Seepage analysis is the key research content of dam safety and stability, and it is of great significance for dam disaster risk control by constructing a high-precision prediction model of seepage quantity for earth-rock dam. In order to further improve the seepage prediction capability of earth-rock dam, a prediction model combining long short-term memory neural(LSTM) networks, convolutional neural(CNN) networks, and attention mechanism (Attention) was proposed. Firstly, CNN was used to mine the deep features of the data, then the time series features of the seepage flow monitoring data was extracted through LSTM, and finally the attention mechanism to the pooling layer and the fully connected layer was added to determine the importance of different time features and assign weights. Through the application analysis of engineering examples, compared with CNN, LSTM and CNN-LSTM models, the CNN-LSTM-Attention model has better prediction effect, and its coefficient of determination R² is as high as more than 0.98, and it can capture the spatial characteristics and temporal dependence of seepage data at the same time, which shows strong reliability and stability in the prediction of seepage flow of earth-rock dam.

In order to help enterprises better adapt to the dynamic environment in the real business, a multiperiod intermodal routing and storage co-optimization model with transport price uncertainty was investigated. Firstly, an integer programming mathematical model was established in the environment of transport price certainty. Secondly, a robust optimization model was established in the environment of uncertain transport prices, and the robust optimization model was transformed into an equivalent linear robust peer-to-peer problem. Subsequently, on the basis of the traditional k-shortest algorithm, iterative greedy algorithm (IG) and adaptive large neighbourhood search algorithm (ALNS), a hybrid heuristic algorithm of MKIGALNS was proposed to solve the problems. Finally, the correctness of the proposed model as well as the effectiveness of the algorithm were verified by different sizes of arithmetic case experiments. The experimental results indicate that in 10 sets of arithmetic cases, the average total operating cost is CNY 439 191 when storage is not allowed and CNY 391 378 when storage is allowed, so the storage decision should be made, which is conducive to the reduction of operating cost. And through the related robust experiments, the total operating cost as well as the multiperiod intermodal operation strategy changes with the change of the uncertain budget value, which reveals the intrinsic connection.

The super-large cross-section tunnel is prone to large deformation when passing through soft rock stratum. The reasonable selection of excavation method is of great significance for construction safety. In order to explore the applicability of the double-side nine-step excavation method to the construction of super-large cross-section tunnels, based on a 500 m² super-large cross-section soft rock tunnel under construction in Chongqing, the mechanical properties of sandy mudstone were revealed by laboratory experiments. The deformation characteristics of surface and super-large cross-section tunnel structures were compared and analyzed by numerical simulation and field monitoring. The excavation sequence, temporary support measures and excavation step length were optimized. The results show that the stress-strain curves of sandy mudstone samples under different confining pressures and different unloading rates are similar, and the triaxial compressive strength and deformation characteristics of rock samples change significantly. With the excavation of the core rock mass of the upper step, the displacement of the super-large section tunnel is abruptly changed. When the temporary support measures are removed, the deformation of the super-large section tunnel is further aggravated. Different excavation steps cause successive disturbance of surrounding rock, resulting in different unloading rates of surrounding rock and affecting the deformation of surface and tunnel structure. The temporary transverse bracing effectively limits the convergence of the arch waist, and the convergence of the arch waist is reduced by about 10.0 mm under all the layout conditions. In addition, the shorter the length of the excavation step, the smaller the deformation of the surface and the super large section tunnel.

