With the rise of three-dimensional road detection technology, more and more roads begin to use three-dimensional road detection vehicles to detect road conditions. Pavement surface condition index (PCI), an important indicator of pavement performance, was used as the research target, and the PCI predicted by using the actual pavement data collected by ARAN9000 three-dimensional multifunctional road detection vehicle. Firstly, the data mining technology is used to consider the factors such as pavement distress, environment and pavement structure. and to process and analyze the data related to the pavement surface condition index of a certain highway in Ontario, Canada, such as data cleaning and feature screening. Then, a machine learning prediction model of pavement surface condition index was constructed, and the complex correlation coefficients (R²) of the multiple linear regression model, the neural network model and the random forest model were 0.562, 0.711 and 0.895. Compared with the neural network model, the accuracy of the random forest model in predicting pavement surface condition index was improved by 0.184, the error was reduced by 1.599, and the training speed was improved by 33s. Finally, the random forest model with high precision is selected for optimization. Due to the large number of input variables, it is impossible to determine which line of data is the outlier through simple statistical analysis, so after establishing and predicting the model, the outlier is determined and deleted through the fitting effect between the predicted value and the real value. Then the modified data were used to retrain the model to achieve the optimal training of the current model. The results show that the prediction efficiency and accuracy of the improved random forest model are higher, and the R² reaches 0.898. The proposed pavement condition index prediction model is accurate and effective, and the prediction results can assist the maintenance department to make more scientific and reasonable maintenance decisions.

The engineering characteristics of frozen soil are closely related to the unfrozen water content, so the determination of unfrozen water content is of great theoretical significance for engineering hydrothermal simulation in cold regions. In order to study the change law of liquid water content during cooling process, the characteristics of three classical unfrozen water content prediction models were compared and analyzed, and the applicable temperature range and parameters variation of the models were discussed. Firstly, based on the existing prediction model of unfrozen water content, 29 groups of experimental data of silty clay were selected to analyze the prediction effect of unfrozen water content, the values of model parameters were determined, and the influence of each parameter on the curve shape of model was studied. Secondly, the Root Mean Squared Error (RMSE) and Average Deviation (AD) of the model were calculated, and the calculation accuracy of the model was discussed. Finally, the upper and lower boundaries of the data scatter diagram were drawn to obtain the reference range of the model parameters, and the relationship between the model parameters and the initial water content was analyzed. The results show that Anderson and Tice's (1972) model has the highest calculation accuracy for specific soil samples; Dall' Amico et al.'s (2011) model has better prediction effect, and the integrity of the model is better; Michalowski's (1993) model has larger prediction error. Anderson and Tice's (1972) model overestimates unfrozen water content in soil, while the latter two underestimate unfrozen water content. With the variation of initial water content, the parameters of Anderson and Tice's (1972) model show a wide range of values, and the prediction has uncertainty; Michalowski's (1993) model takes the second place; Dall' Amico et al.'s (2011) model has the smallest range of variation. The values of parameters a and μ increase with the increase of initial water content, while parameters b, α, n and m have no clear law with the increase of initial water content.

Due to the harsh environment in desert areas, the lack of self-collected road construction materials leads to difficulty in road construction. At the same time, aeolian sand particles are small and unstable, and the foundation treatment is difficult, so using geocell to reinforce aeolian sand as the roadbed structure can provide a new path for constructing highways in the desert. The dynamic response of the subgrade under the impact of traffic load was studied from the two aspects, including vehicle weights and speeds; then, the dynamic stress attenuation coefficient of different subgrade was calculated to put forward the calculation method of geocell-equal generation subgrade thickness. The test zone, the S21 line, is from Urumqi to Altay. The results showed that under traffic load, the stress curve was similar to a sine wave and showed certain hysteresis with the depth. Besides, it was found that the increase of the test speed had little effect on the dynamic stress. By calculating the attenuation coefficient of dynamic stress under different conditions of subgrade fillings, it was found that the attenuation coefficient of the geocell-aeolian sand layer was the largest, followed by the graded gravel layer and aeolian sand layer. The dynamic stress attenuation coefficient showed little relationship with the test speed and vehicle weight, but it was a constant relating to the properties of subgrade filling. The bearing capacity of the subgrade layer was checked by using the equal generation working area thickness method, and the requirements of subgrade bearing capacity can be met when the dynamic stress was transferred to the aeolian sand layer. This research can provide a theoretical basis for the application of geocell reinforcement to aeolian sand in the desert highway.

