Abstract:The determination of the support pressure for face stability of tunnel headings is a critical issue to ensure the normal construction of the tunnel and the safety of the surrounding environment. Most existing studies are based on the assumption of isotropic soil, which have neglected the influence of soil strength anisotropy. Based on the finite element limit analysis software OptumG3, a numerical model for the lower bound support pressure for face stability of tunnel headings in anisotropic undrained clay was introduced, and the validity of the numerical model was verified by comparative analysis of a case study. Then, parameter sensitivity analysis of the lower bound support pressure for face stability of tunnel headings in anisotropic undrained clay was carried out, and the corresponding empirical calculation method was proposed. The results show that: the bearing capacity coefficients Nc and Nγ are exponential and linear with the ratio of tunnel buried depth C/D, respectively; in anisotropic clay, the correction coefficient rm of Nc is in a power function relationship with the soil shear strength ratio k, while Nγ is not affected by the soil shear strength ratio k; the failure model of tunnel heading is similar to a chimney type in the isotropic and anisotropic clay, but the distribution ranges are different, in which the distribution range is larger in the isotropic clay.

Abstract:Earthwork is a main part in the construction process. In order to solve time -consuming, laborious problems and low accuracy of earthwork calculation in construction process by traditional methods, a method for earthwork calculation based on tilt photography was proposed. Firstly, the unmanned aerial vehicle (UAV) tilt photography was used to collect point cloud data of terrain. Then, after point cloud simplification, it established the terrain surface model for different construction periods through Poisson surface reconstruction method. Finally, the volume difference between the two models was calculated as the volume of earthwork after Boolean operations, forming a complete path from data acquisition to model establishment and then to earthwork calculation, and the method was verified and applied through the engineering example. The results showed that the proposed method can meet the accuracy requirements of earthwork in practical engineering applications, providing reference for fast and accurate calculation of earthwork quantity.

Abstract:At present, the dynamic amplification coefficient of bridges defined in domestic and foreign codes cannot fully reflect the influence of various complex factors on the dynamic performance of bridges. In the design stage, it is a normal state for every bridge to be calculated. Accordingly, this article established the high-speed train-trackbridge coupled vibration system model to analyze the dynamic characteristics of 33 bridges under different vehicle types and speed loads. Based on the probability statistics theory, the concept of spectral function was introduced, taking the natural vibration period of structure as the index. The function expression suitable for calculating the dynamic amplification coefficient spectrum of the bridge structure under vehicle bridge coupling was obtained at a certain guarantee rate. Another 10 bridges were selected for vehicle-bridge coupling calculation to verify the applicability of the dynamic amplification coefficient spectrum method. The results show that the method has certain guarantee rate and applicability. Finally, some suggestions are given to improve the accuracy of the method.

Abstract:In order to study the effect of replacement ratios on compressive strength of recycled ceramic coarse aggregate concrete. 10 groups of recycled ceramic coarse aggregate concrete test blocks with different replacement ratios and 1 group of ordinary concrete comparison test blocks were made. Uniaxial compression tests were performed on the test blocks after curing for 7 d and 28 d respectively. The failure process and phenomena of the specimens with different replacement ratios were compared and analyzed. The effects of different replacement ratios on compressive strength and peak strain of concrete were studied. The calculation method of 7 d and 28 d compressive strength of recycled ceramic coarse aggregate concrete was put forward. The research results show that the compressive strength of recycled ceramic coarse aggregate concrete decreases with the increase of the replacement ratio, and the peak strain first decreases and then increases with the increase of the replacement ratio. When the replacement ratio is 40%, the peak strain is the smallest.

Abstract:To simulate the stress characteristics of web gap more accurately in steel plate girder bridge, a global model of a four-span continuous steel plate composite girder bridge was established. Considering various structure of main girder, the local deformations of web gap were analyzed. Based on the deformation characteristics, the simplified structural mechanics model was established, and the correctness of the model was verified by the stress test data in real bridge and finite element calculation results. Considering the small length and large thickness of web gap, the shear stress and normal stress of web gap of web gap were further determined by using this model. The results show that the web gap is affected by the coaction of "rotation" and "displacement". It would be more consistent with the actual stress characteristics when the web gap was simplified as the beam consolidated at both ends, and subjected to the coaction of rotation" and displacement. The ratio of shear stress and normal stress at the end of web gap is independent of the load, related to the length and thickness of the structure. The conclusions could provide a basis for multi-axis evaluation of web gap.

