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20 March 2022, Volume 41 Issue 03 Previous Issue    Next Issue
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Transportation+Big Data & Artificial Intelligence
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Transportation+Big Data & Artificial Intelligence

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Evaluation and Restoration of Passenger Boarding Efficiency under COVID-19 Prevention and Control REN Xinhui, SHI Xiaoting 2022, 41(03): 1-8.  DOI: 10.3969/j.issn.1674-0696.2022.03.01 Abstract ( )   PDF (3418KB) ( )   The prevention and control of COVID-19 has brought about many changes in the process and measures of air passenger safety travel, and maintaining the social distance requirement seriously affects the efficiency of boarding passengers with fast and efficient targets. Based on cellular automaton boarding simulation model, boarding strategies such as random (RD), outside-in (OI), back-to-front (BF), reverse pyramid (RP) and half-block (HB) were chosen to re-evaluate passenger boarding efficiency under the COVID-19 prevention and control. The sensitivity analysis of relevant influencing factors was carried out, and the operable countermeasures and combination of countermeasures that could restore boarding efficiency were put forward. The research shows that keeping social distance will prolong boarding time by an average of 2.4 ~ 2.8 times, resulting in a decline in the boarding efficiency of 58.0% ~ 64.1% of passengers. The aisle distance is the main factor affecting the boarding efficiency. Taking the random (RD) strategy as an example, the boarding efficiency decreases by 17.2% for every 0.4 m spacing increase. Using OI boarding strategy, restricting passengers carry-on luggage and using double cabin doors and other boarding strategies can recover an average of 3.0%, 3.2% and 27.9% of the efficiency loss, and using the combination of countermeasures can recover 40.3% of the efficiency loss, which can effectively recover the reduced boarding efficiency under the guarantee of the safety of epidemic prevention and control. References | Related Articles | Metrics

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Classification of Air Traffic Control Sectors Based on Dynamic Operation Characteristics ZHANG Qiqian, XU Lipeng, ZHANG Saiwen 2022, 41(03): 9-17.  DOI: 10.3969/j.issn.1674-0696.2022.03.02 Abstract ( )   PDF (2779KB) ( )   The scientific classification of control sectors is helpful to understand the operation characteristics of different types of sectors and provide optimization basis for regulation and operation management. In view of the lack of research on sector classification at home and abroad and the current situation of extensive classification special management, an air traffic control sector classification method based on dynamic operation features was studied through machine learning algorithms such as fuzzy clustering and genetic algorithm. Based on the ADS-B radar track data, the index set reflecting the dynamic operation characteristics of the sector was established. Kernel function and genetic algorithm were introduced to improve the fuzzy C-means clustering algorithm, and the improved algorithm was used to classify 97 sectors in East China and Central South China. The optimal clustering number was determined by Silhouette coefficient and KXB (Kernel Xie-Beni) index, and five types of sectors with different operating characteristics were defined according to the clustering results. The rationality of sector classification results was tested by simulation experiments. The research results show that: the clustering accuracy of the improved algorithm on IRIS and WINE data sets is 4.62% and 26.96% higher than that of the traditional FCM algorithm and the improved algorithm has high robustness. The dynamic operation characteristics of the sector is an effective way to correlate and compare the spatial behavior of the aircraft, the complexity of the sector and the workload of the controller. There are obvious differences in the operation characteristics of different types of sectors, which shows that the fuzzy clustering algorithm is effective in dealing with the practical problem of sector classification compared with the traditional hard clustering algorithm. References | Related Articles | Metrics

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Optimization of Maritime Search Vessel Allocation WANG Jun, YANG Chunlin, WANG Meirong 2022, 41(03): 18-24.  DOI: 10.3969/j.issn.1674-0696.2022.03.03 Abstract ( )   PDF (2950KB) ( )   Maritime search is an important part in the process of maritime search and rescue (SAR). In order to complete the search and cover task in a given sea area with the least vessel resources in the shortest time, the allocation of search vessels in multiple sub-sea areas with different probability distributions was studied. According to the probability distribution of the target in each sub-sea area, the time when the ship arrived in each sub-sea area, the ship search ability and other parameter characteristics, a ship allocation model was constructed with the goal of minimizing the expected sum of time to complete the search coverage of each sub-sea area. According to the characteristics of relevant parameters involved in the proposed model, a priority queue algorithm was designed to solve the model, and the genetic optimization algorithm was used to find the optimal solution. The research results show that the proposed model can allocate reasonable search vessels for multiple sub-sea areas with different probability distribution based on the algorithm, and make efficient, reasonable and scientific search vessel allocation scheme for decision makers in the first time. References | Related Articles | Metrics

