Abstract:To analyze the dynamic characteristics and driving mechanisms of tourism transportation carbon emissions in Fujian-Guangdong-Hainan coastal regions,based on the panel data of Fujian-Guangdong-Hainan coastal regions from 2012 to 2022,the carbon emissions of tourism transportation by four modes of transportation,namely road,railway,civil aviation and waterway,are calculated using the bottom-up approach,and their dynamic evolution trends are examined.Combining the Kaya identity and the logarithmic mean Divisia index(LMDI)decomposition method,evaluates the impact and contribution rates of six driving factors:tourist scale,tourism industry contribution,tourism consumption level,tourism transportation intensity,energy intensity,and energy structure.The results show that from 2012 to 2022,tourism transportation carbon emissions in Fujian-Guangdong-Hainan coastal regions initially increased and then decreased overall.Aviation is the primary source of tourism transportation carbon emissions,accounting for 82.00%of the total.Per capita carbon emissions from tourists decline annually,with an average annual growth rate of-13.80%,indicating that carbon emissions grow at a slower rate than tourist numbers.The main factors promoting tourism transportation carbon emissions are tourist scale,tourism industry contribution,energy intensity,and energy structure,with cumulative contribution rates of 91.88%,252.63%,356.79%,and 27.75%,respectively.The key factors inhibiting carbon emissions growth are tourism consumption level and tourism transportation intensity,with cumulative contribution rates of-87.01%and-542.04%,respectively.

Abstract:To explore the strength characteristics of the loess in Ili,remolded loess from the landslide area along the Naba Highway in Ili,Xinjiang is selected as the test object.Through triaxial shear tests,ring shear tests,and radial fracturing tests,the impact of different moisture capacity on the shear strength,residual strength,and tensile strength of the soil is analyzed.Combined with scanning electron microscope tests,the microscopic morphology of the soil samples after ring shear failure is observed.The research results indicate that:1)Under the same moisture capacity,the shear strength of the soil samples significantly increases with the increase of confining pressure;under the same confining pressure,the shear strength of the soil samples significantly decreases with the increase of moisture capacity;when the confining pressure is not greater than 200 kPa,the stress-strain curve of the soil samples shows that after reaching peak strength,the shear strength decreases with the increase of axial strain,eventually approaching the residual strength;when the confining pressure is greater than 200 kPa,the stress-strain curve of the soil samples has no obvious peak point,and the shear strength gradually increases with the increase of axial strain.After the moisture capacity reaches 20％,the stress-strain curve changes from strain hardening to strain softening;when the moisture capacity increases from 14％to 17％,the reduction of the shear strength of the soil samples is the greatest.2)When the normal stress changes from 100 kPa to 400 kPa,both peak strength and residual strength increase with the increase of normal stress,and the curves are similar under the same moisture capacity conditions;under different moisture capacity,the shear strength increases rapidly to the peak strength and then slowly decreases with the increase of shear displacement;when the moisture capacity is not greater than 17％,the curves exhibit strain softening characteristics,while the moisture capacity is not less than 20％,the curves only include two stages:strain hardening and residual strength,without strain softening phenomena.3)The residual strength of the soil samples is linearly positively correlated with normal stress,and the tensile strength decreases with the increase of moisture capacity.The tensile strength of undisturbed soil samples and remolded sample tends to be consistent when the moisture capacity is not less than 17％,and slowly decreases;the tensile strength of the soil samples is close to the residual cohesion,indicating that cohesion is the main source of tensile strength.

