In order to investigate the durability of fibergypsum-based cementation material, a composite material was prepared byincorporating polypropylene and ramie fibers into high-strength gypsum,fly ash, and slag in a ratio of 44:34:22. Sodium methylsilicate wasutilized for waterproofing the fiber gypsum-based cementitious material,and the effects of freeze-thaw cycles on its softening property, waterabsorption, and mass loss were studied after 5,15,25,45, and 90 daysunder the combined action of ${\mathrm{H}}_{2}{\mathrm{{SO}}}_{4}$ or $\mathrm{{NaOH}}$ corrosion andfreeze-thaw. Freeze-thaw strain testing, flexural and compressivestrength testing, as well as industrial computed tomography(CT) scanningwere conducted. The results indicate that fibers can mitigate bothelastic and plastic deformation of the gypsum-based cementitiousmaterial during freeze-thaw cycles. Furthermore, under the combinedeffect of acid-base corrosion and freeze-thaw cycles, NaOH causesgreater damage than ${\mathrm{H}}_{2}{\mathrm{{SO}}}_{4}$ does.After undergoing 90 days of freeze-thaw cycling with sodiummethylsilicate treatment applied to it, the flexural and compressivesoftening coefficients increase by 0.28 and 0.13 respectively comparedto specimens without waterproofing; meanwhile water absorption ratesdecrease by 1.56% while mass loss rates decreased by 9.52%. Asfreezing-and thawing times increase, pore development in specimens isstill dominated by small holes, and crack diameters are mainly between ${0.1}\sim 2\mathrm{\;{mm}}$ .

In order to investigate the durability of fiber gypsum-based cementation material, a composite material was prepared by incorporating polypropylene and ramie fibers into high-strength gypsum, fly ash, and slag in a ratio of 44∶34∶22.Sodium methylsilicate was utilized for waterproofing the fiber gypsum-based cementitious material, and the effects of freeze-thaw cycles on its softening property, water absorption, and mass loss were studied after 5, 15, 25, 45, and 90 days under the combined action of H₂SO₄ or NaOH corrosion and freeze-thaw. Freeze-thaw strain testing, flexural and compressive strength testing, as well as industrial computed tomography(CT) scanning were conducted. The results indicate that fibers can mitigate both elastic and plastic deformation of the gypsum-based cementitious material during freeze-thaw cycles. Furthermore, under the combined effect of acid-base corrosion and freeze-thaw cycles, NaOH causes greater damage than H₂SO₄ does. After undergoing 90 days of freeze-thaw cycling with sodium methylsilicate treatment applied to it,the flexural and compressive softening coefficients increase by 0.28 and 0.13 respectively compared to specimens without waterproofing; meanwhile water absorption rates decrease by 1.56% while mass loss rates decreased by 9.52%. As freezing-and thawing times increase,pore development in specimens is still dominated by small holes,and crack diameters are mainly between 0.1~2 mm.

Understanding the failure mechanism of cracked rock mass under the general stress state is essential for underground engineering construction safety. A series of true triaxial fracture tests on the sandstone with single pre-existing flaw were conducted. The failure modes of the cracked sandstone were analysed, and the multi-scale fracture characteristics and mechanisms of the basic types of crack were identified. Moreover, the influences of the stress state and the pre-existing flaw on the rock failure mechanism were summarized. The results indicate that the rock failure mode is controlled by the true triaxial stress and the pre-existing crack. Based on the multi-scale fracture characteristics, the fracture mechanism of the crack. The rise of minimum principal stress σ₃ can significantly reduce the percentage of the shear crack, while the rise of intermediate principal stress σ₂ conduces to the increase of the percentage of the tensile crack. The pre-existing flaw has a certain promoting effect on the initiation of the tensile crack, however, the true triaxial stress is the decisive factor controlling the rock failure mechanism.

In order to improve the traffic efficiency of aircraft routes in areas affected by strong convective weather and optimize the diversion path of aircraft under the influence of strong convective weather, a multi-objective diversion path planning method based on the non-dominated sorting genetic algorithm III(NSGA-III) was proposed. By constructing a flight environment model and delineating flight restricted areas according to airspace conditions, and on this basis, focusing on the impact of strong convective weather in the area where the aircraft was diverted, the aircraft operation cost was the lowest, the diversion angle was the smallest, and the non-linear coefficient was the smallest, with the goal of minimizing the impact of weather, using NSGA-III to comprehensively considered factors such as safety and economy and other factors, a multi-target diversion plan for a certain airspace route under severe convective weather was carried out, and simulation analysis was conducted. The research results show that NSGA-III can comprehensively consider the four proposed goals and calculate multiple effective alternative diversion paths. Under the conditions of selecting two diversion points and taking into account the economy and rationality of the operation while ensuring the safe operation of the aircraft, a total of 91 alternative routes are available.

