Abstract:In order to discuss the mechanical and deformation behavior of piles in coastal soft soil areas under horizontal load，the corresponding simplified mechanical model was established according to the loading characteristics of piles in coastal soft soil areas.Secondly，the softening effect of coastal soft soil was considered to modify the existing p-y curve model.On this basis，the differential equation of pile deflection in coastal soft soil areas was derived，and its internal force and displacement were solved by the transfer matrix method.A nonlinear calculation method of piles in coastal soft soil areas considering the softening effect was obtained.Finally，the influence of softening parameters，pile diameter，and elastic modulus of pile on the horizontal bearing capacity of piles was analyzed with relevant engineering cases.The results show that the transfer matrix method has high precision and calculation efficiency in the analysis of piles in soft soil areas under horizontal load，which can provide a reference for related projects.When the softening parameter increases by 0.3，the horizontal displacement of the pile at the ground decreases by 24.12% and 43.04%，respectively.When the pile diameter increases by 0.7 m，the horizontal displacement of the pile at the ground decreases by 62.63% and 79.65%，respectively.The influence depth of the pile displacement and internal force increases with the increase in the pile diameter.When the elastic modulus of the pile increases from 25.5 GPa to 36.0 GPa，the deformation of the pile decreases by 6.25% and 23.06%，respectively.

Abstract:The application of carbonaceous shale for subgrade filling not only alleviates the shortage of subgrade filler in carbonaceous shale distribution areas but also meets the strategic requirements of “resource conservation and saving ” and “green development ” for infrastructure construction in China.However，such rocks are weak and susceptible to weathering and disintegration，and they exhibit significant strength deterioration when exposed to water.To fully apply them，their performance must be comprehensively understood.In this paper，the basic properties of the carbonaceous shale were studied，and filler gradation was designed.The tests on compaction characteristics of the filler and particle crushing characteristics after compaction，RCBR （California bearing ratio ） variation characteristics under dry and wet cycle conditions，compression properties of the filler and particle crushing characteristics after compression under dry and wet conditions，as well as the rebound modulus of subgrade during water immersion were conducted.The results show that with an increasing degree of weathering，the original shale tends to become clayey，and the microstructure becomes loose.In the compaction process，coarser filler particles mean that they are more difficult to adjust their position to achieve a stable dense state，and particle crushing is more significant.The filler shows strong softening and disintegration properties when exposed to water.The initial RCBR of the filler is 54%，which exhibits a fast-to-slow decreasing trend under dry and wet cycles and finally stabilizes at about 26%.In the compression tests，additional deformation of the filler by wetting after water immersion is extremely significant，and the crushing particles increase greatly.Particle groups that do not crush at optimum water content also crush after saturation.The rebound modulus of the subgrade without water immersion is 140.4 MPa and declines to 82.1 MPa after 6 h of water immersion，after which the decay of the rebound modulus with increasing immersion time is not significant.For practical application，it is recommended to optimize the gradation of the filler，control the maximum particle size，and adopt subgrade structures that can effectively prevent water and control moisture.In addition，it is necessary to avoid using carbonaceous shale filler in positions with developed surface and ground water.

Abstract:The variable cross-section geocell retaining wall of the Chengdu –Yibin Expressway test road in Sichuan Province of China was studied.First，the construction method of the new-type assembled geocell retaining wall was introduced，and the new-type glass fiber reinforced plastic lightweight panel was used to effectively solve the problem that the panel of the retaining wall is not neat and easy to be damaged.Secondly，the supporting effect of the retaining wall was analyzed by field monitoring.The field monitoring results show that the earth pressure at different parts of the retaining wall is nonlinearly distributed along the height of the retaining wall.The earth pressure at the bottom of the retaining wall is large，but it is small at the top and decreases locally.At the same height of the retaining wall，the earth pressure at the back and the middle of the retaining wall is larger，while that at the wall surface is smaller，indicating that the earth pressure attenuates greatly from the middle of the retaining wall to the wall surface.The monitoring results of the horizontal displacement of the wall show that the horizontal displacement curve is S-shaped，and there are two displacement demarcation points.The horizontal displacement changes obviously at the position where the wall section changes，and the horizontal displacement at the top and bottom of the retaining wall is the maximum and minimum，which are 30 mm and 3 mm，respectively.The settlement monitoring results of the retaining wall show that the settlement of the retaining wall during the construction period is large，accounting for about 70%?90% of the total settlement，and the post-construction settlement is small.The maximum settlement of the wall occurs at the top of the retaining wall，and the maximum settlement is only 23 mm.Finally，the earth pressure distribution and deformation law of the stepped retaining wall are analyzed with the earth pressure calculation theory.The results show that the deformation of the retaining wall conforms to the mode of “rotation + translation + rotation around the bottom of the wall”.The earth pressure at the back of the retaining wall obtained by the calculation method in this paper is close to the measured value and is safer when it is used for retaining wall design.

