In order to study the noise reduction and sound absorption performance of drained asphalt pavement—PAC, the difference of noise reduction and sound absorption effects of conventional AC pavement, single-layer and double-layer PAC pavement is compared and analyzed by improving the indoor noise test of tire accelerated falling method, and then the sound absorption coefficient of single-layer and double-layer PAC pavement is further tested by standing wave tube method, Based on the standing wave interference principle of sound, the sound absorption characteristics of drainage asphalt pavement are described, the influence of void ratio on the sound absorption coefficient of PAC pavement is analyzed, and the data model between void parameters and sound absorption coefficient is established. The results show that:（1）Using the improved indoor tire accelerated falling method and using the sound level meter to measure the A-weighted sound pressure level and 1/3 octave frequency spectrum of noise under three distance conditions, the noise value of drainage asphalt pavement is 2 to 5 dB（A） lower than that of traditional AC pavement, and the noise reduction ability decreases with the increase of distance from sound source and increases with the increase of void ratio. The sound absorption coefficient curve of drainage asphalt pavement is measured by standing wave tube double transfer function method, The average sound absorption coefficient of PAC specimens decreases with the attenuation of the void fraction.（2）The sound absorption coefficient curve of single-layer PAC pavement presents a "single peak type". The sound absorption peak frequencies of single-layer 4cm thick PAC pavement and 10cm thick PAC pavement are around 1100 Hz and 800 Hz respectively. The corresponding frequencies of the sound absorption peaks of the two specimens are within the common frequency range of traffic noise, which is helpful to alleviate traffic noise.（3）Through CT scanning and three-dimensional reconstruction software, the void parameters of PAC specimen are obtained, and the sound absorption coefficient prediction model is established. The sound absorption coefficient calculated by the model has a high correlation with the measured value of standing wave tube method, which verifies the accuracy of the sound absorption coefficient model in predicting the sound absorption characteristics of drainage asphalt pavement.

As the soft soil in the Pearl River Delta area is deep, 50cm diameter cement mixing pile composite foundation is often used for road engineering.A municipal road in Hongwan District of Zhuhai adopts a mixing pile with a diameter of 80cm and a length of 27 m, which brings great difficulty to the construction of the project.In order to ensure the engineering quality, the bit optimization scheme was adopted to improve the blades from the conventional two layer and four groups of blades to three layer and six groups of blades. The projection direction of each layer of blades was vertical, which could increase the mixing times and improve the mixing uniformity.At the same time, double-channel teeth were added to effectively increase the smoothness of slurry flow.The optimized nozzle is improved from a nozzle located at the bottom of the drill bit to the left and right sides of the bottom of the drill pipe to effectively relieve the blockage of the nozzle and silt backflow and other problems.Optimize the grouting pressure. The grouting pressure is generally 0.4-0.6 MPa. After optimization, the upper limit of 0.6 MPa is used in the first stirring and spraying process, and 0.4 MPa is used in the second stirring and spraying process.The advantage is that in the first time of mixing, excess cement grout is ejected for mixing, and in the second time, the total grout dosage can be controlled by reducing the grouting pressure, which effectively improves the quality of pile body and controls the cost.Improve the drilling speed of drill pipe, accelerate the speed when sinking, slow down the speed when lifting, to ensure uniform soil mixing.Through the above measures, the strength of the mixing pile body is improved and the integrity of the pile body is guaranteed.Pile integrity, effective pile diameter, pile length, pile strength uniform accord with the design.The difficult problem of large diameter and deep cement mixing pile is solved, which provides a good reference value for similar engineering.

The linear elastic Bisar software is used to calculate the mechanical properties of a typical semi-rigid pavement structure. Based on the concept of structural strength coefficient, the fatigue life of each pavement structure layer is deduced. The results show that: (1) The maximum value of deflection is obtained at x=3r/2, the maximum of the surface stress is obtained at X=r/2 and Y=0, and the peak of the principal (shear) stress at the bottom of the (bottom). (2) At the same time, the horizontal load, road surface deflection and the maximum stress position of the surfacing surface are invariably applied at the same time. The deflection changes little, and the maximum principal stress increases faster than the maximum shear stress. The maximum. (3) The cracking order of structural layer is as follows: shear cracking of surface layer → bending and cracking of surface layer → bending and cracking at the bottom of base layer → Bending and cracking at the bottom of semi-rigid base → bending and cracking at the bottom of the surface layer, the inner edge of single circle is the destroying source of asphalt pavement, and the initial damage is shear (bending) failure. Therefore, the durable pavement Should consider the principle of structural layer cracking from bottom to top, and to prevent the early destruction of the surface layer. (4) The cracking of the base layer will be reflected to the semi-rigid base and surface layer, which is the first step of structural damage, so strengthening The construction quality of the subbase is an important measure to reduce road damage.

