supported approach bridges on each side and 200 m long roadbed as the research object, using CRH3, CRH2C and CRH380A, with German low interference spectrum (German spectrum) and Chinese ballastless track spectrum (Chinese spectrum) is regarded as the initial track irregularity, the track irregularity caused by the settlement of the side pier of the continuous beam obtained by the mapping relationship is regarded as the additional track irregularity, and the running performance of different types of high-speed railway trains under excitation of different track irregularity spectrum is evaluated respectively. Research conclusions: (1) The calculation results of the dynamic model of vehicle-rail-continuous beam bridge are in good agreement with those of the literature model. (2) The Chinese ballastless track spectrum is obviously better than the German low interference spectrum in comfort, stability and safety. (3) Under the initial track irregularity, the influence on security is in the order of CRH380A > CRH3 > CRH2C, the influence on comfort is CRH3 > CRH380A> CRH2C, and the influence on stability is CRH3 > CRH380A > CRH2C. (4) Under the additional track irregularity, the influence on security and comfort is the same as the initial track irregularity, and the stability varies greatly with the settlement value of the side pier. When using the German low interference spectrum, the influence on stability is in the order of CRH3 > CRH380A > CRH2C, and when using the Chinese ballastless track spectrum, the influence on stability is in the order of CRH2C > CRH3 > CRH380A. (5) The research results can provide some reference for the design and checking of continuous girder bridges with main span in high-speed railway lines.
		2022 Vol. 39 (7): 36-43 [Abstract] ( 3308 ) HTML (1 KB) PDF (801 KB) ( 1904 )

	44	Dynamic Characteristics Analysis of Prefabricated Floating Slab Track in Special Vibration Section
		LIU Jinhui, ZHENG Xiaolian, REN Juanjuan, LIU Wei, WANG Weihua
		Research purposes: In order to meet the vibration reduction requirements of special sections of urban rail transit with a speed of 120 km/h, and to facilitate construction, maintenance and repair, a new fabricated floating slab track structure was proposed. Based on the finite element method and vehicle-track system coupling dynamics, the modal analysis, dynamic index evaluation and vibration reduction effect evaluation of the structure were carried out, and the effects of different slab lengths were compared and analyzed. Research conclusions: (1) When the length of floating slab is 3.55 m, 4.75 m and 5.95 m, the fundamental frequency of structure is 12~14 Hz. The increase of slab length will reduce the natural frequency, while has little influence on modal shape of each order. (2) The running safety, stability and track structure stability of 4.75 m and 5.95 m floating slab all meet the requirements. In order to meet the requirements of all dynamic response indexes, the steel spring supporting stiffness of the 3.55 m floating slab should be greater than 8.5 MN/m. (3) The root mean square differences of frequency division vibration level corresponding to the slab length of 3.55 m, 4.75 m and 5.95 m are 14.32 dB, 15.49 dB and 16.48 dB. The longer the floating slab is, the worse the vibration reduction effect at low frequency 1~5 Hz, but the better the vibration reduction effect at high frequency 20~125 Hz, which is more in line with the vibration reduction requirements of urban rail transit. In the specific structural design, the type of slab shall be reasonably selected according to the construction conditions and actual vibration reduction requirements in combination with the results of environmental impact assessment. (4) For the special vibration reduction section of urban rail transit, the research result can provide theoretical guidance for the selection and application of prefabricated floating slab track.
		2022 Vol. 39 (7): 44-49 [Abstract] ( 3301 ) HTML (1 KB) PDF (1338 KB) ( 1921 )