Abstract:The rigid-flexible composite pavement，as a kind of durable pavement structure，has been widely used for heavy-duty traffic，special geological conditions，bridge tunnel paving，etc.In order to promote the application of durable rigid-flexible composite pavements and clarify the key research issues and development directions，relevant research progress of rigid-flexible composite pavements in China and abroad was reviewed.Based on the structure design theory and construction technology of rigid-flexible composite pavements，the structural mechanical behavior characteristics of rigid-flexible composite pavements were described，and the stress induced by load and temperature of asphalt surface layer and rigid base layer，as well as their interactions were analyzed.The asphalt surface layer on the rigid base layer was directly subjected to the load and environmental effects and improved the stress and temperature fields of the underlying structural layer.It was the key factor influencing the performance and service life of rigid-flexible composite pavements.It was identified that diseases of rigid-flexible composite pavements mainly appeared in the asphalt surface layer.Due to the huge modulus difference between the asphalt surface layer and the rigid base layer，the asphalt surface layer on the rigid base layer was more prone to produce compression-shear failure.The cracking of the rigid base layer and the bonding state between rigid and flexible layers also played an important role in the performance of asphalt pavements.Finally，the technology of improving the performance of rigid-flexible composite pavements was summarized from three aspects：shear resistance of asphalt surface layer，integrity of base panel，and bonding between the flexible and rigid layers.It was an effective way to improve the performance and durability of rigid-flexible composite pavements by conducting integrated structure-high-performance material design based on the structural mechanical characteristics of rigid-flexible composite pavements.

Abstract:In order to study the slippage mechanism of asphalt concrete overlay on continuous reinforced concrete composite pavement （CRCP），the structure of the composite pavement was modeled using the elastic layered system，and the interlayer bonding state of the model was calibrated by the measured data of the road.In the analysis of interlayer mechanical behavior，it was found that when the horizontal force coefficient was 1，there existed a tension-shear zone behind the wheel，which may lead to the failure of this zone prior to the position of the maximum interlayer shear stress.Relevant test data analysis shows that when the horizontal force coefficient is 1，under the action of the normal temperature and standard axle load，the maximum tensile stress position is not destroyed before the maximum shear stress position.Under the action of high temperature and overload，the fatigue life of the maximum shear stress position is lower than that under the normal temperature and standard axle load.The maximum tensile stress position loses bonding between the layers，and the shear stress caused by the load will lead to direct destruction between the layers.In the field road survey，a U-shaped crack is found in the long longitudinal slope and curve position，and the AC surface layer falls off in a large area when the crack is serious.

Abstract:The existing calculation methods for texture depth of asphalt pavements are easily affected by external and human factors.Therefore，a multi-region plane fitting algorithm for the texture depth based on three-dimensional （3D） linear laser data was proposed.The algorithm preprocessed the collected 3D height data matrix of the pavement and derived a slope-based adaptive filtering algorithm for point cloud data.Then，the 3D height matrix was divided into multiple regions，and the local extremum of the center point was determined.Finally，with the three-point and one-surface plane fitting algorithm as the core，the texture depth of asphalt pavements was calculated.The experimental results show that the correlation between this algorithm and the electric sanding method exceeds 94%，and the complexity is 1/3 of the 3D fitting algorithm.The sample acquisition from point to surface is realized.

Abstract:With the long tunnel as the research object，the variation of volatile organic compound （VOC） volume fraction，CO volume fraction，and illuminance in the construction area of the middle of the tunnel under the conditions of hot mix technology and warm-mixed flame retardant technology was tested respectively，and the influence of warm-mixed flame retardant technology on the construction environment of asphalt pavement in long tunnels was analyzed and evaluated.The results show that when the pavement of a long tunnel adopts hot mix technology，the mass concentration of asphalt fume in the whole operation area is relatively high，and that in some areas exceeds the threshold value.The illuminance is below the pedestrian illuminance standard.When warm-mixed flame retardant technology is employed，the mass concentration of asphalt fume in the construction area is significantly reduced.VOC volume fraction is reduced by 26.8%，and CO volume fraction is reduced by 21.9%.The illuminance in the construction area is increased by 103.2%，and the construction environment has been significantly improved.A good construction environment of tunnel pavement is not only conducive to the physical and mental health of the construction personnel but also contributes to the quality of tunnel pavement construction.

