Abstract:Using solid waste in the road engineering field for subgrade filling is an important approach for building green and low-carbon emission roads.However,most solid waste contains heavy metal pollutants to varying degrees,and heavy metals will be released under complex environments including rainfall infiltration and groundwater immersion,thereby causing pollution to the surrounding soil and groundwater if not handled properly.This paper reviewed the current status of research on four aspects,including the comprehensive use of solid waste materials in subgrade engineering,the leaching and migration behaviors of heavy metals in solid waste,and the prevention and control treatment of heavy metals in solid waste.It is found that solid waste has a wide range of applications in subgrade engineering,but little research has been focused on the pollution characteristics of heavy metals in subgrade containing solid waste,and the long-term leaching behavior and migration mechanism of heavy metals in subgrade are still unclear.In order to assess and regulate the pollution performance of solid waste,the migration pattern of pollutants in the subgrade structure needs to be further investigated.By summarizing and comparing the prevention and control treatment technologies for pollutants in solid waste,it is found that geopolymers have broad application prospects in the disposal of hazardous heavy metals in solid waste.

Abstract:In order to reveal the influence of adsorbed bound water on the strength and permeability characteristics of high liquid limit soil,the initial adsorbed bound water content of the high liquid limit soil specimens from Hunan and Hainan was controlled by different concentrations of sodium chloride solution,and thermogravimetric analysis method was used to determine the content.The direct shear test,unconfined compressive strength test,and permeability test were carried out.The results show that the adsorbed bound water content decreases with the increase in salt solution concentration,while the strong bound water content is basically unchanged.The adsorbed bound water has a high viscosity,low activity,and certain solid-like properties.With the decrease in the adsorbed bound water content,the shear strength and compressive strength of the specimens decrease.In the process of permeation,the permeability coefficient first increases and then decreases with the decrease in adsorbed bound water content,but the final permeability coefficient is greater than the initial value.The research results can provide a reference for the use of high liquid limit soil as subgrade filler.

Abstract:Water damage to embankments serious ly affects the normal operation of highways,so it is extremely important to ensure the stability of the embankment.In addition,it is necessary to analyze the mechanism and study the safety control measures for water-damaged landslides of the embankment.A highway subgrade embankment was studied,and the causes and formation mechanism of the landslide were qualitatively analyzed based on the on-site deformation monitoring and stability calculation.Then,the stability coefficients of different reinforcement schemes were calculated.An appropriate reinforcement scheme was recommended by considering the project cost,construction technology,and construction period.The results indicate that uneven settlement of the embankment stratum is the fundamental cause of landslides under the influence of continuous rainfall.As rainfall accumulates in the depression on the left side of the embankment and penetrates into the soil layer,swelling and softening of clay layers and blockage of drainage channels further accelerate the formation of landslides.The composite reinforcement scheme of steel pipe piles and backfill back pressure meets the stability requirements,and the reinforcement effect is good.

Abstract:In order to study the effect of the change in the master curve parameters of the dynamic modulus of asphalt mixture and the interaction on the structural response of asphalt pavement,a three-dimensional model of the asphalt pavement structure was established using the finite element method,and the structural calculations of asphalt pavement with semi-rigid base and flexible base were carried out.The master curve parameters of the dynamic modulus δ,α,β,and γ were taken as the influencing factors,and the maximum tensile strain at the bottom of the asphalt layer and the vertical compressive strain at the top of the subgrade were set as the response targets.The response surface model of the master curve parameters of the dynamic modulus and the critical structural response of the asphalt pavement was established by the response surface method (RSM ),and the influence of the master curve parameters and their interaction on the critical response of the asphalt pavement structure was analyzed.The results show that the effect of the master curve parameters of the dynamic modulus on the critical response of the structure is influenced by the type of response and the type of pavement structure,and the parameter δ has the greatest effect,followed by α.The effects of β and γ are relatively small.The tensile strain at the bottom of the asphalt layer and the vertical compressive strain of the subgrade of the pavement structure with a semi-rigid base are not affected by the interaction between parameters,and the interaction of parameters α and β has a significant effect on the vertical compressive strain of the subgrade of the pavement structure with a flexible base.