Abstract:To address the problems of low accuracy in current bridge crack image detection and large algorithm scale that is inconvenient for deployment on resource-constrained edge devices,a lightweight bridge crack image detection algorithm based on improved YOLOv11n(you only look once version 11 nano)is proposed.By integrating the ShuffleNetV2 module with CCFM(cross-scale fusion module),a Shuffle-CCFM structure is constructed to enhance multi-scale feature fusion capability while reducing algorithm parameters.The iRMB(inverted residual mobile block with attention)is introduced into the C2PSA(cross-channel partial spatial attention)module to form the C2PSA-iRMB module,which improves the algorithm's recognition capability for complex crack details and enhances the correlation modeling capability of spatially distant features within the same crack structure region.WTConv(wavelet transform convolution)is integrated into the C3k2 module to form the C3k2-WTConv module,improving the model's feature extraction capability at different scales.DySample is adopted to replace the traditional upsampling module,adaptively adjusting sampling positions according to feature map content to enhance spatial resolution and detail restoration capability during the upsampling stage.Ablation experiments,comparative experiments,and visualization detection effect experiments are conducted to evaluate the detection performance of the improved YOLOv11n algorithm.The experimental results show that:compared with the YOLOv11n algorithm,after introducing the Shuffle-CCFM structure,C2PSA-iRMB module,C3k2-WTConv module,and DySample module,the improved YOLOv11n algorithm's params NP,computation cost Nf,and weight file size T are reduced by 27.5％,23.8％,and 32.7％,respectively,while mean average precision at intersection over union threshold of 50 EmAP50,mean average precision at intersection over union threshold from 50 to 95 EmAP50-95,and recall R increase by 1.6％,3.8％,0.4％respectively,demonstrating significant improvements in algorithm lightweighting and detection accuracy.The improved YOLOv11n algorithm's detection accuracy and performance indicators for bridge crack images are significantly superior to lightweight algorithms such as YOLOv5n,YOLOv6n,YOLOv8n,and YOLOv10n,making it suitable for deployment on edge devices with limited computational resources.The improved YOLOv11n algorithm demonstrates higher confidence in detection result precision in bridge crack visualization detection experiments,exhibits stronger capability in capturing details of minute-sized and morphologically complex cracks,and possesses stronger anti-interference capability in complex backgrounds.

Abstract:To improve the safety,stability,and economy of the main tower design of long span suspension bridges,this study takes the Longtan Yangtze River Bridge(with a main span of 1 560 m)as the engineering reference.It analyzes the theoretical key points of the design and calculation of the main tower structure,considering basic actions such as vehicle loads,temperature,wind loads,and earthquakes.Additionally,it takes into account the geometric nonlinearity of the bridge structure,vertical load-lateral displacement effects,and the elastic-plastic behavior of concrete materials.Based on comprehensive calculations,adverse sections are selected,and the calculated length coefficients of components are determined under various adverse load combinations.A variable thickness design is adopted for the transverse and longitudinal main tower walls,adjusting the thickness according to the height of the tower columns.A bi-directional compression-bending static analysis and elastic-plastic analysis are conducted on the selected sections to assess the overall stability of the bridge.The calculation results indicate that using a cubic variable cross-section design for the tower wall thickness along the height can meet the structural stress requirements.Stability calculations show that eliminating the middle crossbeam can ensure the safety of the main tower while enhancing the economic viability and aesthetic effect of the bridge.This can provide a basis and reference for the design and calculation of main tower structures of larger slenderness ratio bridges.

Abstract:To assess the feasibility of using gold tailings on a large scale as a subbase material for road subgrades,cement is mixed with gold tailings at different mass ratios w(0％,3％,5％,7％)to prepare specimens of gold tailings.The specimens undergo direct shear tests,consolidation tests,California bearing ratio(CBR)tests,and freeze-thaw cycling tests to evaluate the feasibility of gold tailings as a base material for roads.The results indicate:1)The normal stress and shear strength of cement-modified gold tailings samples are linearly related.At the same w,the shear strength of the cement-modified gold tailings specimens increases linearly with the increase of normal stress;under the same normal stress,the shear strength of the cement-modified gold tailings specimens initially increases and then decreases with the increase of w;the specimen with w=5％exhibits the highest shear strength.2)At the same w,the deformation of the cement-modified gold tailings specimens gradually increases with the extension of consolidation time;with the same consolidation time,the deformation of the cement-modified gold tailings specimens initially decreases and then increases with the increase of w.The deformation of the specimen made with w=5％cement-modified gold tailings is the smallest.3)At the same compaction degree,the California bearing ratio of the cement-modified gold tailings specimens increases initially and then decreases with the increase of w;at the same w,the California bearing ratio of the cement-modified gold tailings specimens increases with the increase of compaction degree;the maximum California bearing ratio is observed at w=5％and a compaction degree of 95％.4)In the freezing and thawing test,the compressive strength and tensile strength of cement-modified gold tailings specimens first increase and then decrease with the increase of w;under sulfate freeze-thaw conditions,the compressive strength of gold tailings specimens without cement addition and those with 5％cement-modified gold tailings decreases with the increase of freeze-thaw cycle times,while the latter shows a significantly reduced decline;increasing the sulfate mass fraction exacerbated the erosion of the cement-modified gold tailings specimens,reducing their compressive strength.The cement-modified gold tailings with w=5％can significantly improve compressive strength,tensile strength,deformation resistance,and durability,meeting the technical requirements for use as road base materials.