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Triggering Process and Risk Factor Coupling of Marine Traffic Accident Based on N-K Model MA Jianwen1,2,3， WANG Bo1,3, HUANG Zishuo2 2022, 41(03): 25-30.  DOI: 10.3969/j.issn.1674-0696.2022.03.04 Abstract ( )   PDF (1262KB) ( )   In order to clarify the inherent law of marine traffic accident risk and the coupling relationship of multiple factors, the triggering process of marine traffic accident was analyzed based on the principle of trigger. The N-K model was used to quantitatively study the coupling relationship among the four risk factors of human, ship, environment and management in the marine traffic system, and the collected data of water traffic accidents from January 2012 to August 2019 were calculated. The results show that the marine traffic accident is positively correlated with the number of coupling risk factors. The coupling risk value of human, environment and management is the largest when the three factors are coupled, and the coupling risk value of human and management is the largest when the two factors are coupled. Therefore, it is necessary to strengthen the control of management and human factors in the marine traffic system, which is important to improve the level of risk pre-control of marine traffic accident. References | Related Articles | Metrics

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PCA-Logistic Prediction Method of Traffic Accident Tendency Based on Psychological Status of Bus Drivers HU Liwei, GUO Zhi, ZHANG Suhang, FAN Zijian, YIN Xiufen 2022, 41(03): 31-36.  DOI: 10.3969/j.issn.1674-0696.2022.03.05 Abstract ( )   PDF (2089KB) ( )   A PCA-Logistic traffic accident tendency prediction method based on the psychological status of bus drivers was proposed. Aiming at the problem that some independent variables in the traditional logistic regression model may have multicollinearity, which may affect the prediction results, the principal component analysis method was used to reduce the dimensions of the independent variables, and the PCA-Logistic traffic accident prediction model was constructed. The two classification thresholds were determined by the Jordan index method to represent the occurrence of traffic accidents in the prediction results, so as to achieve the purpose of improvement. Then, combined with the psychological health questionnaire survey results of 1004 bus drivers and the statistical data whether drivers have had traffic accidents in recent one year, the model was verified, and according to the research results, the targeted measures and suggestions to improve the mental health of bus drivers were put forward. The research results show that: among the 9 psychological factors, somatization, obsessive-compulsive symptoms, depression and hostility are the dangerous psychological factors affecting drivers driving safety; the proposed PCA-Logistic traffic accident prediction model is effective, and the threshold division is reasonable. References | Related Articles | Metrics

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Short-Term Traffic Volume Prediction of Arterial Road Using TVF-EMD Method ZHAO Leina1,2, WANG Yanpeng2, SHAO Yiming2, LI Shuqing2, WEN Xinyu1 2022, 41(03): 37-44.  DOI: 10.3969/j.issn.1674-0696.2022.03.06 Abstract ( )   PDF (3143KB) ( )   In order to describe the hidden non-linear and non-stationary characteristics in the short-time traffic data, improve the prediction accuracy of short-time traffic, and then better build an intelligent transportation platform, a hybrid prediction model based on time-varying filtered empirical modal decomposition (TVF-EMD) and least-squares support vector machine (LSSVM), i.e., the TVF-EMD-LSSVM model, was proposed. Among the TVF-EMD-LSSVM model, the TVF-EMD method was mainly used to reduce the influence of the non-stationarity implied in the data on the prediction results, while the LSSVM model was designed to trace the evolutionary trend of the non-linear information contained in the data. The research results show that compared with empirical mode decomposition (EMD), the decomposition results of TVF-EMD method are more suitable for traffic flow prediction. Meanwhile, the combination of this decomposition technique and LSSVM model can provide better prediction results. Compared with LSSVM model, the mean absolute error, mean relative percentage error, root mean square error and root mean square relative error of the proposed model are reduced by 9.186, 18.947%, 13.591 and 0.316% respectively, and its equalization coefficient is increased by 0.082 1. References | Related Articles | Metrics