Abstract:To explore the effect of flax cell ulose fiber on the humidity and basic properties of cement mortar,this paper adopted flax cellulose fibers with different lengths (0.5 and 5 mm ) and mixing amounts (mass fraction of 0.5%,1%,1.5%,and 2% of cement ).Tests were conducted on rheological properties,mechanical properties,autogenous shrinkage properties,and internal relative humidity development of cement mortar.Setting time,compressive strength,shrinkage rate,and relative humidity were used to evaluate the performance improvement effect of cellulose fiber on cement mortar.The results show that the absorbance rate of flax fiber per unit mass of 0.5 mm is 3.45 times its weight,while the absorbance rate of flax fiber per unit mass of 5 mm is 6.03 times its weight.Flax fiber has significant advantages in humidity compensation,shrinkage inhibition,and crack retardation of cement-based materials.At each curing age,a higher mixing amount of fiber indicates lower compressive strength.Under the same mixing amount of fiber,the compressive strength of the short fiber group is higher than that of the long fiber group.Compared with the baseline mortar group,the short fiber has a more obvious inhibition effect on autogenous shrinkage.A higher mixing amount of flax fiber indicates more significant internal humidity compensation.In addition,under the same mixing amount of fiber,the humidity compensation effect of long fiber is better than that of short fiber,indicating that the water quantity of internal curing is the key to compensating for the internal humidity.

Abstract:To explore the fatigue damage mechanism and micro-mechanical behavior of the pavement of rubber powder asphalt mixture (ARHM- 20) of expressway influenced by heavy vehicles,a three-dimensional microstructural model of the mixture was built based on the discrete element method,and research on the damage mechanism from aggregate motion to macroscopic permanent deformation were conducted.The Burger's constitutive model was used to characterize the viscoelastic properties of asphalt mortar.The macro mechanical parameters of Burger ’s model at different temperatures were obtained through asphalt creep tests,and the micro modeling parameters were obtained based on the macro and micro conversion formulas.The irregular coarse aggregate was made by Solidworks software to make the model closer to the actual working conditions.In this paper,under the distributed loading method,the contact force was extracted after rolling the tire on the ground,and then the force was applied to the model.Based on the actual highway engineering gradation,the rutting test specimen was prepared and the laboratory rutting test was carried out to verify the validity and correctness of the three-dimensi onal microstructure model.The research results show that the discrete element method can be used to study the micro motion-mechanical behavior of asphalt mixture.The macro behavior of rutting evolution is mainly generated by the micro stress distribution and motion evolution of the coarse aggregate in the asphalt mixture.Compared with the asphalt mixture without rubber powder,the ARHM- 20 asphalt mixture has better high-temperature fatigue resistance.

Abstract:In the process of applying construction waste to subgrade,the bearing capacity of the material has an important impact on the service performance of roads.In order to evaluate the meso-mechanical properties of construction waste used as subgrade filler,the bearing ratio test of waste lime-fly ash macadam and soil mixture with different stone contents was carried out by using discrete element software.The strength formation mechanism was revealed by using the discrete element method.The results show that the bearing ratio of the mixture increases with the increase in the stone content and reaches the maximum value when the stone content is 80%.In the bearing ratio test by discrete element simulation,the porosity first decreases and then increases with the increase in the stone content of lime-fly ash macadam soil.When the stone content is 80%,the porosity of the mixture is the smallest,and the best bearing effect can be achieved.As the stone content rises,the particles between the waste lime-fly ash macadam are embedded with each other to form a skeleton structure so that it can effectively bear the load from the penetration rod.

Abstract:To study the effect of hydrothermal coupling aging on the performance of rubber modified asphalt,this article simulated thermal aging and hydrothermal coupling aging tests and investigated the effect of different aging environments on the high-temperature and low-temperature performance of asphalt from macroscopic and microscopic levels through conventional index tests,dynamic shear rheology tests,and gel chromatography tests,as well as the effect of different aging environments on the interfacial properties through low-temperature adhesion tests of asphalt and aggregates.The results show that the effects of hydrothermal coupling aging on the ductility and softening point of rubber modified asphalt are more significant than those of thermal aging.The rutting factor,phase angle,and critical temperature of rubber modified asphalt increase with the increase in aging time,and the temperature sensitivity decreases,meaning that the high-temperature performance of the rubber improves.However,the changes in the hydrothermal coupling aging environment are more significant.Both thermal aging and hydrothermal coupling aging lead to the degradation of the interfacial properties of asphalt aggregates,but hydrothermal coupling aging has a greater influence.The macromolecular content CLMS (%) and dispersity D-value both increase with increasing aging time,but hydrothermal coupling aging increases the degree of growth in the early stage.D-value and CLMS (%) have a good correlation with softening points and ductility.