Abstract:To improve the recovery capability of rail transit networks in response to sudden disturbance events,a resilience assessment model for rail transit networks is proposed,which integrates traffic service efficiency and network operational efficiency.A recovery strategy model for rail transit networks is established with the objective of maximizing network resilience.By combining genetic algorithms with adaptive large neighborhood search algorithms,a hybrid adaptive large neighborhood search genetic algorithm is proposed to solve the resilience maximization recovery strategy model.Taking the rail transit system of Hangzhou as an example,disturbance scenarios such as natural disasters,human-made damages,and special control measures are simulated using random and deliberate attacks.The station recovery sequence and network resilience performance of random recovery strategies,node-degree-first recovery strategies,importance-first recovery strategies,and resilience-maximization recovery strategies are compared and analyzed under three disturbance scenarios.The results indicate that under all three disturbance scenarios,the resilience-maximization recovery strategy achieves the best repair effect on the rail transit network,followed by node-degree-first and importance-first recovery strategies,while the random recovery strategy exhibits the worst repair effect.In the human-made damage scenario,the rail transit network is most severely affected,and at this time,the resilience-maximization recovery strategy improves the network resilience by 6.7％,7.6％,and 25.1％compared to the other three strategies,respectively.Furthermore,when repairing one station,the rail transit network requires approximately 8 hours to recover to optimal performance,while repairing four stations simultaneously only requires about 3 hours to reach optimal recovery.The greater the number of stations that can be repaired simultaneously at the same time point,the faster the network resilience is restored.Implementing the optimal recovery strategy as soon as possible and increasing the repair resource investment in the early stage of the disturbance can significantly improve the recovery efficiency and network resilience of the rail transit network.

Abstract:To alleviate occasional congestion problems after highway traffic accidents,the traffic flow states before and after accidents are simulated using the software VISSIM,and traffic flow data for non-congested and congested states are obtained.The Greenshields model and the Greenberg model are used to fit the speed-density relationship curves for non-congested and congested states,respectively,and a highway traffic congestion duration prediction model is constructed.Through the model,the congestion duration under different upstream arrival flows and different traffic accident blockage times is calculated,and the model's accuracy is verified through simulation.The highway traffic congestion duration prediction model is combined with a genetic algorithm to solve the vehicle speed when vehicles arrive at the queue tail position of the congested section,thereby determining the optimal speed limit.A graded speed limit control strategy is proposed for congestion situations,where multiple gradual speed limits are implemented for vehicles from the upstream section of the accident,allowing the speed to decrease smoothly and restricting the number of vehicles in the congested area.The results show that the mean absolute percentage error between the calculated and simulated results of congestion duration under different upstream arrival flows and different blockage times is 14.37％,indicating that the traffic congestion duration prediction model has high accuracy and can be used to calculate the congestion duration after highway accidents.After implementing the graded speed limit control strategy,when the upstream arrival flow is 3 000 veh/h,the average queue length decreases from 2 141 m to 1 340 m,and the average traffic flow speed in the congested section increases from 28.7 km/h to 36.0 km/h,demonstrating that the graded speed limit control strategy can effectively alleviate highway congestion.