Abstract:The short-term water stability of acidic diorite asphalt mixtures with acid-alkaline composite aggregates mixed with cement （2% cement instead of mineral powder ），slaked lime （30% slaked lime water for stone immersion ），and anti-spalling agent （modified asphalt with 0.3% anti-spalling agent ） was evaluated by Marshall test of immersion，freeze-thaw splitting test，and rutting test.Then，by repeated freeze-thaw splitting test，repeated freeze-thaw and baking splitting test，and repeated acid-etching freeze-thaw splitting test，the long-term water stability of the treated acidic diorite asphalt mixtures in different environments was tested.The results show that the physical and mechanical properties of acidic diorite meet the specification requirements；the short-term water stability of the treated acidic diorite asphalt mixtures is significantly improved and meets the specification requirements.However，the long-term water stability of the acidic diorite asphalt mixtures treated with 0.2% anti-spalling agent is poor at high temperatures.The acidic diorite asphalt mixtures treated with 30% slaked lime water have good long-term water stability and can be recommended for engineering applications.

Abstract:Cracking in emulsified asphalt cold recycled pavements is one of the main constraints on their large-scale application in road engineering.To study the fracture performance indicators of cold recycled asphalt mixture and the improvement measures of crack resistance performance，this study investigated three types of mixtures：ordinary emulsified asphalt，basalt fiber，and styrene-butadiene rubber （SBR） modified emulsified asphalt.This study conducted a four-point bending strength test on notched beams，and acoustic emission tests of the beam with prefabricated cracks were carried out to evaluate the fracture performance of three different emulsified asphalt cold recycled mixtures in road engineering.The evaluation criteria included strain energy release rate，stress intensity factor，energy collected in acoustic emission test，and ringing count-impact number.A comparative analysis of the fracture performance was conducted on three distinct emulsified asphalt cold recycled mixtures，with and without the addition of basalt fiber and SBR modification.The test results show that both the use of SBR-modified emulsified asphalt and the addition of basalt fibers significantly improve the fracture resistance of the cold recycled emulsified asphalt mixture.Compared to the use of SBR modified emulsified asphalt，the addition of basalt is more effective.The parameters of ringing count and impact number can better describe the fracture characteristics of materials.There is a good correlation between the results of acoustic emission tests and the calculation results of fracture mechanics parameters.The acoustic emission signal parameters can we ll describe the fracture characteristics of emulsified asphalt cold recycled mixture during the four-point bending test.The research results of this paper offer valuable insights into the design of the fracture resistance of emulsified asphalt cold recycled mixture and the application of acoustic emission technology in the research of cold recycled mixtures.

Abstract:In order to study the compre ssive，flexural，and shear strength and deformation characteristics of marine silt cement soil，a series of laboratory mix ratio tests were carried out，so as to test the changes in unconfined compressive strength fcu，flexural strength ff，normalized shear strength τqg，normalized principal stress difference （σ1?σ3）/σ3，and compression modulus Es under different dosage of curing agents，curing ages，and cement-to-lime ratios.In addition，the correlation between different parameters was investigated.The results show that the performance of the improved samples with cement and lime is 2%?17% higher than that with cement alone under the same dosage.The strength of cement soil is proportional to the dosage and age of the curing agents and inversely proportional to the cement-to-lime ratio.The strength is mainly formed in the early stage of molding，and the growth rate of the strength at the early stage accelerates with the decrease in the cement-to-lime ratio.The strength of most parameters at a curing age of 14 d has exceeded 50% of those at a curing age of 90 d，and the strength at a curing age of 28 d has exceeded 70%.When the cement-to-lime is 0.5，the above indexes are the best.In addition，there is an obvious linear relationship between different parameters，with ff，τqg，（σ1?σ3）/σ3，and Es being 0.33?0.35，0.35?0.37，9.58?10.31，and 17.27?17.66 times of fcu，respectively.

