## 1 Introduction  
As urbanization continues to accelerate, the existing transportation infrastructure has become inadequate in keeping up with the growing demands of society's activities. To increase the efficiency of transportation, it is essential to rebuild and upgrade obsolete engineering projects. In recent years, there has been a significant increase in upgrading engineering projects, with tunnel upgrades posing a particularly difficult and challenging task [1]. Since tunnels are typically buried underground, the reconstruction process can have a profound impact on the mechanical responses of the existing tunnels. As a result, tunnels are often viewed as crucial engineering projects that can significantly impact the overall investment and construction timeline of upgrading projects. To enhance the transportation capacity of tunnels, a common approach is to construct a new tunnel adjacent to the existing ones [2]. Depending on the circumstances, the newly constructed tunnel may be located close to the existing one. The use of mining methods to construct a new tunnel can result in cracking and damage to the existing tunnels. Inappropriate blasting parameters can pose a severe risk to the stability and safety of the existing tunnel [3]. The drilling and blasting process, with its release of thermal and explosive energy, poses a significant risk of causing structural damage, particularly due to the elevated heat and compression loads, as demonstrated by [PERSON]'s team [4] in their research on the increased structural response of columns. In long tunnels, cross passages must be constructed to enable emergency access in the event of fires or traffic accidents [5]. When upgrading tunnels, the mining method used for constructing cross passages can impact the mechanical state of the surrounding rocks, which may result in damage to the existing tunnel lining structures. To address these issues, it is critical to conduct research on the dynamic responses of existing tunnels when a new adjacent tunnel is being constructed, as well as to develop strategies to minimize the impact of blasting loads on the safety of the existing tunnels [6]. Researchers have extensively studied the dynamic response of twin tunnels under blast loads. [PERSON] and [PERSON] [7] conducted a numerical simulation to analyze the impact of blasting loads from a newly constructed tunnel on an existing tunnel, considering four of the most unfavorable conditions. In their research, the [PERSON] team [8] introduced a novel finite element model for accurately predicting ground vibrations that result from blasting activities. They outlined a comprehensive methodology that incorporates the element of randomness. [PERSON] et al. [9] examined the dynamic effects of blasting loads on adjacent tunnels by utilizing an equivalent blasting load model that considered the millisecond delay effect. [PERSON] et al. [10] systematically studied the influence of blasting excavation on the traversing chamber and surrounding rocks by performing both blasting tests and numerical simulations on the powerhouse. Drilling and blasting methods are widely used in the construction of large-scale underground caverns. The powerful energy generated during explosions significantly affects the safety and stability of the excavated cavern complex within a specific radius of the blast source [11]. [PERSON] et al. [12] utilized the superposition principle and stress wave attenuation theory to develop a model for determining the equivalent load of blasting in large underground chambers. [PERSON] [13] investigated the instantaneous failure process that occurs during rock mass blasting operations. The study specifically analyzed the stress state changes in the rock mass during this process. The findings revealed that the rapid release of stress in the rock mass, caused by blasting excavation on the tunnel face, can induce significant dynamic effects.