Supported stope mining is one of the most common types of mining in the modern day gold mining industry. The excavated regions, where ore is extracted, are supported with a combination of roof-bolting, timber packs, backfill, timber props and mechanical prop technologies. In order to install a support system that will be able to absorb the energy released by the elastic movement of the surrounding rock mass and support the unstable hanging wall, it is necessary for the rock engineer to know how the individual types of support will react to different load conditions in order to design a safe support system. Current support systems are developed using knowledge from past experience and trial and error processes. These are expensive and time consuming methods that can possibly be improved and made more cost effective by using modern design techniques. A study was conducted to determine the feasibility of the application of Finite Element Modelling (FEM) to the deformation of a modern support unit under specified quasi-static and dynamic stope load conditions with the view to assist in the prediction of the operational performance of support units that cannot be experimentally tested due to a lack of test equipment, capabilities and facilities. The study was extended by investigating the theoretical possibility of buckling due to an impact load on the prop and the performance of the prop. To achieve this, a simulation was carried out using ANSYS™ transient structural software to determine whether it is possible to simulate the performance curve of a prop. Computerised methods were used to determine the possibility of failure due to buckling and the implications of buckling, if it occurs, on the performance of a specific support prop design. In summary this study proved that it is possible to simulate the performance curve of a friction prop design in order to compare the result obtained with the required performance, provided that the correct friction coefficients between prop mating surfaces are known. It also presents a methodology to investigate the theoretical effect of high velocity impact load on the buckling potential of a friction prop design and slender columns in general, which is highly applicable to these types of support. The methodologies used in this study can be applied to different designs of friction props, and possibly reduce the development costs and implementation time of these types of support units. / MIng (Mechanical Engineering), North-West University, Potchefstroom Campus, 2014

Empirical design methods are commonly used for rock mechanics evaluations. An appropriate method of rock mass classification is required to use these empirical methods. There are limitations for rock mass classification methods when access to the ore zone is restricted. The Cameco Corporation Eagle Point Mine in northern Saskatchewan, Canada, uses the longhole open stope mining method for the recovery of uranium ore. The Modified Dilution graph is used for the prediction of stope hanging wall dilution. The mine currently uses a rock mass classification based on an estimate of the alteration and strength of a rock mass from geological drift mapping. Since this method is highly subjective, point load testing of diamond drill hole core was completed to attempt to correlate the alteration and strength of different rock types to remove the user subjectivity. The results of the testing indicated a general trend of decreasing rock strength with increasing alteration, albeit with considerable scatter. A repeatable, standardized method of evaluating the stope geometry and inferred rock mass classification for reconciliation purposes was developed. The standardized stope evaluation method removes significant subjectivity currently involved in estimates of stope geometries and the magnitude of dilution. A new lithology based method for interpreting the mine specific geological alteration and strength classification system was developed based on several sources of rock mass classification observations. This resulted in a correlation linking individual rock mass property descriptions between different classification systems for an improved estimate of the Q’ classification value. This improved method of estimating the rock classification Q’ value, as well as conventional techniques for linking classification systems, was used in a stope reconciliation process to predict open stope dilution. Twenty-seven stope reconciliation case histories were documented and used to compare predicted and measured dilution, based on three different approaches for estimating rock mass classification values. The results showed a minor improvement in dilution prediction using the approach developed in this study. The systematic stope reconciliation and rock mass classification approach did highlight areas in the weak pegmatoidal rocks where improved rock classification estimates should be investigated.