In order to analyze the influence of evolution of the dominant order of wheel polygonal wear on the vibration response of the train-bridge coupling system, the key influencing factors and evolution patterns of the dominant order of polygon wear were summarized first. Meanwhile, the coupled dynamic model of the train-bridge system was established by utilizing a combined simulation approach with ANSYS and SIMPACK. Subsequently, the impact of evolution of the dominant order of wheel polygonal wear on the vibration response of the train-bridge coupled system under different operational mileages, train operating speeds, vertical stiffness of fasteners, and variations in wheel diameter, was explored. The research results indicate that the evolution of the dominant order of wheel polygonal wear significantly affects the dynamic response of the train-bridge coupled system. In general, when the wheels experience high-order polygonal wear, the lateral and vertical accelerations at the mid-span of the bridge increase significantly. Moreover, the wheel-rail force and derailment coefficient also increase significantly, with the train wheels experiencing momentary bouncing. This has an impact on both the quality of high-speed train operation on the bridge and the safe operation of the bridge structure, necessitating timely wheel re-profiling.

In order to investigate the feasibility of applying solidified shield muck in road construction, the shield muck from Nanjing Metro was taken as the research object, and the green polymer composite curing agent developed independently was used to solidify the shield muck. The impact of the curing agent dosage and maintenance age on the road performance indicators of the shield muck was analysed using various tests-unconfined compressive strength, direct shear test, California bearing ratio (CBR), resilient modules, and freeze-thaw cycle test. In addition, the micro-characteristics and solidification mechanism of the solidified soil were investigated by scanning electron microscope and X-ray diffraction. The results indicate that the composite curing agent can effectively improve the strength of solidified muck, and with the increase of curing agent dosage and maintenance age, the strength of solidified muck also increases. The CBR and resilient modulus of solidified shield muck substantially improve as the dosage of the curing agent elevates, and the solidified soil can well meet the requirements of the Specifications for Design of Highway Subgrades (JTG D30—2015) and Specifications for Design of Highway Asphalt Pavement (JTG D50—2017). The freeze-thaw resistance of shield muck is poor, while it can be effectively improved after curing treatment. The strength loss and mass loss of solidified soil are less than 20% and 1% respectively. The anti-freezing performance indicators meet the requirements of the specification. After the curing agent has been added to the soil body, the polymer components will absorb water and dissolve, creating a static chelating effect with the mineral ions in the soil, initially reducing the water content of soil and promoting the agglomeration between the soil particles. Meanwhile, the other components of the curing agent generate hydration reaction to form hydrated calcium silicate gel, ettringite and other substances to fill the internal pores of soil, making the soil structure denser and greatly improving the strength.

To explore the reasonable lining section thickness of shallow buried soft soil excavation channels under vehicle loads, two-dimensional finite element models were established using load structure method and strata structure method, respectively. The stress characteristics and safety factors of subway excavation channels under different burial depths, vehicle loads, and lining thicknesses were quantified. The research results indicate that regardless of the presence or absence of vehicle loads, the maximum bending moment of the tunnel is located at the arch foot or arch shoulder, and the minimum safety factor is located at the arch crown. According to the original design reinforcement, regardless of whether there is vehicle load, the safety factor decreases with increasing burial depth and increases with increasing secondary lining. Under shallow burial conditions, the safety factors calculated by the load structure method are smaller than those calculated by the stratum structure method. The calculation results of load structure method show that under vehicle load and surrounding rock pressure, the secondary lining thickness is 60, 90, 100 cm respectively, and the burial depth does not exceed 8, 12, 14.6 m respectively, meeting the safety factor requirements of the specifications. The calculation results of the stratum structure method show that under vehicle load and surrounding rock pressure, when the thickness of the secondary lining is 60, 80, 100 cm respectively, its burial depth does not exceed 12, 15.5, 19 m, which can meet the safety factor requirements of the specifications.