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Influencing Factors of the Satisfaction of Passengers with Cars for Bus in Small and Medium Cities Based on Ordered Probit Model CHEN Jun, FAN Jingkun, LI Xiaowei, MA Ruiyang, ZHU Shalang 2022, 41(03): 45-52.  DOI: 10.3969/j.issn.1674-0696.2022.03.07 Abstract ( )   PDF (1749KB) ( )   Through the investigation and analysis of bus passengers satisfaction and its influencing factors, the targeted improvement of bus service quality will help to promote the transfer of passengers with cars from small car travel to public transport and improve the bus sharing rate. Taking the public bus in Weinan city as the research object, the bus satisfaction data of 690 passengers with cars were obtained by random sampling survey. The functional relationship between bus satisfaction and individual characteristics of passengers, travel activity characteristics and bus service quality characteristics was established by using the ordered Probit model, and the effect of significant influencing factors on bus satisfaction was quantitatively evaluated by marginal effect analysis. The research results show that gender, daily bus traveling time, waiting time, transfer convenience, travel information service, waiting environment, tick price and bus stop setting are the significant factors that affect the bus satisfaction of passengers with cars. Measures such as improving departure frequency, popularizing bus information prompt system, adjusting bus route setting and tick price can effectively improve the overall satisfaction perception level of bus service of passengers with cars. References | Related Articles | Metrics

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Reliability Analysis and Engineering Application of Tunnel Safety Assessment QIN Haiyang1, SU Ning2, TANG Yongjing3 2022, 41(03): 53-57.  DOI: 10.3969/j.issn.1674-0696.2022.03.08 Abstract ( )   PDF (3649KB) ( )   In order to improve the safety and reliability of tunnel structure considering uneven lithology and variable parameters, the characteristics of reliability analysis methods were summarized. Two tunnel reliability analysis methods were obtained: probabilistic method and non-probabilistic method. The former was such as moment method and response surface method, and the latter was such as robust method. The probabilistic reliability method (moment method) was used to analyze the surface settlement caused by the construction of a subway, which was verified by the finite element method. The non-probabilistic reliability method (robust method) was used to analyze the structural safety of a return air tunnel, and the safety evaluation was carried out. The results show that the maximum settlement obtained by the finite element method is 14.2 mm, which does not fluctuate with the change of the settlement warning value S0; the maximum settlement obtained by the robust method is 24.1 mm, the failure probability PF is equivalent to 2.13%, and PF decreases with the increase of S0. The tunnel support resistance is greater than the surrounding rock pressure, and the design of the return air tunnel meets the safety requirements. When the uneven lithology and variable parameters are considered, the reliability analysis can make a more comprehensive dynamic assessment of tunnel safety, which has important engineering application significance. References | Related Articles | Metrics

Transportation Infrastructure Engineering

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Experimental Study on Stress Detection of Steel Strand Based on Self-magnetic Flux Leakage Effect LIU Shangkai1,ZHOU Jianting1,ZHANG Xianghe2,ZHAO Ruiqiang3,ZHANG Xiaoting1 2022, 41(03): 58-64.  DOI: 10.3969/j.issn.1674-0696.2022.03.09 Abstract ( )   PDF (3783KB) ( )   In order to realize the stress detection of steel strand based on self-magnetic flux leakage (SMFL) effect, the tension test of 1 860 grade steel strand was carried out. The variation law of surface magnetic flux leakage intensity changing with the tensile stress was studied. The grading standard of steel strand stress based on SMFL effect was initially established. Meanwhile, the influence of specimen length and lift-off height on magnetic flux leakage intensity was also explored. The results show that the normal component By of magnetic flux leakage intensity is positively correlated with the tensile force value F. The By-F curve has a phenomenon of “steep on both sides and gentle in the middle”, and its gradient changes significantly during the loading process; the gradient curve Ky-F of normal component of magnetic flux leakage field has two turning points, which can divide stress value during the stretching process of the steel strand into three intervals: 0～31.24%, 31.24%～71.79%, 71.79%～100% ultimate bearing capacity. By measuring the change trend of the Ky-F curve, the interval of the stress value of the steel strand at a certain moment can be judged. As the lift-off height increases, the variation range of the leakage magnetic field intensity during the loading process decreases; as the length of the specimen increases, the variation rate of the By-F curve tends to be stable. References | Related Articles | Metrics

