To find the rule on the effect of different temperatures on salt expansion of sodium sulfate saline soil and ensure the safety of road engineering in areas with sulfate saline soil, we tested saline soil samples in a laboratory. By analyzing the variation in soil samples before and after cooling and the variation in water content under different temperatures, we determined the influence of salt expansion on soil components under different temperatures by using computed tomography. Results show that salt expansion intensifies and tends to stabilize under decreasing temperature. Salt expands mainly from 0℃ to the initial precipitation temperature of salt crystals, and very slight precipitation occurs at a negative temperature; thus, salt expansion is very low at temperatures below 0℃. Moisture content decreases as temperature decreases, and the diminishing trend decreases and gradually stabilizes at 0℃. Damage in soil structure increases as temperature decreases. Change in porosity occupied by air is mainly determined by change in water content. Porosity changes acutely with acute changes in water content, and these parameters show an inverse relationship.

The damage mechanism of reflective cracking,particularly on semi-rigid asphalt pavement with large stone porous asphalt mixture (LSPM) is investigated in this study.An asphalt pavement model with multilayered base (i.e., LSPM and semi-rigid layer) using discrete element methodis developed.This study analyzes the influence of the inner structure of asphalt mixture on the stress field around the crack tip,which is under the vehicle load after the cracking of a semi-rigid layer. The focus is on the mechanism of cracking and the influence of the inner structure of the mixture, such as gradation, the geometric feature of coarse aggregate, and space.The crack expansion rate is also analyzed.Results show that, under vehicle load,the crack in the semi-rigid layer causes stress concentration, which decreases around the bottom of the LSPM.The load on the top of the crack tip produces stress level concentration,the unbalanced load produces shear stress concentration, and the stress decreases progressively from the crack tip to the surrounding area. In the LSPM,a large grain size of the coarse aggregate is better than a small grain size. Its overall stress level is low and the crack development rate is slow on the stress field of the crack tip. The LSPM can reduce stress concentration and prevent the development of reflective cracking effect.

Multi-factor evaluation was established based on the analytic hierarchy process (AHP) to analyze the advantages of different road alignment fitting methods and provide guidance on selecting linear fitting methods for road reconstruction and extension engineering. Through this evaluation system, the reliability, precision, and difficulty degree of the least squares, MATLAB, and cubic spline curve methods were evaluated. Results show that the least squares method exhibits the highest precision; the MATLAB method achieves the strongest stability; and in terms of difficulty degree, the cubic spline curve method is the simplest method. AHP is adopted to calculate the scores of the three methods. The least squares method has the highest score. The score of the MATLAB method is 61.05% that of the least squares method, whereas that of the cubic spline curve method is only 42.72% that of the least squares method. The results quantify the evaluation factors and provide suggestions for selecting an appropriate and effective road fitting method under different conditions. The results also provide a reference for evaluating road alignment methods.

The technical characteristics combined with the pre-crack at home and abroad present the early strength of grassroots without the material repair technology.However,the grassroots space mesh microcracks must be implemented in the early period of heavy traffic, and widely related transverse cracks reflective of asphalt pavement cracking probability, which decreases asphalt pavement status, are also improved; a finite element method was analyzed to simulate the ideal type of crack between the two kinds of mechanical asphalt pavement crack under the form of responses, and the surface layer of microcracking technology life asphalt pavement is calculated. This study found that the microfracturing technique reduced the life of the asphalt surface to some extent. However, to solve the problems of the conventional repair techniques for readily reflective cracks and to achieve a rapid restoration of the technical requirements, a microcracking technology rapid repair in the grassroots has indicated a certain feasibility.Considering that crack forms are drawn, the fatigue life of the asphalt surface,the definition and control of the size of the cracks in the construction, and other related issues require further studies under actual crack forms.

An asphalt pavement performance evaluation model based on deflection is established by combining the subjective deflection weight obtained from the improved analytic hierarchy process and the objective deflection weight obtained from the entropy method through the variable weight principle. The established model is used to comprehensively evaluate asphalt pavement performance. This model is implemented in two ways, namely, introduction of high-speed deflectometer and observation of long-term pavement performance; hence, the application of the new pavement performance evaluation model is guaranteed. Results show that the evaluation result of the new model can reflect each index weight proportion of asphalt pavement performance on the basis of the existing specification and real-time parameter evolution rule of asphalt pavement. The new model can reflect the actual pavement quality objectively and accurately.

