Abstract:As the construction of Chinese railway expands from hills to deep mountains and from the inland to the frontier, drill-and-blast tunnels are critical components increasingly confronted with extreme geological conditions and demanding environments. With the rapid development of information and communication technologies such as artificial intelligence, robots, and the Internet of Things, the construction of drill-and-blast tunnels is evolving from full-process mechanization toward greater intelligence and less manpower. This paper systematically reviews the research progress of unmanned construction technology in drill-and-blast tunnels. It focuses on the research status concerning key unmanned technologies, including intelligent construction equipment, digital twin modeling, remote centralized control and collaborative operation of equipment group. The paper also summarizes current achievements and identifies challenges related to equipment intelligence, technology integration, and the establishment of standard systems. Finally, the development trend of integrated application of unmanned construction technology in drill-and-blast tunnels in the future is prospected, in order to provide a reference for promoting the intelligent construction of railway infrastructure .

Abstract:To address the challenges in identifying damage characteristics caused by multimodal Lamb wave propagation, dispersion effects, and signal attenuation in complex structures like steel bridge decks, this study proposes a deep learning-based damage detection method for U-Rib-Deck joints in steel bridge decks. By embed-ding squeeze-excitation (SE) attention mechanisms and long short-term memory (LSTM) networks into convolutional neural networks (CNN), combined with constructing datasets using Hilbert transform envelope curves, effective identification of typical fatigue damages in U-Rib-Deck joints is achieved. The research results demonstrate: ① Under damage conditions, the direct wave packet exhibits a rightward phase shift and amplitude attenuation, confirming the feasibility of using time-domain signal changes for damage detection. ② The SE-LSTMCNN model achieved validation accuracy and test accuracy of 93.67% and 95.00%, respectively, with the recognition accuracy for all types of damage exceeding 90%, indicating the model’s excellent applicability for damage detection tasks in steel bridge deck U-Rib-Deck joints. ③ The classification accuracy of the SE-CNN and LSTM-CNN models improved by 1.00% and 3.33%, respectively, compared to the baseline CNN model, while the SE-LSTM-CNN model further improved accuracy by 7.33% and 5.00% compared to the single-improvement models, validating the synergistic effectiveness of SE attention mechanism and LSTM for damage detection in steel bridge deck U-Rib-Deck joints; furthermore, using the envelope curve dataset increased the model’s validation accuracy by 21.33% compared to raw signals, demonstrating this method’s effectiveness in enhancing the SE-LSTM-CNN model’s ability to identify Lamb wave damage features. ④ The intelligent detection software developed based on MATLAB APP Designer achieved full-process optimization for damage detection, reducing errors from human intervention. This research is expected to provide a new technical solution for damage detection in steel bridge deck U-Rib-Deck joints.

Abstract:To address the efficiency evaluation of organizational management in unmanned construction of drilland-blast tunnels, an evaluation system based on the super-efficiency Slack-Based Measure (SBM) model with undesirable outputs was constructed. Taking a tunnel under construction in the Xizang Autonomous Region as a case study, an evaluation index system comprising four input indicators and four output indicators was established, wherein the overbreak volume was treated as an undesirable output. The evaluation of 30 construction cycles revealed that the average efficiency value was 0.988, with 66.67% of the cycles being DEA-efficient. The sub-process scheduling time and advance distance per cycle were identified as the most critical factors influencing the organizational efficiency. Furthermore, construction cycles at different efficiency levels exhibited significant sensitivity stratification characteristics, indicating the presence of a diminishing marginal effect in efficiency improvement.

Abstract:To address the problem of detail feature loss of low-altitude small objects during multi-layer down-sampling, a small object detection model ES-YOLO is proposed, based on detail feature enhancement and redundant feature suppression. The method is built upon the lightweight YOLOv5s framework and constructs a dual-feature optimization mechanism consisting of spatial detail enhancement (SDE) and redundant feature suppression (RFS) modules. SDE collaborates dynamic upsampling with transposed convolution upsampling to achieve scale-adaptive fine recovery of spatial details and structural consistency reconstruction, enhancing small object texture and boundary information. RFS models feature dependencies across both channel and spatial dimensions to suppress background noise and redundant responses, improving feature purity and object saliency. Experimental results show that ES-YOLO achieves improvements of 12.97 percentage point and 9.22 percentage point in mAP@0.5and mAP@[0.5:0.95], respectively, compared to YOLOv5s on the VisDrone2019 dataset. The proposed model requires only 38.59% of the GFLOPs of YOLOv8m, achieving a significant reduction in computational cost.

