Cement concrete pavements in airfields need to be sealed with all kinds of sealants to prevent the ingress of water or incompressible materials into their joints. Airfield cement concrete pavements have unique in-service conditions, and the sealants in these environments are not only exposed to climatic effects and heavy traffic loads but also to jet fuel and fluids. By analyzing the causes of damage and selecting four types of typical joint sealing materials for cement concrete pavements in civil airports (e.g., silicone, polyurethane, polysulfide, and polythiourethane), the basic physical properties, adhesion, and resistance of these materials are tested. By combining the experimental results with the relevant technical specifications and standards at home and abroad, these materials are divided into high elastic modulus and low elastic modulus based on 23℃ tensile modulus. The surface drying time, cone penetration, elastic recovery rate, tensile modulus, low temperature tensile elongation, tensile bond, fuel immersion characteristics, resistance to heat ageing, and flame resistant properties of these materials are used as performance indices and provide a technical reference for the construction of airport cement concrete pavements.

To control the rutting resistance of a semi-rigid-base asphalt pavement under different traffic volumes, a rutting test is conducted to simulate the actual pavement internal temperature field on full-depth asphalt surface course samples excavated from different sections (different corresponding traffic volumes) and rutting depths in an expressway reconstruction and extension project. The relationship between dynamic stability and rutting depth on the main lane is analyzed. The dynamic stability control criteria, which are dynamic stabilities corresponding to 15 mm rut depth, to fit the traffic volumes of different sections are determined. The accumulative equivalent axles of different sections are collected and calculated. The relationship between the dynamic stability control criterion of each section and its accumulative equivalent axle is analyzed to obtain a fitting equation. A dynamic stability control criterion for the asphalt pavement structure at heavy traffic level is suggested based on this fitting equation. Afterward, a method of determining the dynamic stability control criterion for the entire asphalt surface course under different traffic volumes is recommended.

To develop a new type of modified asphalt, castor oil-contained asphalt is obtained with green renewable castor oil instead of petroleum-based polyols. The second monomer-liquefied methylene diphenyl diisocyanate (MDI) is gradually added to a pitch system with shearing, and castor oil-based polyurethane (PU)-modified asphalt is prepared. The dosages of castor oil and second monomer MDI are calculated with isocyanate index R (—NCO/—OH)=1.8, and the modified asphalt with 10%-30% content of castor oil-based PU is synthesized. The performance of the modified asphalt is characterized through a conventional experiment. Experiment results show that the modifier in the asphalt is dispersed evenly, and the high-and low-temperature performance of the castor oil-based PU-modified asphalt is improved. The high-temperature grade of the asphalt is determined by performing the original grade test and thin film oven test on samples. On the basis of the high-temperature grade, the high-temperature performance of different asphalt samples after aging is analyzed and evaluated via a multiple stress creep recovery test. Test results show that the creep compliance of the modified asphalt is reduced significantly, and the recovery rate is increased compared with that of base asphalt. Increased elasticity and stiffening are achieved. With the increase in modifier dosage, creep compliance declines and the recovery rate increases simultaneously. The modification effect is also improved.

The influence of various interface strength parameters, different reinforcement spacing, and type of slope (enveloped or not) with a geogrid on flexible-support-reinforced expansive soil cut slopes was investigated by numerical simulation. The simulation considered the attenuation of the shear strength of expansive soil due to rainfall, evaporation, and other long-term atmospheric weathering actions in combination with shear strength parameters determined by a laboratory-measured expansive soil nonlinear strength envelope. Results showed that the geogrid can effectively restrain horizontal slope displacement and decrease the soil expansion softening effect to a certain extent, such that the sliding surface of the slope became deep. The change in maximum axial force was small due to a change in interface strength parameters between the geogrid and soil, but the safety factor increased with the increase in maximum axial force. The changes in maximum axial force along the height for different geogrid reinforcement spacing values were basically similar; the values increased initially and then decreased. Small reinforcement spacing equated to a small maximum value. The stability of the expansive soil slope was significantly influenced by reinforcement spacing; small spacing meant good slope stability. The enveloped geogrid indirectly improved the safety, resistance to erosion, and integrity of the slope.