To study the influence of the coexistence condition of acidic and alkalic additives on the mechanical performance of stabilized clay based on the processes for obtaining the basic physical parameters of soil and analyzing the stabilization mechanism of ionic and alkalic soil stabilizers, an experiment on the mechanical behavior characteristics of stabilized clay was performed using different types of ionic and alkalic stabilizers through a series of laboratory tests. The following results are obtained. (1) Typical soil is low liquid limit clay, and the ionic stabilizer with an optimal content of 0.014% mass ratio to dry soil exhibits strong acidity. (2) As a result of its unique molecular structure, the double electric-combined water film becomes thin rapidly during compaction molding, in which the compactness of clay particle structure increases. (3) The 7-day unconfined compressive strength can be improved with different contents of the ionic stabilizer. (4) Except for the high lime soil mixture, the compaction degree of soil exerts a pronounced effect on the stabilization performance of an ionic stabilizer and the least compaction degree should be over 96%. (5) The unconfined compressive strength, indirect tensile strength, and freeze-thaw performance of the acid-alkali-stabilized soil demonstrate a gradually increasing tendency with an increase in curing time, however, the evolution characteristic of strength exhibits an advantageous superposition threshold value when compared to the alkali-stabilized clay. The neutralization reaction and oil membrane of soil particles will inhibit the later reaction processes of carbonation, pozzolanic, and hydration of lime-|cement-stabilized soil.

The evaluation methods for asphalt pavement preventive maintenance both local and abroad are investigated in this study. A comprehensive evaluation model that combines the evaluation index of pavement and material performance in domestic technical specifications and that considers the lack of weight allocation method for evaluation indices is proposed for the preventive maintenance of asphalt pavement. On the basis of the combination of practical engineering experiences, the expert scoring method, and experimental testing data, the model utilizes a new method, i.e., the improved entropy weight-analytic hierarchy process, to calculate the comprehensive weight coefficients of various evaluation indices and to evaluate the effect of preventive maintenance. The preventive maintenance engineering of highway asphalt pavement in Zhangjiakou is used as an example. Results show that the model is feasible. Moreover, the results can provide technical support for the application of preventive maintenance measures to asphalt pavement.

The characteristics of pile-rock structure interface considerably influence the load transmission process of the rock-socketed segment of pile. The expressions for pile side friction are established based on the mechanism of sliding dilatancy. An analytical solution for the friction and axial force of the rock-socketed segment are obtained when the surrounding rock is under the conditions of the sliding dilatancy stage. Then, the distribution of friction resistance and axial force along the rock-socketed segment are discussed based on the obtained analytical solution and the pile tip load sharing ratio. The load transfer process of the rock-socketed segment of pile is analyzed by conducting a field test on a large-diameter rock-socketed pile. The side friction characteristics in soil and rock are expounded. The calculation parameters are obtained inversely by combining with the theoretical formula. Theoretical calculation result exhibits good agreement with measured data.

Fatigue truck models with deterministic parameters were developed int a stochastic vehicle flow model. A response surface method was used to approximate the function between vehicle axle weight and equivalent fatigue stresses with few training data to solve the time-consuming problem of bridge finite element analysis under traffic flow loads. A probabilistic fatigue damage modeling method was presented and applied to the rib-to-deck details of steel box girder bridges. Finally, the fatigue damage model was applied to the reliability assessment of steel box girder bridges, and influences of traffic flow parameters on structural fatigue reliability were studied. Numerical results indicate that the higher occupancy rate of heavy vehicle flow in a slow lane than in a fast lane mainly explains the decrease in the fatigue reliability of corresponding rib-to-deck details. The increase in vehicle axle weight causes a rapid decrease in the fatigue reliability index of steel box girders. The fatigue reliability index of rib-to-deck detail in the slow lane decreases from 3.42 to 0.72 when the annual linear growth factor ranges from 0 to 1%. The stochastic fatigue vehicle flow model and the probabilistic model for fatigue damage exhibit considerable potential in the probability assessment of bridge fatigue damage.

We infer that several equations currently used to calculate the bearing capacity of an oblique section of a member strengthened with an enlarged section have several mistakes in the specifications for strengthening the design of highway bridges (JTG/T J22-2008). The shear capacity of the oblique section of a bending member strengthened with an enlarged section could be more accurately and safely calculated using contrastive analysis of relevant design specifications and engineering calculation examples. We particularly challenged the calculation method in which the new stirrups bear the second increased shear based on the proportion of the section area of all web reinforcements. We proposed two calculation methods which can be applied to the general case of unilateral thickening of the member section and the reinforcement of three sides. We also tested an engineering example. The second proposed method, which considered the comprehensive shear capacity of concrete and stirrups, is simple and relatively safe. This method is unified with the design specification of an ordinary bridge component. The proposed method will be adopted in the technical specifications for strengthening of urban bridges which will be enacted soon.

