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.

Factors to Be Considered for the Design of Face Supports in Longwall Mining Method

“…Just before World War II, longwall automation led to the introduction of steel for support. Hydraulic supports have emerged following a lengthy stage of transition from using steel supports on longwall faces [22]. Mine working stability is determined by several factors, which are dependent primarily on the natural and technical conditions of the conducted mining operations.…”

“…There is no single set of formulas or systems in the designing of hydraulic supports. Almost every country has established its system [22]. There is a relationship between the yield and the setting or operating pressure as follows:…”

“…This distance grows as the cutting machine drives. This distance can range from 0.25 to 0.8 m depending on the depth of the cutting machine [22]. According to underground studies, the distance between the support canopy tip and the face line has an impact on the roof stability.…”

“…The expenditure is lowest on big panels. Face length has an impact on the panel's life and the number of working faces [22]. By increasing the panel width from 100 m to 260 m, the support convergence will increase by 33 %.…”

Geoelectrical tomography data processing and interpretation for Pb-Zn-Ag mineral exploration in Nash Creek, Canada

“…The sulphide mineralized environments are described by strong clay alterations and carbonization [16]. At the study area, widespread brecciation units and alteration zones (associated typically with a pyrite-rich accumulation) pose a problem for traditional electromagnetic exploration methods where low-grade sulphides are imbedded in laterally wide alteration envelopes [17,18].…”