Abstract:To investigate the anti-ultraviolet （UV） aging performance of waste tire pyrolysis carbon black （TPCB）-modified asphalt，TPCB-modified asphalt was prepared and subjected to UV aging tests alongside the base asphalt at various intervals.The micro changes and surface roughness of two kinds of asphalt surfaces were studied by atomic force microscopy （AFM）.The behavior changes in ductility，softening point，and penetration of two asphalts before and after UV aging were tested by asphalt performance tests.The results show that the reduction height of TPCB-modified asphalt is smaller than that of base asphalt，and the surface roughness is larger than that of base asphalt at each time.The performance change value of TPCB-modified asphalt before and after UV aging is smaller than that of base asphalt.Compared with the base asphalt，the asphalt modified with pyrolytic carbon black from waste tires has better UV aging resistance.

Abstract:In order to study the optimal r atio of cement and calcium oxide by double-mixture solidification for improving dredger fill sludge，the soil modification results by double-mixture solidification were analyzed based on orthogonal experiments.Finally，the fuzzy comprehensive evaluation method was used to quantitatively optimize each ratio scheme.The results show that：① Under the same addition ratio （addition amount of 1.0%?4.0%），there is a positive linear correlation between the optimal moisture content and the addition amount，and there is a negative linear correlation between the optimal moisture content and the maximum dry de nsity.Under non-equal addition ratios，the law is not obvious.However，compared to cement，the water-reducing effect of calcium oxide is better.② The unconfined compressive strength of the sample is affected by the relative ratio of cement and calcium oxide，which is positively correlated when cement and calci um oxide are added in the same amount，but in general，cement plays a major role in the strength growth of soil by double-mixture solidification.③ By taking the fuzzy comprehensive evaluation method and considering various factors such as project solidification construction cost，compressive strength，and compaction characteristics，it is believed that the optimal ratio scheme for dredger fill sludge in Shandong Yulongdao Refining and Chemical Project is 2.0% cement + 1.5% calcium oxide for double-mixture solidification.The optimal moisture content of the sample is 23.3%，and the maximum dry density is 1.68 g/cm3.The unconfined compressive strength is 440 kPa.

Abstract:The mixed filler of solidified mud and sand provides an ideal solution for the resourceful disposal of wasted engineering mud，and the compression characteristics of filling engineering are closely related to the strength characteristics and particle breakage characteristics of mixed fillers.This study conducted large size compression tests on mixed fillers with different particle gradations and established a discrete element method （DEM） model that incorporated particle breakage for the side-limited compression tests of solidified mud-sand mixed fillers.The changes in the compression modulus of the mixed fillers and the amount of solidified soil particle breakage during compaction were investigated.The study placed a special focus on analyzing the impact of factors such as the solidified mud mixing ratio and the initial void ratio on the compression properties and the stress-strain relationship of the mixed fillers.It also demonstrated the feasibility of using mixed fillers in filling engineering.The results show that under compacted conditions，the compressibility of the solidified mud-sand mixed fillers is positively correlated with the mixing ratio of clay particles，but negatively correlated with the strength of mud particles.The addition of a certain amount of solidified mud particles can effectively reduce the compressibility of loose sand at low stress levels.However，the compressibility of the mixed fillers slightly improves due to the breakage of mud particles at high stress levels.In the compression process，the degree of particle breakage in the mixed filler increases with the increase in mud mixing ratio and sand initial void ratio，and the final breakage rate tends to approach 80% at the end of compression.

Abstract:Given the potential resource value of rec laimed asphalt pavement，waste rubber powder，and bagasse fibers，it is meaningful to develop the cooperative utilization of various solid wastes.This paper studied the microstructure and thermal characteristics of bagasse fibers，carried out the mix design of a reclaimed asphalt mixture with bagasse fibers and rubber-modified asphalt，and evaluated its road performance.At the same time，the test road was paved successfully and observed for a time.The results show that the hollow lumen with multilayer fiber structure in bagasse fibers contributes to absorbing free asphalt in mixtures and enhances the adhesion between bagasse fibers and asphalt.The thermal properties of bagasse fibers and lignin fibers are approximately the same.However，in the second stage of thermogravimetric tests，the differential thermogravimetry curve of bagasse fibers shows a double-peak structure，while that of lignin fibers reveals a single-peak structure.After adding bagasse fibers，the dynamic stability value of the rubber-asphalt recycled mixture increases by 24.6%，and the failure strain value of the bending test at low temperatures increases by 19.3%.The immersion Marshall residual stability and the freeze-thaw splitting residual strength ratios increase by 4.7% and 8.6%，respectively.The paved test road is in good condition as well.Overall，bagasse fibers have a certain role in improving the road performance of reclaimed asphalt mixtures with rubber-modified asphalt，mainly by promoting the anti-deformability of mixtures，enhancing the skeleton action of aggregates，and increasing the structural strength and toughness of mixtures.