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Seismic Performance of Slot Type Pipe Pier with Low Shear Span Ratio under Different Axial Compression Ratio WANG Guoqing1, SU Sibo1, JIA Xianzhuo2, LI Zhicong3 2022, 41(03): 65-71.  DOI: 10.3969/j.issn.1674-0696.2022.03.10 Abstract ( )   PDF (6370KB) ( )   For the seismic performance of slot connected precast piers, based on a bridge project of Rongwu Xinxian expressway, ABAQUS finite element analysis software was used to conduct numerical simulation analysis on slot connected piers with different axial compression ratio. The bearing capacity, ductility, hysteretic characteristics, skeleton curve, stiffness degradation and energy dissipation capacity of the three kinds of pier models were focused and analyzed. The test pieces of slot connection precast core filling pipe pier were designed and manufactured, and the components were verified by quasi-static test. The analysis results show that the failure mode of slotted pipe pier with low shear span ratio is shear failure. With the increase of axial compression ratio, its bearing capacity increases gradually, but the failure rate of pipe pier bearing capacity is faster and faster, the ductility coefficient decreases gradually, the stiffness increases gradually, and the energy dissipation capacity increases gradually. The slotted pipe pier with low shear span ratio has good seismic performance when the axial compression ratio is about 0.2. References | Related Articles | Metrics

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Stress and Deformation Behavior of Inclined Pile Group under Vertical Load LI Longqi, ZHAO Haoqiu 2022, 41(03): 72-78.  DOI: 10.3969/j.issn.1674-0696.2022.03.11 Abstract ( )   PDF (6458KB) ( )   The finite element software ABAQUS was used for numerical simulation and comparative verification of indoor model tests. Under the conditions of different inclination angles (0°, 5°, 8°, 12°) and different pile spacing (2.5d, 3.0d, 4.0d, 5.0d, 6.0d), the variation characteristics of the load-settlement (Q-S) curve, frictional resistance of pile side (q), vertical displacement (U) and bending moment (M) of pile body were analyzed under vertical graded loading of inclined and vertical pile groups. The results show that when the vertical load (Q) is small, the Q-S curve of inclined group piles shows a linear relationship, and gradually transforms from linear to nonlinear with the increase of Q value. The larger the Q value is, the more obvious the nonlinearity is. The relationship between q and Q is nonlinear; under the same Q value, the working performance of q of inclined pile foundation is different from that of vertical pile foundation. In the vertical pile foundation, there is Umiddle pile> Uside pile> Ucorner pile, and the vertical displacement difference gradually decreases with the increase of pile spacing (l). In the inclined pile foundation, when l is small, there is Uangle pile < Umiddle pile < Uside pile; when l is large, there is Uangle pile References | Related Articles | Metrics

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Shear Resistance of Gravel Soil and the Mechanical Properties of Pile Foundation in Deep Filling Area WANG Linfeng1, CHENG Ping2, TANG Ning1, YANG Liu1, ZHU Hang1 2022, 41(03): 79-86.  DOI: 10.3969/j.issn.1674-0696.2022.03.12 Abstract ( )   PDF (6345KB) ( )   As a common filling material in engineering, the shear properties of gravel soil were greatly affected by water content and stone content. In highway and railway construction, the mechanical properties of bridge pile foundations filling with gravel soil as the bearing foundation were also affected by multiple factors under the action of load. Based on the highway bridge construction project in Qijiangbei interchange section of Chongqing-Guizhou Expressway, the gravelly soil material was taken from the construction site for shear performance tests with different moisture content and stone content. Based on MIDAS/GTS finite element analysis software, the calculation model of pile foundation with gravel soil as filling material in deep filling area was established. The results show that the cohesion of gravel soil firstly decreases gently with the increase of water content, but when the water content exceeds a certain value, the cohesion decreases rapidly, and the angle of internal friction decreases with the increase of water content. The cohesion decreases with the increase of stone content and the angle of internal friction increases with the increase of stone content. The variation range of pile top settlement caused by heap load first is less than that caused by pile load first and then heap load, and the final settlement of pile caused by pile load first and then heap load and last pile load is relatively small. The variation law of pile side friction resistance is related to the loading size and order and depends on the relative displacement between pile and soil. References | Related Articles | Metrics

