In order to reasonably and efficiently carry out the risk assessment of road tunnel construction collapse, the risk assessment model of road tunnel construction collapse was studied by rough set (RS), grid search method(GS) and support vector classification (SVC). Firstly, the index system of highway tunnel construction collapse risk evaluation was constructed by integrating advanced geological prediction. At the same time, the information of 100 tunnel collapse cases was collected and the index data was discretized. Secondly, attribute reduction was conducted based on the condition information entropy of rough set to obtain the reduced core index set. Then, grid search method was used to find the optimal parameters of the support vector classification training set, the risk assessment model of highway tunnel construction collapse based on rough set-grid search-support vector classification (RS-GS-SVC) was established. Finally, the model was used to predict the test samples. The results show that under the condition of the same learning sample, compared with rough set-genetic algorithm-support vector classification (RS-GA-SVC) model and Rough set-particle swarm optimization-support vector classification (RS-PSO-SVC) model, RS-GS-SVC model has higher classification accuracy; Under the same proportion of training set and test set, the prediction accuracy of RS-GS-SVC model is higher than that of GS-SVC model, with the accuracy rates of 93.33% and 90% respectively, and the operation time of RS-GS-SVC model is shorter. It can clearly be seen that the model complexity is effectively reduced and the classification accuracy is improved through the reduction of rough set conditional information entropy attributes.

In order to improve the problem of easy cracking in the negative moment zone of the composite beam, the UHPC(ultra-high performance concrete)-narrow steel box composite beam structure was proposed, and the shear load capacity calculation method of UHPC-narrow steel box composite beam was obtained based on the ultimate equilibrium method and the sub-stacking method. In order to verify the accuracy of the calculation method, one normal concrete narrow steel box composite beam and three UHPC-narrow steel box composite beam specimens were designed with the thickness of UHPC layer and steel fiber as variables, and the test beams were subjected to mid-span reverse loading test to obtain the shear resistance of the composite beam under negative bending moment. The test results show that compared with the normal concrete narrow steel box composite beam, when the UHPC material is used in the wing slab, the crack distribution in the wing slab was more regular, and with the increase of the thickness of the UHPC slab, the crack distribution gradually shows the characteristic of vertical equidistant distribution, and when the thickness of the wing slab was kept constant and the thickness of the UHPC layer was increased by 50 mm, the yield load increases by 12.5% and the ultimate load increases by 8.3%, and the deflection value corresponding to the ultimate load is reduced by 22%. By analyzing the yield deflection as well as the ultimate deflection of each specimen, it can be seen that the yield deflection tends to increase gradually with the increase of UHPC airfoil thickness, and the proportion of the elastic phase of the combined beam keeps increasing. The comparison of the test data with the theoretical calculation results shows that the calculation results obtained by the sub-stacking method can more effectively reflect the contribution of UHPC layer, ordinary concrete layer, steel box, reinforcement and filled part of concrete to the shear load capacity, and the results are more accurate.

In response to the tasks of detection and maintenance in small-diameter pipeline transportation, a small-scale soft pneumatic pipeline crawling robot was designed and developed. The robot employed the technique of analytical implicit triply periodic minimal surface offset to form a solid structure with thickness, and achieved the anisotropy of structural stiffness by adjusting the parameters of implicit equations. Based on this, the radial and linear actuators were designed to meet the flexible motion requirements of the robot inside the pipeline. To optimize the performance of the robot, a joint parameter optimization framework based on MATLAB, Rhino, and ABAQUS was proposed, and an automated parameter optimization process was implemented using Python scripts. Through this framework, the motion performance and adaptability of the robot could be effectively improved. Based on two types of deformation actuators, the overall structure of the pipeline crawling robot was designed, and the manufacturing method and motion control gait were elaborated in detail. Experimental results show that the designed pipeline robot can stably move along the pipeline in two different postures and under certain load conditions, verifying the feasibility of the joint parameter optimization framework. The research results provide valuable references for the parameterized design and optimization research of subsequent pipeline crawling robots, which contributes to the application development of soft robots in the field of small-diameter pipeline detection and maintenance.