Abstract:To improve the resource allocation efficiency of electric vehicle charging infrastructure and reduce operational costs,a charging station site selection method integrating land-use attributes and multi-objective optimization is proposed.Based on the distribution data of points of interest(POI),the K-means clustering algorithm is used as a preprocessing method to initially determine potential charging station locations.By calculating the weight and number of POI types within the coverage area of each potential site,the importance of each site is determined,and an objective function is established to maximize the importance of the charging station candidate points.At the same time,considering the construction and operational costs of the charging stations and the travel loss costs for users,an objective function to minimize the total cost of the charging stations is formulated.A bi-objective planning model for the charging station site selection is built.The model is solved using both the traditional sparrow search algorithm(SSA)and an improved sparrow search algorithm(ISSA),which integrates dynamic adaptive weights,reverse learning strategies,and Cauchy mutations.An example analysis for Jinan city is presented.The results show that the ISSA-based charging station layout effectively avoids issues of excessive concentration or dispersion,with significantly better service coverage and layout balance than SSA.Compared to SSA,the ISSA site selection plan reduces the total cost by 7.43％and increases the charging station importance by 34.34％.The service buffer coverage of the charging stations solved by ISSA outperforms SSA in all types of land-use areas,especially in commercial areas,where the coverage rate of the ISSA plan is 6.79 percentage points higher than that of the SSA plan.The charging station bi-objective planning model and the optimized solving algorithm can effectively improve the rationality of the charging station layout and spatial resource allocation efficiency.

Abstract:To systematically analyze the development level of transportation new-quality productive forces in China,using provincial panel data for 30 provincial-level administrative regions from 2014 to 2022(excluding the Xizang Autonomous Region,the Hong Kong Special Administrative Region,the Macao Special Administrative Region,and Taiwan Province),an evaluation index system for the development level of transportation new-quality productive forces is constructed based on its connotation and characteristics.The system covers five dimensions:transportation innovation foundation,advancement of transportation infrastructure,green development of transportation,transportation efficiency and safety,and transportation economic resources.The entropy weight method,the Dagum Gini coefficient,kernel density estimation,Moran's I,and the obstacle degree model are employed to analyze development levels,regional disparities,evolutionary features,spatial correlation,and obstacle factors.From 2014 to 2022,the national development level rose steadily,but regional development is uneven,showing a pattern of eastern leadership,relative stability in the central region,and lagging performance in the west and the northeast.Intra-regional disparities widened in the east,center,and west,while they narrowed slightly in the northeast;inter-regional differences are the main source of overall disparity.Significant positive spatial autocorrelation is observed,with many eastern provinces in a high-high cluster and other regions mainly in low-low clusters.Optical cable line density,express delivery volume,and software business revenue are identified as key obstacle factors constraining development.Strengthening regional coordination,optimizing resource allocation,guiding spatial agglomeration,and focusing on critical factors can systematically improve the development quality of transportation new-quality productive forces.

Abstract:To quantify the impacts of the CO2 emission factor,fuel consumption,and traffic operating conditions on vehicle CO2 emissions,this study takes Jinan City as the research area.Based on a localized MOVES model,a speed-based CO2 emission factor model is constructed,and the relationship among the CO2 emission factor,fuel consumption,and vehicle speed is established to analyze the influence of different traffic conditions on vehicle CO2 emissions in Jinan.The results show that the CO2 emission factors of different vehicle types differ significantly but follow generally consistent trends with changes in average speed.When the average speed is below 10 km/h,the CO2 emission factors of all vehicle types remain at a high level.As the average speed increases to 10-50 km/h,the CO2 emission factors decrease rapidly.When the average speed reaches 50-100 km/h,the CO2 emission factors gradually stabilize and remain at a relatively low level.At speeds between 100 km/h and 120 km/h,most vehicle types show an increasing trend in CO2 emission factors.From 2017 to 2022,the average peak-hour speed in the core area of Jinan increased from 20.18 km/h to 31.72 km/h.The alleviation of traffic congestion reduced the CO2 emission factors of gasoline passenger cars,gasoline light-duty trucks,diesel light-duty trucks,and diesel heavy-duty trucks by 21.71％,21.23％,18.84％,and 15.35％,respectively.For gasoline passenger cars alone,this translates to an annual reduction in gasoline consumption of approximately 936 000 tons and a reduction in CO2 emissions of about 3.12 million tons.The proposed model is compared with the CO2 emissions factor model based on vehicle specific power,and both show generally consistent trends of CO2 emission factors with vehicle speed.Within the speed range of 15-60 km/h,the constructed model fits the relationship between CO2 emission factors and average speed well,demonstrating its applicability to the study of CO2 emissions from urban road traffic.Improving urban traffic operational efficiency is an important pathway to reducing vehicle CO2 emissions.

