Student Number : 0400188H - MSc(Eng) Dissertation - School of Mining - Faculty of Engineering and the Built Environment / The occurrence of fracturing due to high stress levels is a major factor with regard to hangingwall stability in deep level gold mine stopes. However, rock falls cannot be the result of these fractures alone. Blocks in the hangingwall strata must be defined by a combination of the stress induced fractures and naturally occurring geological planes of weakness. These planes include bedding planes and joint planes. The importance of the natural joints and bedding planes in defining the instability has not been given the attention that it deserves, to the extent that there are apparently no documented, published data available on joint set characteristics. This is perhaps an indication that such data do not exist on the mines. To remedy this situation, detailed scan-line joint mapping exercises have been carried out in several geological environments in two gold mines. The joint data collected on joint geometry included orientation, spacing and length. The results presented in this dissertation are believed to be the first such data available on jointing in gold mines. The main conclusions from the interpretation of these data are that there are two dominant joint sets in stope hangingwalls and at least one of these sets is shallow dipping. In development tunnels there is one predominant set of shallow dipping bedding planes. Both in stope hangingwalls and in development tunnels, steeply dipping random joints constitute half of the mapped joints. The statistical joint data obtained was used to investigate and analyse the potential for rock falls in stopes. This involved the prediction of characteristic block parameters such as expected block sizes and rock fall thicknesses. These predictions show good agreement with measurements made of actual rockfalls (generic results). Most unstable blocks in stope hangingwalls are less than a cubic meter in size. These blocks are more likely to fall between support elements than fail the supports, whilst failure of the fewer large blocks (20%) usually involves failure of support elements. It is concluded that failure probabilities are largely related to joint geometry. Common failure modes for small blocks are single plane sliding and ‘dropping out’ whilst larger blocks usually fail by rotation. The study increases understanding of rock fall mechanisms and the support-block interaction. The results of the analyses of block stability that have been reported in this dissertation show disturbingly high probabilities of failure in the stope face area (or working area), particularly for blocks that are smaller than about 1.5 cubic metres in size. The study has demonstrated the important influence that natural joints have on hangingwall block stability, and the importance of joint mapping to produce statistical joint data that can be used in the assessment of stability against rock falls. Although joint mapping may be a tedious exercise in mines, it has been shown to give similar results regarding heights of rock falls to that interpreted from collection of empirical incident and accident record data over a ten-year period. It is considered that this could provide good input data for the design of stope support.

Deep mixing (DM) is the modification of in situ soil to increase strength, control deformation, and reduce permeability. Multi–axis augers and mixing paddles are used to construct overlapping columns strengthened by mixing cement with in situ soils. This method has been used for excavation support to increase bearing capacity, reduce movements, prevent sliding failure, control seepage by acting as a cut–off barrier, and as a measure against base heave. DM is effectively used in excavations both in conjunction with and in substitution of traditional techniques, where it results in more economical and convenient solutions for the stability of the system and the prevention of seepage. Although DM is currently used for excavation control in numerous projects, no standard procedure has been developed and the different applications have not been evaluated. As this technique emerges as a more economical and effective alternative to traditional excavation shoring, there is a need for guidelines describing proven procedures for evaluation of design, analysis and construction. The main objective of this research is to develop a methodology to design retaining systems using deep mixing technology. The method will be evaluated using numerical analysis of one selected case history.

Deep mixing (DM) is the modification of in situ soil to increase strength, control deformation, and reduce permeability. Multi–axis augers and mixing paddles are used to construct overlapping columns strengthened by mixing cement with in situ soils. This method has been used for excavation support to increase bearing capacity, reduce movements, prevent sliding failure, control seepage by acting as a cut–off barrier, and as a measure against base heave. DM is effectively used in excavations both in conjunction with and in substitution of traditional techniques, where it results in more economical and convenient solutions for the stability of the system and the prevention of seepage. Although DM is currently used for excavation control in numerous projects, no standard procedure has been developed and the different applications have not been evaluated. As this technique emerges as a more economical and effective alternative to traditional excavation shoring, there is a need for guidelines describing proven procedures for evaluation of design, analysis and construction. The main objective of this research is to develop a methodology to design retaining systems using deep mixing technology. The method will be evaluated using numerical analysis of one selected case history.

Thèse doctorat : Génie Civil : Villeurbanne, INSA : 2006. / Titre provenant de l'écran-titre. Bibliogr. p. 262-267.

Thesis (M. Phil.)--University of Hong Kong, 2002. / Includes bibliographical references (leaves 181-186).

published_or_final_version / Applied Geosciences / Master / Master of Science

published_or_final_version / Civil Engineering / Master / Master of Philosophy

Thesis (M.S.)--Oregon State Agricultural College, 1936. / Typescript. Includes bibliographical references (leaves 124-130). Also available on the World Wide Web.

Thesis (MSc.(Anatomy)--Faculty of Health Sciences)-University of Pretoria, 2007. / Includes bibliographical references.

Quantification of cavity excavation produced strong empirical support for the ecological constraints model for the evolution of delayed dispersal in the cooperatively breeding red-cockaded woodpecker. The long times required for cavity excavation select for competition over breeding vacancies in established territories and against excavation of cavities in unoccupied habitat. Duration of excavation varies between woodpecker populations, but may require over 13 years in longleaf pine and over 10 years in loblolly pine. Duration of excavation is extremely variable. Much of the variation is due to variation in effort by excavating woodpeckers, which is in turn partially related to the need for new cavities in relation to the number of available cavities on a territory. An average of only 11 % of an individual's time budget is devoted to excavation, and only one individual per group makes significant contributions to excavation. Once completed, cavities are used for periods that may exceed fifteen years. Cavities in longleaf pine are used for significantly longer periods than cavities in loblolly. Whereas cavities no longer used as nests are abandoned altogether in loblolly, they are still roosted in for many years in longleaf. Final abandonment of longleaf cavities appears to be related to cavity loss. Quantification of cavity turnover revealed that three of the study populations were stable in cavity numbers over the study period, while a fourth underwent alarming declines. The continued use of restrictors and artificial cavities, and the protection of old-growth upon which the woodpeckers depend for excavation, are recommended. / Master of Science