Abstract:To evaluate the fatigue performance of Qingchuan rock modified asphalt mixture,a dynamic wheel-load three-point bending loading fatigue test device based on an accelerated loading test system of 1∶3 scale pavement was designed.The three-point bending repeated loading fatigue test of a composite rutting specimen of double-layer asphalt mixture under tire rolling was carried out.Through the MTS bending fatigue test of a small beam specimen of asphalt mixture,the improvement effects of Qingchuan rock modified asphalt and composite modified asphalt on the fatigue performance of the asphalt mixture were evaluated.The results show that Qingchuan rock modified asphalt can improve the ability of asphalt mixture to withstand repeated bending and tensile loads and enhance the fatigue resistance of asphalt mixture,and its fatigue resistance is better than that of Qingchuan rock asphalt,SBS composite modified asphalt,SBS modified asphalt,and base asphalt.The dynamic wheel-load three-point bending repeated loading fatigue test based on the accelerated loading test of 1∶3 scale pavement provides a more realistic simulation of the wheel load action in the field,reduces the effect of the size effect of the small beam specimen on the fatigue life,and reproduces the force condition of the pavement structure under the wheel load action.

Abstract:Currently,life cycle cost analysis (LCCA ) and life cycle assessment (LCA ) methods are commonly used to assess the economic and environmental impacts of pavement during the whole life cycle.However,there are drawbacks in the application of LCCA and LCA methods,such as a large amount of data and multiple data categories,which lead to a tedious evaluation process.In view of this,some scholars have tried to combine building information modeling (BIM ) with LCCA and LCA methods to optimize the evaluation process.In the pavement field,the combination of LCCA and LCA with BIM is still in its infancy,lacking a summary of relevant research results.Therefore,this paper summarized the research on LCCA,LCA,and LCCA-LCA methods for pavement,as well as their combination with BIM to explore the existing problems and challenges.It is found that the application of BIM can optimize the LCCA and LCA processes and realize the dynamic coordination of design and evaluation.However,the low integration degree and the lack of unified data format standards between modeling software and evaluation software hinder the application and development of BIM.

Abstract:This paper investigated the effects of particle size and content of recycled aggregate on the anti-freezing performance of cement-stabilized recycled aggregate mixture,so as to provide a reference for the fine utilization of recycled aggregate with different particle sizes.The basic performance indexes of recycled aggregates with different particle sizes were tested,and the optimum moisture content and maximum dry density were determined by compaction test.The specimens were prepared with 4% cement content,and the anti-freezing performance of the mixture was evaluated by testing the unconfined compressive strength loss of the mixture after the freeze-thaw cycle.The results show that the optimum moisture content increases,and the maximum dry density of the mixture decreases with the increasing particle size and content of recycled aggregate.When recycled aggregate of 4.75?9.5 mm is added,after five freeze-thaw cycles,the strength of the mixture first increases and then decreases with the increasing content of recycled aggregate.After ten freeze-thaw cycles,the strength of the mixture decreases with the increase in the content of recycled aggregate.When the recycled aggregate of 9.5?19 mm and 19?26.5 mm is added,with the increasing content and particle size of recycled aggregate,as well as the number of freeze-thaw cycles,the strength of the mixture deteriorates.The variation law of the anti-freezing performance of cement-stabilized recycled aggregate mixture is different with the change in content and particle size of recycled aggregate.In general,with the increasing content and particle size of recycled aggregate,as well as the number of freeze-thaw cycles,the anti-freezing performance of the mixture is worse.

Abstract:As a flexible structure,the response of suspension bridges under live load has been the focus of research for a long time.This paper presented an analytical calculation method for structural deformation and internal force of suspension bridges under concentrated live load.Based on the known bridge state parameters and live load parameters,the deformation of the main cable,the deformation of the main beam,the relationship between the main cable and the main beam,and the deformation of the bridge tower were analyzed successively.Then,four kinds of governing equations were established,involving the conserved unstrained length of each main cable,the coordinated force and deformation of each suspender,the closed span and height difference,and the balanced force of the main beam,so that the total number of the governing equations was equal to the total number of basic unknown parameters.Finally,the governing equations were combined into an objective function and solved programmatically.The values of the basic unknown parameters were found to make all the governing equations valid at the same time,and then all the other parameters were deduced.The state of the structure after deformation was expressed.Finally,a suspension bridge with a main span of 1 080 m was taken as an example to verify the feasibility and effectiveness of the method.The results of deformation and internal force under live load were in good agreement with those of the finite element method.