Abstract:To evaluate the green development level of the logistics industry in the Yellow River Basin,maturity theory is adopted to assess maturity from three dimensions:development degree,coordination degree,and coordinated development degree;with maturity as the target layer and the economic-environmental foundation,logistics supply capacity,environmental friendliness,and technological innovation capability as the criterion layer,22 specific indicators are selected to construct an evaluation index system for the green development of the logistics industry;indicator weights are determined by combining the global entropy method and the order relation analysis method(G1 method),and the development degree,coordination degree,and coordinated development degree of the nine provinces and autonomous regions in the Yellow River Basin from 2013 to 2022 are calculated using the technique for order preference by similarity to ideal solution(TOPSIS)and a grey relational degree improved distance coordination degree model.The results show that from 2013 to 2022,the development degrees of the four subsystems,namely the economic-environmental foundation,logistics supply capacity,environmental friendliness,and technological innovation capability,generally increase,but technological innovation capability increases slowly,constraining the in-depth development of green logistics;the development degree,coordination degree,and coordinated development degree of the provinces and regions in the Yellow River Basin all show growth to varying extents,with growth trends in descending order of development degree,coordinated development degree,and coordination degree;Sichuan,Inner Mongolia,Shaanxi,Henan,and Shandong exhibit significant increases in development degree,while the increases in the other provinces and regions are relatively small;the coordination degree is overall at a relatively high level,but interprovincial differences are evident;the coordinated development degree presents a stepped distribution pattern of high in the downstream,flat in the midstream,and low in the upstream;in most provinces,the coordination degree is higher than the development degree,reflecting a structural mismatch between the coordination level and the development level.Green and coordinated development of the logistics industry in the Yellow River Basin can be achieved by strengthening technological innovation and financial support in the middle and upper reaches,enhancing regional policy coordination and resource integration,promoting infrastructure interconnection and regional collaboration,and establishing carbon footprint evaluation and carbon trading guidance mechanisms.

Abstract:To promote the high-quality application of waste asphalt mixtures in recycled asphalt,nano-materials are added to the new and old asphalt mixtures as radar absorbing materials to improve microwave heating efficiency.Based on the difference in fluorescence intensity when the new and old asphalt are excited under a fluorescence microscope,the degree of fusion between the new and old asphalt in recycled asphalt mixture specimens with different absorbent agents(single addition of nano-SiC,single addition of nano-Fe2O3,and composite addition of nano-SiC-nano-Fe2O3,the mass ratio of nano-SiC to nano-Fe2O3 is 1∶2)under microwave induction is observed,and the fusion status of the asphalt is quantified using gray level.The research results show that both single addition of nano-SiC and single addition of nano-Fe2O3 can improve the gray level at the interface of the new and old asphalt in the recycled asphalt mixture specimens.The gray level at the interface of the new and old asphalt after single addition of nano-SiC is better than that after single addition of nano-Fe2O3.After the composite addition of nano-SiC-nano-Fe2O3,the gray level at the interface of the new and old asphalt is superior to that with either absorbent agent alone,with the gray level at the interface of the new and old asphalt in the specimens after the composite addition of nano-SiC-nano-Fe2O3 being 72.14％of the new asphalt.

