## 5 Conclusions  
The transformation of abandoned mine roadways into underground water-sealed oil depots has broad application prospects. Through the investigation of damaged rock samples after immersion in an oil-water mixture, the acoustic emission characteristics, surface displacement field, and energy evolution law of rocks with different immersion times were tested and analyzed; the damage characteristics of the damaged rocks under the influence of immersion time was observed from multiple perspectives. The main conclusions are as follows:  
1. Long-term oil-water immersion changes the structure of rock components, which is mainly manifested in the reduction of internal silicon oxide content, crack development, and increase of pores. Furthermore, the compressive strength of the rock is reduced, and after soaking for 24 h, the compressive strength of the rock decreased by 21% compared to dry rock. 2. With increased soaking time, both the maximum ringing count rate and cumulative count at failure for AE decreased. The dry sample exhibited a maximum ringing count rate of 378 counts, with a cumulative count of 88,279. After 24 h of soaking, the maximum ringing count rate was reduced to 69 counts, and the cumulative count was reduced to 17,288, representing reductions of 81.7% and 80.4%, respectively, compared to the dry sample. The oil-water mixed liquid soaking weakened the mechanical strength of the rock samples. The RA-AF values indicated a decreasing trend in the data density of shear and tensile crack areas as the soaking time increased. The failure mode shifted from tensile dominated tensile-shear failure to shear failure. 3. With external force loading, the surface displacement field of the sample with immersion time less than 16 h appeared to be divided, the surface displacement failure characteristics of the sample began to appear gradually, and the displacement boundary changed from an inclined to a vertical direction. The rock sample with a soaking time of 24 h had a displacement intrusion phenomenon, and different displacements in the intrusion area leading to the occurrence of subsequent macroscopic shear cracks. However, the vertical displacement field distribution of each specimen at the final moment basically corresponds to the macroscopic failure mode of rock. 4. The combined effects of initial damage and oil-water soaking led to a reduction in the rock's structural energy storage capacity. More external energy was used for plastic deformation and the development and expansion of the pores and cracks. As the soaking time increased, the ability of the rock to resist external forces weakened, and the rock became more sensitive to external energy disturbances. Even small amounts of input energy could lead to the initiation and propagation of internal cracks. The research results of this manuscript show that soaking in an oil-water mixture has an obvious weakening effect on the mechanical properties of damaged rock. Therefore, it is necessary to reinforce damaged rock before the reconstruction of underground oil storage, such as by grouting the rock to reduce the internal cracks and increase the self-bearing capacity of the rock. In practical application, an oil-water mixture has an osmotic pressure effect on rock. This manuscript did not consider this factor, and the application of the research results may have certain limitations. Conceptualization, B.W. ; methodology, B.W. and J.B.; software, B.W. and D.C.; data curation, J.C., C.Q. and D.C.; writing--original draft preparation, B.W. and C.Q. ; writing--review and editing, J.B. and J.C.; funding acquisition, B.W. and J.C. All authors have read and agreed to the published version of the manuscript.