Abstract:To enhance the mechanical properties of coral concrete，static mechanical tests were conducted at five polyvinyl alcohol fiber volume fractions （0，0.5%，1%，1.5% and 2%）.The impact compression properties were investigated under four strain rates using a split Hopkinson pressure bar with a diameter of 100 mm.The results show that the incorporation of an appropriate number of fibers can significantly improve the static compressive strength and splitting tensile strength of concrete.Dynamic mechanical tests show that coral concrete has an obvious strain rate effect，and the incorporation of fibers can improve the sensitivity of the dynamic reinforcement factor to strain rate，with the reinforcement effect becoming saturated at 1.5% of fiber incorporation.The fibers serve to crack resistance and energy dissipation in concrete and can significantly improve the concrete damage morphology and impact toughness.

Abstract:In order to explore the feasibility of applying sandstone in the asphalt pavement of expressways，the physical and mechanical indexes of sandstone and limestone aggregate were compared，and the high temperature performance，low temperature performance，and water stability of asphalt mixture were studied from the aspects of grading type，asphalt type，and aggregate lithology.The results show that the road performance of asphalt mixture synthesized by clean and regular sandstone aggregate meets the requirements of current specifications.At the same time，the comprehensive road performance of sandstone asphalt mixture with 1% anti-stripping agent has been improved.

Abstract:To ensure a safe，aesthetic，and lightweight building envelope，an ultra-high performance concrete （UHPC） building envelope and its node connection mode were proposed based on topological optimization and modular composition.Firstly，the UHPC building envelope was optimized by using the method of minimizing structural compliance subjected to given material volume constraints，and the mechanical performance before and after optimization was compared.The modular design was adopted，and the optimization result of the most unfavorable stress area in the model was taken as the basic configuration unit.Then，UHPC tenon and mortise nodes were proposed，which could be simply assembled into modules.By considering the weak mechanical performance of nodes，the finite element analysis （FEA） of the nodes was carried out，and the nodes were compared with the traditional bolt-steel plate nodes.The results show that the UHPC building envelope based on topological optimization and modular composition not only ensures high stiffness and bearing performance but also reduces the volume by around 35%.Compared with the bolt-steel plate node，the tenon and mortise node in this paper has advantages in mechanical performance，so it can achieve the same strength as the traditional bolt-steel plate node.In order to achieve better results，the inward camber of the key teeth of the UHPC tenon and mortise node should not be greater than 60°，and the camber angle should not be less than 90°.

Abstract:Taking the demolition project of Jianhu Bridge as the research background，the demolition of arch bridges with concrete-filled steel tubes under complex conditions was studied.First，the current bridge demolition methods and application status were introduced，and three bridge demolition schemes were put forward according to the difficulties of the bridge demolition.The appropriate demolition scheme for the bridge was selected after comparison，and the sequence of arch bridge demolition was explained.Then，the stress characteristics of the bridge at each construction stage were analyzed，and the theoretical and measured displacement and stress at the most unfavorable stage during demolition were compared.Finally，the influence of material strength and temperature on structural displacement and stress was studied.The results show that the gantry crane method for steel trestle bridges is best suited to the demolition of bridges with navigable requirements and limited space.After the flange is cut，the working space on both sides can be increased，and the self-weight of the beam can be reduced.During the demolition of the web，the stress and displacement of the structure are proportional to the cantilever length of the beam body，and the theoretical stress and displacement are smaller than measured values.The change of material strength and temperature does not affect the force law of the structure，and the structural stress and displacement are inversely proportional to the material strength and proportional to the temperature.

