Target Mine utilizes an open stoping mining method at a depth of some 2200m to 2500m below surface. Stress and seismicity can have a significant impact on the stability of the access development to the open stopes. Narrow tabular stoping is used to de-stress the large development ends and open stopes where possible. Occasions do arise where de-stressing is not possible resulting in higher field stress, which may affect the access development and open stopes.
Due to the variation in stress acting on the excavations, selection of support to assist in stability is critical. The Q-System and Rockwall condition Factor are two methods that are applied to evaluate the development ends. The methodology followed for support design is discussed in detail making use of back analysis and case studies at Target Mine.
As the depth of mining progresses excavations are exposed to higher than normal induced stresses often resulting in rockbursts. In an attempt to limit the effect of the above mentioned, ground control measures and rockburst resistant support are used to prevent or minimize damage to these excavations.
Development support in rockburst prone areas is required to absorb dynamic loads, deformation from violent rock failure and rock dilation during static loading. After reviewing the rockburst damage mechanisms, rockburst support design principles and acceptable criterions used, this paper describes the support selection process followed and modifications made based on field observations. A support design methodology for conducting rockburst support design and testing for underground tunnels based on back analyses is introduced to facilitate cost-effective support design.
Target Mine utilizes an open stoping mining method at a depth of some 2200m to 2500m below surface. Stress and seismicity have a significant impact on the stability of the access development to these open stopes. Narrow tabular stoping is used to de-stress the access and reef drive development ends and large open stopes where possible. As a direct result from the de-stressing, high stress abutments are sometimes created intersecting the access development below.