Multi-objective Optimization Study Of Construction Site Layout Around Tunnel Openings In Mountainous Areas

The size of the road network in the central and western mountainous areas will keep growing as the "Belt and Road" program and the strategy of strong transportation are put into practice.Tunnels are a crucial component of large-scale projects for building mountainous road networks since they save travel time and improve technical standards for transportation.However,due to topographic constraints,the construction site layout around tunnel openings in mountainous areas has problems such as small available sites,difficult site layout and numerous safety hazards,while the existing construction site layout around tunnel openings relies too much on construction experience,leading to waste of construction resources and extended construction period.Therefore,this paper takes the large temporary works of mountain tunnels as the research object,and starts the research on the construction site layout around mountain tunnel cavities from two aspects of site layout theory and site layout optimization to ensure the healthy and sustainable development of mountain tunnel projects.The main research contents include:(1)The theory of construction site layout around mountain tunnel openings.Combined with the relevant standards and specifications,to determine the content and requirements of the construction site layout around the tunnel entrance in mountainous areas,before using the traditional system layout planning method(SLP)to analyze the comprehensive interrelationship of large temporary works around the tunnel entrance in mountainous areas,the Bayesian network model is used to screen the key factors affecting the construction site layout around the tunnel entrance in mountainous areas and calculate their weights,so as to provide a theoretical basis for the SLP method to comprehensively analyze the interrelationship between large temporary works in mountainous areas from both logistics and non-logistics aspects.It provides a theoretical basis for the SLP method to analyze the closeness of the interrelationship between large temporary works in mountain tunnels from both logistics and nonlogistics.(2)Optimization model of construction site layout around mountain tunnel cavities.Based on the conclusion of Bayesian network model analysis,the three objective functions of safety level strength,material flow strength and cost path optimization are constructed,NSGA-II algorithm is selected for the multi-objective problem optimization of construction sites around mountain tunnel openings,and multiple Pareto solution sets of construction site layout around mountain tunnel openings are calculated by using MATLAB software programming;for the construction site around mountain tunnel openings For the multi-scheme decision problem of construction site layout around mountain tunnels,we construct the evaluation index system of construction site layout around mountain tunnels,and introduce the traditional gray target decision model into the decision of construction site layout around mountain tunnels after improving the original sample data quantification,index weighting and calculation of bull’s-eye distance,and analyze the indexes that have greater influence on the decision of the scheme through index sensitivity analysis,so as to provide a basis for choosing the optimal site The sensitivity analysis of the indexes provides the basis for selecting the optimal site layout.(3)Combine with engineering examples to verify the scientific and applicability of layout theory and optimization model in the layout of construction sites around mountain tunnel openings.The results show that the optimal scheme can enhance the safety level strength by 14.9%,improve the material flow strength by 16.4% and reduce the cost path by 11.2% compared with the original scheme,while having greater advantages in terms of scheme feasibility,scheme economy,environmental impact and social benefits.The proposed method helps to solve the problem of optimizing the construction site layout around the tunnel cavity in mountainous areas,and can provide reference for the site layout research of related projects.