Abstract:Crosswind has a great influen ce on the operation safety of vehicles on long-span bridges.To explore the relationship between the characteristic parameters of the crosswind and the traffic operation safety of the long-span bridge,the Yellow River Bridge with frequent crosswinds was taken as the experimental section,and the relationship between traffic accidents and the distribution of crosswinds on the bridge was analyzed.A fitting relationship model of traffic operation coordination of the long-span bridge under the action of the crosswind was established.The study shows that the occurrence of crosswinds in each season is highly discrete.The crosswind is the main cause of vehicle overturning on the bridge,and rear-end collision,scraping,and collision accidents are directly or indirectly affected by crosswinds.Combined with the operation speed distribution of the vehicle,coordination of traffic operation in spring and fall is poor,and the operation speed is consistent with the crosswind distribution.By using the Poly nonlinear surface fitting method,the seasonal function model of operation speed,crosswind speed,and wind direction is established.According to the goodness of fit and significance test results of the model,the goodness of fit R 2 of the model is greater than 0.8,and the fitting results meet the requirements of convergence and statistics.By eliminating seasonal characteristics of crosswinds,a general traffic operation safety model of long-span bridges under the action of crosswinds is established,which improves the applicability of the model.

Abstract:Seamless expansion joint is a new type of bridge expansion joint.In order to study the road performance of resin elastomer for seamless expansion joints,the feasibility of applying resin elastomer to small and medium displacement expansion joints of bridges was explored.Through the rutting test at 60 ℃, low-temperature beam bending test at ?10 ℃,dynamic modulus test,Poisson's ratio test,and overlay test (OT),the high and low temperature stability,deformation performance,and fatigue crack resistance of the resin elastomer were compared.The test results show that the dynamic stability of the resin elastomer at 60 ℃ is more than 31 000 times/mm,and the bending strain at low temperature of ?10 ℃ exceeds 43 000 × 10?6.Under different temperatures and load conditions,the dynamic modulus is 10?12 MPa,and the Poisson's ratio of tension/compression is 0.03?0.05.The fracture energy of OT is 59% higher than that of the TST elastoplastic body.The resin elastomer for seamless expansion joints of bridges has excellent high and low temperature performance,and it is insensitive to temperature and load frequency.Therefore,it is a material with a low Poisson ’s ratio and strong fatigue crack resistance and can better meet the driving and deformation requirements of small and medium displacement expansion joints of bridges.

Abstract:Based on the Wujiagang Yangtze River bridge project in Yichang,the interfacial shear strength and pull-out strength of the second-order thermosetting epoxy asphalt material between RA asphalt concrete and high viscoelastic SMA asphalt concrete in pavement structure were studied under different spraying amount,different first-stage curing time,different curing time,and different service temperatures.In addition,the influence of spraying amount on shear fatigue resistance was studied.The results show that with the increase in the spraying amount of the second-order thermosetting epoxy asphalt,the adhesive performance and shear strength are improved,and the shear fatigue resistance of the structure is enhanced.At a construction ambient temperature of 25?35 ℃,the construction interval of second-order thermosetting epoxy asphalt layer and high viscoelastic SMA asphalt concrete is recommended to be 44?52 h.Closed curing time after construction should be more than 7 days.The second-order thermosetting epoxy asphalt layer can achieve the shear strength of ≥3.8 MPa and pull-out strength of ≥1.7 MPa of the composite pavement structure at 25 ℃,as well as shear strength of ≥1.7 MPa and pull-out strength of ≥0.9 MPa at 60 ℃.The research results have guiding significance for the application of second-order thermosetting epoxy asph alt material in bridge deck paving engineering.

Abstract:In order to meet the span requirements of bridges over the Yellow River and reduce the interference of temporary construction facilities on flood discharge from the Yellow River,the Linyi Yellow River Bridge was studied.The main bridge adopted a continuous long-cantilever closed steel box composite girder of (112 + 28 × 128 + 120) m and was divided into two parts,with the maximum length of the parts being 1 912 m.The steel box composite girder was constructed by incremental launching method without temporary piers,and the bridge deck was installed after the closed steel box girder was in place.The installation sequence of the bridge deck was from the positive bending moment area in the middle of the span to the negative bending moment area at the fulcrum.The research focused on three key technical issues:optimization measures of mechanical properties in the negative bending moment area of the composite girder,fatigue resistance design of diagonal braces,and optimization design of wind resistance of a 2.5 m-high acoustic barrier.The results show that the compression stress on the bottom plate of the steel box girder and the crack width of the bridge deck can be reduced by using the composite structure in the negative bending moment area.The optimization effect of externally tensioned prestressed steel bundles decreases gradually with the shrinkage and creep of concrete.The fatigue resistance of diagonal braces of square steel pipes with the same cross-sectional area is better than that of round steel pipes.The polygonal acoustic barrier can effectively suppress the vortex response of the main girder.