Basalt fiber-reinforced polymer (BFRP) is a high-strength, lightweight material with an anti-corrosion property and a thermal expansion coefficient that is close to that of concrete. When used as an anchor bolt material, the corrosion problem of steel anchors can be solved fundamentally. In recent years, the BFRP bar has been applied in geotechnical anchorage engineering. In this study, the mechanical properties of the BFRP bar were studied by tensile, shear, corrosion resistance, and bonding strength tests with cement-based materials. In accordance with the design specifications of the steel anchor and existing research results, the design parameters of the non-prestressed BFRP anchor in supporting soil slope were proposed. To examine the reinforcing effect of the BFRP anchor, this study adopted the recommended parameters to design a BFRP anchor in an actual soil slope. A field contrast test of the steel anchor was also carried out. Experimental studies yielded the following conclusions. First, the tensile-strength safety factor of the non-prestressed BFRP bar should not be less than 1.6 (permanent) and 1.4 (temporary). The tensile-strength standard value was 80% of the ultimate tensile strength, and the value of the BFRP bar (diameter ≥ 12 mm) commonly used as an anchor was 710 MPa. The bonding-strength standard value between the BFRP bar and cement was equal to the average value divided by 2.1 of the pull-out test, and the common value was 2.8 MPa. The monitoring field test data proved that the designed BFRP anchor demonstrates better control displacement and can effectively retain soil slope. Moreover, the reinforcing effect of the BFRP anchor was equivalent to that of the steel anchor. Thus, the design of the BFRP anchor is reasonable, and the equal strength substitution method can be used to design the BFRP anchor.

To study the critical height of secondary salinization of silty soil subgrade, this paper examines the salt migration law in the secondary salinization of the non-saline soil subgrade in the Yellow River impact plain area via laboratory and numerical analyses using COMSOL Multiphysics. The results show that (1) if the top of subgrade has not yet formed poly salt, then the internal roadbed will also not form poly salt. and it shows the trend of gradually decreasing from the bottom to the salt distribution in the subgrade; (2) the relationship among the weak internal saline soil formation of critical height, the groundwater mineralization degree, and the underground water level at the top of the subgrade can be used to establish an approximate correlation and regression formula for the Yellow River impact plain area for estimating the weak internal saline soil formation of critical height; and (3) the influence of the groundwater mineralization degree on the secondary salinization of silty soil subgrade in the Yellow River impact plain area is significantly higher than those of the buried depth of groundwater and the filling height of subgrade.

On the basis of Chinese and foreign specifications and the latest research findings, an appropriate parameter determination method for bridge reinforcement with prestressed carbon-fiber-reinforced polymer (CFRP) plates was proposed to determine the key design indices and calculation coefficients. Each item of prestress loss was studied and a novel calculation method was proposed to determine the usage amount and effective stress of prestressed CFRP plates for reinforcement design, in consideration of the relevant construction technology and anchorage system. The feasibility and reliability of the suggested method in this paper were verified by using an RC simply supported beam bridge reinforcement project as an example.

To ensure the alignment of free cables in self-anchored suspension bridges, a control strategy based on finite element (FE) methods was analyzed. FE methods for construction control were presented in this paper by applying backward and forward methods and unstressed state methods. Accurate FE simulation methods for sensitive regions (i.e., the tangent point between the cable and saddle as well as the state of the splay cable) were obtained, and the precise alignment of free cables was also calculated. The cable strands were also revised piecewise based on their characteristics after calculating the unstressed length of the main cable. Practical FE methods for simulating the pre-offsetting of the saddle and clip in free cable states were also proposed. The alignment of the free cable and other relevant parameters of self-anchored suspension bridges can be accurately computed using these proposed methods, which also generate superior controlling results in practical engineering.

To achieve green wave traffic and improve the operational efficiency of arterial traffic, this study considers the relevance of intersections and optimizes four trunk optimal control parameters, namely, signal cycle, phase sequence, split, and offset from the perspective of coordination. On the basis of traffic wave theory, vehicle queuing is explained, and the internal mechanism of green wave traffic in a large flow by-wire system is determined. An offset optimization model is established to avoid the queuing of vehicles at the downstream intersection. We select 13 intersections along Coastal Road in Qingdao City as the research object and then use optimization schemes to verify the feasibility of the arterial coordinated control optimization method and the practicability of the established model. Results indicate that cycle, phase sequence, split, and offset are important indicators of arterial coordination optimization control. Moreover, remarkable results are obtained with the optimization of the intersection offset optimization model based on traffic wave theory for the optimization of total travel time and the number of stopping vehicles.