Main Line:Bridge Engineering

	50	Analysis of Adaptability of the 32 m Simply-supported Box Beam Used in the 350 km/h High Speed Railway with Speed Increasing to 400 km/h
		WANG Wei
		Research purposes: The train speed of high speed railway is one of the important indicators to measure the development level of national railway and 400 km/h is the goal or development direction pursued by many countries. China Railway has organized the "CR450 Scientific and Technology Innovation Project" in 2021. Based on the test data of 32 m simply supported box beam of Beijing-Shanghai highspeed railway in the speed range of 420 km/h of EMU, the adaptability of 32 m simply supported box beam used in the 350 km/h high speed railway to 400 km/h operation of EMU was done by the analyses of its natural frequency, vertical stiffness and dynamic response under the action of EMU. Research conclusions: (1)The measured vertical natural frequency of 32 m simply supported box beam is 6.68~7.03 Hz, which is greater than the fundamental frequency limit of 5.1 Hz determined by the relevant literature according to the 440 km/h simulation calculation. (2) The vertical stiffness of the 32 m simply supported box beam can ensure the safety and ride comfort of EMU running at 400 km/h. (3) The structure bearing capacity of the 32 m simply supported box beam meets the operating load requirement of EMU running at 400 km/h. (4) The maximum measured vertical vibration acceleration of 32 m simply supported box beam is 0.27 m/s², which is less than limit value of 5.0 m/s² specified in Code for Design of High Speed Railway. (5) Within the speed range of 420 km/h of the EMU, the measured wheelset lateral force of main line is generally less than 20 kN, the measured values of the lateral amplitude at the midspan of beam and the top of pier are small, and the measured lateral relative displacement of the rail support on both sides of the adjacent beam ends of the ballastless track is less than the limit value of 1 mm specified in Code for Design of High Speed Railway. The vertical and lateral stiffness of 32 m simply supported box beam used in the existing 350 km/h high speed railway can ensure the safety and ride comfort of EMU running at 400 km/h. (6) The research results can provide technical support for raising the speed of 32 m simply supported box beam used in 350 km/h high speed railway to 400 km/h.
		2022 Vol. 39 (7): 50-54 [Abstract] ( 3531 ) HTML (1 KB) PDF (417 KB) ( 1899 )

	55	Distribution Law of Longitudinal Seismic Force for Multi-span Simply Supported Girder Bridge of High-speed Railway
		ZHANG Yongliang, WANG Chunyang, LIU Zhengnan, ZHU Hailong, JI Xiang
		Research purposes: In order to study the influence of CRTSⅡ slab ballastless track system on the longitudinal seismic force of bearing and end-spine structure, integrated track and bridge model and conventional model are established respectively for the multi-span 32 m high-speed railway simply supported girder bridge. When considering the constraint of track system, the distribution law of the longitudinal seismic force in pier bearings is studied through adjusting pier height and span number. By discussing the relationships among the seismic force of pier bearings, abutment bearings and end spines, the distribution law of the longitudinal seismic force in the whole bridge structure is further analyzed. Research conclusions: (1) Considering the effect of longitudinal constraint, the longitudinal seismic force of the fixed bearing for multi-span simply supported girder bridge presents a parabolic distribution that is small at the boundary and large in the middle span, while the longitudinal seismic force of the fixed bearing in the conventional model is distributed in a straight line. The bearing has an obvious region where the seismic response has been amplified, and the area, located near the middle span of the bridge, is related to the pier height and span number. (2) The amplification area coefficient increases with the increase of span number and decreases with the increase of pier height. When the span number is 50, the longitudinal seismic force of the bearing near the middle span is about 20 percent larger than that in the conventional model. (3) The distribution law of longitudinal seismic force of bearing relates to a dual effect incorporating the impact of track system on natural vibration period and the influence scope of boundary effect. (4) The research conclusions could be applied to the seismic design of simply supported girder bridge with gentle terrain and approximately equal height for all piers, which goes for high-speed railway.
		2022 Vol. 39 (7): 55-60 [Abstract] ( 3477 ) HTML (0 KB) PDF (723 KB) ( 1907 )

