A study of the behaviour of the rock mass surrounding the Ventersdorp Contact Reef (VCR) at Kloof Gold Mine aiming at improved support design
Date
1997
Authors
Quaye, George Boadi
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
The difference in behaviour of the rock mass surrounding the VCR stopes was believed to
be due largely to the different combinations of hangingwall and footwall rock types. The
desire to develop a thorough understanding of this behaviour led CSIR, Mining Technology
to identify and define of geotechnical areas on all mines exploiting the VCR by CSIR, Mining
Technology. The results presented in this report were obtained from "fie of such
geotechnical area on Kloof Gold Mine, where the VCR is overlain by soft lava and underlain
by quartzite conglomerate.
The study was carried out in #3 shaft on both the southern and northern sides of the 33/27
longwall at Kloof Gold Mine. The strategies adopted to study the rock mass behaviour
included laboratory testing of rock samples, convergence and extensometer monitoring,
mapping of mining induced stress fractures and geological features, and the use of a
conceptual model to investigate the mechanisms which could be responsible for the
observed behaviour. The results obtained from the convergence monitoring indicated that
the closure rate is generally less than 5 mm/day and could be attributed to the low face
advance rate. The extensometers did not reveal any appreciable separation of beddingparallel
discontinuities in both the hangingwall and footwall strata. Detailed mapping of
mining induced stress fractures and geological features showed that the area is highly
faulted. Extensive rock falls were noted between the composite timber packs.
Stereographic projection of the orientation and inclination of the various discontinuities later
revealed that the observed rock falls between the composite timber packs in the area are
due largely to the unfavourable intersection of mining induced stress fractures and
geological features. Detailed Investigation of the distribution and frequency of both
geological features and mining induced stress fractures have been seen to be essential for
effective support design studies. A slight reduction in strike spacing between support units
could help improve the effectiveness of the support system in the northern panels. The test
results obtained from the laboratory have been used as input parameters in a conceptual
model to understand some of the mechanisms that could account for the observed
behaviour.
Description
A project report submitted to the Faculty of Engineering, University of the Witwatersrand,
Johannesburg, in partial fulfillment of the requirements for the degree of Master of Science
in Engineering.
Keywords
Kloof Gold Mine (Transvaal, South Africa), Ventersdorp Contact Reef., Rock mechanics -- South Africa., Mining geology -- South Africa.