In the last couple of decades, geocell reinforced soil systems have been used in challenging new applications. Although the widely different application of cellular confinement systems demand a better understanding of the fundamental behaviour of the functioning of the cellular reinforced soil systems, surprisingly little research on the fundamental behaviour of the structures and the interaction of the components has been done. A research project has been initiated at the University of Pretoria and this thesis constitutes the first step in achieving an understanding in the functioning of geocell reinforced soil systems. This thesis is focused specifically on the geocell support pack I configuration. However, the research output is not limited to this configuration and may find wider application. The support packs were studied at a width to height ratio of 0.5. The fill material used in this study is classified gold tailings from the Witwatersrand Complex and the geocell membranes were manufactured from a thin (nominal thickness of 0.2 mm) High Density Polyethylene (HDPE) sheet. This study provides an understanding of the functioning of the geocell support pack by studying the constitutive behaviour of the fill and membrane material and their interaction, as well as the influence of multiple cells on the composite structures. The behaviour of the classified tailings material is interpreted in terms of Rowe's stress-dilatancy theory and a simple robust constitutive model for the material behaviour is developed. The stress-strain behaviour of the HDPE membranes is strain-rate-dependent and two simple mathematical models for the strain-rate-dependent stress-strain behaviour of the membranes are developed. An analytical calculation procedure for obtaining the stress-strain behaviour of the fill confined with a single geocell is developed with which some of the shortcomings of the previously presented theories are addressed. This procedure uses the models for the fill and membrane behaviour developed as part of this study. The interaction of adjacent cells in a multiple cell geocell structure, influences its behaviour. This thesis shows that, with exception of low axial strain levels, the efficiency of a structure consisting of multiple cells of a certain size is lower than a single cell structure with the same cell size and fill. These results are contrary to previously published opinion. A method for quantifying the efficiency of a multiple cell pack is also developed. / Thesis (PhD (Geotechnical Engineering))--University of Pretoria, 2006. / Civil Engineering / unrestricted

Instability in stope panels in shallow mines manifests itself as rockfalls from the hangingwall. Rockfalls from unstable stope panels vary in size from rockfalls between support units, to rockfalls spanning between pillars or solid abutments, to rockfalls bridging several panels and pillars. A suitable and reliable design methodology for stable stope panels at shallow depths is therefore required. This methodology must consider all manifestations of instability in stope panels and take account of the factors governing the stability. Very few mines design stope panels according to a systematic design procedure or methodology. Rock mass characterisation, estimation of rock mass properties, identification of potential failure modes, appropriate stability analyses and other elements of the rock engineering design process are often neglected. Instead, panel lengths are often dictated by the equipment in use and by previous experience under similar conditions. Consequently, unplanned stope panel collapses occur on most near-surface and shallow mines. Although these incidents often occur during blasting, they pose a major threat to the safety of underground workers and the economic extraction of orebodies. Hence, a rock engineering design methodology for the design of stable stope panels between pillars is of vital importance for optimum safety and production in shallow mining operations. Using the proposed design methodology, rock mechanics practitioners and mine planners should be able to identify and quantify the critical factors influencing the stability of stope panels. The critical factors should then be used as input to the design of stable stope panels that will provide the necessary safe environment for underground personnel working in stopes. It is concluded that the design of stable stope panels should be a process of defining the means of creating stable stope panels for the safety of underground workers and optimum extraction of the orebody. Therefore, a method is required whereby all rock properties, their variability, and an understanding of all rock mechanisms affecting the stability of stope spans are used as a fundamental base. A procedure for identifying the mechanisms and rock properties relevant to the specific problem is then required. In this way, existing knowledge should be used in an optimal way to design site specific stable stope spans. Hence, it is proposed that the design methodology for stable stope panels is a process consisting of the following steps: 1. Define objective. 2. Rock mass characterisation. 3. Estimation of in situ rock mass properties. 4. Consider an “ideal” stope panel. 5. Identification of potential failure modes. 6. Stability analyses. 7. Identify all significant hazards and assess the significant risks. 8. Geometric optimisation. 9. Determination of support requirements. 10. Design of support. 11. Evaluation. 12. Recommendation and implementation. 13. Monitoring of excavation and support behaviour to validate design and permit modifications. / Dissertation (MEng (Mining))--University of Pretoria, 2006. / Mining Engineering / unrestricted

