LOAD CALCULATIONS AND SELECTION OF THE POWERED SUPPORTS BASED ON ROCK MASS CLASSIFICATION AND OTHER FORMULAE FOR ABU-TARTUR LONGWALL PHOSPHATE MINING CONDITIONS

Abstract

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.