## 1 Introduction  
The secondary lining of tunnels is responsible for bearing the rock pressure and operating loads in tunnels [1, 2]. However, concrete cracking is a common occurrence in the lining due to various environmental factors that the tunnel may be exposed to during operation [3]. Overlapping tunnel construction methods, which are frequently utilized due to space limitations, can also lead to cracks in the secondary lining. The propagation of such cracks can result in severe structural issues such as leakage [4], spalling [5], and partial lining failure [6], reducing the durability and load-carrying capacity of the lining [7]. Numerous scholars have conducted research on the construction mechanic effects of tunnels adjacent to existing structures. [PERSON] [8] developed a monitoring program that utilizes actual field data based on the principal component analysis method, which can monitor tunnel behavior and prevent large deformations and cracking. [PERSON] [9] studied the ground and structural disturbances caused by multi-line overlapping tunnels in China, while [PERSON] [10] investigated the dynamic response of the new railway tunnel to the existing railway tunnel's blasting vibration and its impact on the existing tunnel lining structure before and after the vibration. Such studies have proved valuable in analyzing and controlling cracks in the secondary lining. [PERSON] [11] used a three-dimensional finite element analysis to investigate the undrained tunnel face stability in clay with a linearly increasing shear strength with depth. This work provides valuable insights into the instability pattern of tunnels. Asymmetric loading effects are the primary cause of secondary lining cracking [12], which have been the subject of much academic attention. Over the last few decades, engineers have been interested in the structural collapse of tunnels under asymmetrical loads [12]. Numerical models have been used to demonstrate the lining cracking and failure processes in shallow-buried tunnels [13; 14], deep-buried tunnels [15], and those exposed to asymmetrical loads. Two-dimensional numerical models have also been developed to estimate deformation and displacement behaviors of lining in asymmetrically-loaded tunnels while considering factors such as the shifting transversal gradient, surrounding rock grade, and covering thickness [16]. [PERSON] presented an asymmetrical rock pressure calculation approach for super-shallow-buried tunnels [17]. Studies have also investigated the bearing capacity and most likely lining fracture sites [18; 19]. However, limited research has been conducted on the causes and timely distribution of cracks, particularly in the case of closely spaced overlapping railway tunnels. This study investigates the causes of secondary lining cracks in the lower tunnel resulting from the construction of an upper tunnel, based on finite element numerical simulation and field crack measurement data collected from a railway tunnel project in Chongqing. Four cross-sections with different horizontal spacing were selected to establish two-dimensional numerical models consistent with the construction conditions on site. The models analyzed the force and yielding of the lining of the two tunnels under different working conditions, from which the location of the cracks was determined and compared with the monitoring results to verify the feasibility of the numerical method. The temporal and spatial distribution of cracks was analyzed, and construction suggestions are proposed. In order to predict and monitor the stability and safety of tunnels, artificial intelligence techniques are beginning to receive increasing attention. Visual examinations of tunnels do not offer a reliable and objective evaluation of their condition [20]. The use of artificial intelligence in tunnel monitoring is of interest.