Abstract:Although a concrete bridge su pport system is a temporary structure,it still has a supporting capacity.With the development of bridge engineering,concrete bridges with high piers and long spans are gradually applied in deep reservoir areas,and the forces on scaffolding are more and more complex.Traditional manual calculations in structural mechanics can no longer completely reflect the stress-strain states of scaffolding with irregular configurations,special parts,and uncommon conditions.Thus,it is necessary to use a numerical method to calculate the supporting capacity of scaffolding and design construction schemes.This paper took a concrete wading bridge with high piers as an example.An evaluation method based on the finite element method with the Midas civil software is proposed for analyzing the safety of a support system from the aspects of strength,rigidity,stability,and cost-effectiveness.The results show that although disc-type full scaffold structures are simple in construction,with low steel consumption,various stand bars,uniform stress distribution,and small deformation (a maximum deflection of only 2.82 mm ),their strength and stability are not as good as beam support systems.In addition,they have higher requirements for sites.Therefore,when disc-type full scaffold structures are applied to high-piers and large-span bridges,buckling analysis should be carried out on the whole model to prevent instability and collapse.Conversely,beam support systems usually do not suffer from strength and stability failures and have few requirements for sites.However,they are difficult to construct and require high steel consumption.Furthermore,deformation is increased due to the lack of vertical support in the midspan.Therefore,form-finding analysis must be carried out strictly when they are applied to complex bridges involving the “pre-camber ” problem.In addition,on the premise that mechanical indexes are met,measures can be taken to achieve higher cost-effectiveness,such as adjusting the net distance of Bailey beams and strengthening lower chords.In this case,the net distance was adjusted from 80 to 100 cm,which can save about 10% in steel consumption.

Abstract:To study the dynamic response and damage characteristics of the super-wide concrete self-anchored suspension bridge under the blast loading,a real bridge with these characteristics was selected as the background,and the numerical simulation was used to analyze the dynamic response of the top surface crack shape and the vertical displacement of the bottom plate of the super-wide box girder under the close blast of the bridge deck.Firstly,the refined finite element model of the whole bridge was established by using SolidWorks and HyperMesh.Secondly,the blast loading was applied by Ansys/LS-DYNA and *LOAD_BLAST_ENHANCED (LBE ) method,and the reliability of the calculation method was verified by combining the blast test results of concrete members in the literature.Finally,the dynamic response of the bridge under different explosive equivalents and different lateral and longitudinal blast positions was analyzed parametrically.The results show that when the TNT equivalent is 300 kg,the stress of the concrete unit right below the blast center reaches the limit value and fails,forming an elliptical crack.With the increase of TNT charge,the peak value of vertical displacement at the center of the bottom plate directly below the blast center increases continuously,with the vertical displacement reaching 135.9 mm after 50 ms of blast under 1000 kg charge.With the increase of the distance to the explosion center,the vertical displacement of the bottom plate decreases,and the increase speed of the vertical displacement slows down.The internal force change of the suspender correlates with the vertical displacement of the bottom plate of the connected box girder.The larger the vertical displacement of the bottom plate of the box girder,the higher the first peak value of the internal force change of the suspender.Under the same explosive equivalent,when the explosion center is at different positions in the lateral and longitudinal directions of the bridge,the difference in the dynamic response and crack shape of the super-wide box girder is mainly caused by the different support and restraint effects of the cross diaphragm and web.The research results can provide important references for anti-blast protection and reinforcement of self-anchored concrete suspension bridges.

Abstract:为了兼顾疲劳荷载谱的分析精度和实用性，该文提出了适用于单车加载和车流加载的荷载模型损伤效应比例系数和循环作用特征长度指标，通过研究典型疲劳车辆疲劳损伤效应一般规律，构建从单车作用到车流随机作用的疲劳荷载谱损伤分析方法。结果表明：单辆疲劳车引起的疲劳损伤可以在集中荷载效应基础上进行比例换算，由影响线绝对面积换算的循环作用特征长度指标对单车疲劳分析有较好的适用性。随机车流引起的疲劳损伤受到桥梁跨径和车流密度的共同影响，在短跨径桥梁中，损伤效应对车流密度不敏感，车流密度的增加甚至会造成一部分结构内力幅的减小；当跨径超过一定临界值时，车流密度的影响显著加剧；由影响线积分面积换算的循环作用特征长度指标更适用于车流疲劳损伤效应分析。荷载谱等效应力幅应结合交通流状态谱进行分析，多车道损伤效应系数指标的构建应考虑车辆相遇概率、循环作用特征长度指标的影响。

