Seismic monitoring of storage facilities in caverns

Seismic monitoring is a tool that is well suited to tracking the stability of large underground and surface works, in terms of local disorders due to internal causes and their reaction to exterior factors (earthquakes, mining activity, etc.).

Seismic monitoring is based on the fact that faults almost never occur suddenly. They are preceded by tremors or vibrations of varying amplitude that can be detected by geophones.

By listening to the noise produced by the movements of rock massives and by identifying and analysing minor disorders that occur, it is possible to detect instable zones and to investigate the stability of underground works.

This method is applied to two types of storage:

• leached salt caverns with the detection of insolubles blocks falls when leaching or readjusting caverns
• mined caverns to avoid blocks falls

The goal for all seismic networks used for underground storage is to avoid direct controls, once the storage facility is in operation. This involves: 

• confirming the long-term stability of the storage facility,
• assessing the impact of any seismic activity on the tightness of the storage facility.

Therefore, the priority goals of seismic monitoring are:

•  to permanently monitor the storage facilities to check for measurable seismic activity,
• to detect, locate and analyse any seismic incidents that may make the underground works unstable, and, secondly, to identify and quantify (particle velocity, frequency, etc.) any external factors (vibrations, earthquakes, etc.).

Photo captions:

Example of a falling block

Example of an earthquake