In order to solve the defects of poor water stability and easy disintegration of red clay, industrial solid waste [fly ash (FA), phosphogypsum] combined with cement (C) was used to improve red clay. The mechanical properties, water stability and micro-mechanisms of the industrial solid waste-cement amended red clay were investigated through indoor tests. The results show that the strength of the improved soil shows a trend of increasing and then decreasing with the increase of the ratio (R) of phosphogypsum replacing fly ash.When the cement doping is 7% and R=7%, the maximum dry density of improved soil increases by 2.6%, the 7-day unconfined compressive strength (UCS) increases by 11%, and the 28-day UCS increases by 57%, which meets the bearing standard of subgrade for road use. There is no obvious change in the water-filled specimen after the 7-day maintenance, the resistance to disintegration is enhanced, and the water stability coefficient of the specimen reaches 92.9% in the 28-day maintenance. The water stability coefficient of the specimen reaches 92.9%, and the water stability coefficient increases 1.61 times. The microscopic analysis shows that the replacement of fly ash by phosphogypsum promoted the generation of new hydration products of ettringite and calcium-silicate-hydrate (C-S-H), which transforms the soil body from fragmented granular to a denser gel network structure, enhances the bonding between the red clay particles, and fills up the pore space at the same time. The results verifies the feasibility of industrial solid waste-cement-amended red clay as roadbed fill, provides a solid theoretical foundation and basis for engineering practice, and broadened the reuse of industrial solid waste.

To investigate the impact of temperature on axial stress in large-span concrete variable-section continuous beam bridges under various wind speed fields, a method was proposed to calculate vertical temperature gradients separately based on inconsistent deck slab thickness and simulate lateral fluctuating wind speed fields using the spectral method. Firstly, vertical temperature gradient variations and their depths were calculated by employing the concrete heat-conduction equation, daily maximum and minimum temperatures, and deck slab thickness of the variable-section continuous beam bridge. Secondly, bridge modeling was performed using MIDAS Civil, and ZKH standard static live loads were simulated to represent moving train loads. Finally, static array wind loads and pulsating wind loads were applied to the bridge. The results indicate that the axial stresses in the left and right lanes obtained from the proposed method, which uses vertical temperature gradients and their depths derived from the concrete heat-conduction equation, daily temperature extremes, and bridge deck slab thickness, are larger compared to existing studies. Under the same wind speed field model, the harm to the bridge is greatest under gradient heating, followed by gradient cooling, while no temperature change results in the least impact. When the bridge is subject to the same temperature model, both the axial stress values and amplitudes of the bridge under pulsating wind loads are larger and more severe than those under no wind or static wind conditions, posing greater hazards to the bridge. The research findings can provide references for the structural design and safe operation of large-span concrete variable-section continuous beam bridges.

The alignment monitoring of steel arch bridges constitutes an essential component of bridge health monitoring systems. Three-dimensional laser scanning technology was utilized, and the traditional density-based spatial clustering of applications with noise(DBSCAN) algorithm was improved by integrating the random sample consensus(RANSAC) algorithm to extract the alignment of steel arch bridge ribs. Three-dimensional laser point cloud data, characterized by its comprehensiveness and detailed representation, is capable of fully presenting the structural shape and deformation information of the bridge. The RANSAC-integrated improved DBSCAN algorithm, constrained by the structural features of the steel arch bridge, effectively achieves the removal of discrete points as well as point clouds from the bridge deck, cross bracing, lateral connections, and web members. Point clouds extracted using the RANSAC-integrated improved DBSCAN algorithm are fitted to identify key points, and a comparison is made with results obtained manually. The extraction errors for the key points of the arch ribs are all within the millimeter range, with the maximum error being 9.2 mm and the minimum error being 0.1 mm. This extraction method is demonstrated to more accurately and effectively accomplish the alignment extraction of steel arch bridges, achieving millimeter-level precision in alignment extraction. It significantly reduces labor and time costs, provides better robustness for the complex structures of steel arch bridges, and adapts well to practical production demands.

To mitigate the impact of highway accidents on traffic capacity and driving safety, a coordinated control strategy was proposed involving both service areas and toll stations. Firstly, the proposed coordinated control strategy was described in detail. Secondly, to simulate traffic flow more accurately under highway accident scenarios, the cellular automata model was enhanced by introducing different random deceleration probabilities, acceleration/deceleration rates, and lane-changing conditions for different vehicle types. Finally, the effectiveness of the proposed control strategy was validated through simulation. The results indicate that, compared to scenarios without control measures, implementing service area control can reduce average vehicle delay, fuel consumption, and cumulative carbon emissions by 62.90%, 69.50%, and 69.50% respectively. Moreover, using the coordinated control strategy of service areas and toll stations can further reduce these metrics by 55.76%, 59.58%, and 59.58% respectively. Precise control measures can significantly reduce the impact of accidents.