<p>Еолски седименти представљају идеалан материјал за примену методе луминесцентног датирања. Један од главних разлога је њихов минеролошки састав који углавном чине кварц и фелдспат. Ови минерали поседују читав низ луминесцентних карактеристика који их чине погодним за луминесцентно датирање а поред тога, могуће је релативно једноставно извршити њихову екстракцију и сепарацију од других неминералних састојака. У случају лесних платоа (еолски транспортованих седимената), може се претпоставити да су индивидуална минерална зрна била потпуно изложена сунчевој светлости и да су у довољној мери ресетована пре депозиције. Истраживана секција Велики сурдук на Тителском лесном платоу, изабрана је за датирање, на основу своје моћности, високе стопе седиментације и комплетности које овај локалитет чине најдетаљнијим палеоклиматским архивом последња два глацијално- интерглацијална циклуса у овом делу Европе.<br />Употребом класичног SAR протокола за датирање утврђено је да кварцна зрна са<br />Тителског лесног платоа представљају прецизне дозиметре до ~120 Gy, после чега долази до очигледног засићења сигнала. Највиша утврђена доза фелдспата измерена модификованим SAR пост-IRIR^200,290 протоколом је била 854,0&plusmn;24 Gy. Пост-IRIR^200,290 протокол није утврдио сатурацију код минералних зрна фелдспата, што је умногомо подигло поуздану старосну границу за датирање на секцији Велики сурдук, а највероватније и на осталим лесним профилима у Србији. Примена различитих протокола и мерења аплицираних на различите групе минерала и њихове фракције дају овим истраживањима далекосежан методолошки значај. На овај начин је доказано да у поменутом временском опсегу OSL датирање грубог кварца даје поуздане старосне процене до 35,8&plusmn;3,7 ka док су зрна фелдспата датирана до чак 237,7&plusmn;12,8 ka. Кварц има апсолутно највећу подударност са очекиваним геолошким временом до MIS 2 за разлику од фелдспата који показује бoљу подударност са претпостављеном геолошком хронологијом до MIS 7.</p> / <p>Eolski sedimenti predstavljaju idealan materijal za primenu metode luminescentnog datiranja. Jedan od glavnih razloga je njihov minerološki sastav koji uglavnom čine kvarc i feldspat. Ovi minerali poseduju čitav niz luminescentnih karakteristika koji ih čine pogodnim za luminescentno datiranje a pored toga, moguće je relativno jednostavno izvršiti njihovu ekstrakciju i separaciju od drugih nemineralnih sastojaka. U slučaju lesnih platoa (eolski transportovanih sedimenata), može se pretpostaviti da su individualna mineralna zrna bila potpuno izložena sunčevoj svetlosti i da su u dovoljnoj meri resetovana pre depozicije. Istraživana sekcija Veliki surduk na Titelskom lesnom platou, izabrana je za datiranje, na osnovu svoje moćnosti, visoke stope sedimentacije i kompletnosti koje ovaj lokalitet čine najdetaljnijim paleoklimatskim arhivom poslednja dva glacijalno- interglacijalna ciklusa u ovom delu Evrope.<br />Upotrebom klasičnog SAR protokola za datiranje utvrđeno je da kvarcna zrna sa<br />Titelskog lesnog platoa predstavljaju precizne dozimetre do ~120 Gy, posle čega dolazi do očiglednog zasićenja signala. Najviša utvrđena doza feldspata izmerena modifikovanim SAR post-IRIR^200,290 protokolom je bila 854,0&plusmn;24 Gy. Post-IRIR^200,290 protokol nije utvrdio saturaciju kod mineralnih zrna feldspata, što je umnogomo podiglo pouzdanu starosnu granicu za datiranje na sekciji Veliki surduk, a najverovatnije i na ostalim lesnim profilima u Srbiji. Primena različitih protokola i merenja apliciranih na različite grupe minerala i njihove frakcije daju ovim istraživanjima dalekosežan metodološki značaj. Na ovaj način je dokazano da u pomenutom vremenskom opsegu OSL datiranje grubog kvarca daje pouzdane starosne procene do 35,8&plusmn;3,7 ka dok su zrna feldspata datirana do čak 237,7&plusmn;12,8 ka. Kvarc ima apsolutno najveću podudarnost sa očekivanim geološkim vremenom do MIS 2 za razliku od feldspata koji pokazuje bolju podudarnost sa pretpostavljenom geološkom hronologijom do MIS 7.</p> / <p>Aeolian sediments represent an ideal material for the application of the luminescence dating method. One of the main reasons is their mineralogical composition which consists mainly of quartz and feldspars. These minerals possess a whole range of luminescence characteristics that make them suitable for luminescence dating, and in&nbsp;&nbsp; addition, it is relatively easy to extract and separate them from other non-mineral ingredients. In the case of loess plateaus (eolically transported sediments), it can be assumed that individual mineral grains were completely exposed to sunlight and were sufficiently bleached before deposition. The investigated section Veliki surduk on the Titel loess plateau was chosen for dating, based on its thicknes, the high rate of sedimentation and completeness which makes this site one of the most detailed paleoclimatic archives of the last two glacial and interglacial cycles in this part of Europe.