# Genetic Algorithm-Based Intelligent Selection Method of Universal Shield Segment Assembly Points
## 1 Introduction  
Shield construction is an advanced tunnel construction method in soft soil, which is widely used in subway tunnels [1, 2], water conservancy tunnels [3, 4] and highway tunnels [5]. During construction, the shield machine pushes forward on the assembled segments and assembles new segment rings under the support of the tail shield, and the assembled segment rings form the final tunnel [6, 7, 8, 9, 10]. As a kind of advanced tunnel lining, the universal segment ring is a kind of ring with a certain amount of wedge. Only one type of universal segment ring is needed for the whole construction process to complete the tunnel assembly. Only one set of models is needed, and its proportion in the construction is increasing [11, 12, 13]. To improve the quality of formed tunnels, some scholars have studied the load on the segment ring [14, 15], while others have focused on the selection of the segment assembly point. The selection of the segment assembly point is the first step in segment assembly and is a critical step in tunnel construction. However, at present, the construction of the universal segment of the assembly point is mainly determined by the shield machine drivers with experience, which not only limits the construction speed and increases the work intensity of drivers, but also the quality of the selected assembly point is not guaranteed due to the subjective factors of drivers [16, 17]. The unreasonable selection of a segment assembly point often leads to serious engineering accidents, such as uncontrolled attitude of the shield machine, broken segments and the inability to fitthe design tunnel axis (DTA) [18]. Therefore, the intelligent and reasonable selection of universal shield segment assembly points is an urgent problem to be solved. Basically, two approaches are used to select the segment assembly points in the current study. The first approach is to select the assembly points with the aim of reducing the deviation between the actual axis and the DTA. Some research has been conducted in this regard. In the papers [16; 17; 19], the authors derived the calculation method of the center of the front face of the segment ring after assembling the segment with different assembly points used the exhaustive method to calculate the curve-fitting deviation corresponding to all assembly points and then selected the point with the smallest deviation as the best assembly point. However, in practice, various construction factors have a huge impact on the selection of the assembly point of the segment, and a selection method that only reduces the deviation of the axis fitting has little applicability in actual construction. Therefore, more studies focus on the second approach of the selection of an assembly point, which is to select the assembly point with the goal of adjusting construction factors. [PERSON] et al. [20] derived a calculation method for the amount of change in the shield tail gap for selecting different assembly points, which provides a reference for assembly point selection considering the shield tail gap, but this study does not explain how to choose the assembly points. [PERSON] [21] determined the objective function for optimizing the shield tail gap difference and curve-fitting deviation, but how the weights of each parameter are taken is not described. [PERSON] et al. [22] established the objective function of segment assembly point selection considering the shield tail gap, thrust cylinder stroke difference and lining trend, and the weights of each parameter were determined manually in real time, but this weight-taking method is easily influenced by human subjective actions, and the process is tedious. [PERSON] [23] established an objective function with shield tail gap, thrust cylinder stroke difference and curve-fitting deviation as the influencing parameters, but the weights are still given empirically. [PERSON] et al.