The overall dissolution and weathering of limestone slope have significant temporal and spatial variability, so it is difficult to obtain the mechanical parameters of complete slope accurately and effectively according to conventional specifications, and the reliability of the numerical simulation result would be weaken or even to be completely invalid, and it is difficult to provide effective reference information for field construction. Therefore, a method for obtaining the mechanical parameters of slope based on GPR and displacement back analysis is proposed. On the basis of a limestone slope in No. 2 section of Yizhou-Hechi expressway in Guangxi, the water-rich and crushing properties of the slope are detected by GPR, and the slope is divided into different graded units. Then, a displacement gauge is installed on the non-cavity unit block to measure the displacement value of the unit block, and the mechanical parameters such as elastic modulus, poison’s ratio and cohesive force of different unit blocks are obtained by using BMP90 displacement back analysis method accordingly. The grid model of complete slope is established by using MIDAS-GTS finite element numerical simulation software, and the sliding displacement value of the slope is calculated by using the mechanical parameters of different unit blocks obtained by back analysis and the whole assignment of specification. In order to compare and verify the numerical simulation result of the sliding displacement value, the field synchronous monitoring and measurement of the displacement is carried out. Compared with the results of synchronous field displacement monitoring and measurement, it is found that the numerical simulation values based on slope unit division and its back analysis result are close to the monitored values, which indicates that the mechanical parameters obtained by this method are more consistent with the real values of slope than the mechanical parameters of complete slope generally assigned according to the specification. The study can provide relevant reference for numerical simulation analysis of limestone slope stability in dissolved areas.

Mass concrete, a common structure in bridge engineering, is frequently threatened by cracking. Based on the gravity anchorage of a long-span suspension bridge that has been in operation for more than ten years, the causes of the cracks growing year by year in the anchorage were analyzed in this paper. The refined numerical model of the anchorage was established via the space finite element software. Taking full account of the environmental characteristics of the bridge site, the temperature sensitivity of the anchorage was simulated and analyzed, and the stress distributions on the surface of each side of the anchorage at different temperatures were analyzed. The calculation results showed that there is little correlation between anchorage cracking and anchorage bolt force. Under condition 2 temperature increased 20 ℃, the principal tensile stress of anchorage reached to 1.5 times of the allowable stress, Under condition 6 anchorage surface from 40 ℃ suddenly dropped to 20 ℃, the principal tensile stress reached to 2.4 times of the allowable stress. Thus, under the dual effects of internal and external constraints, the cold hit effect of the mass concrete anchorage resulted in the sudden drop of the surface temperature of the anchorage concrete to produce "internal constraint cracks", and the overall temperature rise caused the expansion of the anchorage concrete to produce "external constraint cracks". The two types of cracks led to the vertical cracks of the anchorage. Besides, the environmental and construction factors were the main causes of cracking of transverse construction joints. At last, the anchorage was reinforced with high-performance concrete with an anti-crack reinforcement mesh, which presented good results in the follow-up observation, providing a certain reference value for similar projects.

It is very important to determine the reasonable design wind speed at the bridge site in coastal open area for the study of wind resistance performance of long-span bridges. On the engineering background of Hongqimen Grand Bridge in Foshan City, Guangdong Province, first, taking the centre of the main span of the bridge as the circle center, the topographic model of the bridge site with a geometric scale of 1∶500 is designed, the terrain, vegetation and buildings within a radius of 1 km are simulated. Then, the wind speed distribution at the bridge site in the coastal open area is studied by using terrain model wind tunnel test. Afterwards, conservatively selecting the mid-span measuring point as the research object, and taking the average surface roughness coefficients of different flow directions as the correction parameters, the design wind speed values of the specification method and the weighted average method are modified. Finally, the concept of landform partitioning is put forward firstly and the practical analysis process is given. According to the weight of geomorphic area and the weight of relative position of measuring point, the influence of nonuniform local landform and its relative position on surface roughness coefficient is studied quantitatively. The result shows that (1) in the coastal open area, the wind speed profiles of different wind directions match well with the specification recommended power exponent law, the distribution of surface roughness coefficients obtained from the fitting test data is relatively concentrated, the correlation is strong, and the surface roughness coefficients under most working conditions do not exceed the class B surface roughness coefficient in Wind-resistant Design Specification for Highway Bridges (JTG/ T 3360-01—2018), indicating that the incoming wind direction and the location of measuring points have little influence on the development of wind speed profile; (2) the corrected wind speed is 1.7% better than the value obtained by conventional method, and the recommended value of design wind speed at the bridge site is given; (3) the geomorphic weight is 16% higher than the position weight. The study result is beneficial to refine the reasonable value of surface roughness in the coastal open area.