In order to study the instability mechanism and prevention measures of subgrade engineering diseases prone to overall slip during the filling process and opening operation period of soft foundation embankment on expressway mountain slope, and to achieve the purpose of quickly and effectively treating subgrade engineering diseases and ensuring engineering safety of subgrade during construction and operation period, taking the overall instability of a typical mountain slope embankment section of an expressway in China as an engineering case, engineering investigation, geological investigation, Geo slope simplified Bishop calculation, FLAC3D numerical simulation, and field settlement and displacement measurement were carried out. The results show that the low shear strength and poor stability of the foundation soil at the embankment section mainly led to the deformation of the subgrade fill at the top of the anti-slide pile at the foot of the slope. Based on the accurate understanding of the mechanism of instability, the corresponding engineering treatment are proposed, that is, on the basis of setting anti-slide piles at the foot of the original embankment slope, adding a certain depth of basement replacement to ensure that the embankment and foundation are prevented from shallow slippage. Then, the safety factors of subgrade slope stability before and after treatment are compared and calculated by Geo-slope software, and the effect of treatment measures is pre-evaluated, the safety factor increases from 0.831 before treatment to 1.452 after treatment, meeting the specification requirements. The FLAC3D software is used to compare and analyze the water level displacement, the settlement of foundation, and roadbed before and after treatment. Compared with before treatment, the horizontal displacement and settlement of foundation and roadbed after treatment are obviously reduced, and the stability is greatly improved. The numerical simulation results are basically consistent with the measured results during in situ testing, which verifies the reliability of treatment measures. According to the specific engineering problems of soft foundation embankment on slope, only when the mechanism of instability is known accurately, then effective treatment measures could be adopted.

The endurance time method (ETM) is a novel dynamic seismic analysis, which employs intensified artificial earthquakes as the input. This method can ensure both the structural dynamic effect and computation efficiency when conducting the seismic evaluation of complex structural systems. Based on these advantages, this study investigated the applicability of ETM in the self-centering bridges incorporating prestressed concrete-filled steel tube (CFST) piers. A 3D finite element model of a typical four span continuous-beam bridge which adopted prestressed CFST piers was established by OpenSees software. Compared with the incremental dynamic analysis (IDA) results, the feasibility of ETM to predict the seismic response of self-centering bridges was validated. Also, the effect of prestressing force in piers on the seismic performance of self-centering bridge systems was studied by ETM. Numerical results show that ETM can be used in the seismic evaluation of bridges with prestressed self-centering piers. The seismic response, such as PT force and residual displacement, can be well predicted by using this method. In addition, the influence of prestressing force on the seismic response of bridges is related to the type of bearings and the intensity of earthquakes. For the superstructure, the displacement of main deck can be reduced by increasing prestressing force, but the shear force of fixed bearings increases accordingly. For the substructure, the piers with sliding bearings are less influenced by prestressing force, while seismic internal force of fixed piers increases with the occurrence of prestressing force. Therefore, it is necessary to comprehensively consider the structural system arrangement and seismic basic intensity of site during the seismic design of such bridges.

This article aims to solve the wind stability problem of the super-long-span suspension bridge. According to the characteristics of the ruled surface of the hyperbolic paraboloid, the structure system of the hyperbolic parabolic space mixed cable suspension bridge is proposed. On the basis of the parallel cable suspension bridge, a carbon fiber hyperbolic parabolic space cable network is added. The parallel steel cables bear the vertical load. The hyperbolic parabolic carbon fiber space cable improves the spatial rigidity of the suspension bridge. The two cable systems work together and complement each other. Combined with the engineering background of a 5 000 m Strait Suspension Bridge, the configuration study of the hyperbolic parabolic space cable suspension bridge was carried out, and the ANSYS finite element analysis model was established to analyze and study the structural internal force and dynamic modal characteristics. The research shows that the hyperbolic parabolic space mixed cable suspension bridge has excellent spatial stiffness and wind stability performance, its torsional frequency and torsional frequency ratio are significantly improved, the critical wind speed of flutter is greatly improved, and the long-span suspension bridge is fundamentally solved Wind stability problem.

