# Optimization of Tunnel Construction Schedule Considering Soft Logic
###### Abstract  
Tunnel construction projects are a classic type of repetitive project, and hold a crucial position in the construction industry. The linear scheduling method (LSM) has been in the spotlight in scheduling optimization for repetitive construction projects since it was first proposed. However, the possibility of changing the construction sequence during application is very often overlooked, which is not in line with actual engineering practices. Incorporating soft logic into LSM and considering the characteristics of tunnel construction, we propose an optimization method for the tunnel construction schedule to shorten the duration by opening up an additional working surface. A mixed-integer programming (MIP) model is developed, which considers various constraints, such as construction sequence and work continuity. The exact algorithm and genetic algorithm (GA) are designed via Python, and the validity is verified through practical cases. A comparative analysis was conducted between the two algorithms and their outcomes demonstrates that the method can satisfy the restrictive constraints of tunnel construction projects. In addition, improvement strategies for tunnel construction management are recommended. t 20242024142580 20242024142580 20242024142580 2024202  
Given the accessibility of computational programs and commercial software packages, traditional Gantt charts and network planning techniques, such as planning review techniques and the critical path method (CPM) [6], are extensively applied to construction projects for planning and scheduling. Nevertheless, these methods have a restricted degree of adaptability to repetitive construction projects and do not allow for efficient planning for them [7]. As a result, linear scheduling methods (LSMs) for repetitive projects have been gradually applied in the field of construction engineering [8]. The most representative methods are the line-of-balance (LOB) [9] and linear scheduling method (LSM) [10; 11]. The LSM has been proven to have significant advantages as an approach to the scheduling of repetitive construction projects [12]. Most of the studies related to the LSM assume that the logical relationships are fixed, meaning that the construction of the whole project is carried out in a fixed sequence [13]. Such assumptions differ from the actual conditions. The project may be accomplished by multiple construction teams and the construction sequence may be subject to shifts due to environmental changes [14]. The same activities in different units and different activities in the same unit are linked by logical relationships, which can be \"fixed\" and \"soft\" [15]. In contrast to fixed logic, the implementation order of the construction units in soft logic relationships is changed. An increasing number of scholars have focused their studies on the optimization of construction schedules considering soft logic. The scheduling optimization of repetitive construction projects has been extensively studied in recent years. However, there are still research gaps regarding aspects related to the optimization of the tunnel construction schedule, especially the lack of consideration of the situations in which the construction sequence can be changed. To address these issues, an optimization model for the tunnel construction schedule is developed by combining LSM and soft logic relationships. The study is aimed at the optimization of the tunnel construction schedule, and the major contributions are as follows:  
1. By introducing soft logic relationships into the field of tunnel construction management, this study takes sufficient account of the changes in the construction sequence compared to the traditional fixed sequence in order to optimize the tunnel construction schedule. 2. A mixed-integer programming (MIP) model for tunnel construction schedule is proposed based on LSM and soft logic relationships, which intuitively represents the constraint relationships related to logic, continuity, time, space, and construction team scheduling. 3.