The construction process of steel-concrete composite girders is simulated by using 3D finite element model and suspension bracing method. The influences of multiple factors such as self-weight of suspension bracket, wind load, longitudinal spacing of suspension points, concrete deck slab thickness, concrete casting process and suspension bracket removal on the mechanical properties of the main steel girder and the composite girder are analyzed. The mechanical behavior of the steel-concrete composite girders during the construction process by suspension bracing method is revealed. The result shows that (1) The normal stress and displacement of the steel girder increase with the increase of the weight of the suspension bracket and they have relatively large impact on the increase. (2) The wind load during construction process will produce large transverse displacement of the main steel girder, the transverse wind load should be considered in the load combination analysis and necessary measures should be taken to limit the transverse displacement of the main steel girder during the deck casting process. (3) The displacement and stress of the main steel girder will show a parabolic change with the change of the longitudinal spacing of the suspension points, so the optimal value of the longitudinal spacing of the suspension points is recommended to be 4 m. (4) The maximum mid-span displacement and stress of the main steel girder increase with the increase of the deck slab thickness, and the weight of the deck slab occupies the main position in the whole system force. (5) In the process of casting deck slabs with the suspension bracing method, the stress and deformation of the main steel girder increase with the concrete construction stage of the deck slabs. In order to ensure that the geometric shape of the bridge at each stage is consistent with the theory result, the design elevation of each section should be pre-raised during the construction process according to the vertical displacement and deformation of the main steel girder caused by the construction of each casting stage. In addition, the upward rebound of the main steel girder caused by the removal of the suspension bracket must be fully considered when setting the pre-arch of the steel-concrete composite girder.

Taking the "closed-door" tunnel collapse with high safety risk as the research object, based on the innovative technical route of "three-section and four-step" method, it is verified by engineering example and the summary is carried out. On the basis of successfully treatment of many such large tunnel collapses, the relatively common "three-section and four-step method" safety treatment technology for treatment tunnel collapse treatment is innovated ("three-section" refers to the collapsed section and the collapse-affected sections at both ends, "four-step" refers to the steps of sequential construction). This technical method takes the tunnel collapse section, the visible collapse affected section immediately adjacent to the tunnel collapse section, and the invisible collapse affected section as the treatment objects. The main technical method of "three-section and four-step" method is: after the tunnel collapse, first, according to the actual engineering geological condition of collapse section and the collapse affected section, collapse condition, collapse cavity stability, deformation, design and construction of the collapse affected section, to comprehensively analyze and judge the safety risk of each section, and evaluate the safety risk in sections. Second, according to the result of safety risk evaluation, to determine the reasonable construction sequence and steps according to the way of gradually advancing from the position with low safety risk to the position with high safety risk. According to this technical method and the corresponding technical scheme, the treatment of the "close-door" tunnel collapse is completed. Taking the "close-door" tunnel collapse of Wangmazi tunnel No. 1 emergency parking zone for example, through scheme comparison and selection, the tunnel collapse is treated safely and effectively treated by using the "three-section and four-step" treatment technical method and the corresponding technical scheme. Practice has proved that the "three-section and four-step method" is a safe and effective technical method to treat the "closed-door" tunnel collapse, it has versatility, operability and safety.

Since the resumption of highway tolls on May 6, 2020, the national highway network toll collection system based on ETC has been basically stable. With the rapid rise of ETC users, ETC-inefficient transaction increase, which brings great challenges to highway operation services. On the basis of full investigation, this paper analyzes the methods and cases of applying vehicle road cooperation to improve the efficiency of highway toll operation service, puts forward the key work direction to improve the highway operation service level in the future, and discusses the implementation idea of constructing vehicle cooperation service system based on ETC system.