Abstract:Bridge deflection response is on e of the most important indicators used for structural condition assessment of bridges.There are currently many methods and devices for deflection measurement,but they are not satisfying in terms of economy,applicability,and measurement accuracy at the same time.This paper proposed a rapid and highly accurate method for measuring mid-span deflection of small and medium-span bridges.By using the high accuracy of displacement transducers in direct contact measurement,an auxiliary measurement device was developed to transfer the deflection of the measurement points on the bridge to the displacement transducer in the form of a rigid connection,thus achieving accurate and dynamic testing.A coupled vehicle-bridge-derrick system model was developed,and model tests were carried out simultaneously to compare the displacement deviation between the measurement points on the bridge and the monitoring point under vehicle loading and verify the feasibility of the proposed method for dynamic response testing.The effect of transverse wind load on the transfer accuracy of the device was simulated and calculated.The results show that the measurement deviation caused by the transverse wind load is less than 5% for the 12 m-long transfer rod,proving that the proposed test method has high accuracy and practicality.

Abstract:Anti-collision steel pontoo n has good plasticity and energy absorption properties in ship-bridge collision.To explore the factors affecting the anti-collision performance of the anti-collision pontoon,a collision model composed of ship,anti-collision pontoon,and pier system was built based on finite element software Ansys/LS-DYNA.The collision mechanism and process were numerically simulated,and the effects of connection type between anti-collision pontoon and pier,peak angle of pontoon,and anti-collision pontoon stiffness on the collision force of the pier were investigated.The three-stage division method of collision force curve was put forward.The analysis shows that the fixed inwall of the anti-collision steel pontoon and connection to the pier surface can reduce collision force.The maximum collision force increases with the increase in distance between anti-collision pontoon and pier.The appropriate value range of the peak angle of the pontoon is 80° ?100°.The steel plate thickness of the collision zone of the anti-collision pontoon has an optimal value.With the increase in steel plate thickness of the non-collision zone,the maximum collision force will increase,but the increase amplitude will decrease when it exceeds 8 mm.

Abstract:Based on a large deep foundation pit project,the deformation characteristics of the pit support enclosure system,force characteristics,and changing trend of surrounding ground surface settlement during the excavation process of the narrow and long deep foundation pit with steel braces were studied through automated monitoring and numerical simulation.Midas GTS was used to establish the pit model,and the effects of the horizontal spacing of the steel brace,the distance of the third steel brace from the bottom of the pit,the preloaded axial force of the steel brace,and the change of the pile diameter of the pit enclosure on the deformation and force of the retaining pile structure and the surrounding ground surface settlement were investigated for the sections with and without steel brace,respectively.The results show that:① The horizontal spacing of different steel braces has different control effects on the deformation of the retaining structure and the surrounding ground surface settlement;smaller horizontal spacing of steel braces indicates smaller values of pile displacement,pile bending moment,and ground surface settlement of the foundation pit;② the position of the third steel brace has little effect on the stability of the foundation pit;③ the deformation of the retaining pile in the foundation pit and the surroundi ng ground surface settlement can be effectively controlled by applying the preloaded force of steel braces;④ with the increase in the diameter of the retaining pile,the deformation of the retaining structure and ground surface settlement values are reduced.Once it exceeds a certain pile diameter,the sensitivity of the pit deformation and the surrounding surface deformation to the diameter of the retaining pile will be weakened;⑤ for the foundation pit project with the completion of the base slab pouring,the steel brace does not have an obvious effect in controlling the deformation of the pit structure,the force,and the surrounding ground surface settlement.Through the comprehensive consideration of engineering conditions,the steel brace can be removed.

Abstract:The construction of foundation pits in granite residual soil layers is prone to causing upheaval deformation and structural damage in shield tunnels below.Based on the engineering case of a newly operated metro tunnel collinear with the above long-distance deep foundation pit in Shenzhen,a three-dimensional finite element model was established to investigate the variation law of the heave and horizontal convergence of the shield tunnel caused by the deep foundation pit excavation.The correlation between the longitudinal stress of the lining structure and the damage was analyzed.The results indicate that the tunnel deformation caused by foundation pit unloading is primarily vertical heave,accompanied by slight section deformation.After adopting the jump excavation method and the stripped soil reinforcement above the tunnel crown,the average tunnel heave is reduced by 14.4%,and the lateral displacement of the envelop enclosure is reduced by 49.1%.The shield tunnel damage caused by the above unloading is mainly the spalling at the circumferential joints of the tunnel crown.The reason is that the compressive shear cracks occur and expand on the intrados of the circumferential joints of the tunnel crown under the combined action of bending moment and shear.

