A Model For On-site Construction Waste Management

With the rapid development of urbanization in China, a vast scale of construction activities have been taken place in recent years. During the "Twelfth Five-Year Plan" period,an area of more than 19,208 square kilometers of residential houses have been completed,and it is expected that the new building of residential houses in downtown will increase by 5,300 square kilometers in the following "Five-Year Plan" period. Due to the lack of laws and policy incentives, the enthusiasm of management innovation in Chinese construction enterprises is generally on a low level, which has caused a large amount of construction waste generated from the large-scale construction activities. If enough attention have not been paid to the new generated construction waste, it will intensify environmental problems as well as a serious waste of resources. There is a general agreement among researcher that most of construction waste is generated on site, and taking the waste minimization measures in construction phase to reduce the construction waste is the key to solve this environmental problem at source. However, most of the studies are conducted from static perspective to identify and analyze factors, which ignore the interactive relations among them. In order to improve this deficiency of these studies, a systematic perspective is adopted in this research. With the help of interpretative structural model (ISM) and system dynamic (SD)theory, this article discusses the factors of construction waste management on-site and the interactive influence of these factors, and a result analysis and improvement suggestions are proposed.In this study, based on the related research, twenty factors influencing construction waste on-site management are distinguished from five aspects: material management,technology feasibility, regulatory framework and contractors' willingness. Under the guidance of directed graph, the interactive relations among the factors are described and analyzed. On the basis of ISM model, SD model is built. The model comprises three sub-systems, namely waste generation sub-system, waste sorting on-sit sub-system and waste dispose sub-system. Finally, by the means of simulation, the resulting model is validated using data collected from a new residential project in Chengdu, China.The result of ISM model demonstrates that the twenty factors identified can be categorized into three types and six levels. In line with the results, the construction waste management on-site is mainly affected by four factors with significant importance, including the operability of waste sorting on-site, the limitation of site space and surroundings, the fee of landfilling, and the efficiency of waste sorting on-site. While the directly affected factors are the transport of material, the storage condition of material, the dispose of toxic waste,and the available on-site sorting labor. The simulation results of SD model reveal a fact that the waste reduction effect is rising steadily, along with the advancement of the construction period, the maximum value of 0.5168 is achieved at the end of the time limit of the project.Currently, waste on-site sorting rate is only 0.7, and it is predicted that the amount of generated construction waste will increase to 17,278.6 tons, which will take 516,056 Yuan on waste disposal cost.