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Applicability Study on Calculation Method of Landslide Thrust and Safety Coefficient LI Huanhuan1, NI Wankui2, CHEN Shufeng1, LI Gang1 2022, 41(03): 87-92.  DOI: 10.3969/j.issn.1674-0696.2022.03.13 Abstract ( )   PDF (3586KB) ( )   Based on the explicit method of transfer coefficient (called conventional explicit solution for short), the calculation formula of landslide thrust considering pile reaction force was derived (that is, the improved explicit solution of transfer coefficient, which is abbreviated as the improved explicit solution). Then, the calculation model was established by using the FLAC 3D software platform, and the difference between the conventional explicit solution and the improved explicit solution was analyzed by the strength reduction method. The applicability of the conventional explicit solution, the improved explicit solution, the conventional implicit solution and improved implicit solution to calculate landslide thrust was discussed. The difference between the strength reduction method and the traditional limit equilibrium method to calculate the safety factor was discussed. The results show that the landslide thrust calculated by the improved explicit solution is larger than that of conventional explicit solution; using the landslide thrust calculated by the improved explicit method for support design can achieve the design safety factor; the landslide thrust and safety coefficient calculated by strength reduction method are smaller than those calculated by traditional limit equilibrium method. It is recommended that the improved explicit method of transfer coefficient is suitable for calculating landslide thrust, and the traditional implicit method of transfer coefficient is suitable for calculating the landslide safety factor. References | Related Articles | Metrics

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Experimental Study on the Effect of Bottom Ash Powder on the Performance of Porous Asphalt Mixture ZHAO Yao1, HU Yu1, WU Fan1, ZHOU Jiajie1, LENG Huimei2 2022, 41(03): 93-99.  DOI: 10.3969/j.issn.1674-0696.2022.03.14 Abstract ( )   PDF (3229KB) ( )   The feasibility of using municipal solid waste incinerated (MSWI) bottom ash powder (BAP) to replace limestone powder in different proportions for porous asphalt mixture (PAM) was discussed, and the influence of replacement rate on the properties of the mixture were studied through experiments. Marshall test method was used to design the mix proportion of conventional porous asphalt mixture. On this basis, the mix proportion design of porous slag asphalt mixture with different replacement rates of BAP (mass fractions of 25%, 50% and 100% respectively) was carried out, and the influence of BAP replacement rate on the optimal asphalt dosage was analyzed. Based on the laboratory test results, the effects of BAP replacement rate on the high temperature performance, low temperature performance, water stability and water permeability of the mixture were analyzed. Results indicate that the performance indexes of the designed porous slag asphalt mixture can meet the requirements of the corresponding specifications. The optimal asphalt content and water permeability of the mixture are highly affected by the replacement content of BAP; however, the high and low temperature performance and water stability of the mixture are limited affected. References | Related Articles | Metrics

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Pavement Performance and Modification Mechanism Analysis of Ceramic Fiber Asphalt Mixture WANG Xiushan1, ZHOU Hengyu1, ZHANG Xiaoyuan1, FAN Taotao2 2022, 41(03): 100-106.  DOI: 10.3969/j.issn.1674-0696.2022.03.15 Abstract ( )   PDF (12255KB) ( )   As a novel thermal resistance material, ceramic fiber has the potential to improve the high temperature performance of the asphalt mixture. Through rutting test, immersion Marshall test, freeze-thaw splitting test and low-temperature bending test, the pavement performance of ceramic fiber modified asphalt mixtures was evaluated. The action mechanism of ceramic fiber modified asphalt mixture was analyzed by scanning electron microscopy (SEM). The results show that after adding ceramic fiber, the high-temperature properties and physical and mechanical properties of the mixture are significantly improved, and the water stability and low-temperature properties are slightly enhanced. Further microscopic analysis shows that the ceramic fibers distributed in the asphalt mixture can increase the content of structural asphalt and enhance the viscosity of asphalt through adsorption, so as to improve the interfacial force between asphalt and mineral aggregate. Furthermore, fiber in the mixture can form a three-dimensional dispersed network system and transfer stress, and then play the role of reinforcement and crack resistance, which plays an important role in improving the road performance of asphalt mixture finally. References | Related Articles | Metrics

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Stirring and Dispersing Uniformity of PVA Fiber Bundle Based on Texture Features CAO Yuanwen1, XIA Jie1, LIAO Ke1, ZENG Jianmin2, CHENG Zhihao3 2022, 41(03): 107-112.  DOI: 10.3969/j.issn.1674-0696.2022.03.16 Abstract ( )   PDF (3823KB) ( )   In order to improve the uniformity of PVA fiber bundle mixing and dispersing in cement matrix, the PVA fiber bundle stirring and dispersion test was carried out and the uniformity was studied by digital image processing technology and adopting gray level co-occurrence matrix theory, which was based on the texture characteristics of PVA fiber bundles. The statistical texture characteristics of PVA fiber under different working conditions were obtained, and the variation curves of the relationship between the angular second-order moment, entropy value and mass ratio, stirring speed and stirring time were given, and the uniformity evaluation was analyzed. The research results show that the statistical texture characteristics of PVA fiber can be used to quickly and accurately evaluate the mixing and dispersing uniformity of PVA fiber. The optimal mass ratio of PVA fiber bundle to fly ash is 1∶45, the optimal mixing speed is 700 r/min and the optimal stirring time is 3 min, which can improve the stirring and dispersing effect of PVA fiber bundles. References | Related Articles | Metrics

