## 5 Forward Simulation Results of Different Salt Cavity Shapes
### Influence of Horizontal Connection Channel Height  
The height of the residue in the horizontal connection channel of the BWSC is crucial for determining the total volume and utilization method of the residue. There are two potential states for the residue in the connecting channel: fully filled and partially filled. However, due to the limitations of sonar measuring instrument, it is very difficult to obtain relevant information about the connecting channel by measuring the cavities on either side. A case study from the Chuzhou salt mine in Jiangsu Province illustrates this point. Drilling exploration of an old butted well salt cavity's horizontal connection channel revealed that the channel is fully filled with residue, with a height of approximately 9 m. This is significantly smaller compared to the over 200 m cavity height. The detection results provide valuable insights into the overall morphology of the butted well old cavity. It's worth noting that the salt rock grade at the Chuzhou salt mine is relatively low, with a high content of insoluble substances, and the connecting channels are small in height. This makes the mine a useful comparison for studying the height of the connection channel in old cavities at other salt mines. In this section, we focus on a forward simulation comparison study to investigate the influence of different connection channel heights on seismic response waveform, specifically under the condition of full residue filling. Figure 22 displays the seismic record profile of variable density at different horizontal channel heights. As shown in the figure, the seismic reflection characteristics of the cavity remain unaffected by the increase in horizontal channel height. The top surface of the cavity still exhibits the distinctive pattern of \"two peaks sandwiching a strong valley\". The position of the reflection waveform on the residue's top surface inside the cavity correlates with the channel height. Additionally, the single cavity's \"ring-shaped\" feature is prominent and remains constant irrespective of the channel height. And the entire BWSC model exhibits an eyeglasses-like waveform. As the proportion of channel height relative to the cavity height increases (up to 25%), the top and bottom surfaces of the horizontal channel become progressively more distinguishable. In addition, as the channel height increases, the top surface of the channel also exhibits a characteristic of \"two peaks sandwiching a strong valley\", similar to the cavity roof reflection. Figure 23 illustrates a superposition diagram combining waveforms and salt cavern models with different horizonal channels. As the height of the horizontal channel increases, the seismic reflection undergoes a transition. Initially, it presents an overall \"one valley, one peak\" pattern. However, as the channel height increases, this changes to \"one peak, one valley\" on the top surface and \"one valley, one peak\" on the bottom surface. The valley reflection on the top surface aligns with the top boundary of the model's horizontal channel, while the reflection waveform at the channel's bottom gradually shifts downward with increasing channel height. Evidently, as the channel height increases, the offset becomes  
Figure 22: Seismic record profiles of variable density at different horizontal connection channel height. The blue dashed line is employed to enhance the visualization of the relative positions of the reflected waveforms originating from the horizontal channels across the various models. more pronounced (as shown in Figure 24), making it challenging to accurately represent the true position of the channel bottom. Notably, the peak reflection of the residue within the cavity consistently appears as the first peak beneath the two peaks of the cavity's top surface. This peak remains an \"upward-opening arc\" feature and unaffected by the height of the channel. Similarly, regardless of how the channel height changes, the top surface of the residue always remains in the upper half of the circular waveform of the cavity.