Abstract:Addressing the issues of background interference,distant small objects,and feature loss in autonomous driving road scene object detection,an improved model based on You Only Look Once version 10n(YOLOv10n)is proposed.The receptive field attention convolution(RFAConv)module is introduced to replace the Conv module,extracting multi-scale receptive field spatial features and dynamically allocating weights through attention mechanisms to enhance the model's complex image processing capabilities.A small object enhance pyramid(SOEP)module is incorporated,utilizing an improved cross stage partial-omniKernel(CSP-OmniKernel)module for feature information integration,significantly improving small object detection performance.The global channel-spatial attention(GCSA)module is introduced to enhance feature map representation through the coupling mechanism of channel attention,channel shuffle,and spatial attention,capturing global dependencies in feature maps and enhancing feature extraction capabilities,forming the RSG-YOLOv10n complex road scene small object detection model.Ablation experiment,model performance comparison experiment,generalization validation experiment,and visualization detection effect experiment are conducted.Experimental results show that:after introducing the RFAConv,SOEP,and GCSA modules,the RSG-YOLOv10n model's precision P,recall R,mean average precision at 50 intersection over union threshold EmAP50,and mean average precision averaged over intersection over union thresholds from 50 to 95(with a step of 5)EmAP50-95 is improved by 6.3 percentage points,2.5 percentage points,3.5 percentage points,and 2.8 percentage points respectively compared to the YOLOv10n model,with significantly enhances detection accuracy;compared with lower parameter models(YOLOv5n,YOLOv8n,YOLOv10n),similar parameter models(YOLOv3-tiny,YOLOv6n,YOLOv7-tiny),and higher parameter model(RT-DETR-L),the RSG-YOLOv10n model achieves the highest detection accuracy with lower parameter count and floating-point operations;the RSG-YOLOv10n model performs road scene object detection on a generalization validation dataset composed of various adverse weather images including sandstorms,heavy snow,and dense fog,with EmAP50 and EmAP50-95 increasing by 0.9 percentage points and 1.3 percentage points respectively compared to the YOLOv10n model,demonstrating high robustness and generalization capability;the RSG-YOLOv10n model exhibits strong feature extraction and small object detection capabilities in visualization detection experiments for road scenes with dense occlusion,complex lighting,adverse weather,and coexisting near and distant objects.

Abstract:To study the effect of the quality fraction of modified corn straw fibers on the high and low temperature performance of asphalt mixtures and the uniformity of fiber dispersion,asphalt mastic stone mixture(stone mastic asphalt,SMA)with modified corn straw fiber quality fractions of 0,0.2%,0.4%,0.6%,and 0.8%are prepared.Rutting tests and low-temperature beam bending tests(-5,-10,-15℃)are conducted,and variance analysis(with a variance statistic of 66.47 and a probability of less than 0.000 1)and effect size analysis are performed.Combined with the standard deviations of low-temperature tensile strength,bending stiffness modulus,and tensile strain,as well as the quality fraction of modified corn straw fibers,a fiber dispersion uniformity index is proposed.The results show that when the quality fraction of modified corn straw fibers in the asphalt mixture is 0.4%,the dynamic stability is maximized at 4 268 times/mm,which is an increase of 50.4%compared to the control group without modified corn straw fibers.The low-temperature tensile strength and tensile strain are significantly improved,while the reduction in bending stiffness modulus is minimal,indicating an optimal balance between tensile strength,stiffness,and ductility.The dispersion uniformity index is maximized at 1.042,reflecting the best fiber dispersion,consistent with the results of high and low temperature tests.

Abstract:To improve the stress state of the suspension bridge floor system,which mainly experiences forces on the crossbeam,a reinforcement modification plan has been proposed that involves replacing the hangers and adding steel pipe truss longitudinal beams.Taking a tied arch bridge as the background,the dynamic performance of the reinforced arch bridge structure is analyzed under the combination of permanent load,live load,and temperature load.The results indicate that the failure of a hanger has a significant impact on the internal forces of adjacent hangers on the same side,meeting the requirement of Technical Code for Concrete-filled Steel Tube Arch Bridges:GB 50923-2013 for a safety factor of three;the farther the distance from the broken hanger,the lesser the impact on the internal forces of the remaining hangers,while the effect on hangers on the opposite side of the broken hanger is relatively small;the failure of a hanger noticeably affects the displacement of the tie beam;the key parts of the steel pipe truss after the hanger failure are subjected to force verification,and the results meet the requirements of the Standard for Design of Steel Structures:GB 50017-2017.This reinforcement modification plan ensures the safety of the remaining structure after a hanger failure.

