The safe operations at longwall face depend on the type and capacity of the powered roof supports. At Abu-Tartur longwall phosphate mine, two types of powered roof support with various capacities were tried earlier. The two leg shield power supports was applied finally. The main problem at Abu-Tartur longwall mines is the high frequency of roof rock falls during face advance. Roof collapse is due to an inadequate capacity of the chosen powered supports. So, in this paper the load exerted on the shield support is calculated by different methods and taking into consideration the actual roof conditions by rock mass classification system to select the suitable type of the supports. From these calculations, it is found that the average maximum pressure on the supports is about 416t/m with the yield pressure on the shield support of a value of 520t/m. Different items are recommended such as; increase the rate of the advance, exploit ore in two consecutive shifts, decrease the period of the face stoppage and small thickness about 30cm from phosphate ore should be left in the roof during exploitation to ensure stability during face advance. The following shearer is recommended to increase rate of face advance. The specification of this shearer are model Cat EL 3000/2011with typical length 15.2 m, seam thickness range from 2.5 to 5.5 m, cutting drum diameter up to 2.7 m, haulage speed up to 32 m per min, cutting drum speed 54.3 rpm and bits drum hardness up to 68.4 Mpa is to secure high rate of face advance. Shield support model Kottadih, CDFI,France, 2x470 is selected for Abu-Tartur mining conditions to support the face during working.

Rock mass classification systems consider one of the design tools, which are used in conjunction with engineering assessments and other design approaches. There are many classification systems, which are widely employed in rock engineering. In this study one of these systems is used for the selection of the optimum panel width in phosphate mine Abu-Tartur area. Geological Strength Index (GSI) is one of these systems which enables for calculations of the panel width. Data for the GSI system are obtained from geological reports, some field measurements and laboratory tests. The obtained panel width (wall length) for Abu-Tartur area is calculated to be about 100m (102m) which differs strongly from the applied length in the area (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.

Pillars are designed to ensure regional stability or local support in stopes and along drifts, or to yield under a measure of control. In all cases, the strength of the material and the variations in strength must be known both for the pillar and for the roof and floor. The stability in longwall faces depends mainly on the interaction between the roof strata, face support, roadway support and dimensions of pillars. The main aim of this paper is to apply rock mass classification systems to longwall pillar design at Abu-Tartur mining area. The pillar load is estimated taking into account the physical and mechanical properties of phosphate deposit and roof rock, panel width, mining height, depth below surface. Two methods from classification systems are used in calculation pillars stress and strength to pillars design namely Geological Strength Index (GSI) and Rock Mass Rating (RMR) systems. GSI values for immediate, main roof rocks and phosphate ores are determined from geological conditions, as lithology, structure of the interlocking of rock blocks and the conditions of the surfaces between these blocks. RMR value can be determined by correlation it with GSI system. The pillar widths calculated by applying rock mass classifications (GSI& RMR) are 49m and 64m at a factor of safety 2 and panel width 100m with extraction ratios of 70 and 64 % respectively. The data used in calculations are collected from geological reports of the company and from laboratory tests of phosphate ores and shale rocks in the roof.

The phenomenon of subsidence is the movement at the ground surface caused by underground excavations, which can cause severe damage to buildings or structures on the surface and infrastructure. These excavations exert redistribution of the original stresses around the openings. Different methods have been adopted to predict and quantify the subsidence with the subsidence parameters. These methods can be classified into three categories 1) Empirical methods based on the analysis of the field measurement, 2) Mathematical theories, 3) Numerical models including Finite Elements, Boundary Elements and Distinct Elements methods. In this paper, the surface subsidence data were collected over working longwall panel at Abu-Tartur phosphate mines after the face had been advanced 280m. Different mathematical theories namely Bals', Peng's, Knothe's and Peck's theories are applied to predict the subsidence trough over the excavated panel. The obtained results are compared with the measured ones. It was found that Peck's theory coincides well with the measured data. The degree of ground surface tilt, surface curvature and strain are derived from Peck's theory.

The main purpose of mine workings is the exploitation of ores and minerals that are used in different aspects of life. The most common underground method all over the world is the longwall mining method. The increasing demand for minerals and ores and the difficult mining conditions at greater depths make the longwall mining system a good candidate in mining. The equilibrium condition is disrupted when the longwall face advances, and as a result, the surrounding rocks eventually fracture and cave. Moreover, the induced pressure due to caving or fractures of the immediate roof rocks and the tilting of the main roof exerts an excessive load on the hydraulic supports in the longwall faces. Induced disturbances of the overburden rocks must be thoroughly investigated since this will enhance our understanding of rock pressure and ground control. The main objectives of this paper are to review the importance of the longwall mining system as an exploitation method and its applications around the world. as well as the main factors affecting the stability of supports in longwall faces, especially hydraulic supports. From this study, it can be seen that the most important technical factor that affects face stability is the rate of face advance. In addition, the significant natural factors affecting the stability of workings are roof conditions and the geometry of the panel.