## 1 Introduction  
Currently, as shallow Earth resources are progressively depleted and shallow underground spaces near exhaustion, the strategic and practical imperative of seeking resourcesand space in the Earth's deep interior has become urgent [1; 2; 3]. Worldwide, deep underground exploration has been a hot issue--for example, at the SNOLAB in Canada [4] for dark matter exploration and within the Gateway to the Earth Program in the UK. Serving as a frontier base for deep rock mechanics and geoscience exploration, the Jinping ultra-deep diversion tunnel--the world's deepest hydraulic tunnel system--hosts the China Jinping Underground Laboratory (CJPL), the deepest underground laboratory globally. With overburden depths reaching 2525 m, initial maximum principal stresses of 64 MPa (locally exceeding 100 MPa in specific tunnel sections), and seepage pressures of up to 10 MPa [5], its unique geo-environment provides world-class conditions for innovative research on deep rock mechanics. Investigating the stability of the Jinping diversion tunnel will help promote deep resource exploitation and research into deep rock mechanics. Currently, extensive research focusing on the Jinping ultra-deep tunnels and CJPL has been conducted. At the experimental mechanics level, studies have systematically characterized the short- and long-term mechanical properties of Jinping marble through a series of tests, including uniaxial [6], triaxial [7; 8; 9], creep [10; 11; 12], and dynamic response experiments [6; 13]. For example, [PERSON] et al. [14] investigated the spatio-temporal distribution and evolution of the stress fields during excavation-induced disturbances at CJPL. [PERSON] et al. [15] elucidated the attenuation and degradation of the mechanical parameters in Jinping marble during progressive failure processes. [PERSON] et al. [12] conducted preliminary explorations into the long-term creep mechanical characteristics and failure modes of Jinping marble under excavation disturbance conditions. Meanwhile, at the numerical modeling level, researchers have predominantly employed finite element [11] and discrete element [16] methods to evaluate the stability of the deep tunnels and high-steep slopes at Jinping. These studies have preliminarily identified damage zones in the surrounding rock and studied the engineering mechanical properties of the Jinping tunnels. Although existing studies have conducted comprehensive investigations into the mechanical behavior of Jinping marble, critical knowledge gaps persist in the following areas. Firstly, the Jinping ultra-deep tunnels face secondary fracture propagation induced by high-stress excavation disturbances, necessitating explicit consideration of the degradation of the rock mass's mechanical parameters and the associated mechanical responses. Secondly, the coupled effects of high seepage and high stress on the long-term stability of the surrounding rock in the Jinping ultra-deep diversion tunnels still demand further exploration. To address these challenges, this study investigates different cross-sections of the Jinping ultra-deep diversion tunnels under varying overburden depth conditions. Leveraging Abaqus's user material subroutine UMAT, we implemented the Nishihara creep model within the software. The time-dependent mechanical behaviors of intact rock units, fractured rock units, and laboratory rock samples containing pre-existing fractures were numerically simulated, thereby validating the correctness and applicability of the customized subroutine. Subsequently, representative cross-sections of the Jinping ultra-deep diversion tunnels at depths of 1400 m and 2400 m were analyzed to evaluate the stress distribution and long-term mechanical creep responses in the fractured surrounding rock, considering the pore pressure and engineering disturbances over a 20-year period. Furthermore, the long-term mechanical behavior of the surrounding rock during the Jinping diversion tunnel expansion project was predicted using advanced simulations.