Abstract:The use of double-row steel pipe pile cofferdams in subsea engineering is gradually increasing, but there is less analysis on the influence of cofferdam parameters on the deformation and force of steel pipe piles. The calculated results are compared with the measured results to verify the reasonableness of the finite element model. By studying the influence of pile distance on the force deformation of steel pipe pile cofferdam, it is concluded that with the simultaneous increase of double-row pile distance, the internal force deformation of steel pipe pile increases, and then slow down. The pile distance increases by the same magnitude, and the influence of the outer pile distance on the cofferdam is greater than the increase of the inner pile distance. When the number of piles is certain, increasing the outer row pile distance can control the deformation more effectively than evenly distributed steel pipe piles. This paper may provide reference for the design and construction of similar projects.

Abstract:Scientific identification and analysis of the impact of industry factors on carbon emission will be an important basis for formulating targeted emission reduction measures to achieve carbon peak in 2030. Taking the airport aircraft carbon emission of 31 provinces (including autonomous regions and municipalities) from 2007 to 2016 in China as a sample, the study firstly analyzed the temporal and spatial evolution characteristics of China's airport aircraft carbon emission. Then， it used the LMDI decomposition method to discuss the degree of airport openness and airport connectivity strength, transportation intensity and energy consumption intensity on aircraft carbon emissions. Finally, it put forward emission reduction suggestions for improving route planning, optimizing network structure and fleet assignment in response to the impact. The results show that the average annual growth rate of aircraft carbon emission in airports across the country is about 9.46%. The carbon emission level of airport aircraft in the eastern and southwestern regions are relatively high, with Guangdong having the largest added value, Tibet the smallest value, Hebei the fastest growth rate, and Shanghai the slowest growth rate. The changes in the degree of airport openness, airport connection strength, and transportation intensity promote the growth of carbon emission. Among them, the degree of airport openness has the most significant impact on carbon

Abstract:The structure of subway engineering is relatively complex, which leads to modeling difficulties and low efficiency. There is no common component type of subway in the existing Revit modeled components, so there are relatively few subway engineering cases adopting Revit modeling. Aiming at this problem, a rapid modeling method for subway entrances and exits was proposed, and the Revit API was combined with the C# for the Revit’s secondary development. Taking the structural construction drawing of a certain subway entrance as an example, it used Revit to identify the two-dimensional drawings to quickly generate a solid 3D model of the subway entrance, and quickly placed the corresponding structure of the steel bar structure on the basis of the entity solid model. By applying this method to an actual project, it effectively improves the efficiency of Revit’s modeling of subway entrances and exits, and provides the convenience for the use of BIM technology in subway projects.

Abstract:Public policy is an important means to promote the realization of national macro-strategic goals, so the research to the relevant policies for the carbon neutral development of the civil aviation and further improvement are particularly important for the realization of the industrial and the national energy saving and emission reduction targets. The research adopts bibliometrics and content analysis method to sort out and analyze the relevant policies issued by the Civil Aviation Administration of China since the "11th Five-Year Plan" period. It is found that the current policies are characterized by a late starting time, a small number of policies and short length, and an absolute majority of guiding documents. And there are mainly the following four problems: the policy objectives of carbon neutral development are not clear; the macro of policy measures is overwhelming; the use of policy tools is insufficient and there is a lack of independent policy evaluation institution. Administrative departments in this industry should strengthen policy research, formulate specific carbon neutral policy objectives, make full use of various policy means, optimize the policy measures and the system and mechanism of policy evaluation, so as to further improve the system of policies and regulations and improve the quality of policies.

Abstract:In order to study the environmental benefits of urban rail transit projects brought by carbon emission reduction, construction and operation data were integrated to construct a carbon payback period calculation model for urban rail transit projects. Taking 5 rail transit lines in Changsha city as the research object, based on a reasonable forecast of future passenger traffic, the carbon footprint changes of these 5 lines during construction and operation from 2014 to 2050 were quantitatively analyzed. It is found that the urban rail transit project has significant carbon emission reduction benefits. All five lines can fully recover the carbon emissions of the construction stage by 2050, and afterwards, carbon emissions trading will also generate positive benefits. At the same time, it maintains that the carbon emission reduction benefits of rail transit projects are directly affected by the saturation of passenger traffic.