Abstract:To study the impact of groundwater level changes on the displacement of a comprehensive utility tunnel in loess areas,a numerical model of the buried comprehensive utility tunnel is constructed using the finite element software PLAXIS 3D.To verify the reliability of the numerical model,a scaled model of the buried comprehensive utility tunnel is established according to similarity theory,with a scale ratio of 1:20.By varying the groundwater level height,river channel water level,and burial depth,the changes in the displacement of the comprehensive utility tunnel are simulated and analyzed.The results indicate:1)The scaled model tests can validate the reasonableness of the seepage parameters set in the numerical model,which can be used to analyze the impact of different groundwater levels on the displacement of the comprehensive utility tunnel.2)As the vertical drop of the groundwater level increases,the further away the road surface is from the comprehensive utility tunnel in the vertical direction,the greater the settlement of the road surface;when the vertical drop of the groundwater level is 5-7 m,the settlement difference between the road surface above the comprehensive utility tunnel and that of the adjacent non-tunnel areas gradually decreases;when the vertical drop of the groundwater level is 8 m,the settlement of the road surface above the comprehensive utility tunnel is significantly higher than that of the adjacent non-tunnel areas.As the vertical rise of the groundwater level increases,the further away the road surface is from the comprehensive utility tunnel in the horizontal direction,the smaller the displacement of the road surface,and the greater the maximum displacement difference between the road surfaces in the comprehensive utility tunnel area and the adjacent non-tunnel areas;the maximum displacement difference of the plane foundation at the bottom of the comprehensive utility tunnel increases,which is significantly greater than the maximum displacement difference of the road surface at the same groundwater level height.3)The vertical and lateral displacements of the comprehensive utility tunnel exhibit periodic changes with variations in the river channel water level;during the dry season,the river channel water level decreases,which leads to increased settlement and lateral displacement of the comprehensive utility tunnel,while during the wet season,the river channel water level rises,causing the comprehensive utility tunnel to return to its original position,with the displacement near the river channel and road surface being significantly affected by the fluctuations in the river channel water level.4)As the groundwater level decreases,the shallower the burial depth of the comprehensive utility tunnel,the greater the settlement;the displacement of shallow-buried tunnels is significantly affected by changes in the groundwater level.In practical engineering applications of comprehensive utility tunnels,shallow burial is not advisable in high water level areas.

Abstract:To precisely obtain the deformation patterns of retaining and protecting for foundation excavation under the coupling field effects,based on an actual high water head project,finite element software Plaxis is used to conduct finite element simulations of the foundation pit excavation support system under multi-field coupling effects.During the engineering excavation,key deformation indicators such as horizontal displacement of weak links in the support structure,surface settlement,and bottom uplift are monitored in real-time,and the measured results are compared and analyzed with the simulation analysis results.The results show that:1)The maximum horizontal displacement during the foundation pit excavation considering high water head coupling effects occurs about 7.5 m from the top of the pile,with a maximum horizontal displacement of 41.771 mm;The maximum surface settlement is located approximately 5.0 m from the foundation pit,with a maximum settlement of 32.682 mm;The maximum uplift at the bottom of the pit is found in the area between the symmetric center and the pile body,with a maximum uplift of 19.600 mm;The simulated deformation patterns are generally consistent with the field measured data.2)The measured data lie between the numerical simulation results that consider fluid-solid coupling effects and those that do not,and overall,they are closer to the former.3)The maximum simulated results of horizontal displacement of support piles,settlement of surrounding soil,and uplift at the bottom of the pit can serve as warning thresholds for on-site monitoring.As the excavation depth increases in high water head areas,the deformation increases,and timely support should be implemented.

Abstract:To address the deformation issues of ultra-high pier columns in traditional hydraulic climbing formwork construction techniques,a hydraulic climbing formwork system positioning method is adopted.The support frame is positioned and assembled according to the construction plan,and the hydraulic climbing formwork is initially assembled.Three-dimensional scanning technology is used to re-measure and fine-tune the positioning of the pier columns,ensuring that the hydraulic climbing formwork system can be accurately installed.Using parameters such as the angle between point normal vectors and curvature differences as segmentation criteria,an optimized region growing algorithm is employed for plane segmentation of the point cloud of the pier columns.The obtained key three-dimensional point cloud data is converted to a two-dimensional plane,and the coordinate range is determined through linear fitting,which is then used to reverse calculate the coordinates of the control points of the pier columns in three-dimensional space.The software Revit is used to establish a three-dimensional model of the pier columns and perform plane segmentation,analyzing the deformation of four planes in the z direction.For each plane,66 feature point coordinates are extracted,and the least squares method is used for surface fitting and deformation calculation.The results indicate that the maximum relative difference between the actual deformation and the designed deformation in the x direction for the four planes is 0.0030 cm.The deformation of the pier columns during construction is minimal,meeting the construction control requirements.Through three-dimensional scanning technology,the deformation of pier columns during the construction process can be effectively predicted.