A bus running on straight roads, general curves, or sharp curves is subjected to vehicle dynamics simulation tests under different overspeeding degrees to study the effects of different overspeeding degrees on driving safety when a bus runs on a curve. TruckSim software is used in the simulation, and lateral offset and tire load transfer rate are selected as analysis indicators. The effects of different overspeeding degrees on lateral stability when the bus runs on curves are quantitatively analyzed. Simulation results indicate that (1) overspeeding degree is negatively correlated with the lateral stability of a bus running on a general curve or a sharp curve. (2) A high overspeeding degree corresponds to poor lateral stability and high likelihood of an accident. (3) Under the same overspeeding degree, a bus running on a general curve likely deviates from the curve path and causes accidents, such as running off roads and enter into adjacent or oncoming driveways. A bus running on a sharp curve easily experiences a rollover accident.

The concept of a high-speed passenger traffic location line is proposed by analyzing intercity rail traffic location and network evolution characteristics to improve the effectiveness of intercity rail transit network layout planning. Then, a multilevel intercity rail transit network planning and optimization model is constructed. The model is divided into two levels, namely, the backbone network and the preliminary network. The backbone network optimization model is the minimum spanning tree model, which uses the reciprocal of economical relation intensity as its weight. The preliminary network model is a multi-objective function, which maximizes economical relation intensity and connectivity and minimizes the total length of rail transit lines. The optimization model provides a new method for intercity rail transit network planning. Finally, the rationality and effectiveness of the network layout are verified using the line network within the Wuhan urban agglomeration area as an example.

Different parameter results are produced using various methods with the same sample, which follows the lognormal distribution. Therefore, massive historical data of an expressway toll are collected to fit the lognormal distribution of the travel times of cars and trucks. Maximum likelihood estimation is compared with least squares estimation based on five indexes:the sum of squared errors (SSE), the SSE of the cumulative distribution function, the coefficient of determination, the relative error of the skewness coefficient, and the relative error of the kurtosis coefficient. Experimental results show that the maximum likelihood estimator is more efficient than the least squares estimator in fitting the cumulative probability distribution. The unit distance travel time reliability model for the section is established, and the parameter estimation method and the appropriate threshold are provided. Finally, the proposed model is validated using the Shaanxi expressway network in a case study. The results show that travel time reliability is affected by travel distance and departure time. In addition, departure time more significantly affects the travel delay of cars than that of trucks.

This study considers the goal of expressway traffic incident emergency rescue and proposes an emergency resource configuration optimization method with the objective of minimum total area rescue resources in a network. First, a regional expressway road network was processed via network abstraction under the assumption that rescue resource configuration points were fixed. Then, an emergency resource scheduling model based on phased collaboration was built to minimize emergency response time and fulfill the largest resource requirements of accident points. Finally, LINGO and MATLAB software were applied to analyze and verify the models. Results show that the resource allocation amount of each configuration point and network is significantly lower after optimization. Total resources are reduced by 36%. The proposed resource scheduling model contributes to reasonable emergency resource scheduling.

To analyze carbon emission during hot in-place recycling asphalt pavement construction, the construction period is divided into material production and pavement construction using the life cycle analysis method. Then, a carbon emission model is established according to the multiplication principle of the carbon emission coefficient and activity data. On the basis of an engineering example, carbon emission during pavement construction is calculated; carbon emission with different new material ratios, recycled material haul distances, and utilization rates of recycling asphalt mixture is quantified; and the carbon emissions of four pavement maintenance technologies are compared. Results show the following conditions. (1) The carbon emissions of material production and pavement construction account for 20% and 80%, respectively. (2) Carbon emission increases by 2% with an increase of 1% in hot in-place recycling new material ratio. (3) The haul distance of recycled asphalt mixture is 42 km when hot mix plant recycling with 100% utilization rate of recycled asphalt mixture produces equal carbon emission with hot in-place recycling. When the haul distance is over 42 km, the carbon emission of hot in-place recycling is less than that hot mix plant recycling. When the utilization rate of recycling asphalt mixture is lower than 75%, the carbon emission of hot in-place recycling is always less than that of hot mix plant recycling regardless of haul distance. (4) Compared with that in hot in-place recycling, the increase in amplitude of carbon emission on micro-surface, ultra-thin overlay, and mill-and-resurface asphalt pavement is 53%, 72%, and 79%, respectively.