In order to ensure the roadside traffic safety of the multi-bridge and multi-tunnel section on the expressway in mountainous areas and optimize the roadside traffic facilities, and reduce the road traffic accidents caused by the over-frequency changes of the driving environment among the bridge group and tunnel group and their intervals, combining with the driving rules, the prediction model of the numbers of roadside accidents, passenger and freight vehicle accidents in multi-bridge and multi-tunnel section on the expressway in mountainous areas is established by using statistics, machine learning and other related theories. In order to analyze the influence of driving environment of expressway on drivers visual, psychological and operational characteristics, 10 prediction indicators are selected from the aspects of road alignment, traffic structure, traffic environment and weather condition. The action mechanism between roadside accidents and 10 predictive indicators is explained by employing Spearman correlation analysis. The roadside accident prediction model based on BPNN, GA-BPNN and PSO-BPNN are established. MAE, RMSE and MAPE are used as the model evaluation indicators to select the optimal model. The roadside accident data including rollover, side collision and collision with fixed objects are verified by examples by using the accident patterns of Chongqing-Hunan Expressway in the past 5 years. The result shows that (1) the roadside accidents of the roadside accidents of multi-bridge and multi-tunnel section on expressway in mountainous area are comprehensively affected by 10 prediction indicators, which are positively correlated with the length of road section, the proportion of curved roads and the proportion of bridges, and the influence of length of road section is the greatest; (2) compared with BPNN and GA-BPNN prediction models, the errors of MAE, RMSE, and MAPE of PSO-BPNN are reduced by 18. 5%, 17. 65%, and 24. 16% on average, and the model prediction error is smaller and the accuracy is higher; (3) the accurate prediction of the number of roadside accidents and the number of passenger and freight vehicle accidents can provide effective decision-making support for the optimization design of roadside facilities.

In order to improve the safety of truck traffic on continuous downhill sections of highways, optimise traffic safety management or the design of traffic safety facilities, study in depth the risk of rear-end accidents of trucks on continuous downhill sections of highways, based on actual measurement data, put forward the evaluation index of rear-end risk considering the speed difference and headway time distance-Collision Deceleration Rate（CDR). Collision Reduction Rate (CDR). Firstly, the principle of risk of rear-end accidents of trucks on long downhill road sections is analysed, and the data of trucks travelling on long downhill road sections in a special control area of a western motorway are used to determine the risk influencing factors as speed difference and headway time distance; then, the distribution law of effective CDR data is analysed and calculated through fitting distribution test, and the 85% quantile value of its distribution is taken as the threshold value of dangerous CDR; finally, the collision potential index (CPI) is combined with the concept (CPI) to establish a CDR-based continuous downhill truck rear-end risk probability model. Based on the tailgating accident data in the special control area of the motorway, the CDR-based continuous downhill truck tailgating risk probability model is applied and tested, and the results show that: in the fitted distribution test, the CDR samples of the studied continuous downhill section obey lognormal distribution, and the threshold value of hazardous CDR is 0.4916 m/s²; there are more significant differences in the tailgating probability risk at different measurement points, while the tailgating risk at different The correlation coefficient between the accident rate data and the probability risk data is r(X,Y)=94.5%, which is a strong correlation, i.e. the trend of the accident rate data and the probability risk data is consistent, indicating that the CDR-based probability model of tailgating accident risk can provide a scientific assessment basis for the risk study of continuous downhill sections of highways, and the research method can be used for The study method can also be used as a reference for other sections of highways.

Expressway projects have a significant investment, long construction period, and many influencing factors. It is necessary to explore the theory and practice of the modernization of expressway construction management and to improve their construction management level further. Based on systematically summarizing the development process and focus of highway modernization, this paper clarifies the concepts and core essentials for the modernization of expressway construction management and simplifies it as the concept of "intelligentization, construction, and quality". It analyzes the connotation of expressway construction management modernization from elements, three-dimensional structure, and modernization system. Based on humanization, professionalization, standardization, intelligentization, technological innovation, and green environmental protection, etc., this paper proposes a modernization system framework for expressway construction management, and forms the corresponding connotation analysis table, and further clarifies the connotation, goal, idea, and implementation key of the modernization of the expressway construction management. The threshold entry and level evaluation of the highway construction management modernization are discussed by the two stages of establishment and evaluation, and following the logical thinking of Connotation/Ideas-Goals-Criteria and Standards, an evaluation index system is proposed based on the practice of Guangdong Province expressway construction management. The research results have reference value for further improving the level of expressway construction management and help to realize the modernization of the expressway system and capacity for governance.