In order to make clear the testing method and judging standard of testing the void under cement concrete pavement slab by falling weight deflectometer(FWD),based on the formation mechanism of the void of cement con-crete pavement slab bottom,the basic principle of the testing technology,testing point arrangement requirements,void judging method and standard of FWD are studied and analyzed in this paper.During the test by FWD on site,the testing point should be cleaned,a constant load applied and small temperature difference should be selected.According to the engineering application case and FWD verification test,when the deflection ratio of midpoint of edge and midpoint of the slab is greater than 2 or the deflection ratio of corner and midpoint of the slab is greater than 3,it should be judged comprehensively that there is void under cement concrete plate slab.
Overlong and overweight prefabricated bent have made higher requirements on transportation and lifting equipment and hindered the technical development and engineering promotion of fully assembled bridges,which has become a key problem to be solved urgently.The development of lightweight and high performance prefabricated bent caps with reasonable structure is an alternative solution to the above problems,which is worth paying attention to.In this paper,the key technologies and typical engineering applications of light weight bent caps are systemati-cally reviewed;Secondly,the research progress of the mechanical properties is discussed in detail.The future re-search direction is expounded as well;Finally,the calculation method and flow of flexural and shear capacity are summarized.The results show that when the prefabricated mold shell and the core concrete bonding strength is higher,the mechanical properties and failure mode of the prefabricated shell cover beam are similar to the destruction mode.UHPC hollow thin-bent cap has strong shear and crack resistance.However,the promotion of lightweight bent caps engineering still faces the problems such as the internal mold fixation and demolition,design and construction tech-nology standard formulation,lightweight pier node reliability connection and its seismic performance,which ur-gently need the improvement and breakthrough.
Taking a tunnel in weak surrounding rocks as an example,the influence of different advanced support re-inforcement forms on the tunnel structure and excavation face stability were analyzed by numerical simulation.The different reinforcement forms were compared and analyzed.The analysis results indicate that when the distance be-tween the surface grouting reinforcement and the tunnel arch is close to 1.2 m,the control effect on the settlement of the tunnel arch is significantly improved;The thicker the pipe shed support reinforcement area,the better the con-trol effect on tunnel arch settlement;Under the surface grouting reinforcement,pipe shed support reinforcement and combined support,the extrusion deformation trend of the excavation face is basically the same,with the maximum extrusion deformation value in the middle;Under the combined support,the vertical extrusion deformation value in the middle of the excavation face is the smallest,which is reduced by about 38.5％,27.3％,and 9.1％compared with unsupported,surface grouting reinforcement and pipe shed reinforcement respectively;On the same horizontal line,the lateral extrusion deformation value of the excavation face is basically the same.At the place 3 m from the tunnel excavation section to the tunnel face,the length of the lateral extrusion stable deformation value in the middle of the face is longer.While at the place 6 m,the length is shorter.The relevant research results can provide reference for the support of tunnels in weak surrounding rocks.
The main bridge of Hongzhou Bridge of Nanchang City in Jiangxi Province is a self-anchored suspension bridge with steel-concrete composite beams and double towers with double cable plane.The main pier is set with two independent cofferdams.The cofferdams are made of circular cofferdams supported by lock-gate steel pipe piles and piers.The pier structure is reasonable.During the construction,the inner support of the pier is first installed on the drilling platform.And then,guided by the ring beam the lock steel pipe pile is driven by the combination of DZ-90 vibration hammer and YC-5 hydraulic impact hammer after the total lowering.At the same time,the vertical degree,rock depth and plane position of the lock steel pipe pile are controlled to optimize the closing process.Finally,the pier construction is quickly completed.The relevant research can provide reference for similar projects.
The urban rail transit has been rapidly developed in Beijing.With the continuous construction and opera-tion of new lines and the network continues to be encrypted,the demand for multi-line interchange increases.In order to meet the requirements of the passengers travelling,some earlier constructed stations without reserved trans-fer conditions need interchange renovation under non-stop operation.Taking the public zone renovation of Sanyuan-qiao Station of the existing Beijing subway line 10 under non-stop operation as an example,the renovation content and operation demand of the existing station are analyzed,the impact of the non-stop renovation is summarized,and specific response strategies such as step-by-step renovation are put forward.At the same time,passenger flow organization of the scheme is verified and optimized by analogue simulation.The relevant conclusions can provide a reference for the non-stop renovation of the public area of similar stations.
