Returning waste material underground, as backfill, has been practiced for many years so as to improve the economical and environmental performance of underground mining operations. A specific type of backfill, which is used to fill mined areas that will not be exposed to further mining, is called hydraulic backfill. Cemented backfill has also been used to provide mechanical support for underground mining. Such backfill has allowed mining companies to extract more ore, while simultaneously improving working and environmental conditions. Cemented backfill, however, represents 50 to 85 percent of operating costs compared with the 5 to 10 percent that hydraulic backfill consumes. / The objective of this thesis is to investigate use of sodium silicate as a partial or total replacement for cement in stabilised backfill. Sodium silicate is a viscous material that is usually used to activate pozzolanic materials such as slag and fly ash. The chemical compound has many applications, namely, in waste treatment, cement and other construction materials. / In order to determine the influence of sodium silicate on backfill performance, a series of laboratory experiments were carried out on samples with different binder compositions, such as: cement; slag and cement; slag, cement and sodium silicate; and slag and sodium silicate. Additionally, the effects of mixing time and addition order on the backfill samples' performance were studied. The subsequent thesis focuses mainly on the strength of paste and slurry backfill samples containing sodium silicate in addition to the observation of a number of experimental variables, which include: pulp density (relative amount of water), curing time, and binder dosage. In order to investigate the overall suitability of sodium silicate for use in stabilised backfill, other properties such as porosity, elastic modulus, and trends of water release are also studied. / The results of the research endeavour demonstrate that sodium silicate-fortified backfill materials behave favourably compared with cemented backfills. Sodium silicate, thus, has potential as a backfill binder or additive.

Thesis (Ph. D.)--West Virginia University, 1999. / Title from document title page. Document formatted into pages; contains vii, 145 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 71-72).

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Over the last three decades, mine backfilling has progressively integrated into underground mining operations. The high stresses associated with mining at depth in the Canadian Shield, also requires innovative approaches to mine backfilling to withstand the loading both during and after mining operations. Not only new or modified minefill systems are required, but also new techniques are needed to increase the speed of the mining cycle for optimizing the mining operation. Three major purposes of mine backfill are known as (1) providing safe working condition, (2) maximizing ore recovery and (3) improving underground stability. Therefore, mine backfill has contributed greatly to the economics and environmental aspects of mining industry. / In order to improve the mechanical behaviour of fill, cementitious materials are used. These cementitious materials are expensive. As a result the consumption of these cementitious materials has to be optimized and minimized in a way that the required strength is met. The objective of this research is to investigate a new type of backfill, which is known as gelfill. Gelfill binders usually consist of alkali activators such as sodium silicate and the other cementitious materials. Sodium silicate has been used in waste treatment and activation of artificial pozzolans such as blast furnace slag and fly ash. / The work presented in this thesis is to evaluate the use of sodium silicate in gelfill. Consequently, the influence of mixing time, mixing sequence and curing time are studied on gelfill and silica sand hydraulic backfill. Various tests including unconfined and confined compressive strength were conducted in order to investigate the mechanical behaviour of samples. By conducting mercury intrusion porosimetery (MIP) and scanning electron microscopy (SEM), microstructure and mineralogical properties of specimens were studied. / The result of this thesis demonstrates that gelfill compared with silica sand hydraulic backfill has better mechanical properties. In addition, other variables, including: mixing time and sequence, have a significant effect on gelfill.

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Thesis (Ph. D.)--West Virginia University, 2009. / Title from document title page. Document formatted into pages; contains xiv, 215 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 143-147).

A thesis submitted to the Faculty of Engineering, University of the Witwatersrand. Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy / Hydraulically placed cemented backfill is increasingly being used as a means of stope support in South African hard-rock mines. The addition of binder provides backfill with a primary compressive strength. the property for which the material has traditionally been utilised. Binder-induced cohesion, however, is not the only factor determining the quality of cemented backfill and the material's utility can be enhanced significantly by applying all of its attributes to the task of stope support. The main purpose of this thesis is, therefore, to examine those factors which influence the performance of cemented backfill, and to provide relevant and useful information for the design of improved cemented backfill mine support for tabular mining excavations. In an extensive laboratory investigation, a number of relevant factors were tested for their influence on the loading behaviour of cemented backfill. Twenty two cemented backfills. grouped according to aggregate type, water content, binder content and binder type, were analysed to determine the influence of composition on their material properties. This study was augmented by several test series on the effects of curing conditions on cemented backfill quality. In a second major investigation, the effects of geometrical parameters, including sample volume and sample width to height ratios were analysed. A further study dealt with the effect of spatially separating sample backfill ribs under normal compression, as well as at high closure rates. It is concluded, that by co-ordinating the composition design of cemented backfills with the spatial configuration of backfill support elements, it is possible to modify all phases of the cemented backfill loading response. This implies the control of the binder-induced compressive strength at low strains, the large-scale yielding behaviour of backfill support, as well as the stiffness of the backfill body at high stresses. In the light of stope support requirements. particularly under rockburst conditions, the capacity of backfill support to yield and absorb rapid stope closure and then to decelerate the hangingwall by the rapid strain-hardening of the, now, large width to height ratio backfill mass, has the potential of substantially increasing mine safety in tabular stopes, / Andrew Chakane 2020

A dissertation submitted to the Faculty of Engineering, University of Witwatersrand, in fulfillment of the requirements for the degree of Master Science in Engineering / The Electricity Supply Commission of South Africa (Eskom) have identified open cast coal mine backfill areas as potential disposal sites for the large volumes of coal ash produced by their power stations. As Eskom's power stations are mainly situated in agricultural and coal rich areas of the provinces of Mpumalanga and the Free State, the sterilisation of substantial areas of agricultural soil and coal deposits is thus reduced. The construction of a tailings dam or dump on uncompacted open cast mine backfill creates various problems related to the settlement of the backfill. The scale of the operation, the large particle size and heterogeneous nature of the backfill and its method of placement complicates the prediction for settlement of the backfill. Areas in excess of 74 000 ha could be subjected to opencast mining in Mpumalanga and for future development of these areas more information regarding the magnitude and mechanics of mine backfill settlement is required. This dissertation describes two large scale field tests in which the settlement of mine backfiil was studied during the construction of a test section of an ash tailings dam and the construction of a dry ash dump. / Andrew Chakane 2019