## 3 Results  
After simulating the 30-year operation of a vertical single-cavity gas storage reservoir in FLAC3D, and after the calculation by FLAC3D software, we obtained the displacement maps of the salt cavities under cyclic gas pressure for different numbers of mudstone interlayers. As the operating time increases, the displacement distribution of the surrounding rock changes, especially the vertical and horizontal displacements. Figure 3 illustrates the cloudy distribution of the vertical displacement of the surrounding rock after 1, 5, 10, 15, 20, and 30 years of operation for a single-cavity vertical gas storage reservoir with a number \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Rock Mass** & \begin{tabular}{c} **Bulk** \\ **Modulus/GPa** \\ \end{tabular} & \begin{tabular}{c} **Shear** \\ **Modulus/GPa** \\ \end{tabular} & \begin{tabular}{c} **Cohesive** \\ **Force/MPa** \\ \end{tabular} & \
\begin{tabular}{c} **Tensile** \\ **Strength/MPa** \\ \end{tabular} &
\begin{tabular}{c} **Internal Friction** \\ **Angle/\({}^{c}\)** \\ \end{tabular} \\ \hline salt rock & 8.67 & 3.95 & 1.93 & 1.20 & 37.5 \\ sandstone & 13.04 & 6.81 & 2.9 & 1.6 & 36 \\ mud rock & 13.04 & 6.81 & 2.9 & 1.60 & 36 \\ Calcareous & 8.45 & 3.85 & 0.50 & 0.50 & 30.0 \\ gypsum rock & 10.92 & 5.54 & 2.2 & 1.4 & 35 \\ Light gray & 13.04 & 6.81 & 2.9 & 1.6 & 36 \\ anhydrite rock & 13.04 & 6.81 & 2.9 & 1.60 & 36 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Physical parameters of rock layer. of eight interlayers, while Figure 4 illustrates the cloudy distribution of the horizontal displacement of the surrounding rock for the same reservoir over the same period of time. The plots offer valuable insights into the temporal displacement of the gas storage enclosure. The observation of displacement cloud maps at varying time points allows for the comprehension of the deformation of the surrounding rock during the operation of the gas storage reservoir. A detailed examination of the test results reveals that the cavities under different numbers of mudstone interlayers all exhibit a contraction towards the interior. In contrast, the deformation of the upper surface of the cavity is consistently greater than that of the lower surface, and a symmetrical tendency is observed on the lateral walls. This phenomenon can be attributed to the fact that the cavity is situated in a gradient distribution of low stress states, with high-pressure gases filling the cavity and exhibiting an isobaric distribution. Consequently, the top and bottom of the force are not uniform. The gradient distribution of ground stress causes the ground stress on the top of the cavity to potentially be greater than that on the bottom, so the deformation of the top will be relatively larger. And the high-pressure gas is distributed as isobaric inside the cavity, which means that the stress state inside the cavity is uniform. However, the ends of the  
Figure 4: Vertical displacement of the surrounding rock of a single-cavity vertical gas storage reservoir with time: (**a**) One year; (**b**) Five years; (**c**) Ten years; (**d**) Twenty years; (**e**) Thirty years. cavity are in a state of uneven stress and may have been subjected to greater stresses, so the deformation at the ends of the cavity will be greater. In addition, the further away the surrounding rock is from the cavity, the less it is affected, but by and large, it shows a symmetrical distribution up and down along the short axis of the cavity. This is because the surrounding rock away from the cavity is less affected, but the deformation of the cavity will affect the surrounding rock, so that the deformation along the short axis of the cavity presents a symmetrical distribution on the whole. Thus, these factors combine to characterise the deformation of the cavity under different conditions. As illustrated in Figure 4, the vertical displacement of the surrounding rock of the vertical single-cavity gas storage reservoir is increasing over time.