Abstract:The non-uniform corrosion of spinning strands will induce concrete cracking.A non-uniform expansion model of corrosion products of strands was established，and a mesoscopic numerical model of concrete cracking caused by non-uniform corrosion of strands was built.Concrete was considered as a three-phase composite material composed of mortar matrix，aggregate，and interface layer.The concrete cracking behavior caused by the non-uniform corrosion of strands was simulated by embedding cohesive elements.The rationality of the proposed model was verified by existing experimental data，and the influence of protective layer thickness and aggregate content of concrete on the width of corrosion-induced cracks was discussed.The results show that the proposed non-uniform mesoscopic numerical model can reasonably simulate the whole process of concrete cracking caused by non-uniform corrosion of strands.Considering the non-uniform corrosion characteristics of the strand can effectively improve the prediction accuracy of corrosion-induced cracking.The width of corrosion-induced cracks increases with the decrease in the protective layer thickness of concrete and decreases with the increase in concrete aggregate content of concrete.

Abstract:To improve the efficiency of the review simulation model of the bridge monitoring unit and study the influence of different parameters of the single-tower mixed beam cable-stayed bridge on the bridge ’s completed state in the construction process，this paper，taking the cable-stayed bridge of Tongji Road in Foshan with a span of （200+68+46） m as the engineering background，adopted the single control variable method and response surface-Monte Carlo method for sensitivity analysis.Taking the main beam alignment，main tower alignment，main beam stress，and the variation of cable-stayed bridge force as control objectives，this paper studied the influence of the variation of main beam weight，initial tensile force，and other parameters on the state of the completed bridge.The results show that the dead weight of the main beam and the initial tensile force are sensitive parameters.Construction temporary load is a sensitive parameter，and girder stiffness and cable elastic modulus are non-sensitive parameters.

Abstract:Steel arch frame replaced such construction methods as floor bracket or segment cantilever assembly and it was applied to arch circle cast-in-place across deep water canyons in mountainous areas，which had certain advantages and was worth promoting and applying.By introducing the key construction technologies of Sanchahe Bridge，including steel arch frame cantilever fastener method assembly，arch water tank method precompression，and main arch ring layered pouring，the common problems in the construction process of crossing the deep water canyon were solved effectively.Based on Midas Civil overall modeling of finite elements，the key construction technologies adopted by the bridge were numerically simulated and analyzed，and the successful construction of the bridge was guided and monitored，aiming to provide a reference for similar engineering construction and force calculation and analysis.

Abstract:The main bridge of Zhungeer Yellow River Super Major Bridge is a （160+440+160） m double tower double cable plane full floating system concrete grider cable-stayed bridge.The main beam is a 28.4m wide double box prestressed concrete structure.It was constructed by cantilever pouring with a front fulcrum hanging basket.The maximum weight of the cantilever pouring section is 5 800 kN.To ensure the integral rigidity of the hanging basket，the hanging basket bearing platform adopted the steel box girder structure.The long and large components were connected by high-strength bolts made in sections to facilitate the transportation and installation of the hanging basket.The hanging basket adopted the “secondary lengthening ” technology to reduce the quantities of high-altitude support erection；The one-click start automatic synchronous control technology was adopted for the lowering，walking，and lifting of the hanging basket.A series of new processes and innovative technologies are designed for the cable-stayed cable force conversion device and the hanging basket installation support.

Abstract:In the construction of a deep-water embedded cap foundation，it was required to excavate the mud surface to the depth below sealing concrete and clean the bottom carefully，ensuring the height and quality of bottoming concrete.For hard rock under good geological conditions，there exist such problems as difficulty in excavation，long excavation time consumption，and high construction cost.Based on the construction of the main pier caps of the Chongqing Jiahua Metro Bridge，this paper adopted the method of combining theoretical analysis，numerical calculation，and engineering implementation verification，which developed an emended cap unsealed bottom key construction techniques for deep-water hard rock.This construction technology used the method of excavating the wall foundation groove and pouring the foundation groove concrete to replace the large volume of bottom-sealing concrete as a way to achieve the purpose of providing a dry working environment for the construction of the cap.With this method，shorter underwater excavation time，reduced underwater concrete amount，improved construction efficiency，lowered construction time and are achieved.

Abstract:In view of inaccurate vibration prediction of foundation pit blasting，the influence of blasting point position and foundation pit height on vibration during foundation pit blasting excavation was studied by using finite element simulation software.First，based on the foundation pit blasting excavation of the Mawan Cross-Sea Passage，a numerical simulation was carried out to verify the applicability of the model.Then，under unchanged blasting center distance，the distance from the blasting point to the edge of the foundation pit and the foundation pit height were changed respectively，and the influence of these two factors on surface vibration was studied.The results show that a greater distance from the blasting point to the edge of the foundation pit indicates a smaller vibration velocity of the corresponding distance measuring point.As the height of the foundation pit increases，the vibration velocity of the corresponding distance measuring point gets larger.The influence of foundation pit height on surface vibration velocity is greater than that of blasting point position.The research results can provide some reference for the vibration prediction of foundation pit blasting and have practical engineering significance.