To improve the ability of city agglomeration to resist emergency disruption, the model of a city agglomeration compound traffic network was constructed with a new perspective on investigating its vulnerability. First, on the basis of complex network theory, the city agglomeration compound traffic network structure was analyzed thoroughly and its model was established using the site mapping method. Then, facing the compound traffic network structure of urban agglomeration, both the different attack strategies and the measures of the vulnerability of a city agglomeration compound traffic network were proposed. Finally, taking Hohhot-Baotou-Erdos city agglomeration as an example of our empirical study, the city agglomeration road network and rail transit network were formed, and the topology characteristics and vulnerability of the compound traffic network were analyzed to identify critical sites and lines within the network. Results show that the construction of urban agglomeration compound traffic network can effectively reduce the vulnerability of a single-mode network. Moreover, strengthening the protection of the identified key sites and lines further increases the likelihood of reducing the vulnerability of urban complex transportation networks and the risks of traffic network paralysis caused by sudden disasters.

In mountainous cities, as an important part of urban road grade crossings and tunnels, reasonable net distance directly affects urban road construction and traffic operation quality. The definition of the net distance between an urban road grade crossing and a tunnel given light adaptation indicates that drivers must recognize traffic signs, change lanes away from the car's range, and observe safe distance in intersections. By analyzing various factors of demand distance, the urban road grade crossing and tunnel net distance calculation model, and an urban road grade crossing under different running speeds, a reasonable tunnel net distance was proposed. This work provides engineers a reference for similar engineering designs.

Merge points on expressways are areas where a high number of accidents occur, and the connected vehicle technology is an effective means to improve the safety of these areas. In this study, a novel vehicle coordinated control method is proposed to reduce the occurrence of security conflicts and congestion by providing early warning to the driver to adjust driving behavior. Vehicle conflicts are calculated and predicted based on the position and speed of vehicles that are located within the range of the communication by connected vehicle technology. First, the safety hazard of the merge area is analyzed. Second, the time range of the ramp truck to reach the merge area is calculated according to the characteristics of the truck. The speed range in which main road vehicles can reach the merge area is calculated using the same time range as that in the ramp vehicle. The optimal main road vehicle speed is recommended in the area to avoid possible conflicts in terms of safety and efficiency. Finally, the communication module of the system is developed using Vissim simulation software, and the effect of safety coordinated control is evaluated in terms of safety and traffic efficiency.

Routing is the key technology of a vehicular ad hoc network (VANET). On the basis of the high mobility of nodes and the vast frequent changes of the network topology of ad hoc networks, this study proposed an improved greedy perimeter stateless routing with speed-density direction (GPSR-SD) routing protocol, which is based on the GPSR protocol. The proposed routing protocol is combined with the speed-density model to estimate the density information of a vehicle node traveling on a road. It considers the traveling speed of the vehicle node and the density of the road to select the next hop forwarding node and improve the selection of the forwarding node, thereby increasing communication reliability. The proposed routing protocol can effectively reduce the hole phenomena caused by the movement of the node, improve the average packet delivery ratio, and reduce average end-to-end delay. Simulation results of the NS2 platform indicate that GPSR-SD performs well.

The concept of urban public transport information attention was defined to determine travel information demand and spatiotemporal differentiation of urban public transport. On the basis of the Baidu index of urban public transport attention in 31 cities in China from 2011 to 2014, this study applied the standard deviation and the Theil index to analyze absolute and relative differences in urban public transport information attention. Then, the coupling coordination degree model was established to measure the coordination of information attention and service level of urban public transport. Results showed that the relative difference gradually diverged, whereas the absolute difference increased from 2011 to 2014. The regional rank changes of urban public transport information attention gradually diminished from east to west, the spatial coupling coordination between information attention and service level of urban public transport was low, and the differences between regions were significant.