Abstract:To achieve accurate online acquisition of time-varying cable forces in cable-stayed bridges, a new method for real-time identification of online time-varying cable forces is proposed based on the data-driven adaptive chirp mode decomposition (DD-ACMD) algorithm. This method adopts the sliding window technique to update the vibration signal of the inclined cable, and determines its prior information and target modal components through the power spectrum density (PSD) analysis of the vibration signal. Afterwards, the DD-ACMD algorithm was used to identify the instantaneous frequency of the cable vibration, and the time-varying cable force of the inclined cable was calculated using the axial loading beam theory. The accuracy of the method was tested by a numerical case of inclined cable, and the results showed that the average error in identifying the time-varying cable forces under high noise level is 0.45%, with a maximum error of 1.84%.

Abstract:To study the reinforcement effect of steel plate thickness and anchor strength on the joint of shield tunnel, this study used Abaqus finite element software to establish left and right half standard block pipe joint models with an inner diameter of 5.4 m and an outer diameter of 6.0 m. Based on a load structure calculation model, the mechanical properties of subway tunnel segment joints reinforced with steel plates and adhesive were studied. The results show that the mechanical properties of the segment joint after reinforcement are affected by the concrete matrix, steel plate and anchor bolt. The use of 10 mm thick steel plate can increase the stiffness of the joint by 40%. When the thickness of the steel plate is in the range of 20~30 mm, the bending moment of the structure increases with the increase of the external load. When the thickness of the steel plate exceeds 20 mm, the damage mode of the structure does not change much, and the stress of the steel plate is mainly concentrated in the bearing area away from the joint surface. In addition, when the number of anchor bolts is fixed, the increase of diameter can effectively improve the cooperative force of segment joints after reinforcement. Due to the limitation of concrete strength in the compression zone, the effectiveness of further increasing the steel plate thickness diminishes, resulting in a decreasing rate of improvement in joint stiffness. The thickness of 10~20 mm steel plate is the best. This study can provide theoretical support for the design of segmental segments reinforced by steel ring lining.

Abstract:To investigate the damage mechanism of the wide and narrow joints of CRTS Ⅱ slab ballastless tracks and identify damage, a field investigation was conducted on a passenger-dedicated line in the East China region, followed by long-term monitoring of track slab temperature and joint displacement. Based on the DBSCAN clustering algorithm, temperature data representing energy input and displacement data representing energy output during high-temperature seasons were screened and abnormal feature data were extracted. By incorporating the standard deviation, which represents data dispersion, to analyze the energy accumulation and sudden release process within the track slabs, a comprehensive computational model combining data-driven and physical mechanisms was established. A novel method for identifying wide and narrow joints damage based on abnormal feature extraction was proposed. The results show that, during the period with prolonged high temperature in summer, there is a long-term inconsistency between the temperature of the track slab and the displacement of the joints. The established physical model supplemented eight additional abnormal characteristic data for damage identification analysis of wide and narrow joints. In addition, prolonged high temperatures lead to energy accumulation and sudden release within the track slabs, with more pronounced energy changes observed at wide joint locations, thereby causing significant damage to the wide and narrow joints.

Abstract:The study investigates the elastic shear buckling performance of corrugated steel webs with variable thickness, taking the 1000-type variable thickness corrugated steel webs as the main research object. A numerical analysis model under pure shear stress state is established using ANSYS finite element software for shear buckling analysis, and the influence of height-to-thickness ratio, length-to-thickness ratio, corrugation angle, and type on its elastic shear buckling performance is investigated. The results indicate that when the height and length of the web are fixed, the shear buckling load of the variable thickness corrugated steel webs increases by nearly 4% compared to the equal thickness corrugated steel webs; the shear buckling load of the variable thickness corrugated steel webs decreases with the increase of height-to-thickness ratio and length-to-thickness ratio, and the decreased amplitude of the shear buckling load increases when the height-to-thickness ratio is greater than 263 or the length-to-thickness ratio is greater than 636; the shear buckling load of the variable thickness corrugated steel webs increases with the increase of the fold angle; compared with equal thickness corrugated steel webs, different types of variable thickness corrugated steel webs all have improved shear buckling loads, among which the 1000 type variable thickness corrugated steel webs has the largest increase in shear buckling load. When the design value of the height-to-thickness ratio of the webs is less than 263, or the design value of the length-to-thickness ratio is less than 636, the elastic shear buckling performance of the variable thickness corrugated steel webs is better than that of the constant thickness corrugated steel webs.