Abstract:To provide a reasonable meth od for calculating the surrounding rock pressure in shallow buried unsymmetrial pressure tunnels under variable slope conditions for tunnel design,to establish a model for calculating the surrounding rock pressure in shallow buried unsymmetrial pressure tunnels under variable slope conditions,and to employ the principle of ultimate equilibrium to derived the formula for calculating the surrounding rock pressure.The intermediate variable β' is introduced as the base for selecting the unsymmetrial pressure tunnels surrounding rock pressure calculation method under variable slope conditions,and the derived formulas in this paper are verified by comparing the calculated values of the normative formulas with the measured values of the tunnel surrounding rock pressure.Results of the study:The equations in this paper are verified to be reasonable and practical by comparison.Analysis of the calculation formula shows that when the natural slope angle increases,the horizontal side pressure coefficient λ1 increases;when the cohesive force increases,the horizontal side pressure coefficient λ2 tends to increase first and then decrease;when the variable slope angle increases,the horizontal side pressure coefficient λ2 will decrease.Studies have shown that the presence of variable slope in a deviated tunnel will affect the surrounding rock pressure on the side of the variable slope section of the tunnel,and it is necessary to use the formula for calculating the surrounding rock pressure for the variable slope conditions in this paper.

Abstract:In order to study the dynamic response rule of overlying buildings during blasting construction in shallow buried tunnels,the urban tunnel in Fuzhou was taken as the engineering background,and the on-site monitoring and Ansys/LS-DYNA simulation were used to analyze the structural response of overlying buildings.The monitoring results show that the building is most obviously affected by blasting in the vertical direction and has an obvious elevation amplification effect,and the maximum vibration velocity is 2.45 cm/s.The vibration velocity in all directions gradually decreases and tends to be stable with the increase in explosion center distance and decays rapidly when the explosion center distance is small.The dominant frequency of vertical vibration is closer to the natural frequency of the building and is mainly concentrated between 25 and 35 Hz.The numerical simulation results are consistent with the monitoring results,and further analysis shows that the maximum peak vibration velocities under grade Ⅲ?V surrounding rock at the same measuring point are 2.29,2.51,and 2.79 cm/s,respectively.A higher grade of surrounding rock indicates a stronger vibration response of surface buildings.The mechanical response of structures such as building columns and plates is closely related to the change in vibration velocity.The vibration velocity in all directions caused by blasting should be fully considered for building protection.

Abstract:In order to explore the as sociation characteristics between influencing factors of accidents from existing traffic data and provide precise and fine-grained decision support information for highway operation and management departments,a constrained improved Apriori algorithm was established to mine the association rules affecting highway traffic accidents by considering four dimensions:driver,environment,road,and vehicle.On the basis of the traditional Apriori algorithm,the improvement of antecedent and consequent constraints of the rule may increase the accuracy and efficiency of mining association rules.Based on the analysis of 3 178 highway traffic accident data,it is shown that the improved Apriori algorithm reduces the number of invalid association rules by accurately mining the correlation between potential factors and accident levels and improves the accuracy of association rules and mining efficiency.There is a strong correlation between driver gender,age,lighting intensity,vehicle type and the severity of highway traffic accidents.Wet and slippery road surfaces can escalate traffic accidents into general accidents.The lighting conditions under the dark night are the main factors that escalate mi nor accidents into general and serious accidents.

Abstract:This paper selected a weaving area on Jingshi Road in Jinan,China as the investigation object to study the characteristics of traffic conflicts and the safety level of each lane in the weaving area between the entrance of an urban trunk road and a signal-controlled intersection.In this research,a signal period was set as the investigation interval,traffic conflicts were identified as the research basis,and the collision time (TTTC) was selected as the index.Severity thresholds of traffic conflicts were established by using the cumulative frequency method,and a model was constructed to represent the relationship among the overall traffic volume,traffic density,and the number of traffic conflicts in the weaving area.Principal component analysis was conducted to evaluate the safety of each lane in the weaving area between the entrance of the urban trunk road and the signal-controlled intersection.The evaluation indexes included the severity level of traffic conflicts and the traffic flow of each lane.The results show that in weaving areas with low traffic volume and density,traffic conflicts increase with rising traffic volume and density.When the overall traffic volume reaches 288 vehicles/ (3.5 min ) and the traffic density reaches 419 vehicles/km,the traffic flow becomes a forced flow.In addition,safety evaluations of each lane reveal a significant distinction in safety levels,with lanes adjacent to the entrance of the trunk road exhibiting lower safety.It has proven that principal component analysis provides accurate and reliable results for evaluating lanes in weaving areas.