Abstract:In order to realize the reasonable allocation and scientific management of maintenance resources of ballastless tracks，it is very important to deploy intelligent sensors at key positions of railway lines to monitor the key parameters of service state of ballastless tracks. Combined with the actual needs of high -speed railway maintenance, health monitoring scheme and BIM technology were visually integrated. The collision detection function of sensor layout, operation process optimization and operation process simulation were realized. The monitoring data were transmitted to the background database management system through the network and linked with the BIM models. The analysis and evaluation algorithm were embedded in BIM analysis model and database to realize real-time early warning of disease and timely find out the disease problems on site. Research shows that applying BIM technology to the intelligent monitoring project of ballastless tracks can effectively improve the installation accuracy and efficiency of monitoring equipment. It provides strong support for the preventive state maintenance of the lines and comprehensively improves the maintenance management level.

Abstract:In order to study the fatigue performance of Q460ME steel plate for rail vehicle body, MTS landmark electro-hydraulic servo fatigue testing machine was used to carry out fatigue tests on Q460ME steel plates with two types of thickness specifications. The stress ratio was -0.1 and the loading frequency was 60 Hz. The tests were carried out based on lifting method. The conditional fatigue limit parameters under different survival rates were calculated by means of stress concentration factor correction. The test results were compared with DVS1612 standard. It can be shown that the stress concentration factor of the test sample is 1.25, the lifting diagrams of Q460ME steel plate with two types of thickness specifications can be closed, and the fatigue limit values calculated by the lifting diagram decrease with the increase of thickness, in which the fatigue strength values of Q460ME with 5 mm and 8 mm thickness are significantly higher than that of S355 steel in DVS1612 standard. Obvious crack source, crack propagation zone and instantaneous fracture zone can be seen in the fracture section of three thickness specimens of Q460ME steel plate. The fatigue crack source occurs at the corner of the rectangular section surface and is a single crack source. There are obvious "beach" fatigue striations in the crack propagation zone, which are fan-shaped and perpendicular to the local crack propagation direction. The instantaneous fracture zone is ductile fracture, which reflects the good toughness of the sample

Abstract:The geometric state control of high-speed railway ballasted lines is the key task of daily operation and maintenance. This paper takes the Hefei-Nanjing high-speed railway on-site maintenance work as the background, proposes a geometric state maintenance control method for high-speed railway ballasted lines, compares and analyzes the uneven vector height deviation before and after the maintenance, and evaluates the maintenance effect in combination with the high-speed railway vehicle and track dynamic analysis. The research results show that the use of large machine tamping, manual fine-tuning operation, rail grinding and other control methods can effectively reduce the deviation of level, triangle pit, orbit, vertical vector height, and the improvement rate of most indicators is more than 40%, which effectively improves the running comfort of high-speed railway ballasted lines. The analysis of vehicle-track dynamics shows that the derailment coefficient and wheel load reduction rate after maintenance are reduced by about 50%, and the vertical vibration acceleration of the vehicle body has decreased by 66.67%, which effectively improves the running comfort and safety. The proposed method may provide reference for the maintenance and repair of ballasted high-speed railway.

Abstract:Aiming at the low efficiency of using traditional image recognition methods to diagnose self-explosion faults in aerial images of insulators, and the current image detection method based on deep learning is mostly carried out through the cascade network, which is difficult to directly locate the Self-explosive defect block, a method for directly detecting the self-explosive defect block is proposed. The number of defective samples is expanded through Generative Adversarial Networks to solve the problem of insufficient defective samples. In addition, the Faster R-CNN detector is improved to enhance its ability to locate small-scale targets through feature fusion strategy. Experiments show that when using this strategy to directly detect insulator Self-explosion defects, it can also achieve good results close to the cascade network, and greatly reduce the workload, save the training time, so it is feasible.

Abstract:Due to the fact that the effect of node blocking on traditional task dynamic scheduling results in poor emergency task dynamic scheduling, this paper proposes a data center emergency task dynamic scheduling method based on queue migration. It builds an emergency task dynamic scheduling model, analyzes the cloud platform task dynamic scheduling process according to the model, and completes the optimization operation from the background, so that the emergency task request is sent to the appropriate queue of the dynamic scheduling center for dynamic scheduling, thus obtaining the best mapping from the emergency task to the processing unit. It analyzes the time characteristics of data processing emergency tasks, solves the processing blocking problem of each node, and determines the effective time and waiting time of data processing tasks. Combined with controlling the queue migration process of dynamic scheduling nodes, the dynamic scheduling process of emergency tasks in data center is designed. Experimental results show that this method can complete all tasks with the completion rate of more than 95% and the cut-off missing rate of always less than 18%, and it has a good dynamic scheduling effect.