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Experimental Study on Dewatering of Hydraulic Dredging Sludge Frame by Vacuum Method YANG Yang1, LIU Congyang2, WU Liqing2, QIU Zhenfeng2 2022, 41(03): 113-119.  DOI: 10.3969/j.issn.1674-0696.2022.03.17 Abstract ( )   PDF (5838KB) ( )   Nowadays, hydraulic dredging is a common way to dredge urban river channels, but its generated silt has high water content, large volume and difficult separation of mud and water. The frame vacuum preloading method was put forward, and its dehydration effect and influencing factors were explored through experimental research. The technology of frame vacuum preloading dewatering could effectively solve many problems of traditional vacuum preloading and had a good effect of sludge dewatering. The sludge drainage rate decreased sharply from the maximum value, the drainage volume increased rapidly, the final drainage rate was low, and the drainage volume finally tended to be stable. The smaller the spacing of the filter pipes in the frame structure, the larger the initial drainage rate of the test tank and the larger the drainage. When the size of the test model increased, the dehydration effect was improved. The volume of silt decreased obviously, and the smaller the spacing of filter pipes in the frame structure was, the larger the reduction of volume decreased. With the increase of size, the reduction of sludge volume increased gradually. The smaller the spacing of the filter pipes in the frame structure, the greater the shear strength of the cross plate of silt. With the increase of model size, the shear strength of cross plate of silt decreased gradually. The change law of moisture content of silt was opposite to that of shear strength of cross plate. References | Related Articles | Metrics

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Superelevation Design of Dedicated Ramp for Passenger Car PAN Binghong, ZHOU Xizhen, TIAN Qiuyue 2022, 41(03): 120-129.  DOI: 10.3969/j.issn.1674-0696.2022.03.18 Abstract ( )   PDF (4024KB) ( )   In order to ensure the safe driving of vehicles on dedicated ramps and make full and effective use of road resources, the research on superelevation index of dedicated ramps was enriched to further improve road safety and service level. China’s regulations on the setting of circular curve superelevation and the setting of maximum superelevation value abroad were combined. The characteristics of passenger and freight separation highway was considered. The setting of the maximum superelevation value of passenger car and truck mixed roads recommended in the “Technical Standards of Highway Engineering” and “Guidelines for Design of Highway Grade-Separated Intersection” was referred to. Firstly, based on the factors such as passenger car driving safety, passenger comfort, environmental factors, construction and maintenance and traffic composition, it was proposed by using the mechanical analysis and calculation method that the maximum superelevation value of the dedicated ramp for passenger cars in non-ice and non-snow conditions should be 10%, and the maximum superelevation value in the snow and ice environment should be 8%. Secondly, the advantages and disadvantages of the point mass-rigid body calculation model (PMR) and the point mass-suspension calculation model (PMS) were analyzed and compared, and a superelevation calculation model suitable for passenger car ramp was proposed. Thirdly, based on the current situation of vehicles generally over-speeding on the special ramp for passenger cars, the AASHTO recommended superelevation and lateral force coefficient distribution model was optimized and improved from the perspective of safety, and a new superelevation and lateral force coefficient distribution model based on dangerous speed and suitable for the superelevation calculation of special ramp for passenger cars was proposed. The proposed model could not only ensure the lateral stability of low-speed or normal driving passenger cars, but also significantly improve the lateral stability and comfort of high-speed passenger cars. Finally, according to the new allocation model, the recommended setting values of superelevation for the dedicated ramps for passenger cars with different design speeds and radius was proposed. References | Related Articles | Metrics

