## 1 Introduction  
Ensuring the safety and stability of underground tunnels is essential for the successful construction and operation of underground engineering projects. Underground tunnels are extensively utilized in civil, hydropower, and mining engineering. In practical engineering, underground tunnels are usually excavated and constructed adjacent to pre-existing tunnels due to the limited underground space. The drill-and-blast (D&B) method is a prevalent and cost-efficient technique for extracting rock masses in tunneling [1]. blasting vibration is known to alter circumferential stresses, create shear and compression waves [2], and affect restricted structures. It has the potential to adversely impact adjacent tunnel linings [3]. Therefore, managing these negative effects, suggesting appropriate vibration control limits, and checking the safety of existing reinforced concrete tunnels are important technical tasks while constructing next to existing tunnels. Previous research and engineering practices have employed peak particle velocity (PPV) to quantify blast-induced stress wave damage to nearby tunnels [4]. This has resulted in the development of many empirical damage scales that correlate with observed PPVs. The threshold vibration limit for structural safety is determined by the structure's significance, construction quality, and structure type. It varies between countries based on the safety standards. For instance, the South Korean Seoul metro region has an allowable PPV threshold for tunnels of between 1-2 cm/s [5]. In China, AQSIQ [6] has described the empirical threshold PPV along with the frequency of blast waves for various tunnels, where the allowable PPVs for traffic tunnels were 10-12, 12-15, and 15-20 cm/s for frequency ranges of \(\leq\)10 Hz, 10-50 Hz, and \(>\)50 Hz, respectively. [PERSON] et al. [7] and [PERSON] et al. [8] proposed analytical methods to investigate the dynamic response of underground tunnels. Scaled experiments have been performed to investigate the response of concrete tunnels using surface explosion by [PERSON] et al. [9] and [PERSON] et al. [10] and underground blasting by [PERSON] et al. [11]. Tunnel constructions subjected to explosive stresses are being increasingly analyzed using numerical approaches as an alternative to experimental testing and theoretical methods [12]. They are both limited in their ability to capture all the relevant details. [PERSON] et al. [5] performed a numerical simulation and examined blast-induced vibrations in terms of particle velocity, displacement, and lining stress. Blast location, tunnel depth, and explosives were parametrically studied, and the blast protection zone recommendation was provided. [PERSON] et al. [13] examined tunnel blast excavation that affected the surrounding rock mass and the adjacent tunnel lining system. PPV-based damage control was then suggested. Additionally, it was demonstrated that if the PPV was less than 0.30 m/s, there was no failure in the linings or at the rock-lining interfaces. [PERSON] et al. [3] studied the behavior of existing railway tunnels during the blast excavation of adjacent tunnels. The response was measured in terms of blasting vibration velocity with stress and strain. [PERSON] et al. [14] proposed a correlation between PPV and effective tensile stress in tunnel lining structures. Furthermore, the observed PPV was higher on the side facing the blast compared to the opposite side. [PERSON] et al. [15] researched the dynamic response of the civil air defense tunnel when it was subjected to blasting loads. They proposed a criterion based on maximum tensile strength theory and predicted that the threshold PPV at the top of the arch should be kept lower than 7.84 cm/s. Based on numerical simulation findings, [PERSON] et al. [16] studied group tunnels under blasting excavation, and each tunnel's dynamic response and most susceptible location were analyzed.