Abstract:In order to study the safety of optimized concrete median barrier without planting soil,the technology combining computer simulation,sled test,and full-scale impact test of real vehicles was adopted for analysis and verification.In addition,a scheme was proposed to improve the anti-overturning ability of the barrier without planting soil by strengthening the supporting block,and the scheme of setting a 20 cm-high supporting block between the barrier walls was optimized.The safety of the barrier scheme was evaluated by taking the most unfavorable large truck as an example.The results show that the protection level of the optimized concrete median barrier without planting soil is SAm, and the actual application of barriers will provide effective safety protection for vehicles on highways.

Abstract:As one of the common diseases of asphalt pavement,rutting has significant impacts on the service life and traffic safety of the pavement.Mild rutting in asphalt pavement during preventive maintenance can lead to increased use of maintenance materials due to rutting deformation.Accurately calculating the amount of materials needed to fill rutting in maintenance designs is of great significance for ensuring maintenance quality and efficiency.Based on the requirements of maintenance engineering,this paper analyzed the problems in maintenance designs that use traditional methods and the data they generate for rutting detection.A design method was proposed for rutting prevention and maintenance in asphalt pavement,assisted by digital holographic 3D detection.With this detection technology,continuous high-precision 3D data of road surfaces were obtained,and a 3D model was constructed.The amount of materials needed to fill rutting was accurately calculated through simulation,indicating that the proposed method can effectively improve the accuracy of preventive maintenance.The results from physical testing show that the proposed design method can achieve a negative deviation of material usage for rutting prevention and maintenance within 5%.The method is highly effective compared with maintenance designs based on tr aditional detection methods and data (with a negative deviation of material usage exceeding 50%).

Abstract:Chlorine salt snow-melting agent has been widely used because of its excellent ice-melting and snow-removing performance,low price,and easy access.In order to explore the problems of different temperature applicability,non-uniform standard,and rough spreading methods of chlorine salt snow-melting agents,this paper analyzed the influence of temperature,solid and liquid state,and spreading methods on the ice-melting performance of three commonly used chlorine salt snow-melting agents,namely NaCl,CaCl2,and MgCl2,through an improved SHRP ice-melting test.The test results show that the ice-melting performance of the chlorine salt snow-melting agent has strong temperature sensitivity.MgCl2 and CaCl2 snow-melting agents have an exothermic effect during the melting process.The ice-melting efficiency of the same chlorine salt snow-melting agent in the solid state is higher than that in the liquid state.The ice-melting efficiency of the same kind of chlorine salt snow-melting agent is different under different spreading methods,and the linear spreading shows the strongest ice-melting performance.Based on the test results,it is suggested to use the solid-state linear spreading method and select the appropriate snow-melting agent according to the ambient temperature.

Abstract:The deflection basins of roads under moving load imply the distress information of subgrade and pavement.Therefore,how to use the information of deflection basins under moving load to rapidly test road distresses non-destructively has received much attention.In this paper,the finite element model of semi-rigid base asphalt pavement was established.By setting different types and degrees of finite element distress models,the continuous changes of surface deflection basins under moving load were analyzed.The results show that when the load moves to the distress area,the center deflection value of surface deflection basins in each distress model will become larger.When transverse cracks appear in the pavement structure layer,the shape of the deflection basins will change.The through transverse cracks have the most obvious influence on the shape of the deflection basins.The influence of the locally loose base and subbase on the shape of the deflection basins is more obvious than that of the loose surface.When a void appears at the top of the subgrade,the shape of the deflection basins is almost unchanged.Subgrade mud pumping will seriously affect the shape and size of surface deflection basins.

Abstract:The cement mixing pile is used to reinforce the deep peat soil foundation in Malaysia's east coast railway construction.The key in this project is to determine the cement mix proportion and additives.Considering the high organic matter content and strong environmental acidity of coastal peat soil,physical and mechanical tests of peat soil and laboratory uniaxial compression tests of cement soil under different mix proportions and influencing factors were conducted.Test results show that the mean compressive strength decreases by 0.35 MPa with the increase in cement-water from 0.5 to 0.9.Adding mineral powder gives a relatively poor curing effect while adding fly ash or gypsum contributes an obvious improvement.The curing agent increases the early strength by about 189.29% with strength beginning to increase from 7 d.Compared with ordinary Portland cement,sulfate-resistant cement increases the curing effect on peat soil by 9.5%,and this technique shows a better curing effect on peat soil with an increase of the mean compressive strength by 127% compared with soft plastic silty clay.