Transportation Equipment

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Fault Time Series Prediction Method of Straddle Monorail On-Board Air Conditioning System DU Zixue1, JIANG Dawei2, WU Jing3 2022, 41(03): 130-135.  DOI: 10.3969/j.issn.1674-0696.2022.03.19 Abstract ( )   PDF (1464KB) ( )   As an important part of urban rail transit, air conditioning system directly affects the comfort of passengers. The prediction of the time series of air conditioning system faults is helpful to reasonably formulate maintenance strategy and parts procurement scheme, so as to control the cost effectively. Aiming at the prediction problem of time series of air conditioning system faults, the seasonal autoregressive integral moving average model (X12-ARIMA model) was constructed by combining with Census X12 seasonal adjustment method, which was based on the analysis of the periodic fluctuation law and change trend of the number of faults. And the BP neural network model was established based on residual series. The predicted value of the improved X12-ARIMA-BP model was obtained by adding the predicted value of the two models, and compared with the predicted values of X12-ARIMA model, BP neural network model and ARIMA-BP variable weight combination. Taking Chongqing Rail Transit Line 3 as an example, four kinds of models were used to simulate and predict the fault number, based on the monthly failure data of air conditioning system for 7 years. The research results show that compared with the actual value, the mean absolute percentage error of the improved X12-ARIMA-BP model is 18.54%, which is 6.38% lower than that of X12-ARIMA model, 11.01% lower than that of BP neural network model and 4.75% lower than that of ARIMA-BP variable weight combination model. Compared with the other three kinds of prediction models, the improved X12-ARIMA-BP model has the best prediction effect. References | Related Articles | Metrics

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Comparative Experiment Study on Working Resistance of Type I and Type C Blades Based on the Same Blade-Edge HE Yutian1,3, LYU Pengmin2, ZHANG Jianbing1,3, GUO Longlong1,3, WU Wen2 2022, 41(03): 136-142.  DOI: 10.3969/j.issn.1674-0696.2022.03.20 Abstract ( )   PDF (4418KB) ( )   Blade shape has a significant effect on working resistance during soil bulldozing process, and the effect is usually measured by experimental comparisons. The edge position was introduced as a quantitative parameter for comparative analysis to make the working resistance of different shape blades on the same comparison premise. Taking sand as the pushing medium and I-shape blade and C-shape blade as the pushing tools, four identical edge positions were determined for the two kinds of blades, and the soil pushing test was carried out on the self-designed test device. Through comparative analysis, it is found that: under the condition of the same edge position condition, the working resistance of the C-shape blade increases significantly faster than that of I-type blade in the gradual increase stage, and soon reaches the stable stage of pushing. When the edge positions of the two blades are smaller or larger, the working resistance is close, and the maximum difference is no more than 4.2%. However, when the rake angle determined by edge position is close to the actual blade, the working resistance of the two blades shows opposite results at different working depths. That is, when the working depth is shallow, the working resistance of I-shape blade is relatively small, which can be reduced by 13.8% at most; when the working depth is deep, the C-shape blade is more conducive to the soil bulldozing, and the working resistance can be reduced by 16.1% at most. Therefore, the working resistance of the blade is closely related to the position of the edge, but under certain conditions, the influence of the working depth needs to be considered. Moreover, when the shape of the blade is different, the edge position can be regarded as a quantitative parameter in the working resistance comparison. References | Related Articles | Metrics

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Safety Risk Analysis of Cargo Loading and Unloading Operation of Gantry Crane Ship Based on AHP FAN Xiaobiao, WEI Zeliang, CHENG Zhiyou, ZHAO Junda, ZHOU Xidong 2022, 41(03): 143-148.  DOI: 10.3969/j.issn.1674-0696.2022.03.21 Abstract ( )   PDF (1687KB) ( )   In order to evaluate the maritime risks caused by ship safety risks more scientifically, the loading and unloading operations of gantry cranes were taken as the research object. According to the factors affecting the safety risks of gantry crane loading and unloading operations, the analytic hierarchy process was used to study and establish a safety risk evaluation model. The safety risk weight of loading and unloading goods by gantry crane with people, ship, environment and loading and unloading equipment as the main influencing factors was calculated. The influence degree of each factor on the safety of gantry crane loading and unloading operations was analyzed. The calculation results were analyzed, and the safety suggestions for loading and unloading goods by gantry crane were put forward. The research results show that the proposed safety risk assessment method and evaluation model consider the main factors affecting the safety risk of cargo loading and unloading operation of gantry crane, and reflect the characteristics of maritime risk caused by the safety risk of cargo loading and unloading operation of gantry crane. References | Related Articles | Metrics