In order to simplify the process of evaluating the technical condition of bridges and improve the accuracy and standardization of the evaluation,a bridge evaluation system was developed based on the JTG/T H21-2011"Standards for Technical Conditions Evaluation of Highway Bridges".Python language and object-oriented pro-gramming methods were applied to read disease information from tables and perform fuzzy recognition between recorded diseases and disease types to achieve rapid identification and classification of recorded diseases;The bridge instances,component instances and disease instances were created and all of the relationships among them were binded to achieve bridge evaluation.The system was ensured to be suitable for project evaluation of various bridge types and disease record methods.A certain bridge in Beijing was evaluated by the system.723 diseases recorded in the table were quickly classified.Subsequently,the bridge was rated.The overall rating results of each member,component,part and the bridge were the same as those by manual verification.The system was applied in bridge inspection projects in 2022 and 2023,which had proven that it can meet the needs of bridge assessment with a large number of diseases,and accurately classify and evaluate recorded diseases quickly.
There are tight constraints on space resources in urban development of Shenzhen.The large-scale munic-ipal pipelines laying space,operation and maintenance space and restrictions of surrounding land development have exacerbated the contradiction between municipal supply infrastructure space and urban development.How to bal-ance the diverse interests between municipal supply,urban public safety and urban development has become a dif-ficult problem in the governance of super-large cities with small site space and high-intensity development repre-sented by Shenzhen.Taking the integrated energy pipeline corridor in the east of Shenzhen as an example,the de-lineation method of municipal corridors has determined in this paper.A refined management and control system for municipal infrastructure corridors has been established which including methods,transmission and mechanisms of management and control.This paper has been balanced to solve the urban governance problems existing in large municipal infrastructure pipelines laid in super-large cities with tight land use.The relevant suggestions can provide reference for the construction of municipal corridors in similar areas.
During the construction process,the calculation of suspension bridges exhibits large displacement non-linear characteristics,and the bridge state depends on the initial stress-free state of each component,load magni-tude and boundary constraint conditions.When the interaction between material variation and loading process over time is not considered,the stress-free state control method can be used for calculation.However,in the process of nonlinear solving,different choices of incremental steps may cause results converging to different equilibrium states.Therefore,the topological invariance condition after structural stress is introduced.The stress-free state control method is extended to the calculation of the cable after beam hoisting construction and cable after beam tensioning construction control process suitable for suspension bridges with significant nonlinearity.It is proved that the bridge state is only related to the stress-free line shape of the main beam and the stress-free length of the cable,and is in-dependent of the order of hoisting and tensioning.The operability,efficiency and high accuracy of the stress-free state control method have been verified by the actual construction control process of bridges.
For large-scale park projects with complex terrain,it is necessary to compare and select of multiple schemes about soil and rock volume balance in the early stage of design.The calculation of soil and rock volume is directly related to the project cost budget and optimization of design scheme,so that the soil and rock volume balance is par-ticularly important in the site leveling of the park.Being difficult to operate,low in accuracy and time-consuming,traditional soil and rock volume calculation method is difficult to meet the needs in the early stage of design.By vi-sualization,collaboration,optimization,informatization and other characteristics of BIM technology,Luyi software is used to preprocess the design plot,Civil 3D to creates natural terrain and designs the plot surface.Two types of terrain surfaces perform Boolean operations to obtain the excavation and filling volume.Based on the output compre-hensive plot volume,the park site design is constantly optimized,so as to achieve the excavation and filling balance of soil and rock volume.By creating a geological model,the ratio of excavated soil to rock and the amount of soft foundation replacement can be calculated more efficiently.The height distribution of layered filling can be accurately expressed by BIM technology to achieve accurate design and investment.
This article classifies the equipment and management rooms of urban road tunnel,calculates the number of rooms and decide the location strategy according to the length of the tunnel,construction method,professional requirements of the equipment and the current environmental situation.It estimates the area of the rooms by the needs of each professional layout.Finally,it summarizes the setting method of these type of rooms,which provides reliable design basis for each profession of the urban road tunnel project.
In the construction process of the waterproof adhesive layer on bridge decks,the construction process of spreading glass fiber and gravel is usually used to improve road performance.However,the glass fiber and gravel will have a particular impact on the road performance of the waterproof adhesive layer during the service period.The im-pact was investigated through indoor tests.The results show that spreading gravel will reduce the bonding perfor-mance in its service life during the bridge deck waterproof adhesive layer construction.Therefore,synchronized gravel sealing is not suitable for high-performance composite modified asphalt waterproof adhesive layer;Spreading alkali free glass fiber will improve the overall performance of the waterproof adhesive layer,and improve the high-temperature stability of its service life,but will have an adverse effect on the shear fatigue performance.
