Mining

 

ESG Solutions microseismic location accuracy mine

Locating and Interpreting Seismicity in Mines

For over 20 years, ESG has provided microseismic monitoring solutions to the international mining industry.  Our microseismic monitoring systems have been deployed in hundreds of underground  and open-pit mines around the world and we continue to invest in developing new and improved microseismic solutions for mining applications.

ESG’s microseismic monitoring systems and services provide a continuous stream of real-time information that help mining and ground control engineers understand how the mine responds to excavation and extraction operations.  This additional knowledge enables engineers to effectively plan mine operations, decrease costs and assess hazards.

How a Microseismic System Works:

A microseismic system is made up of a number of unique components including:

  1. Microseismic for Mining SchematicSensors:  Uniaxial and triaxial accelerometers and/or geophones.
  2. Junction Box - (JB): A NEMA-4 enclosure that houses essential acquisition and communications equipment including the Paladin® digital seismic recorder which serves as the backbone of ESG’s microseismic data acquisition system.
  3. Ethernet communication: Fiber (underground) or radio (surface) for reliable, full waveform data transfer.
  4. Acquisition PC: Acquisition Server, watchdog, optional large external storage drive and uninterruptable power supply (UPS).
  5. Processing PC: Fast multi-core Processor and powerful dedicated video card.

Seismic sensors, including geophones and accelerometers, detect seismic energy released by microseismic events.  These analog signals are transmitted via copper cables to the ESG Paladin® digital seismic recorder housed inside a Junction Box.
 
Each ESG Paladin® is a web-enabled digital seismic recorder equipped with its own IP address to facilitate identification, remote monitoring and calibration.   Once the signal has been registered and digitized by the  Paladin®, it is transmitted via Ethernet communication or other network (i.e. fibre, radio) to the Acquisition computer.  In the case of underground mines, acquisition computers are typically housed on the surface within an office setting.
 
ESG’s Hyperion Network Acquisition Software (HNAS) is installed on the Acquisition computer and provides continuous, full waveform data acquisition and triggering in real-time.  The full ESG Hyperion Seismic Software (HSS) is then installed on a separate Processing computer, and provides a platform for data processing.  Processing may include event identification, location and magnitude evaluation, and visualization using ESG's web-enabled 3D interactive visualization module to view source parameters within 3D mine view.

Underground Mine Monitoring

ESG's complete microseismic monitoring systems for mining applications bring together rugged components that have been tested, developed and refined over 20 years for reliable performance in the harsh environmental conditions of underground mines. ESG provides continuous microseismic monitoring at underground mines around the world. These systems are used to monitor a wide range of mining activities such as:

  • Caving (sub-level, block caving)
  • Vertical retreat mining 
  • Room & pillar 
  • Under cut & fill 
  • Open stope

Understanding Rockmass Behaviour

Microseismic monitoring gives mining engineers information about the local state and stress conditions of the rockmass. By receiving real-time information on the location of seismic events, engineers and operators can learn where these events are occurring relative to mine openings and active workplaces and visualize how these conditions are changing over time. By understanding how the rock mass is behaving, operators can infer which mining activities are affecting the overall structure, and by how much.

Enhanced Workplace Safety

A seismic monitoring program can be used to identify potential hazards caused by changing rock conditions. In particular, microseismic monitoring can detect abnormal seismic activity that could be a precursor to dangerous events such as rock bursts, rock falls or fault slips.  If abnormal or heightened seismic activity is detected, workers can be deployed away from actively seismic areas to other quieter areas of the mine. The advanced notification of potential dangerous events minimizes both the exposure of the workforce to these hazards as well as downtime from unplanned delays.

Optimize Mine Design, Sequencing, and Operations

If a microseismic monitoring system is deployed early in the life of the mine, it can become a valuable tool for mine sequence optimization. Through use of seismic monitoring, operators and engineers can gain knowledge of the rock mass more quickly and get a better idea of how ground conditions are changing. Microseismic data can also be used as a parameter to validate pre-existing geomechanical mining models and increase decision-making confidence. Mining operations and methodology can then be adjusted in response to modeled predictions.

