## 3 Literature Review
### Scheduling Method  
Many studies have been conducted to derive more advanced types of scheduling using various technologies and algorithms to achieve optimized scheduling in the construction industry. Several studies have been conducted on construction scheduling techniquesusing mathematical algorithms. For example, [PERSON] and [PERSON] proposed a method to introduce a scheduling approach for linear projects involving maximum time and distance constraints in addition to the minimum constraints [16]. This method classified activities based on their importance and influence on duration and demonstrated their effectiveness by applying them to low-pressure pipeline construction projects. This study investigated the key seven activities encompassed within the entire earthwork project, thus allowing the consideration of the overall earthwork scheduling. However, the application of the seven activity levels may pose challenges in practical implementations at construction sites. [PERSON] proposed a multipurpose, linear programming model for scheduling linear iterative projects by considering cost factors associated with project duration, resource idle time, and project-by-project delivery time [17]. The proposed model allowed project managers to create alternative schedules based on a variety of cost factors and proposed a holistic approach to schedule decisions beyond the simple minimization of timeframe or the maximization of task continuity. This study also proposed a model by setting the number of activities to seven, primarily conducting time-based research without considering other conditions, such as the equipment involved in the activities. Most recent studies on the optimization of construction scheduling employed meta-heuristic algorithms as research methods, such as ACO, PSO, and genetic algorithm (GA), which have high versatility in solving optimization problems. [PERSON] and [PERSON] used the ACO-based algorithm to solve the scheduling problem, and it was confirmed that the algorithm performed better than other algorithms in terms of result quality, execution time, and scalability [18]. [PERSON] et al. proposed a new approach based on PSO methods to solve the problem of task movement in construction projects, thus demonstrating its effectiveness in real-world project scenarios [19]. [PERSON] used a GA to optimize the scheduling process by integrating mathematical and genetic operators to solve the problem of scheduling with limited resources based on a simplified bridge construction case as an example [20]. These studies commonly employed state-of-the-art algorithms to propose efficient and accurate scheduling methods under the given conditions of predefined information, such as activities, duration, and costs. Previous studies primarily aimed to optimize scheduling methods or automate the scheduling process using various state-of-the-art algorithms to improve existing practices. Such research is undoubtedly essential for efficient construction scheduling. However, these studies have limitations in addressing the fundamental issues of basic earthwork scheduling. While most of the research related to optimization of construction scheduling was actively conducted about a decade ago, optimization and automation in construction scheduling are still not adequately realized. Optimizing scheduling is a good approach when the right conditions are provided, but this approach has limitations. One limitation is that the optimization algorithms rely on the data provided, and if the detailed level of activities is not considered a priori, the results (irrespective of their accuracy) will not be in a form usable at construction sites. To address these fundamental issues, it is crucial to focus on the detailed level of activities that act as a type of bridge for proper scheduling. This should be a top priority for optimizing construction projects. Thus, considering the detailed level of activities is a critical factor for appropriate scheduling. However, research related to this aspect is lacking compared with its importance.