	61	Reasonable Wall Thickness Calculation of Offshore Super-long and Large Diameter Permanent Steel Casing
		ZHANG Haishun, CHEN Ningxian, TANG Yougang, HU Ruihai
		Research purposes: As an auxiliary measure for hole formation of pile foundation, the permanent steel casing of the main bridge of Macao-Taipa Fourth Cross-sea Bridge has a diameter of 2.8 m and a length of nearly 100 m, which is not considered to participate in force. The steel casing of offshore pile foundation is usually constructed by pipe rolling machine or full casing rotary drilling machine. It was very important to ensure reasonable wall thickness of permanent steel casing without deformation when it was not pulled out eventually, which was closely related to construction safety and economic cost. In order to avoid economic waste caused by excessive wall thickness of steel casing, and large deformation caused by insufficient wall thickness in the process of sinking, a 3D model of steel casing and surrounding soil and water was established to simulate the construction process of steel casing subjected to torsion under pressure. Research conclusions: (1) The full-rotary full-casing drilling machine or pipe rolling machine is suitable for sinking of super-long and large-diameter steel casing on the sea. According to the rotary and pressing motion of steel casing, the calculation method of eight loads is given. (2) By means of the research on hoop stress and axial stress, buckling stability of permanent steel casing wall of pile foundation with different pile positions and pile lengths, the steel casing should be in accordance with the permanent structure design on the basis of the bidding documents require. The static calculation and local buckling calculation of safety factor are given, and the reasonable wall thickness of steel casing is determined. (3) The research conclusion can provide a reference for the stability and safety analysis and reasonable wall thickness of permanent steel casing in the drilling pile drilling process using full casing full rotation or pipe rolling machine for super-long and large-diameter offshore pile.
		2022 Vol. 39 (7): 61-67 [Abstract] ( 3474 ) HTML (0 KB) PDF (987 KB) ( 1976 )

Main Line:Tunnel Engineering

	68	Analysis of Dynamic Response of the Arbitrary Shaped Tunnel in Shallow-buried Saturated Soil
		CHANG Jianmei, TIAN Jiayi, YIN Rongyu, FENG Huaiping
		Research purposes: The surrounding rock of tunnels widely distributed in the eastern coastal areas of China is rich in water, which will pose a great threat to the safe construction and operation of tunnels under the action of seismic waves. At present, the shape of tunnel cross-section is complex and changeable, so the analysis and study of the dynamic response of arbitrary shaped tunnel in saturated soil plays an important value for the seismic design and construction of these areas. Based on the analytical solution method, this paper first establishes the analytic solution by common mapping and wave function expansion method under Biot saturated porous media dynamics theory. After the model and calculation process are verified to be correct and effective, the effects of incident wave number, porosity of saturated soil medium and Poisson's ratio on dynamic response of tunnel are studied. Research conclusions: (1) Incident wave number has significant influence on the dynamic stress concentration of tunnel. The dynamic stress response at low wave number is significantly greater than that at high wave number, and the distribution pattern of dynamic stress at high wave number tends to be more complex. (2) The porosity has little influence on the pore pressure response, and the pore pressure response distribution is basically consistent. In the case of higher porosity, the pore pressure concentration coefficient at the side wall increases, so the reinforcement treatment of surrounding rock at the side wall should be considered in design and construction. (3) The influence of Poisson ratio on pore pressure response is significant. The increase of Poisson's ratio not only affects the distribution law of tunnel pore pressure response, but also affects the amplitude of the response, which may induce the local increase of pore pressure in the vault, arch bottom, arch shoulder and arch foot. (4) The research conclusions can provide support for seismic design and safety construction of tunnels with various shapes in water-rich area.
		2022 Vol. 39 (7): 68-73 [Abstract] ( 3259 ) HTML (0 KB) PDF (1204 KB) ( 2012 )