Open-pit Mine Monitoring

ESG provides microseismic monitoring of open-pit mining operations. These systems can be used to monitor:

  • High wall slope stability
  • Surface movement
  • Active areas of fractures and faults
  • Natural seismicity

Monitoring Slope Stability

Microseismicity detected and measured behind an open-pit wall and can provide valuable information about the stability of a high wall slope.  In particular, the ability to observe how a slope responds to mining activities provides operators with insight into how to manage operations while ensuring the safety of all workers.

Monitoring Surface Movement

Combining information about microseismic activity taking place behind a pit wall with conventional methods of measuring surface movement (i.e. radar or laser) enables operators to predict where surface movement may occur in the future. 

Identifying Active Faults or Fractures

Close inspection of microseismic event location and magnitude along geological structures may indicate that a pre-existing fault or fracture is active or being affected by mining activities.  Microseismic monitoring also has the ability to identify or confirm the existence of unknown faults or fractures.  ESG’s advanced clustering algorithms are powerful enough to recognize events locating along geological structures where other companies have missed this relationship.

Block Caving

In caving operations, microseismic monitoring can be used to identify the fractures taking place in the seismogenic zone. 

Evidence of interaction or activation of previously unknown geological structures may allow operators to slow down production or remove people and equipment from nearby headings.  In contrast, a reduction in observed seismicity may indicate a build-up of stress in the rock mass, which if it fails suddenly, could harm the mine and pose a threat to worker safety.  Seismic information helps operators better understand what is taking place in the rock mass, providing an opportunity to make corrections to the production plan, adjust mining rate and strategy, or implement safety measures.  

Seismicity observed during caving operations can also be used to help evaluate proposed rock failure mechanisms.  If the leading failure mechanism identified by seismic monitoring doesn’t agree with models to predict the cave behaviour, then mine operations may be exposing themselves to significant risk in later stages of operation.  Seismic monitoring provides an opportunity for operators to calibrate and adjust models, and implement corrective actions to avoid conditions that could close a portion of a mine.

For examples of the use of microseismic systems in block caving operations, please see these resources:

Article: Mining Magazine March 2013 - Harnessing Microseismic Monitoring

Publication: International Symposium on Caving 2010 - Monitoring Open Stope Caving at Goldex Mine

Publication: ARMA 2014 - Seismic Event Location and Source Mechanism Accounting for Complex Block Geology and Voids

Coal and Soft Rock

Coal and soft rock mines have their own unique set of challenges with respect to ground control.  Microseismic systems can provide valuable feedback about stress build-up, fault interaction and water inflow issues to mitigate safety and financial risk.

Coal Mines

Primary ground control challenges in underground coal mines include roof skin deformation, roof collapse, and outbursts of coal, gas, and water. Microseismic monitoring provides valuable information on rockmass behavior and fracture propagation caused by stress redistribution, active geological structures, or gas build up within the coal strata and the surrounding rockmass.  ESG offers intrinsically safe and explosion proof certified seismic monitoring equipment designed specifically for the hazardous conditions in coal mines. 

For examples of the use of microseismic systems in coal mines, please see these resources:

Case Study: Underground coal mining in Anhui Province, China

Publication:  Applications of Microseismic Monitoring in China’s Underground Coal Mines

Soft Rock and Solution Mines

Soft rock mines such as salt and potash mines can benefit from microseismic monitoring systems or regional strong ground motion systems, especially if there is a concern about activating nearby faults.  Water inflow issues can also be challenging at soft rock mines, due to the high solubility of the deposits.  Microseismic methods have been used to help identify and track water inflow, to understand where water inflow is occurring as well as migration patterns through the rock.

Solution mining operations extract water-soluble minerals by dissolving the minerals in water and pumping the resulting brine through one or more drilled wells.  Microseismic systems have been beneficial in evaluating the integrity of the caverns generated in mineral deposits through this process.

Soft rock mines concerned with water inflow issues, and solution mining operations are excellent candidates for innovative downhole microseismic monitoring methods.  Available wells need to remain accessible for injection operations, meaning that they are not candidates for lower-cost permanent installed systems.  ESG’s innovative longer-term retrievable deployments can offer cost-effective temporary downhole microseismic monitoring without requiring wells to be taken out of operation.

Case Study: Controlled Solution Salt Mine Collapse in Romania

Publication: Microseismic Monitoring of a Controlled Collapse in Field II at Ocnele Mari, Romania

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