The rudder in the coaxial twin-rotor is a complex mechatronic position-following control system, and its control accuracy plays a key role in manipulating the flight attitude. Because the common rudder is lacking in adapting to the unique flight environment of the aircraft, the accuracy of tracking declination and the stability performance need to improve. The manipulation principle and structure of micro UAV were analyzed, the mathematical models of position loop, current loop double PID steering gear control system and transition position loop Fuzzy PID steering gear control system were established respectively. Combined with the actual flight conditions, the dynamic and static characteristics of the coaxial twin-rotor steering gear control system were analyzed by using Fuzzy editor and Simulink module. The results show that the rudder control system with current loop PID and position loop Fuzzy PID control has 28.6% less overshoot, 28% less adjustment time and faster response than the dual PID control system. Meanwhile, the Fuzzy PID parameters are adjusted in real time to track the changes, which can adapt to the complex and variable flight conditions of the coaxial twin-rotor more quickly. The obtained control system based on dual-loop Fuzzy PID shows high accuracy and meets the requirements of stable, accurate and robust working under complex working conditions, which is of great significance for the control system design of coaxial dual-rotor aircraft.

The development of hydrogen-powered aircraft is a key strategy for the aviation industry to achieve carbon neutrality. Compared to high-pressure gaseous hydrogen, cryogenic liquid hydrogen will be the main fuel for future hydrogen-powered commercial aviation. However, the occurrence of cavitation in liquid hydrogen during transport has the potential to result in an unstable or even interrupted fuel supply to the engine, which could ultimately lead to catastrophic risks to flight safety. Using numerical simulation method, based on homogeneous mixed flow model, Navier-Stokes (RANS) method and Zwart cavitation model, the cavitation flow characteristics and development law of liquid hydrogen in aircraft transport pipelines were deeply studied, and partially compared with normal temperature water. The results show that the cavitation number, the outlet/inlet pressure ratio, and the length/diameter ratio have a significant influence on the occurrence and development of cavitation. The condensation process of liquid hydrogen is considerably slower than the evaporation process. The effect of the cavitation number on the evaporation process is minimal, but it has a significant effect on the maximum condensation rate. The critical pressure ratio for the disappearance of cavitation in liquid hydrogen is lower than in water. At the same pressure ratio, water cavitates more easily than liquid hydrogen, with a greater number of cavitation bubbles and a thicker cavitation region. Reducing the length/diameter ratio can inhibit the occurrence and development of cavitation in liquid hydrogen. It is recommended that the diameter of the contraction section be increased to achieve a higher outlet flow, rather than shortening the length of the pipeline.

In order to enhance the safety and efficiency of operations in the double-channel U-shaped apron area of large airports, an optimized operational procedure for the double-channel U-shaped area was studied. Firstly, the utilization and partitioning of taxiways in the double-channel U-shaped apron area were designed, and the positions of pushback holding points were optimized. Secondly, based on the partitioning of the double-channel U-shaped apron area and the optimized positions of pushback holding points, different operational procedures for aircraft were designed for various scenarios. Then, evaluation indicators were designed from the perspectives of safety and efficiency, and corresponding evaluation models were established. Finally, simulation experiments were conducted using Wuhan Tianhe Airport as the object. The results show that the proposed optimized operational procedure can reduce the total operation time by 13.3%, total waiting time by 31.4%, and waiting rate by 22.4%. The flight density was gradually increased until reaching the maximum theoretical capacity of the U-shaped apron area, and further verification was conducted. The results indicate that the proposed optimized operational procedure performs better across different indicators under varying flight volumes, verifying its effectiveness and providing theoretical references for current and future operational procedures of double-channel U-shaped apron areas.