	74	Failure Analysis of Tertiary Semi Diagenetic Tunnel Based on Discrete Element Theory
		LI Yao, ZHU Haoyang, LUO Yanbin, CHEN Jianxun, YUAN Shuai, LIU Weiwei, XU Zilong, ZHANG Lixin
		Research purposes: In order to reveal the deformation and failure mechanism of super long-span tunnel in tertiary semi diagenetic stratum with high water content, in this paper, the dynamic process of deformation and instability of Bailuyuan tunnel without support is simulated by discrete element analysis, and the variation law of particle indirect contact force and the derivation process of surrounding rock cracks in the process of tunnel collapse are studied. Research conclusions: (1) Tunnel collapse has experienced four stages of sharp deformation, local failure, failure development, and overall collapse. (2) During the deformation and failure of the tunnel, the cracks at the sidewalls on both sides of the tunnel gradually develop into through joints with an included angle of 44° with the ground. (3) When tunnelling in the high water content section or water-rich section of the tertiary semi diagenetic strata, a reasonable grouting scheme should be put forward on the basis of proper treatment of waterproof and drainage, the systematic bolts should be cancelled, and the feet-lock bolts should be highlighted. (4) The research results can provide a theoretical basis for the design and construction of such tunnels.
		2022 Vol. 39 (7): 74-79 [Abstract] ( 3432 ) HTML (0 KB) PDF (2580 KB) ( 1946 )

	80	Analysis of the Influence of Excavation Disturbance and Non-Darcy Seepage on Tunnel Water Inflow
		FU Helin, AN Pengtao, WU Yimin, CHENG Guowen
		Research purposes: The change of permeability coefficient caused by tunnel excavation disturbance and Non-Darcy seepage in the disturbed area are important factors affecting the prediction accuracy of tunnel water inrush. In order to improve the prediction accuracy of water inrush, a simplified calculation model of tunnel water inrush in the disturbed area is constructed. The calculation expressions of water inrush and external water pressure of the structure are deduced based on the theory of underground hydraulics, Non-Darcy's law and linear superposition principle, and the degradation analysis is carried out. After that, the sensitivity of characteristic parameters is studied. Finally, the rationality of the model and the correctness of formula derivation are tested by comparing with the field measured data. Research conclusions: (1) The increase of the thickness and permeability coefficient of the disturbed area weakens the water blocking capacity of the surrounding rock, resulting in the increase of the water inflow of the tunnel. Improving the construction technology level and reducing the degree and scope of disturbance can weaken the variability of the permeability coefficient of the surrounding rock in the disturbed area, which has a positive effect on the water blocking during the operation period of the tunnel. (2) Properly improving the impermeability of the grouting ring can effectively reduce the water inflow of the tunnel, but with the increase of the impermeability of the grouting ring, the effect on the reduction of the water inflow of the tunnel tends to be gradual. (3) Considering the change of permeability coefficient of surrounding rock in disturbed area and the influence of Non-Darcy's seepage, the prediction error of water inflow can be reduced from 8.9% to 4.2%. (4) The research results can provide theoretical guidance for considering the influence of excavation disturbance on tunnel water inflow.
		2022 Vol. 39 (7): 80-85 [Abstract] ( 2633 ) HTML (0 KB) PDF (604 KB) ( 1893 )

Blast Technology

	86	Numerical Simulation Research on the Dust Dynamic Diffusion of Cutting Deep Hole Blasting
		GUO Yao, MENG Haili
		Research purposes: With the frequent occurrence of catenary operation accidents caused by dust pollution in electrified railway network, higher requirements are put forward for cutting blasting in close proximity to existing railways. Based on this, starting with the qualitative analysis of the diffusion law of blasting dust, this paper analyzes the dynamic diffusion characteristics of cutting deep hole blasting dust and the diffusion distribution range of dust with different particle sizes by using ANSYS Fluent numerical software, and puts forward the blasting construction scheme at different distances close to the existing line. Research conclusions: (1) The movement process of blasting dust can be roughly divided into three stages: the enlightenment stage, the stretch stage and the expansion stage. The duration is controlled within 1.5 s, 5 s and over 60 s respectively. (2) The dust above the blasting area is mainly concentrated around the blasting area, while the dust in front of the free face spreads along the direction of air flow, and the maximum vertical height that dust particles can reach is about 14 m. (3) When 10 m ~15 m away from the position of the blasting free face along the direction of air flow, dust particles with particle size > 100 μm are basically deposited by gravity; at 15 m ~20 m, dust particles with particle size between 40 μm and 100 μm also settle rapidly; beyond 25 m, dust particles with particle size < 20 μm are dominant. (4) When the distance between the edge of the blasting area and the catenary is less than 20 m, the blasting throwing direction should be parallel to the existing railway direction, and the direction of air flow at the initiation should also be parallel to the existing cable direction. At the same time, if water mist dust removal measures are adopted, the time of water mist generation should not be later than the initiation time of the main blasting area by 1.5 s, and the height of water mist should be controlled at 14 m. (5) The research results can be popularized and applied in the field of close to electrified railway or strict control requirements for blasting dust.
		2022 Vol. 39 (7): 86-93 [Abstract] ( 2786 ) HTML (0 KB) PDF (2271 KB) ( 1932 )

