| The elevated concentration of greenhouse gases(mainly carbon dioxide,referred to as carbon emission)resulted from human activities has increased the greenhouse effect,and amplified global warming,thus threatening human being's survival and development.The transport sector with higher carbon emission contribution,the fastest growth rate and greater potential,especially the highway transportation that dominates China's transport carbon emission,has become the focus of carbon emission reduction for China as it is the country with the largest total carbon emission in the world.During the highway usage phase,the types of vehicles,the types of fuels and fuel sources are becoming more complex and diverse.Meanwhile,new materials,new technologies,new processes and new equipment are gradually introduced to highway construction and maintenance phases.In order to avoid to mistake the transfer of carbon emission in the processes or regions as a low-carbon measure,it is necessary to quantitatively analyze the carbon emission from entire highway life service cycle including phases of construction,usage,maintenance and disposal.This thesis built the theoretical framework of carbon emission analysis on the whole life cycle of highway,analyzed the sources and influential factors of carbon emission from the two main phases of construction and maintenance,and develped their carbon emission calculation models separately.Based on the Life Cycle Assessment(LCA),the thesis analyzed the impact of differences in materials,energy and construction machinery on highway emission reduction,then carried out the empirical research,and revealed the characteristics of life-cycle carbon emission of highways in mountainous areas in Zhejiang and Shaanxi Province.The main work of the thesis includes:Firstly,the theoretical framework and analysis methods of carbon emission during the whole life cycle of highway based on Attributional Life Cycle Assessment(ALCA)was proposed.Under this theoretical framework,the life cycle of highway was divided into three phases: construction,use and maintenance.In addition,the typical activities and the scope of carbon emission of each phase were defined,and the relationship of the carbon emission sources including structure,materials,equipment,technology,construction management among three phases was clearly defined.Secondly,based on the “segment-item-based” accounting method of highway construction project,and combining the method of carbon emission factor,atual project quantity data and quota,the “segment-item-based” structured carbon emission calculation model for highway construction phase was developed.Thirdly,considering the two parameters of maintenance type and time,the carbon emission calculation model for maintenance activities was developed.Then,the discrete analysis method of vehicle carbon emission during the continuous period of highway maintenance was proposed with the basis of the matching relation between the capacity of the work zone and the traffic demand.Then based on the “bottom-up” method,carbon emission calculation models of traffic delay,queue delay,speed change and queuing speed change in discrete time period were established separately.Finally,time-phased users carbon emission estimation model of highway work zone in maintenance phase were established.Fourthly,the concept of highway carbon emission reduction potential based on LCA was proposed from the perspective of reducing the carbon emission of highway by the low-carbon strategies from other sectors,and the calculation and analysis methods of relative highway emission reduction potential were developed.Facing the needs of the highway maintenance,combining the above models with actual highway project data,the findings of the research on important parameters and case studies show that:(1)the carbon emission calculation results of 20 asphalt highway projects and 18 concrete highway projects in Zhejiang Province find that average total carbon emission are variety but nearly 1250 tons/lane-km for asphalt highway,1.5 time higher than that of average total carbon emission for concrete highway and 27% higher than that of studies without considering bridge and tunnel.The findings of further study on the carbon emission of a single expressway construction in the mountainous area of Shaanxi Province including the auxiliary facilities such as hardware and safety facilities,show that the total carbon emission of the expressway is 6819.0 tons/lane-km and 100-year service life carbon emission of road segment,bridges and tunnels is 9336.0 tons/lane-km,6254.6 tons/lane-km and 10429.2 tons/lane-km respectively.(2)The carbon emission of preventive,corrective and rehabilitation activities during the whole life of the asphalt highway pavement in mountainous area of Shaanxi Province is 593.5 tons/lane-km,and 56.8% of the carbon emission come from vehicles that detoured to other routes resulted from maintenance work zone.(3)The carbon emission intensity of asphalt highway pavement corrective maintenance,mainly from materials and fuel production related to asphalt concrete mixing,as well as the detoured vehicles,is 6 to 22 times of that of the onsite construction equipment operation.(4)Among the three types of low-carbon strategies of materials,energy and construction machinery,advanced construction technology can reduce the carbon emission of asphalt highway pavement maintenance by 28%~57%.The asphalt recycling and power energy structure adjustment can reduce the carbon emission of asphalt concrete mixing by 36% and 36% respectively,and low-carbon diesel production can reduce carbon emission from key construction activities such as paving by 10%.The findings of the thesis are meaningful for the correct understanding of the calculation methods,characteristics and influential factors of the carbon emission from construction and maintenance phases for highway with different terrain and engineering characteristics.In addition,these results are help for the construction materials selection,maintenance equipment management and traffic organization,and the exact low-carbon strategy making. |
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