A solid waste based soil solidification agent was prepared by raw materials of slag,desulfurization gyp-sum,fly ash and cement.The mix ratio was optimized through orthogonal tests and controlled variable experiments.And the influence of delay time on the mechanical properties of solidified soil was studied.The results show that the cement content has the greatest impact on the unconfined compressive strength of solidified soil,followed by slag:desulfurization gypsum,while slag∶fly ash has the smallest impact;The optimal mix ratio is 0.3％cement content,4∶1 of desulfurization gypsum for slag and 3∶1 of fly ash for slag;Under different ratios and dosages of solid waste based soil solidification agents,the unconfined compressive strength of solidified soil decreases with the extension of delay time.Finally,the feasibility of the agent under delayed construction conditions was verified through practical engineering.
Sediment plays an important role in water environment and water ecology.Investigating sediment pollution is of great significance for assessing water environmental quality and controlling water ecological risk.Haicang Lake is an urban lake in Xiamen City with functions of drainage and landscape.According to the investigation of the nu-trients,organic matter and heavy metals in surface sediment of Haicang Lake,the distribution characteristics was analyzed as well as the potential ecological risk.It was found that the contents distribution of TN,TP and OM were significant different.One in the East Haicang Lake was higher than in South and North Haicang Lake.According to the results of the nutrients comprehensive pollution index and the organic pollution index,there was serious nutrients pollution and the organic pollution in surface sediment of Haicang Lake.The pollution in East Haicang Lake was more severe than in South and North Haicang Lake.In terms of heavy metals,it showed different distribution char-acteristics with different elements.The contents of Cu,Zn,Cd and Hg in the East Haicang Lake were significantly higher than those in the South and North Haicang Lake.The contents of Cr and Ni were average distributed.The contents of As and Pb were at a low level and the average value in the East Haicang Lake was lower than the South and North Haicang Lake.The results of the geo-accumulation index method indicated that Cd and Hg were moder-ately polluted at some points;The results of potential ecological risk index method showed that the surface sediment of the lake was at a severe potential pollution.And Cd and Hg were the main risk factors;The heavy metals pollution and potential ecological risk were higher than the ones in South and North Haicang Lake.
When 3D design of water conservancy and hydropower projects are conducted by 3DExperience(3DE),there is a problem of being unable to import data files exported from the HintCAD system(HintCAD)to generate road models on 3DE platform.In order to solve the problem,a parameterized excavation and embankment cross-section sketch template are designed firstly;Secondly,the data files from HintCAD is analyzed to get the road design pa-rameters;An interactive program is developed to select the centerline of the road and the terrain surface.The ana-lyzed parameters are associated with the parameters of the instantiated excavation and embankment cross-section sketch model;Then,the cross-sectional scanning function interface of the 3DE platform is used to generate road models of excavation and embankment;Finally,the road model is obtained by making Boolean operation of it and the terrain surface.This method promotes the digitization and 3D development of the water conservancy and hy-dropower industry,and improves the quality and efficiency of design for pumped storage power stations.
Rainwater and sewage separation renovation is an important measure to solve the problem of the black-odorous water body and improve the quality of urban water environment.The directly discharge sewage into rivers can be controlled from the source to achieve long-term management of urban water environment.Taken the renova-tion of rainwater and sewage separation project of municipal pipe network in a certain city as an example,the main problems are sorted out.Based on the analysis of the key points and difficulties in the process of rainwater and sewage separation renovation,corresponding renovation plans for different types of current drainage systems of two current systems,one current system,cover ditches,narrow streets and underground culvert in the urban area are proposed to achieve the maximum rainwater and sewage diversion on the premise of ensuring implementability in ur-ban drainage networks and combining the near and long term.In addition,the adoption of regional sponge transfor-mation can effectively reduce runoff and runoff pollution,and further improve the renovation effectiveness.Finally,detailed designs of flow calculation of the intercepting main pipe and pipeline crossing treatment are given to provide reference for the similar renovation.