Terminal,Station yard and Building

	94	Research on the Deformation Monitoring Method of Eaves Board of No-plateform-column Canopy with Distributed Optical Fiber
		ZHANG Hao, ZHANG Lei, ZHAO Weigang, ZHANG Guangyuan, LIU Boqi
		Research purposes: No-plateform-column canopy is widely used in high-speed railway stations in China. Under the long-term influence of wind load, eaves board, roof panels and other structures are easy to loosen, warp or even fall as a whole, affecting the safety of railway operation. In the daily maintenance of canopy, there are some problems such as the limit of skylight point, the blind area of maintenance and the lack of maintenance means, so it is urgent to find an effective method to monitor the canopy structure. The distributed optical fiber sensor has the characteristics of full distribution and is suitable for health monitoring of large area eaves board. Based on the finite element software ANSYS, the stress and deformation of the canopy and its eaves board when the high-speed railway passes the station are simulated and analyzed, the layout scheme of optical fiber sensor is designed, and the damage and deformation of the eaves board are monitored through model test. Research conclusions: (1) Under the action of train wind, the eaves board bears the impact of two times of alternating positive and negative pressures when the front and rear of the train pass by. (2) Under the condition of rivet damage at the boundary of eaves board, the distributed optical fiber sensor can effectively monitor the deformation process of the eaves board. The damage was accurately located and the alert threshold of deformation was determined according to the strain variation of the fiber. (3) The stiffening ribs on the board can obviously restrain the deformation and deformation transmission of the eaves board, and can prevent the expansion of the damaged area to a certain extent. (4) The research results can provide reference for health monitoring of railway platform canopy eaves board and other plate and shell structures.
		2022 Vol. 39 (7): 94-101 [Abstract] ( 2281 ) HTML (0 KB) PDF (1289 KB) ( 1906 )

	102	Research on the Vibration and Noise Characteristics and Control of the Under-line Bridge-construction Integration Station
		LIU Jiahai, HU Yongli, LIU Fangbo, YANG Jizhong
		Research purposes: In order to understand the formation mechanism, transmission path and distribution characteristics of vehicle-induced vibration and noise in the under-line station, a 'train-track-structure-soil' coupling dynamic model was established to study the vehicle-induced vibration of the station caused by the train passing through the station. The acoustic finite element method was used to calculate the secondary structure noise, and the statistical energy analysis was used to calculate the environmental noise in the station hall. The low vibration noise design of the under-line bridge-construction integration station was carried out according to the research results. Research conclusions: (1) Compared with the bridge-construction separation station, the vibration level of the waiting hall of the bridge-construction integration station increases by 30 dB above 30 Hz, while the difference of vibration level is only 3.5 dB in the low frequency range below 30 Hz, which is more sensitive to human body. (2) Due to the hard connection between the bearing layer and the surrounding structure, the vibration of the bearing layer of the bridge-construction integrated station is smaller. The secondary structural noise is 5.5 dBA lower than that of the bridge-construction separated station, and the environmental noise is 1.4 dBA lower than that of the bridge-construction separated station. In general, it has better acoustic and vibration comfort for passengers. (3) The use of heavy damping track can effectively suppress the vibration of the station building. The vertical vibration acceleration of the floor is reduced by more than 10 times, and the noise reduction of the secondary structure can reach more than 25 dBA. The sound absorption and insulation measures in the platform layer and the hall layer can reduce the environmental noise in the waiting hall by more than 15 dBA. (4) The relevant vibration and noise control schemes can provide reference for the vibration and noise reduction design of integrated transportation hubs.
		2022 Vol. 39 (7): 102-108 [Abstract] ( 2899 ) HTML (0 KB) PDF (1169 KB) ( 1871 )