<br />Using the classic SAR protocol for dating, it has been found that the quartz grains from the Titel loess plateau are precise dosimeters up to ~120 Gy, followed by an apparent saturation of the signal. The highest established dose of feldspars measured by the modified SAR postIRIR^200,290 protocol was 854.0&plusmn;24 Gy. The post-IRIR^200,290 protocol did not determine the saturation of feldspar minerals, which has largely raised the age limit for luminescence dating at the Veliki surduk section, and most probably, also on other loess profiles in Serbia. The application of various protocols and measurements applied to different groups of minerals and their fractions give these research a far-reaching methodological significance. In this way, it has been proven that in the mentioned time range, OSL dating of coarse grain quartz yields reliable age estimates up to 35.8&plusmn;3.7 k while the feldspar grains are dated to as high as 237.7&plusmn;12.8 ka. Quartz has the highest match with the expected geological age to MIS 2 as opposed to feldspar, which shows better correspondance with the assumed geological chronology to MIS 7.</p>

La minería es considerada un trabajo de alto riesgo debido a la exposición a diferentes peligros, alineado al trabajo de investigación se menciona la inestabilidad de los tajeos que está estrictamente relacionado a los daños que pueden ocasionar a los colaboradores y como señala el MINEM, entre el 2015 y 2020, del total de accidentes ocurridos en la minería, el 28.7 % corresponden a accidentes relacionados a desprendimiento de rocas, deslizamiento de bloques y derrumbes totales. Esto evidencia la necesidad de realizar evaluaciones geomecánicas en todos los niveles de la minería para ejecutar trabajos seguros y mantener la continuidad operativa. Por consiguiente, el presente trabajo de investigación se enfoca en determinar la dimensión geométrica óptima del tajeo N°1 de la Unidad Minera Debra Luz, de modo que la evaluación de cada superficie del tajeo sea estable y de esa manera señalar que el tajeo en general es seguro para la operación. El escenario de la investigación es en vetas angostas, característica que eleva el nivel de importancia del aporte puesto que la técnica a usar se ha implementado generalmente en métodos de explotación de grandes dimensiones. La técnica a usar será el Método Gráfico de Estabilidad de Mathews que permite evaluar mediante dos parámetros de ingreso, Número de estabilidad (N´) y Radio Hidráulico (RH), si el diseño propuesto se encuentra en una zona estable o no. El N´ es un factor asociado al macizo rocoso, valor constante, y el RH es una variable relacionada con las dimensiones del tajeo. Además, en el desarrollo de la investigación interviene el uso del Modelo Numérico de Elementos Finitos para determinar el esfuerzo de compresión inducida máxima y el factor de seguridad asociado al tajeo N°1 que indica si la labor es estable o no. El valor del ensayo de compresión uniaxial de la roca intacta de la caja techo de la galería SE es 150.3 MPa. Según Gonzales de Vallejo et al. (2002), este valor se encuentra en el rango considerado roca muy dura. La constante “k” para el caso de estudio se obtuvo igual a 1.55 que significa que la mayor ocurrencia de falla en el tajeo podría deberse a los esfuerzos horizontales. La dimensión optima que mantiene estable el tajeo es de 1.25 x 25 x 30 m, donde cada superficie del tajeo fue evaluada mediante el gráfico de estabilidad. Se obtuvo valores de factores de seguridad mayores a 1.3 mediante el modelo numérico, siendo estable. / Mining is considered a high-risk job due to exposure to different hazards, In line with the research work, mention is made of the instability of the stopes that is strictly related to the damage that can be caused to collaborators and, as the MINEM says, between 2015 and 2020, of the total number of mining accidents, 28.7 % relate to accidents related to rock fall, block slip and total landslides. This shows the need for geomechanical assessments at all levels of mining to perform safe work and maintain operational continuity. Therefore, this research paper focuses on determining the optimal geometric dimension of the N°1 stope of Debra Luz Mining Unit, so that the assessment of each stope surface is stable and thus indicate that the stope in general is safe for operation. The research scenario is in narrow veins, a characteristic that raises the level of importance of the contribution because the technique to use has generally been implemented in methods of exploitation of large dimensions. The technique to use will be the Mathews Stability Graph Method that allows to evaluate by two input parameters, Stability Number (N ) and Hydraulic Radius (RH), whether the proposed design is in a stable area or not. N is a factor associated with the rock mass, constant value, and the RH is a variable related to the stope dimensions. In addition, the research involves the use of the Finite Element Numerical Model to determine the maximum induced compression stress and the safety factor associated with the N°1 stope that indicates whether the work is stable or not. The value of the uniaxial compression test of the intact rock of the SE gallery hanging wall is 150.3 MPa. According to Gonzales de Vallejo et al. (2002), this value is in the range considered very hard rock. The constant "k" for the case study was obtained equal to 1.55 which means that the greatest occurrence of failure in the stope could be due to horizontal stresses. The optimal dimension that keeps the stope stable is 1.25 x 25 x 30 m, where each surface of the stope was evaluated using the stability graph. Values of safety factors greater than 1.3 were obtained using the numerical model, being stable. / Tesis