Abstract:In order to study the reasonable constr uction method of super-span highway tunnels，the Xinghuacun No.1 tunnel included in the reconstruction and expansion project of the Xiaocaohu –Urumqi section of the Lianyungang –Khorgos Expressway in Xinjiang was studied.The numerical simulation method was used to analyze the deformation and stress of the supporting structure of the Grade tisurrounding rock in the super-span highway tunnel constructed by the center diaphragm （CD） method，the upper-bench CD method，and the three-bench and seven-step excavation method.Under the premise that the deformation and the stress of the supporting structure met the design requirements，the advantages and disadvantages of each construction method were considered，and the most reasonable construction method was determined.The field test was implemented to analyze the feasibility of the construction method.The results show that：① The tunnel deformation calculated by the CD method，the upper-bench CD method，and the three-bench and seven-step excavation method are all less than 21 mm，and the safety factors of the supporting structure at the initial stage are 2.48，2.41，and 2.28，respectively，which are greater than the minimum safety factor required by the tunnel design rules.The deformation and the stress of the supporting structure all meet the design requirements；② the advantages and disadvantages of the three construction methods are compared，and the optimal construction method for the grade Ⅳ surrounding rock in the Xinghuacun No.1 tunnel is determined as the upper-bench CD method after considering tunnel geological conditions and other factors；③ according to the field test results，the grade Ⅳ surrounding rock is constructed by the upper-bench CD method.The maximum arch subsidence is 14.6 mm，and the maximum peripheral displacement is 15.0 mm，indicating a good tunnel deformation control effect.The minimum safety factor of the supporting structure at the initial stage is 6.94，which meets the design requirements.

Abstract:In order to reduce the adverse effect of back heading blasting on the completed supporting structure at the entrance of a double-hole eight-lane super-long-span tunnel with Ⅴ-grade surrounding rock，the Niuzhaishan tunnel project in Pingtan was taken as an example.The original design of the double-side heading method is easy to cause the collapse of the temporary steel support that has been completed when blasting happens near the back heading.In view of this，this paper put forward scheme 1 of canceling the temporary transverse support and the up-and-down step method with vertical support （scheme 2）.It then used the finite element method to calculate and simulate the influence of three different excavation methods on the deformation and stress of the tunnel.The calculation results show that the difference in crown settlement caused by the three schemes is small，and the maximum difference is about 11.8%.The surrounding rock stress caused by the second scheme is the largest，but the second scheme cancels the lateral support of the left and right side heading and the vertical support of the lower steps of the left and right side heading，which greatly simplifies the construction process.Finally，according to the monitoring data，the tunnel structure is safe and stable.It can be seen that scheme 2 is not only reasonable and reliable but also speeds up the construction progress and saves the cost.

Abstract:In order to study the influence of concrete barrier slope parameters on the protective effect against vehicle collision，the vehicle models and concrete barrier models were established.The validity of these models was verified using the real vehicle test data.Then，the collision analysis was conducted on the single-slope concrete barrier with different slopes，improved concrete barrier with different slope parameter combinations，and reinforced concrete barrier with anti-climbing function by using the validated models，respectively.The results show that the slope is the key parameter that affects the protective performance of the single-slope barrier，and vehicles cannot be effectively protected if the slope is too small or too large.The comprehensive protective performance of the barrier is relatively better under the standard parameter value of 80°.The slope angle （α and β），vertical height （a，b，and c），and slope width （s） of the improved concrete barrier are the key parameters affecting its protective performance.The comprehensive protective performance of the improved concrete barrier is relatively better under the condition of the standard slope parameters （α=84°，β=55°，s=12.5 cm，b=18 cm，and c=7.5 cm）.The anti-climbing function has little effect on improving the protective performance of the improved concrete barrier.However，the barrier will have an obvious effect on preventing vehicle rollover when combined with the new jersey safety barrier.