Land use and traffic safety is a hot topic of mutual concern in the fields of urban geography and transportation. However, existing research on the impact of land use on pedestrian traffic accidents often incorporates a unified framework of built environment and mainly adopts measures such as land use mix or the proportion of land use types, lacking detailed analysis on land use types, thus making it difficult to translate their findings into actionable design strategies. Taking Yuzhong District, Chongqing City as an example, the land use types were finely characterized based on point of interest (POI) data, and the extreme gradient boosting (XGBoost) model was applied to explore the nonlinear relationships between land use types, pedestrian, road conditions, road environment, and the severity of pedestrian traffic accidents. The study finds these as follows. ①Land use types play an important role in the severity of pedestrian traffic accidents, with hospitals, residential areas, and educational land being the most influential. The presence of hospitals, residential areas, and educational land within a 300-meter buffer zone around accident sites reduces the severity of pedestrian traffic accidents. ②Road sections with curved and sloped road alignments are high-risk areas for severe pedestrian traffic accidents; entrances and exits of road sections, narrow road sections, and intersections have a mitigating effect on the severity of pedestrian traffic accidents. The findings provide policy insights for refined land use planning and governance to reduce the severity of pedestrian traffic accidents.

To solve the path planning problem of mobile robots in complex orchard environments such as irregular and rugged terrain in hilly and mountainous areas, an improved grey wolf algorithm based 3D path planning method for mobile robots was proposed. By simulating the actual geographical environment, a three-dimensional orchard terrain and obstacle model was established, and a path planning objective function model was structed. By introducing the sparrow search algorithm (SSA) the initialization method, convergence factor, local search ability, and global search ability of the standard grey wolf optimization (GWO) were improved. The simulation experimental results show that the proposed algorithm has the advantages of fast optimization speed, optimal path planning distance, and fast convergence speed compared to other algorithms, indicating the effectiveness and superiority of the proposed method.

To study the wind pressure distribution characteristics of long-span roofs of airport terminals at different mountain heights in mountainous areas, a rigid model wind tunnel pressure measurement test of airport terminals roofs at mountain heights of 0 m, 30 m, 60 m, and 90 m was conducted to compare and analyze the effects of the heights on the surface mean and pulsating wind pressure, non-Gaussian characteristics of pulsating wind pressure, peak factor, and extreme wind pressure of the roof surface. The results show that the increase in mountain height significantly increases the mean and fluctuating wind pressure coefficient at the windward leading edge of the roof, and also intensifies the degree of flow separation at the leading edge of the roof. This causes the skewness, kurtosis, and probability density function of the fluctuating wind pressure at the windward leading edge of the roof to deviate significantly from the standard Gaussian distribution, exhibiting strong non-Gaussian characteristics. At the same time, the Hermite moment model was used to calculate the peak factor, and it was found that the peak factor of most measuring points on the roof surface was mainly distributed in the range of 3.5~4, which was much higher than the recommended value of 2.5 in GB 50009—2012. The extreme wind pressure value at the front edge of the roof also increased with the increase of the mountain height, and there was a similar variation pattern at the edge of the roof under all wind directions. Among them, the most unfavorable extreme negative pressure on the roof surface at a mountain height of 90m decreased by 44.9% compared to the 0m mountain height. Research can provide useful suggestions and references for the design and construction of terminals in similar airports.

Laser ultrasonic detection technology possesses unique advantages combining ultrasonic and optical methods, enabling non-contact detection while enhancing temporal and spatial resolution. To enhance the excitation efficiency and defect detection accuracy of laser ultrasound, optimization of laser source parameters is necessary to improve energy exchange efficiency and reduce costs. Research has been conducted on the propagation characteristics of laser ultrasonic sound fields under various conditions. Numerical simulations of the process of laser ultrasonic action on X80 pipelines were performed using COMSOL Multiphysics finite element software, and the accuracy of the model was verified. The relationship between laser source parameters and ultrasonic field was studied by combining the set laser pulse width and laser spot radius, and further analysis of the relevant data was carried out using MATLAB. The analysis results indicate that when the pulse width is set to 20 ns and the spot radius is set to 300 μm, laser ultrasonics exhibit relatively optimal excitation efficiency in X80 pipelines. This provides important reference for improving the excitation efficiency of laser sources.