Taking an urban rail transit viaduct as an example,the content,methods and key points of seismic analy-sis of urban rail transit viaduct are proposed based on GB 50909-2014"Code for seismic design of urban rail transit structures".The finite element model of the bridge is established by Midas Civil software to analyze the seismic per-formance of the viaduct under different earthquakes.The analysis shows that the plastic hinge of the low pier pre-cedes the high pier under the longitudinal bridge earthquake.The plastic hinge of the high pier precedes the low pier under the transverse bridge earthquake;The normal stress of the main beam and the shear stress at the consolidation of the pier beam should be considered in addition to the seismic performance of the pier when seismic design is con-ducted;The reasonable arrangement of the tie beams of double-limb thin-wall pier can effectively improve the seis-mic performance of the bridge structure.The relevant conclusions provide important reference for the analysis and research of similar bridges.
The Honshu-Shikoku Liaison Bridge Passage is an important land transportation line connecting the two main islands of Honshu and Shikokuin Japan.It consists of 17 large-span sea-crossing bridges and hundreds of large and small bridges along the whole line.They are maintained by the Honshu-Shikoku Liaison Expressway Co.,Ltd.,which is typical bridge clustersmaintenance mode,the maintenance strategies with the goal of 200-year ser-vice life of bridgeadopted by the Honshu-Shikoku Liaison Expressway Co.,Ltdare summarized in recent years,as well as the new technologies and equipment developed or applied in the maintenance work in order to provide useful references and inspirations for similar projects in China.
The characterization of the asphalt pavement crack rate evolutionary law is helpful for decision of scientific maintenance.Based on the analysis of the crack distribution characteristics of the several typical expressways asphalt pavements in central Sichuan from 2010 to 2018,the fitting methods of the crack rate evolutionary laws are discussed.The curve characteristics of the power function are analyzed.Furthermore,the crack rate evolutionary laws of 5 typical road sections around Chengdu of Sichuan Province are systematically analyzed,and the application of the law in the asphalt pavement maintenance decision-making is evaluated.Studies have shown that the crack suppres-sion effect of the 4 cm overlay of modified asphalt AC-13C is mainly reflected in the first 2 to 3 years after its appli-cation.The power function curve can characterize the evolutionary law of asphalt pavement crack rate;The factors of implementation of maintenance measures,the original pavement structure and material characteristics have certain interference impact on the growth of crack rate.After re-curing,the rate of cracking increases faster than that after the previous curing;The cracks number or fluctuation characteristics of the crack rate can be used as important fac-tors for decision-making and post-evaluation of asphalt pavement maintenance.
Taking R sewage treatment plant in Puning City as an example,the project design scale,pollutant con-centration,sewage treatment process flow,implementation mode and actual operation are systematically analyzed.The design scale of the plant is 12 500 m3/d,which adopts the sewage treatment process flow of primary treatment system(coarse grid,fine grid,sand settling tank and fine grid)+secondary treatment system(hydrolysis acidifica-tion tank,A AO biochemical tank)+deep treatment system(MBR biochemical tank,ultraviolet disinfection tank).Through data analysis,the actual water output of the plant is 20 000 m3/d,which is 160％of the designed water out-put;The mass concentration of actual influent CODCr,NH3-N and TP are much lower than the designed one.The plant can overloaded treat the inlet water and meet the discharge requirements of the standard.The total investment of the project is ¥106 699 600,and the direct operating cost is ¥0.54/m3.Due to the higher groundwater level in the southern China,groundwater is more easier to enter the drainage network,resulting in a low intake concentration of the sewage treatment plant.Therefore,the project design needs careful investigation and accurate design in the early stage to save the total investment and reduce operating costs.
As a class of green inorganic cementitious material,geopolymer is an ideal substitute for ordinary Port-land cement because of the advantages of excellent mechanical properties,superior durability,ecological protection and high utilization of industrial solid waste resources.Geopolymer is divided into alkali-activated geopolymer and acid-activated geopolymer.The phosphoric acid-based geopolymer is a new type of geopolymer material produced by geopolymerization of silicate precursor materials under the activation of phosphoric acid solution or phosphate so-lution.In order to clarify the mechanical properties and engineering application,the research on metakaolin phos-phoric acid-based geopolymer by domestic and foreign scholars in recent years were analyzed.Firstly,the reaction mechanism was introduced.Secondly,the effects of metakaolin type,phosphate activator concentration,curing system,admixture and fiber type on the mechanical properties were analyzed.Then,the engineering application progress was summarized.Finally,its development trend was prospected.