In response to the shortcomings in the construction of temporary support for tunnels, a assembly of temporary support was proposed, and the new structure was studied from the aspects of temporary support shape, assembly structure, and stress deformation. Taking the Shaojiatang Tunnel as the background, on-site monitoring data was collected and compared with traditional temporary support structures using finite element software. It can be concluded that excavation of the tunnel’s rear tunnel will have adverse effects on the deformation of the previous tunnel. Vertical temporary support has better control over the left and right arch waists, surface settlement, and total convergence deformation of the tunnel. Compared with traditional curved structures, it decreases by 16%, 20%, 55%, and 14%, respectively. Moreover, vertical temporary support can restore stability faster and shorten the dismantling distance. By using vertical temporary support, the initial support force of the tunnel is smaller and safer compared to the curved support, and the maximum vertical and lateral stresses are reduced by 58% and 73%, respectively. The mechanical characteristics of temporary support local structures were simulated using ABAQUS software. The results show that the forces and deformations of both prefabricated vertical and traditional temporary support structures can meet the requirements of the specifications. However, prefabricated temporary support structures have more advantages in construction efficiency and economic benefits, and choosing prefabricated temporary support is more suitable.

In order to facilitate the counting of turning traffic flow and to enhance the detection speed and accuracy of turning traffic flow at intersections, a deep learning-based method was suggested for detecting, tracking, and counting turning traffic flow at urban crossings. Initially, the YOLOv5s, which was lightweight and efficient, was chosen as the target detection framework after conducting a comparative analysis. Unmanned aerial vehicle (UAV) aerial photography was utilized to record video footage of traffic movement at urban intersections, resulting in the development of a dataset of vehicle aerial photography photos. The pre-training weights and the most recent weight files were utilized to conduct training and testing on the self-constructed dataset. The model evaluation shows that the vehicle detection model using YOLOv5 exhibits great detection speed and accuracy. The model’s box_loss value declines rapidly and stabilizes at 0.038, while the mAP_0.5 value climbs swiftly and stays near 0.91.After that, the DeepSORT model was used as the backend multi-vehicle tracking technique, and a corner-to-centroid coordinate transformation was used to simplify the extraction of vehicle trajectories. The precision of the driving trajectory line was evaluated thereafter. To improve the robustness of trajectory points’ coordinate information, a corner-point-center-of-mass point coordinate transformation was suggested to tackle the issue of corner points in the detection frame. A sixth-degree polynomial was used to model the vehicle trajectory. Unsuitable trajectory lines were rotated and optimized to meet the function mapping requirements and ensure good fitting of all trajectories. Turning vehicles were detected and counted by using a predetermined threshold to determine the turning angle. Ultimately, to validate the performance of the proposed turning vehicle flow detection method, vehicle detection experiments were conducted at a city intersection as an illustration. The manual counting values were compared and analyzed against the detection results obtained using this method. The results show that the average detection accuracy for the four flow directions is 92.9%, with a maximum of 95.7%, meeting the standard detection requirements for turning vehicle flow in real intersection scenarios.

In order to study the influence of the tank environment on the results of the seaplane model test, for the first time in this field, a series of whole aircraft model tests were conducted using the same seaplane model in two towing tanks to study the aerodynamic and hydrodynamic characteristics of the whole aircraft model in the two towing tanks, the test results and environmental differences were analyzed. The results show that the towing tank environment has a significant impact on the aerodynamic characteristics of the seaplane model, but by compensating the aerodynamic characteristics of the seaplane model in each towing tank during the test, the interference of the test environment on the water resistance results could be avoided, so as to obtain a more satisfactory water resistance test result. Among the boundary effects of the towing tank, the blockage effect has the greatest impact on the aerodynamic characteristics of the seaplane model. Compared with 2.51% relative blockage ratio 0.67%, the aerodynamic drag coefficient of the seaplane model is 0.1~0.2 larger, and the lift coefficient is at least 0.2.Because the typical high-speed coasting state is used for aerodynamic compensation to calculate, so the compensation effect is only achieved at the corresponding speed and produce some deviation at other speeds, resulting in a certain deviation in the test result, but it will not have a significant impact on the test result because the deviation is so small. The research findings provide guidance for model hydrodynamic tests and performance analysis of seaplanes in China.