Search

Abstract: Auxiliary ventilation is performed by carrying intake or return air in ducts. The complete elimination of air leakage from or into the ducting system is impossible due to duct quality and numerous joints in ducting system. The auxiliary ventilation systems for long drivages often require the use of multiple fans. Fans are installed in series and separated from each other in fixed or variable lengths. There are many methods proposed for the analysis air flow problems in leaky ducts. Due to the lengthy calculations, computers are often needed to conduct the analyses. In this study, a method known as “series–parallel combination of the duct and leakage path” has been introduced and a computer program has been developed based on this method. In order to design the conditions of an auxiliary ventilated drivage, in situ measurement have been made in Western Lignite Enterprises (GLI) OMERLER underground coal mine (Turkey) and the related data necessary for this study was collected. The presently developed program was tested using these data, and it was found that the measured and calculated values are quite close. The effective operational parameters governing auxiliary ventilation have been investigated and the effects of these variables on the volume rate of air flow reaching long drivage face have been examined by using linear regression analysis. Finally, it was concluded that the increase of duct diameter has prime importance in achieving the adequate air flow to the face and that for the auxiliary fans considered in this study the selection of fan does not greatly affect the volume rate reaching the face in a long duct line. [Copyright &y& Elsevier]

Abstract: Laboratory tests were conducted on 12 different carbonate rocks to investigate index properties of deteriorated rocks due to physical weathering. Physical weathering due to freeze–thaw and thermal shock action for 20 cycles, was simulated, following the procedure suggested by standard methods. Index properties, P-wave velocity, uniaxial compressive strength and Schmidt hardness, for the three series of the rock samples were determined for fresh, freeze–thaw and thermal shock conditions. It was found that the index properties of rocks treated with freeze–thaw and thermal shock decrease in varying levels with respect to initial values. A model equation predicting the index properties of rocks due to freeze–thaw and thermal shock treatment was developed by multiple regression analysis of measured data. This model explains decrease in index property of a deteriorated rock depending on its initial property and porosity of rock with the coefficients for a specific index property, given in the paper for the both freeze–thaw and thermal shock treatments. Model was validated by statistical tests. In order to estimate the index property for any cycle of freeze–thaw or thermal shock treatment, this model equation was incorporated into a previously suggested model to eliminate a decay constant required for that model to be determined for a specific rock in the laboratory. So, the final model equation could accurately predict a property of a deteriorated carbonate rock depending on treatment cycle, and initial index property and porosity. This was also proved by comparing the model with compressive strength data of a researcher for freeze–thaw cycles. [Copyright &y& Elsevier]