公路桥梁物化阶段环境影响货币化分析

Monetary analysis on the embodied environmental impact of highway bridges

为科学定量地评估公路桥梁物化阶段环境影响,并明确降低桥梁工程负面环境影响的关键着力点,基于生命周期评价方法引入支付意愿理论建立公路桥梁物化阶段环境影响货币化分析模型,将环境影响评价结果统一到经济维度,使其兼具环境和经济含义。应用该模型对渝湘高速五布河特大桥进行分析,从时间和空间2个维度出发研究桥梁基础结构、下部结构、上部结构和桥面系4个部分环境影响值分布特征,并采用MATLAB软件开展蒙特卡洛模拟,对各具体施工环节环境影响值进行不确定性分析。研究结果表明:桥梁材料生产阶段是物化阶段环境影响控制的重点,该阶段各影响类型中由于全球变暖造成的环境影响尤为明显。基础、下部和上部结构在材料生产阶段的环境影响值自下而上呈递增趋势,在施工建造阶段呈递减趋势。打桩钻孔机械、起重及垂直运输机械和泵类机械被确定为关键机械类型,是施工建造阶段环境影响值的主要贡献来源。桥墩-混凝土和主梁-混凝土2个施工环节的总体不确定度最大,以变异系数作为衡量指标,钢筋施工环节总环境影响不确定度小于混凝土施工环节,各环节总环境影响不确定度小于各类环境影响不确定度。研究结果符合工程实际,验证了模型的适用性,可为公路桥梁环境影响评价工作提供科学依据和有益参考。

In order to evaluate embodied environmental impact of highway bridges quantitatively and scientifically,as well as dig out the key points of reducing the negative environmental impacts,a monetary analysis model of highway bridges under environmental impact was established based on the life cycle assessment method and the willingness-to-pay theory.It can integrate the environmental impact evaluation results into the economic dimension to give them both environmental and economic meaning.The model was applied to analyze the Wubuhe Bridge on Chongqing-Changsha Expressway and explore the distribution characteristics of the environmental impact values of the four parts,which were the basic structure,lower structure,upper structure,and bridge deck system from the perspectives of time and space.Meanwhile,the MATLAB software was adopted to perform Monte Carlo simulation and analyze the uncertainty of the environmental impact value in each specific construction process.The results indicate that the production stage of materials is the key point for controlling the embodied environmental impacts.The global warming is particularly significant among various types of impacts on environment.The environmental impact values of the base,lower,and upper structures gradually increase from bottom to top during the material production stage,and decrease during the construction stage.The piling drilling machinery,hoisting and vertical transportation machinery,and pumping machinery are the key types of machinery,which are main contributors to the environmental impact value during the construction stage.The overall uncertainty of main girder-concrete is the largest,followed by bridge pier-concrete,and taking the coefficient of variation as a measure,the uncertainty of reinforcement construction is less than that of the corresponding concrete construction process,while the uncertainty of total environmental impact is lower than that of various types of environmental impact.The research findings are in accordance with engineering reality,validating the applicability of the model as well as providing scientific basis and beneficial references for the environmental impact assessment of highway bridges.