A significant number of subsalt oil and gas fields are distributed worldwide. Due to the high costs associated with coring operations in salt formations, conducting creep experiments on specific salt rock cores is challenging. To address this issue, a method for creating artificial salt rock cores was developed wherein the degree of recrystallization was controlled by adjusting the preparation temperature and pressure. By testing the acoustic velocity, density, and uniaxial peak strength of salt rock cores under different preparation conditions, the optimal preparation conditions were identified. Creep experiments verified that the artificial salt rock cores exhibit similar creep characteristics to natural salt rock cores, indicating the feasibility of using artificial cores as substitutes for natural ones. Based on indoor creep experiments, a viscoelastic constitutive model of salt rock was constructed. The result showed that the rheological characteristics of the decelerating creep stage conform to the Kelvin model, while the steady-state creep stage aligns with the Heard model. A UMAT subroutine was compiled to describe the creep characteristics of the decelerating and steady-state stages, demonstrating a good fit and indicating the applicability of the viscoelastic model constructed in this study. Creep experiments on composite salt rocks with different contents of anhydrite showed that the presence of anhydrite inhibits the creep of salt rock. The higher the anhydrite content in the salt rock, the lower the creep rate of the rock. Therefore, in salt layers containing anhydrite, the density of drilling fluid used during drilling can be appropriately reduced.

In order to comprehend the scale and connectivity of sandbodies in late oilfield development, it is imperative to conduct a detailed characterization of fluvial sandbodies in the upper Guantao Formation of Gudong oilfield. Through comprehensive analysis of core, well logging, and seismic data, the sedimentary characteristics of braided river and meandering river were determined under the control of dense well array. The results indicate that the upper Guantao Formation has undergone a sedimentary evolution process from braided river to meandering river. The lower Guantao Formation exhibits braided fluvial reservoir with braid bar, braid channel, and overbank sand microfacies, while the upper Guantao Formation features meandering fluvial reservoir with microfacies types such as point bar, abandoned channel, crevasse splay, and floodplain. By conducting core-log calibration analysis, the logging response characteristics and sandbody development laws of braided and meandering rivers were determined. The channel sandbody of a braided river is cut and overlapped in multiple stages while being distributed across multiple branches on a plane. On the other hand, the meandering fluvial channel sandbody develops in isolation but forms strips on a plane. Under the control of dense well array, we have quantitatively determined the scale of sandbody development for both braided and meandering rivers. Additionally, the relationship between sandbody thickness and width for different river types were established which holds significant guiding significance for identifying sandbody connectivity and 3D geological modeling.

Due to the similarity in site selection between underground pipelines and power facilities such as high-voltage power lines and urban rail transit power supply systems, underground pipelines are increasingly affected by stray currents generated by power facilities. The impact of AC stray currents on the corrosion rate of pipeline coating defects were simulated and analyzed. The effects of parameters such as AC current magnitude, soil conductivity, internal pressure of the pipeline, stress, distance to grounding electrode, and pipeline radius on corrosion were investigated in the study. The results indicate that when the stress on the pipeline is less than the yield strength, the effect of stress on the corrosion caused by AC stray currents is relatively small. However, after the deformation of the pipeline increases, serious corrosion will be induced by stress. The greater the AC current, the greater the corrosion at the defects of the pipeline coating. The lower the AC frequency, the greater the corrosion at the defects of the pipeline coating. The closer the distance to the grounding electrode, the greater the corrosion at the defects of the pipeline coating. The higher the soil conductivity, the greater the corrosion at the defects of the pipeline coating. The smaller the pipeline radius, the greater the corrosion at the defects of the pipeline coating. These research findings are of significant importance for ensuring the safe operation of oil and gas transportation pipelines under the influence of AC stray currents.