To explore the influence of surfactant on performance of diluted asphalt and its mixture, the mixture of heavy oil viscosity reducer AMS and Span80 is added to diluted asphalt, the influences of surfactant on the mixing and compaction of diluted asphalt mixture are investigated through the tests of viscosity-temperature relationship, surface contact angle, mixing adhesion rate and compaction characteristics. The experimental result shows that (1) The mixed oil-soluble surfactant can significantly reduce the surface tension of asphalt-aggregate interface and reduce the viscosity of the diluted asphalt, in which the influence on interface is dominant. The addition of the mixed surfactant can ensure the mixing effect of the mixture under the condition of reducing the diesel consumption. (2) The addition of the mixed surfactant can reduce the viscosity of diluted asphalt, and has significant effect on improving the construction workability of diluted asphalt. It can significantly change the liquid-solid interfacial tension between asphalt and aggregate, and make the asphalt mixture still achieve good construction performance under the condition of reducing the content of diluent. (3) The addition of the mixed surfactant can make asphalt spread better on aggregate surface, reduce resistance and is easier for paving. (4) During the compaction process, the addition of the mixed surfactant can play lubricating effect between asphalt and aggregate, make the final compactness of the diluted asphalt mixture greater, improve the wetting and paving ability of asphalt on the aggregate surface, improve the mixing uniformity of the mixture and make it easier for paving and compaction. (5) At the surfactant dosage of 1.0%-1.5%, the improvement of the paving and compaction characteristics of the diluted asphalt mixture can achieve the effect of adding 4%-6% diesel oil, the 1.0%-1.5% mixed surfactant can replace 4%-6% diesel diluent, so that the mixture can achieve the same mixing uniformity and compacting performance.

Generally, cable-stayed bridges are long-span bridges, and their consisting cables have been confirmed as the main load-bearing components. Hence, an accurate evaluation of cable forces is vital to determine the stress state of bridges. Considering the effect of stiffness on cable force and determination of short cable in practical engineering, cable length, slenderness ratio, and characteristic parameters in the existing specification are taken into account via a specific parameter, represented by ξ. The effect of cable stiffness on cable force serves as a variable, which requires further investigations. As indicated by the research results, the effect of the cable bending stiffness on the cable force reduces with increasing the cable length, slenderness ratio, and cable characteristic parameter ξ. For cables under hinged boundary conditions, the stiffness contribution to the cable force reaches more than 5% for cable lengths less than 6.5 m. Under fixed boundary conditions, the stiffness contribution to the cable force exceeds 5% for cable lengths less than 11 m. Short cable determining criteria are proposed according to the analysis results. In addition, the ranges[DK]’ values of the cable length, slenderness ratio, and ξ factor of short cables are given. The achieved results suggest that cables less than 11 m in length should be conservatively defined as "short cables". Further, complementary analyses reveal that the cables with a slenderness ratio less than 175, and ξ-factor lower than 23 can be classified as short cables.

Pile side friction is an important component of the bearing capacity of socketed piles, and plays a crucial role in improving the vertical bearing capacity of socketed piles. In order to study the load-bearing mechanism of socketed piles, on the study background of on-site monitoring of the bearing capacity of socketed piles of Qingchi Grand Bridge on Guiyang-Jinsha-Gulin Expressway, the development mechanism of pile side friction under construction loads is analyzed. Based on the shear characteristics of the pile-rock interface of socketed pile and theoretical analysis, the expressions of pile side friction and shear displacement are derived. A load transfer model of socketed pile is established based on the load transfer theory, and the model is solved by using the 4th-order Runge-Kutta method through Python. The on-site monitoring data of engineering piles are in accordance with the calculation result, indicating the correctness of the established load transfer model and the rationality of the calculation method, which can be used for study the mechanism of side friction of socketed piles. According to the monitoring data and the load transfer model, the characteristics of the axial force and shear displacement of the pile foundation section in the shear slip stage under different construction loads are analyzed. The result shows that (1) Under construction loads, the pile side friction of socketed pile plays a role from top to bottom gradually and bears most of the construction loads. (2) When the shear displacement reaches the ultimate shear displacement, the pile side friction remains stable gradually, and the construction loads are borne by the pile end resistance gradually. (3) The sectional axial force of socketed pile calculated by using the load transfer model is in accordance with the monitoring result, upon that the established load transfer model and calculation method have practical engineering significance. (4) The calculated ultimate pile end resistance is significantly smaller than that calculated according to the Design Specification for Highway Bridges and Culverts Foundations (JTG 3363—2019). This indicates that the original design of the ultimate pile end resistance is overly conservative and needs to be reasonably revised.

The cross passage for the separated double-hole road tunnels plays an important role in emergency rescue. At present, the design research on the width of the cross passage in large-scale subsea tunnel projects in China is still blank. Using the research methods of data investigation, theoretical analysis and comparative demonstration, the reasonable width of the vehicle cross passages in the design process of the Jiaozhou Bay Second Subsea Tunnel is studied. The research content includes research of main driving parameters of fire trucks in the subsea tunnel, investigation and analysis of the minimum turning radius of rescue vehicles inside the tunnel, comparison and demonstration of the clear width required for rescue vehicles to enter and exit the main line tunnel from the cross passage, comparative analysis of the width required for rescue vehicles to enter and exit the service tunnel from the cross passage and research on the project cost of different width cross passages, etc. The result shows that (1) when a vehicle turns at right angles, the 3 lane widths of the main line tunnel are (3.75+3.5+3.5) m, which meets the requirement of minimum width before turning; (2) when the width of the vehicle cross passage is 4.0 m, it needs to be widened locally if fire trucks turn into the cross passage at the edge of the cross passage from the left, middle and right of the main line; (3) when the width of the vehicle cross passage is 6.0 m, the fire trucks can transfer from the main line tunnel to the vehicle cross passage at one time, and from the vehicle cross passage to any lane of the main line tunnel at one time, which can provide favorable conditions for tunnel rescue; (4) when the pavement width of the cross passage increases to 8.0 m, it can turn in or out between the cross passage and any lane of the main line tunnel, and it only adds the function of turning into the vehicle cross passage from the left lane at one time compared with the 6.0 m wide pavement. Comprehensively considering the use function, the difficulty of project construction and the economy, it is recommended that the pavement width of the vehicle cross passage be 6.0 m. The research result can be applied to project design to provide reference for subsequent subsea tunnel project design and construction.

