الفهرس 
Abstract
Rock mass classification systemsOnly 14 pages are availabe for public view
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Abstract
Underground working in Abu-Tartur longwall phosphate mines are fully stopped since 2010 till now 2013, because of the highly roof falls. The main objective of this work tries to introduce solutions to the mining problems causing roof failure. The problems are solved by:
i- Geological studies to determine Geological Strength Index (GSI), required for estimating in situ rock and ore properties (compressive strength & deformation moduli).
ii- Laboratory testing of ore and roof rocks samples to obtain their strengths.
iii- Calculating in situ strength required to calculate pillars width.
There are many methods which are applied to mine designs. The application of rock mass classification systems is one of these methods. The aim of this thesis is to apply rock mass classification systems to mine design, taking into consideration Abu-Tartur longwall phosphate mines as a case study. Most types of rock mass classification systems related to mine designs are reviewed. It is found that there are two systems of rock mass classification compatible with the mining conditions of Abu-Tartur longwall phosphate mine.
These two systems of rock mass systems are namely. Geological Strength Index (GSI) and Rock Mass Rating (RMR) systems. GSI values for immediate, main rocks and phosphate ores are determined from the geological conditions such as lithology., structure of the interlocking of rock blocks and the conditions of the surfaces between these blocks. RMR value can be determined by correlating it with GSI values by simple relation. Data required for the GSI system are obtained from geological reports, some field measurements and laboratory tests.
Results which obtained from this study are; the panel width (wall length) for Abu-Tartur area is calculated and found to be (102m), which differs strongly from the applied length in the mines (150m). So, it is recommended to apply this obtained length to secure safe mining conditions without roof falls which is the main problem facing underground mining in this area.
It is also found that the average maximum pressure on the supports is about 416t/m with a yield pressure of 520t/m on the shield support. Different recommendation are obtained such as; increase the rate of face advance, exploit ore in two consecutive shifts, decrease the period of the face stoppage and leave a thickness of about 30cm from phosphate ore in the roof during its exploitation to ensure stability of the roof during face advance. Also, increase rate of face advance of the shearer with the following specifications:
The model Cat El 3000/2011 with typical length 15.2m, seam thickness range from 2.5 to 5.5m. cutting drum diameter up 2.7m, haulage speed up to 32 per min, cutting drum speed 54.3 rpm and bits drum hardness up to 68.4 Mpa to secure high rate face advance. Shield support of model Kottadih, CDFI, France, 2x470 is selected for Abu-Tartur mining conditions to support efficiently during the face working.
Pillars width are calculated by applying rock mass classifications (HSI&RMR) and it is found to be 51m if we apply GSI values and 44m if we apply RMR values for a factor of safety = 1.3 and panel with of 100m with extraction ratios of 74 and 72% respectively.
Nomograms to check pillar stability are constructed based on GSI system, computer program based on RMR system for calculating pollar width and its safety is constructed also. There is a simple relation between RMR and GSI values as follows RMR = GSI + 5.
By applying of the computer program it was easy to construct relations between (Wp & RMR), (F.s&RMR) and (r&RMR) where Wp=pillar width, F.s = factor of safety and r = extraction ratio.
Also a nomogram for the design of panel width and pillar width for Abu-Tartur mining conditions is constructed.
Finally it is recommended to apply the following mining conditions:
i- Panel width Wl = 100m, pillar width Wp= 44m with extraction ratio r = 72%, or if the panel width equals Wl = 150m, the pillar width will be Wp= 50m with extraction ratio r = 77%.
ii- Use shield support of the following specifications model Kottadih, CDFI, France, 2x470 instead of applied Joy mining machine model.
We hope that this work will be helpful to mitigate or prevent roof failures.