Development of an early warning system for predicting rock bursts and rock induced displacements in seismically active mining blocks at Mufulira underground mine (deeps section).

Mufulira Mine has been in operation since 1933. The Mine is situated on the Copperbelt region of Zambia. It is predominantly rich in copper mineralization. Due to increase in mine depth which currently stands at 1,557 m, the mine has been experiencing geomechanical challenges such as rock failures due to excessive stress changes around some mining blocks. This has necessitated changes in mining sequences to suit the present geomechanical conditions such as development of de-stressing cross-cuts between 62 and 64 blocks. Additionally, blocks have been subjected to shotcrete support method to prevent possible rockbursts/rock falls which can endanger safety of men working in these areas. This study applied laboratory geotechnical investigations for intact rock mass to determine unconfined compressive strength (UCS), secant and tangent Young’s Modulus (E Sec and E Tan), and secant and tangent Poisson's Ratio (ν Sec and ν Tan), Brazilian and Triaxial Compressive Strength tests as well as geological field mapping methods to understand the Geomechanics mechanisms controlling rock burst prone mining blocks at Mufulira mine. Laboratory findings indicated high values of Brazilian (Tensile strength) ranging from 7 MPa to 12.1 MPa, Uniaxial Compressive Strength (UCS) ranging from 126 MPa to 226 MPa and Triaxial Compressive Strength ranging from 124 MPa to 466 MPa were obtained. Damage mapping conducted in the footwall drives, cross-cuts and mining drives excavations indicate that there is a changing stress as one moves away from the retreating stope face to the east. An early warning monitoring system at Mufulira mine has been developed through modification of the existing micro-seismic monitoring system to allow the quantification of exposure to seismicity and provide a logistical tool to guide the effort into the prevention and control of, and alerts to, potential rock mass instabilities that could result in rock bursts. Two geophones have been interconnected in series and connected to the network system via the optical fibre junction box within the seismically active mining blocks to enhance accuracy in picking up rockbursts and rockfalls. Geomechanics properties of rocks determined in the laboratory experiments, geotechnical and geological mapping results were used to suitably place the geophones in suitable proximities within the seismically affected mining blocks. This modified micro-seismic monitoring system is susceptible to change if mining locations change due to changes in geotechnical and geological parameters such as rock types, jointing and fracturing.

Grantor dc:publisher

The University of Zambia

Year dc:date.issued

2024

Author dc:creator

• Mukuka, Moses

Language dc:language.iso

en

Repository record dc:identifier.uri

https://dspace.unza.zm/handle/123456789/9243

OAI identifier oai:identifier

oai:dspace.unza.zm:123456789/9243