## 1 Introduction
used the three-dimensional finite element software ANSYS to study the seepage problem of large dam foundations [20]. [PERSON] et al. and [PERSON] et al. conducted research into seepage problems using the three-dimensional finite element method [21; 22]. The coupling of the seepage field and the stress field is an important aspect of multi-field coupling, which is called \"fluid-solid coupling\" in the field of mechanics and is often referred to as \"water-rock (soil) interaction\" in the field of geosciences. The study of seepage stress coupling theory began with the analysis of reservoir-induced earthquakes in the 1950 s and was improved and developed by [PERSON] et al. [23]. In recent years, many scholars have conducted research on the coupling problem of seepage and stress. Others developed seepage mechanics models for different soil masses and established relevant empirical formulas for permeability coefficients [24; 25; 26]. [PERSON] and [PERSON] proposed a hydraulic-chemical coupling model [27]. Some scholars conducted multi-physical field coupling studies on hydraulics, chemistry, mechanics, etc., and proposed a coupling model of hydraulics-chemistry-mechanics [28; 29; 30]. The foundation of the dam has a certain degree of permeability; therefore, under a certain upstream and downstream water head, a stable seepage field will be established, and the dam body will bear the uplift pressure generated by the seepage field. The uplift pressure has an adverse effect on the anti-sliding stability of gravity dams. In recent years, many scholars have studied the application of uplift pressure and the factors that affect uplift pressure in the finite element calculation process of concrete gravity dams. Currently, in the process of analysing the anti-sliding stability of gravity dam foundations, the combined force of seepage pressure and buoyancy caused by upstream and downstream water level differences is primarily simplified as uplift pressure for treatment. This approach ignores the adverse impact of seepage pressure along the river on the anti-sliding stability of the gravity dam foundation. Without considering the seepage force along the river, the stability calculation results are often biased towards danger. In areas with developed magmatic rocks, due to magma intrusion and contact with fractured zones, the strength of the rock mass is relatively low, and the permeability and porosity are relatively high. However, there are currently few scholars who use the finite element strength reduction method under seepage stress coupling to study the impact of magma intrusion on the anti-sliding stability of gravity dam foundation. The research team has achieved relatively mature research outcomes in analyzing geotechnical anti-sliding stability considering seepage fields, which have been successfully applied in slope engineering projects [31]. These methodologies were further implemented in the anti-sliding stability analysis of the reservoir gravity dam project. The studied gravity dam is located in Ningbo, China, where geological investigations revealed well-developed structural discontinuities (joints, faults, and large fracture zones) particularly on the left bank and riverbed. Notably, drilling surveys confirmed the absence of a natural impermeable layer at the dam site. These conditions create dual challenges: compromised anti-sliding stability and complex seepage control requirements in fractured zones. While previous studies have addressed gravity dam stability under conventional conditions, this work specifically investigates the critical yet understudied factor of seepage-stability coupling effects. Using the finite element strength reduction method, we systematically examine: (1) foundation stability under seepage conditions and (2) optimized seepage control strategies to reduce uplift and seepage pressures. Our findings provide practical guidance for designing reinforcement measures in seepage-affected gravity dams, filling an important gap in current engineering practice.