Based on the 5 000 m super span Qiongzhou Strait suspension bridge with as the engineering background. On the basis of the parallel steel cable suspension bridge, the hyperbolic paraboloid carbon fiber cable net is added to form a new structural system of super long span hyperbolic paraboloid spatial mixed cable suspension bridge. The parallel steel cables bear vertical loads, and the hyperbolic paraboloid carbon fiber spatial cables improve the spatial stiffness of the super long span Strait suspension bridge,and the two groups of cables are mixed to work together.The model of MIDAS finite element analysis is established to analyze the internal force and dynamic modal characteristics of the structure.The results show that:the ratio of torsional frequency to bending frequency and torsional frequency of hyperbolic paraboloid spatial mixed cable suspension bridge are significantly improved, and it has good wind resistance stability. The flutter critical wind speed of parallel steel wire cable suspension bridge is 23.35 m/s, and that of hyperbolic paraboloid spatial mixed cable suspension bridge is 78.34 m/s. In order to resist the super strong typhoon once in a hundred years in Qiongzhou Strait, the technical measures of setting temporary additional anti wind cables are put forward based on the principle of ship anchor cables. The flutter critical wind speed can reach 104.6 m/s. Therefore, the wind stability problem of the 5 000 m Qiongzhou Strait super long span suspension bridge is fundamentally solved.

Aiming at the city wide deck cable-stayed bridge, a double separated deck and four-cable-stayed bridge with univalent hyperboloid single column bridge tower was proposed.The bridge deck with double separated steel box girder replaces the bridge deck wide steel box girder, the univalent hyperboloid single column bridge tower replaces the double column bridge tower, and the four-cable-stayed bridge replaces the double cable-stayed bridge.The univalent hyperboloid single column tower bridge has a thick bottom, which can ensure the bearing capacity of the single column tower structure; the waist of the bridge tower is small and the driver's vision is wide; the wider top of the bridge tower can facilitate the scattered anchoring of stay cables.Combined with the 200 m+420 m+200 m double separated deck and four-cable-stayed bridge with the univalent hyperboloid single column tower, the engineering parameters are designed, the Midas finite element analysis model is established, the static analysis and dynamic modal analysis are carried out, and the structural rationality of double separated deck and four-cable stayed bridge with the univalent hyperboloid single column tower is verified.

According to the design requirements of the pedestrian gallery bridge in a river park, a specific design of a landscape bridge with cable-stayed arch ribs in the shape of flying swallow and the saddle-shaped roof is proposed. Its orthographic projection is ellipse in. And the side elevation of arch ribs is flying-swallow shape with its tail curled up. The top of the bridge is transparent glass with hyperbolic paraboloid surface. Special-shaped spatially curved steel pipes are adopted for the flying-swallow type cable-stayed arch ribs. The bridge deck adopts elliptical plate beam structure, the curvilinear shape of which has unique aesthetic value. On the basis of practical project, parameter design, Midas finite element model, internal force calculation and modal analysis are carried out to verify the structural rationality of the bridge designed.

This paper proposes a hyperbolic parabolic space cable pedestrian suspension bridge structure system based on the egg-shaped arched tower based on the wind resistance requirements of a super-long-span pedestrian suspension bridge. Parallel cables bear vertical loads, and two sets of cable systems of hyperbolic parabolic carbon fiber space cables and wind-resistant cables improve torsional stiffness, work together, complement each other, and significantly increase space rigidity. It can fundamentally solve the problem of wind stability of extra-long-span pedestrian suspension bridges, and can build 500-meter-long super-span pedestrian suspension bridges.

Disasters such as collapse and water inrush are prone to occur when tunnel crosses the soft fault fractured ground. To settle the difficulties encountered in the construction of a highway tunnel crossing the F139 fault broken zone, the comprehensive advanced geological predictions, construction measures and real-time monitoring and measuring systems are conducted in field using tunnel seismic prediction (TSP), ground penetrating radar (GPR), three-bench seven-step method, 3D laser scanning technology, etc. The results demonstrate that the tunnel, starting from the mileage YK20+490, will get into the core influence zone of the F139 weakly fault broken zone. The development of the fractured structural surface and the water-rich condition are in front of the working face visually characterized based on comprehensive geological prediction. Ensuring that the tunnel passes through the F139 fault fractured zone with smoothness and safety, the implementation of comprehensive construction measures effectively curbs the occurrence of disasters of collapse and water inrush in tunneling. According to the comprehensive monitoring and measuring systems, the vault settlement and the horizontal convergence both show a sharp increase firstly, then remain a steady trend, followed by a slowly increase, and finally a stabilization. The maximum vault settlement and convergence displacements are 39.1 mm and 37.5 mm, respectively, which meets the allowable deformation specifications. After 15 days of excavation and support, the accumulated deformation of the surrounding rock shows a law of first increasing and then decreasing from the left wall to the vault to the right wall. The deformation near the vault is the largest with 21~23 mm, and the deformation near the side wall is the smallest with only 4 mm.