Risk Management and Research

	109	Construction Risk Analysis of Subgrade Engineering in Perilous Mountainous Areas
		BAO Xueying, LI Haiwen
		Research purposes: In order to realize the dynamic assessment of the construction risk of subgrade engineering, a subgrade engineering construction risk assessment model based on the dynamic weight-2-dimensional cloud model is proposed by taking the subgrade engineering in the special environment in the perilous mountainous area of Southwest China as the research subject. Research conclusions: (1) Based on the risk influencing factors existing in general subgrade construction, and considering the complex geological environment and characteristics of subgrade construction in perilous mountainous areas, the risk assessment system of subgrade engineering construction in perilous mountainous areas is constructed, and the dynamic risk information of subgrade engineering construction feedback is taken as the benchmark, and the dynamic weight model is used as the index to give weight. (2) A 2-dimensional cloud model for risk assessment was constructed with risk probability and risk loss as the basic variables, and a certain section of subgrade engineering from Xingwen to Bijie section of Chengdu-Guiyan Railway was taken as an example. The model was used to evaluate the risk of its construction, and MATLAB is used to draw the risk cloud diagram to intuitively reflect the degree of risk, and finally the risk level is determined by calculating the nearness degree to ensure the accuracy of the evaluation result. (3) The results show that the risks of subgrade construction in perilous mountainous areas mainly come from the natural and geological risks as well as the material, equipment and construction technology risks caused by them. (4) The research result can provide a reference for the risk prevention and control of subgrade construction in perilous mountainous areas.
		2022 Vol. 39 (7): 109-115 [Abstract] ( 3426 ) HTML (0 KB) PDF (913 KB) ( 1916 )

	116	Research on the Risk Transmission in the Construction Stage of Urban Rail Transit Project
		LIU Weiqing, ZHANG Hao, XU Zhifen
		Research purposes: A large number of participants, as well as the connections between them, constitute a network of project activity nodes in the process of urban rail transit project construction. The internal and external risk factors of the project interact with the activity nodes, and these factors conduct risk transmission along the links between nodes in the network, so the impact is difficult to control. Therefore, this research uses the infectious disease model of network transmission dynamics for reference, simulates the risk transmission mechanism, adjusts different parameters, and explores the changes of risk transmission speed and scope, so as to provide reference for construction managers to implement risk decision-making. Research conclusions: (1) Using the SIR warehouse model to simulate the risk transmission process of the active node network during the construction phase of urban rail transit projects, the results show that reducing the effective transmission rate or increasing the unit's successful elimination rate can effectively curb risk transmission. (2) When the actual risk conductivity is greater than 1, it means that the information carried by risk factors is uncertain for participants. Once a risk event occurs, passive solutions need to reduce or cut off the connection between participants and risk factors in time. Safe and reliable resources can replace materials with risk impact in time to avoid the collapse of the overall network. (3) When the actual risk conductivity is less than 1, it means that the risk factors are relatively complete and accurate for the participants. Participants can take proactive precautions. According to the risk factors that have been mastered, the risk management capability of each activity node in the construction phase of urban rail transit projects is improved, and project management systems and emergency plans are formulated to help participants affected by risks return to normal operation as soon as possible.
		2022 Vol. 39 (7): 116-121 [Abstract] ( 3021 ) HTML (0 KB) PDF (710 KB) ( 1861 )