To explore the influence of the installation height and angle of traffic signs and their interaction on the driver[DK]’s fixation characteristics within the recommended range of national standards, selecting the common nonstop sign in the urban road as the test sign, a simulated driving scenario of a two-way four-lane urban road is built by using the virtual reality software UC-win/Road 10.0 and the driving simulator FORUNM 8, and 32 drivers are summoned as the subjects for eye movement test. Through the simulation test of sign recognition in the simulated cockpit with the driver wearing an eye tracker, the indicator data (fixation duration, number of fixations, time of first fixation) of the driver recognizing the stop sign with different combinations of height and angle of traffic signs are obtained. After preprocessing the data, such as outlier elimination, residual normality, and variance homogeneity test, the influence of height, angle, and their interaction on the above indicators is analyzed by using the two-factor ANOVA method with interactive effects. The result shows that（1）In single-factor analysis, different installation angles only have a significant influence on fixation duration, and the fixation duration caused by the positive installation is higher than that caused by tilt angle;（2）There are no significant differences in the influences of different installation heights on the driver’s fixation duration, number of fixations and time of first fixation;（3）The interaction of installation height and angle has a significant influence on the driver’s fixation duration and number of fixations. Among the 4 combinations of height (high and low) and angle (positive and oblique), the fixation duration and the number of fixations caused by "high×positive" are much higher than those of other combinations, showing that the nonstop sign installed by this combination can attract the most interest and attention of drivers. It is recommended to install this nonstop sign on the two-way four-lane urban road.

In view of the parameter estimation of gross vehicle mass and road gradient during the driving of battery electric vehicles, according to the characteristics of the vehicle mass with steady variability and road gradient with time variability, on the basis of vehicle longitudinal dynamics, an method for estimating gross vehicle mass and road gradient based on a hybrid algorithm is proposed, and the method is applied to the starting stage of battery electric vehicles. The gross vehicle mass is estimated by using the forgetting factor recursive least square algorithm with good estimation efficacy for steady variables, and the output result of mass is regarded as one of the input parameters for gradient estimation. The road gradient is estimated with adaptive Kalman filtering, and the noise influence that cannot be concluded with external noise statistical characteristics is reduced by introducing a noise estimator with forgetting factor to improve the estimation accuracy of road gradient. The electric vehicle starting test is carried out on the selected flat ground and micro-slope sections, and air resistance is ignored based on the characteristics of low speed during vehicle starting. The required data are collected with the Global Navigation Satellite System (GNSS) terminal and vehicle controller area network (CAN) bus to perform offline calculations. The result shows that (1) a road section with variable gradient is selected to verify the validity of the algorithm, and the gross vehicle mass estimation result of the section is converged within 10 kg of the true value eventually with small error in the gradient estimation result; (2) the estimations of gross vehicle mass and changing of road gradient can be accurately estimated by using hybrid algorithm; (3) the mass estimation result of the twice starting test has the same convergence trend and the mass error is less than 2%, although the gradient estimation error is increased slightly, it is still less than 0.6%, which indicates the high estimation accuracy at starting stage of battery electric vehicle by using the hybrid algorithm.

To support the commercial application of autonomous driving technology in taxis, and to solve the issues such as whether, what, and how to obtain transport operation qualifications for application subjects that have not been clearly defined by China, to avoid some cities not allowing intelligent connected vehicles to operate on charges due to the "lack of upper level legal support", and to promote the current related transport operation management regulations to adapt to the management needs of the commercial operation and development of intelligent connected vehicles, the following 4 principles for the governance of autonomous passenger transport are proposed: adhere to the principle of inclusiveness and prudence, and create a space for platform development; adhere to the principle of full chain supervision and implement comprehensive supervision, innovate regulatory concept and method to improve collaborative regulatory efficiency, respect the extension of existing institutional design and fully considering new regulatory trend and requirements. It is proposed in the key regulatory system that it is recommended to adopt an administrative licensing approach for the admission system; the operating subjects allows multiple subjects to jointly apply and relies more on the self-regulation of the operating subjects; to explore a sandbox regulatory model for vehicle technology management, and to ensure vehicle operational safety based on test and demonstration application results; practitioners are required to have the ability to be familiar with and master the autonomous driving technology system in their professional abilities, and reference can be made to the service quality requirements for cruiser and ride hailing drivers; the pricing mechanism is managed according to market adjustment prices and maintains reasonable and relatively stable markup standard; to increase the coverage of carrier liability insurance and encourage the exploration of new types of insurance for the insurance mechanism. It is suggested to propose a regulatory system for autonomous driving taxis, to research and develop management measures for autonomous driving passenger transport services at the industry level, to establish a regulatory platform for autonomous driving passenger transport services, to strengthen interdepartmental regulatory cooperation, to promote third-party organization construction, to exert the self-discipline role of associations, and to timely revise relevant regulations on road passenger transport.