## 1 Introduction  
Under the \"dual carbon\" policy, China's energy structure is undergoing continuous adjustments, leading to the closure of numerous mines [1, 2, 3]. Consequently, the development and utilization of abandoned mine spaces have become a research hotspot in China's mining industry [4, 5]. Repurposing deep abandoned mines into underground oil storage facilities promotes resource recycling [6, 7]. As shown in Figure 1, an underground water-sealed oil storage is mainly composed of three parts: the oil storage system, the vertical injection and extraction system, and the water curtain system. Among them, the underground oil storage system is the core component and key carrier for underground oil storage [8, 9]. The oil storage chambers are typically reinforced and modified from roadways or chambers within abandoned mines, with a water cushion layer established at the lower part of the chamber to implement water-sealed oil storage. The surrounding rock of the oil storage chamber will be soaked in oil-water for a long time [10]. However, before being abandoned, underground roadways experience stress disturbances from mining activities and overburdened loads, which damage the surrounding rock [11]. When subjected to soaking in an oil-water mixture, the stability of the damaged rock becomes difficult to ensure. Therefore, investigating the mechanical behavior of the surrounding rock under different liquid content conditions is of great significance for the construction of underground oil storage facilities in abandoned mines. Numerous scholars have investigated the weakening characteristics and mechanisms of fluid-rock interactions in coal and rock masses. [PERSON] et al. [12] conducted a feasibility assessment for the conversion of an abandoned gypsum mine into an oil storage facility. Their tests indicated that the stability and sealing capacity of the hard gypsum strata were not affected by crude oil. However, water infiltration reduced the strength of the gypsum rock, potentially compromising the stability and sealing performance of the water-sealed oil storage cavern. [PERSON] et al. [13] investigated the interaction between water and rock by comparing changes in ion concentration, pH value, and total dissolved solids in water, and mineralogical analysis of rock. Their findings revealed that water-rock interactions could lead to rock dissolution. [PERSON] et al. [14] investigated the fracture mechanics of sandstone under cyclic wetting-drying and prolonged soaking conditions. Their research demonstrated that periodic water-rock interactions significantly affected the crack resistance of the rock, with fracture toughness decreasing notably as the number of cycles increased. [PERSON] et al. [15] analyzed rock microscopic test results and found that long-term water-rock coupling led to the pronounced development of rock mass cracks, poor cementation between particles, and loose overall structure, which had a negative impact on rock strength. [PERSON] et al. [16] explored the influence of water content on mechanical parameters such as uniaxial compressive strength, Young's modulus, Brazilian tensile strength, and point load strength index. They established different negative exponential functions to describe the relationship between water content and these mechanical parameters. A review of previous studies indicates that most research on fluid-rock interactions has focused on analyzing rock structural changes, failure modes, mechanical properties, and damage model establishment under soaking in single liquid (water) or cyclic wetting-drying conditions. However, the effects of oil-water mixtures on rock composition, fundamental mechanical properties, and the damage mechanism of damaged rock have not been systematically analyzed. At present, the research on the interaction between oil-water mixture and rock is mainly found in petroleum engineering. The research content focuses  
Figure 1: Schematic diagram of an underground water-sealed oil storage cavern.