Abstract:To improve the recycling level of reclaimed asphalt pavement(RAP),reduce the secondary aging of recovered asphalt during the thermal regeneration process,and ensure the road performance of recycled asphalt mixtures,a warm mix recycled asphalt binder is prepared by adding reclaimed asphalt,bio-oil regenerant,and warm mix agent to 70#matrix asphalt.The quality ratios of reclaimed asphalt to matrix asphalt are 0,20%,40%,60%,and 80%,with the mass of the bio-oil regenerant being 10%of the reclaimed asphalt mass and the mass of the warm mix agent being 2%of the total mass of matrix asphalt and reclaimed asphalt.The flow characteristics,deformation resistance,and fatigue performance of the warm mix recycled asphalt binder are measured through rotational viscosity tests,multi-stress creep recovery tests,and linear amplitude sweep tests at high temperatures.Different AC-20 type warm mix recycled asphalt mixtures are prepared,and their high-temperature performance,low-temperature performance,water stability,and fatigue life are measured through rutting tests,low-temperature beam tests,freeze-thaw splitting tests,and four-point bending fatigue tests.The test results indicate:1)As the quality ratio of reclaimed asphalt to matrix asphalt increased,the rotational viscosity of the warm mix recycled asphalt binder increases,shear strain decreases,creep recovery rate increases,non-recoverable creep compliance decreases,shear stress initially increases and then decreases with increasing shear strain,peak stress increases,and fatigue life decreases,with reduced sensitivity to strain;The high-temperature deformation resistance slightly decreases compared to the binder without the bio-oil regenerant,while the fatigue performance is effectively improved.2)As the quality ratio of reclaimed asphalt to matrix asphalt increases,the dynamic stability of the AC-20 type warm mix recycled asphalt mixture increases,rut depth decreases,bending stiffness modulus increases,failure tensile strain decreases,splitting strength before and after freeze-thaw decreases,freeze-thaw strength splitting ratio decreases,and fatigue life decreases.The high-temperature deformation resistance is reduced compared to the mixture without the bio-oil regenerant,while the low-temperature deformation resistance,freeze resistance,and fatigue resistance are significantly improved.When the quality ratio of reclaimed asphalt to matrix asphalt exceeds 60%,the road performance of the AC-20 type warm mix recycled asphalt mixture can still reach the level of ordinary hot mix asphalt mixture.

Abstract:To investigate the coupled effects of Bjerknes force and buoyancy on the pulsatile load characteristics of underwater explosion bubble,an experimental platform for underwater explosion bubble generation and measurement is designed.Bubbles are generated by heating underwater copper electrodes through a bubble generation device,the bubble pulsation process is recorded using a high-speed camera,and the rigid wall load pressure is measured using pressure sensors.By adjusting the orientation of the rigid wall to change the direction of Bjerknes force,bubble pulsation experiments are conducted under two working conditions:Bjerknes force opposite to buoyancy direction and Bjerknes force perpendicular to buoyancy direction.The morphological changes,load characteristics,and pressure peak variation patterns during bubble pulsation are analyzed for different dimensionless distances γ.The experimental results show that under the condition where Bjerknes force is opposite to buoyancy direction,when γ is 0.7,1.0,and 1.3 respectively,the bubbles exhibit conical,pear-shaped,and spherical structures during the collapse stage;under the condition where Bjerknes force is perpendicular to buoyancy direction,when γ is 0.7,1.0,and 1.3 respectively,the bubbles exhibit football-shaped,conical,and water-droplet structures during the collapse stage;when Bjerknes force is opposite to or perpendicular to buoyancy direction,the bubble load pressure peak first increases and then decreases with increasing γ,reaching maximum at γ=1.0.Under the same γ condition,the bubble load pressure peak when Bjerknes force is opposite to buoyancy direction is consistently higher than that when Bjerknes force is perpendicular to buoyancy direction,and the pressure peak difference value first increases and then decreases with increasing γ,reaching its maximum value at γ=1.0.