Detecting Characteristic Microseismic Signals and Precursory Signals Related to the Cavity Roof Stability for Solution Salt Mining in Dingyuan, China

Session: Environmental and Near Surface Seismology: From Glaciers and Rivers to Engineered Structures and Beyond [Poster]
Type: Poster
Date: 4/29/2020
Time: 08:00 AM
Room: Ballroom
Description: 

Microseismic monitoring has become a powerful tool for understanding the stress regime and fracture distribution in many application areas, including coal mining, tunnel digging, shale gas hydraulic fracturing and enhanced geothermal system developing. For solution salt mining that involves injecting fresh water into the salt body to dissolve salts, microseismic monitoring has been used for monitoring the roof stability of the salt cavity around the world. However, this monitoring technique has not been utilized in China where there are many solution salt mines. Here we conducted a pilot microseismic monitoring study in Dingyuan salt mine located in Anhui Province, China, where three cavity-collapsing incidents occurred in the past. 11 three-component seismic stations covering the mining area were installed into 5-meter deep holes starting May 2017. The geophones have the resonance frequency at 5 Hz and the data sampling frequency is 500 Hz. From May 2017 to November 2017, for the first time we detected a characteristic paired signal consisting of a long duration segment (>15s) and a subsequent short duration segment (<4s), which are separated by tens of seconds in time. During this time period, 88 paired signals were detected. The first segment of paired signal is related to the fracturing process before the detachment of a block from the cavity roof. The 2^nd segment of the paired signals is due to the hitting of the cavity floor by the fallen block. The time separation between the two segments is related to the cavity height. Therefore, from analyzing the detected paired signals, it provides an opportunity to understand the roof stability and roof evolvement. Our microseismic monitoring array also captured a small cavity collapse incident. By the careful analysis of continuous data, we found precursory signals before the cavity collapse, which will be very useful for the real-time hazard assessment of solution salt mining.

Presenting Author: Haijiang Zhang

Authors