## 1 Introduction  
In China, the country's transportation infrastructure facilities are increasingly improved. In 2021, the total operating mileage of China's railways exceeded 150,000 km and the operating mileage of China's high-speed railways exceeded 40,000 km. More than 4000 km of railways have been added, including 2150 km of high-speed railways [1, 2]. More and more high-speed trains are running on high-speed railways between cities. As a typical vibration load, the vibration load of high-speed trains induces the dynamic response of the pile-soil foundation and nearby structures [3, 4, 5, 6]. Under a long-term vibration load, nearby structures may have problems such as cracking and concrete block spalling, and the original damage and destruction have a more adverse impact on the structure [7, 8]. Therefore, it is of great significance to study the characteristics and propagation law of the dynamic response of a pile-soil foundation with an adjacent tunnel under vibration train load and to provide a theoretical basis for the safety evaluation of the adjacent tunnel of similar projects under train load. For the effect of high-speed train loads, [PERSON] et al. [8; 9] used the frequency response function and peak vibration acceleration as evaluation indexes to carry out a model test of train single-point vibration load and studied the dynamic response of a tunnel structure and its surrounding soil under train vibration load. In an engineering case where significant settlement occurred during a railway trial run, [PERSON] et al. [10] used numerical simulations to investigate the excess pore water pressure in soft soils caused by cyclic train loads and to predict the long-term settlement of the foundation under train operation. The results showed that, without proper treatment, the railway will experience more severe settlement. [PERSON] et al. [11] conducted a large-scale pile embankment model test to analyze the soil pressure, settlement, and strain of pile foundations under the action of high-speed trains on a pile network composite foundation. The analysis results showed that the cumulative settlement of the foundation under the action of long-term vibration still tends to increase. [PERSON] et al. [12] studied and verified the dynamic response of geosynthetic reinforced pile foundations (GRPF) under train loads using a three-dimensional time-domain viscoelastic finite element method (FEM), considering different train speeds and pile group arrangements during high-speed train operation. [PERSON] et al. [13] investigated the settlement pattern of soft clay subgrade under cyclic principal stress rotation caused by high-speed train load. [PERSON] et al. [2] and [PERSON] et al. [14] investigated the dynamic characteristics of XCC pile-raft foundation under high-speed train loads and a heavy-haul embankment reinforced by micro-piles by model tests and 3D numerical simulation. The operation of high-speed trains can have a certain adverse effect on ordinary soft ground and pile-soil composite foundations, which can even threaten the safe operation of high-speed trains in severe cases if not handled properly. Due to the constraints of urban underground space resources, there are crisscross tunnel projects. When a tunnel project close to a high-speed railway appears, there must be a greater risk from the construction point of view alone [15; 16; 17; 18; 19]. In contrast, a pile-soil composite foundation with the presence of an adjacent tunnel under high-speed train loads is more complex than the ordinary pile-soil composite foundation, and the differences in dynamic response characteristics are unknown. Moreover, there is also a lack of relevant research on the safety evaluation of an adjacent tunnel under the action of train load.