Abstract:During the construction and expansion of expressways and national and provincial highways，more diversified requirements have been put forward for the median barrier，including reliable protective performance，small footprints，beautiful traffic environments，and economic costs.However，the existing median barrier achievements still have some shortcomings.In order to better meet the design and use needs of median barriers for highways，theoretical analysis，computer simulation，and full-scale impact tests with real vehicles were adopted，and the force characteristics of different types of median barriers were analyzed.A new design concept of beam-column integration was put forward.Through systematic research on the barrier height，width，beam，column，foundation，and other structures，a land-saving and beautiful median barrier was developed.The median barrier had a protective performance at SAm level and an overall width of 50 cm.It could save construction land，and the single beam-column integrated structure enabled a more penetrating landscape，required less material consumption，and made the cost more economical，with excellent comprehensive performance.

Abstract:In view of the insufficient protection grade of the guardrail in old bridges，a combined guardrail suitable for the low concrete wall guardrail in the old bridge was designed and developed by using finite element analysis while not damaging the main structure of the bridge.The protection grade was verified to reach SA grade through a full-scale vehicle collision test.The guardrail was designed with new high-strength alloy steel，with light weight and beautiful appearance.There was no need to dismantle the original concrete foundation in the old bridge，which is convenient for construction and requires low cost.Therefore，it is worth being popularized and applied in the project of reconstruction and improvement of bridge guardrails.

Abstract:To address the application of an ultra-thin wearing course in expressway asphalt pavement maintenance engineering，the ultra-thin wearing course system based on the balance design concept was systematically studied.In this paper，the action mechanism and application characteristics of modifiers were analyzed，and the proportion design test of the ultra-thin wearing course was designed based on the balance design method.Finally，according to the proportion design test，the optimal proportion of the ultra-thin wearing course material was selected for test road paving.Research shows that the direct-cast high viscosity modifier is convenient for transportation and storage，improves the elastic recovery of asphalt mixtures and reduces permanent deformation.Under the condition of good gradation and intercalation，a reasonable increase in asphalt dosage can effectively improve the high-temperature stability，low-temperature crack resistance，and water stability of the ultra-thin wearing course asphalt mixture.With the increase in modifier content，the high-temperature stability of the asphalt mixture is gradually improved，which reaches the optimum when the asphalt content is 6.8% and the modifier content is 0.9%.Considering the performance and economic factors of the asphalt mixture，the best material ratio of the ultra-thin wearing course is determined and successfully applied to the test road of an expressway maintenance project.The test results show that the ultra-thin wearing course provides good water tightness，anti-sliding performance，and noise reduction performance.

Abstract:The current bridge maintenance sy stem in China primarily relies on bridge inspection data to prioritize the state of bridges and allocate a limited budget accordingly.This strategy focuses on repairing bridges with low performance，concentrating on restorative maintenance but ignoring preventive maintenance.In view of the total lifecycle cost，the repair-oriented method may require a lower initial investment but leads to significant resource consumption in the mid to late stages.Based on existing highway bridge maintenance systems，an intelligent maintenance system relying on Chinese standards and bridge inspection data and combining repair and prevention was developed.The system model mainly consisted of two modules：the bridge performance degradation model and the intelligent maintenance decision model.Firstly，the long-term performance of the bridge was predicted based on dynamic Markov and Weibull models using long-term inspection data and mathematical statistics.On this basis，a mathematical model following preventive maintenance concepts was established，and it was optimized and solved by using swarm intelligence algorithms.Finally，a prestressed concrete box girder bridge on the Banyin Passage in Shenzhen was studied，and the model was tested using actual bridge inspection data.The results show that compared with traditional maintenance methods，the intelligent maintenance system can reduce maintenance costs by up to 10%.

Abstract:Owing to poor gradation and high liquid limit and plasticity index，the application of gravel laterite on road paving is limited in West Africa.To overcome this issue，laterite granule combined with sand at different content was explored.The performance including the particle composition，limit water content and CBR value was investigated.The results indicate that sand treatment can improve the gradation，enhance the compactness，and reduce the plasticity index.The improved gravel laterite can meet the requirements of subbase，cushion，and base courses.Cement treatment can improve the mechanical properties of laterite grains.Cement and sand content affect the unconfined compressive strength significantly，with an optimal sand content range identified.Specifically，laterite granules mixed with sand and stabilized with 2.5% PK 58 cement and 3.5% PK 6 cement meet the specifications for cushion layer materials in inverted structures in West Africa.The overall findings contribute to localization design and the optimization of indigenous materials in West Africa，broadening their application scope and enhancing their use in construction projects，offering valuable insights for Chinese engineering projects in West Africa.