Abstract:To explore the variation laws of horizontal displacement of foundation pit retaining piles and surface settlement outside the pit under finite soil conditions, an excavation model test was carried out on a foundation pit with semi-infinite soil mass on one side and finite soil on the other three sides. The variation laws of internal force, deformation of retaining piles and surface settlement outside the pit under the condition of limited soil mass were obtained and the relationship between the horizontal displacement of retaining piles and surface settlement was further analyzed. The results show that the horizontal displacement of retaining piles is positively correlated with the soil width B, and the reduction of soil width can effectively reduce the horizontal displacement at the top and along the body of retaining piles; the maximum surface settlement increases first and then decreases with the increase of soil width B. Under the condition of limited soil width, the soil width has a significant influence on the surface settlement outside the foundation pit, and there is a critical value of soil width B; the maximum bending moment of the retaining pile body is positively correlated with the soil width B, and the soil width has a small influence on the position of the maximum bending moment. The research can provide theoretical basis and basis for the design and construction of limited soil foundation pit in the future.

Abstract:To enhance the monitoring and detection of abnormal driving behavior of vehicles in snow and ice conditions,this paper proposes a data-driven method for identifying abnormal driving behaviors by integrating multichannel CNN-BiGRU with MHA. Abnormal driving data are obtained by LAIF model, combined with driving characteristics and data features under ice and snow environments, abnormal driving behavior indicators are constructed to characterize 6 kinds of abnormal driving behavior, namely rapid acceleration, rapid deceleration, rapid turning, rapid lane change, serpentine driving and skidding, and the ADASYN is introduced. The model proposed in this paper is compared and analysed with other models.The CNN-BiGRU-MHA detection model has an overall accuracy of 96.34%, which is better than other detection models indicating that the model can effectively detect the abnormal driving behavior of cars in ice and snow environments, and provides a theoretical basis for early warning of abnormal driving behavior.

Abstract:Southwest China is a typical region characterized by rich natural resources but relatively low economic development, leading to unbalanced development. Using panel data from Southwest China spanning 2010 to 2022, this study employs the entropy weight method, coupling coordination degree model, and spatial econometric modeling to systematically examine the spatial spillover effects of high-speed rail network development on the coupled coordination between urbanization and ecological environment in the region. The key findings are as follows: The coupling and coordination degree of urbanization and ecological environment in Southwest China is predominantly at low and medium levels, with a continuous improvement trend, exhibiting typical characteristics of spatial agglomeration and disequilibrium; The betweenness centrality of the high-speed rail network has a significant positive impact on the coupling and coordination of urbanization and ecological environment; The high-speed rail network exerts a stronger promotional effect on coordination through indirect effects, demonstrating notable spatial spillover effects. In the long term, enhancing the high-speed rail network level is conducive to the harmonious development of the coupling and coordinated relationship between urbanization and ecological environment in Southwest China, and can narrow the development disparities among cities in the region. However, due to the more prominent indirect effect of the high-speed rail network on urban coordinated development, its impact exhibits a certain lag.

Abstract:By comparing the open-water characteristics and cavitation characteristics between the contra-rotating propeller boss cap fins (CRPBCF) propeller and the benchmark propeller, this paper investigates the influence of CRPBCF on the hydrodynamic performance of propellers. The CRPBCF model was constructed through geometric transformation of VP1304 propeller blades. Numerical simulations were conducted using the overset grid technique and large eddy simulation (LES) in STAR-CCM+. The computational results were validated against experimental data, demonstrating good accuracy and reliability. The results demonstrate that the CRPBCF propeller exhibits superior hydrodynamic performance compared to the benchmark propeller. At an auxiliary propeller speed of na = 37.5 r/s, it achieves maximum efficiency gains of 4.18% and thrust improvements up to 7.28%. In terms of cavitation characteristics, a distinct vapor volume fraction isosurface of 20% is clearly observed in the wake flow of the benchmark propeller, whereas no such phenomenon was observed for the CRPBCF propeller. This demonstrates that CRPBCF can effectively suppress the generation of hub vortex cavitation (HVC). In summary, the results demonstrate that the CRPBCF propeller not only enhances propulsive efficiency but also delivers greater thrust under low advance coefficient conditions while effectively suppressing the occurrence of HVC.