关键词: 重大工程, 隧道洞渣, 废弃物利用, ESG, 多目标优化, 改进的自适应NSGA-II算法

Abstract: Under the background that sustainable development has become one of the major strategies of modernization, abiding by ESG principles has become one of the important conditions for the success of mega projects. The waste utilization of mega projects has significant social, environmental and project governance benefits, which is in line with ESG concept. It is of great theoretical and practical significance to explore the role of tunnel spoil utilization on ESG objectives of mega projects. Tunnel spoil has the characteristics of large quantity and various types, while the utilization of tunnel spoil has the characteristics of diversification and wide impact, which leads to the complexity of decision-making on the combination of spoil utilization approaches. How to explore the combination with the highest ESG contribution from numerous tunnel spoil utilization combinations is the research question to be addressed in this research. There are many constraints in the optimization of tunnel spoil utilization combination, and there are multiple objectives in ESG and economic aspects, leading to a multi-objective optimization problem. Therefore, multi-objective optimization methods are adopted in this research. After systematically sorting out the role of waste utilization on ESG objectives of mega projects and its internal mechanism, an ESG-oriented optimization framework of tunnel spoil utilization combination is proposed. The framework establishes a mapping relationship between the "combination of tunnel slag utilization methods - environmental and social objectives - project governance objectives", and transforms the optimization problem of tunnel spoil utilization combinations into a multi-objective optimization problem between the environmental and social objectives, project governance objectives and economic costs. Based on the developed multi-objective optimization model, an optimization method – improved adaptive NSGA-II (I-A-NSGA-II) is proposed by introducing fast non-dominated ordering, elite strategies, adaptive crossover and mutation and improving congestion distance computation. I-A-NSGA-II provides a reference for the decision-making of spoil utilization in mega projects. This paper takes the utilization of tunnel spoil of a mega project as a reference, and constructs simulation data as an arithmetic example to test the feasibility and effectiveness of the proposed method. This paper defines the connotation of ESG in spoil utilization of engineering projects and expands the application scenarios of ESG theory. Meanwhile, this paper leads the research focus of tunnel spoil utilization from the evaluation of a single method or the comparison of multiple methods to the optimization of the combination of multiple methods, which enriches the decision-making research of spoil utilization in mega projects.

Key words: mega project, tunnel spoil, waste utilization, ESG, multi-objective optimization, improved adaptive NSGA-II