Estimation of First and Periodic Roof Weighting Effect Interval in Mechanized Longwall Mining Using Numerical Modeling

The main factors that make longwall mining projects economical are roof control and prediction of roof behavior in roof caving and face advance. Sudden and unexpected roof fall not only endangers the safety of employees but also destroys and damages the extraction equipment and components. In addition, there are financial and economic impacts because the extraction operation is interrupted. Therefore, determining the first roof weighting effect interval (FRWEI) and the periodic roof weighting effect interval (PRWEI) are very important in longwall mining. There are several methods to determine the FRWEI and PRWEI. This paper investigated the behavior of steep layers during the roof caving process in the gob space by numerical modeling, and then estimated the value of the FRWEI and PRWEI at the E3 panel of the Tabas Parvadeh coal mine. The roof failure criterion was based on the Sakurai equations. According to the numerical modeling results, the FRWEI value is 11 m and the PRWEI value is between 2.5 and 4.5 m.