The caving of the roof is very important aspect on which safety of the whole panel is dependent. The uncaved span of the roof causes strata loading on the supports. The uncaved roof strata that overhang behind the supports creates additional stress when caving lags behind and the abutment zone does not advance ahead of the face during mining. As a result, the productivity and safety of long wall operations are disturbed continuously. Therefore, the monitoring and forecasting of strata behavior is imperative for improving productivity and safety. The Real Time Instrumentation (RTI) system was successfully developed and implemented in one of the Indian longwall mines for forecasting the status of strata caving. The innovative RTI system has in-built facilities to analyse strata behavior and initiate warning module during adverse behavior in real time. This paper will discuss the role of RTI system in successful longwall operations.
Indian mining operations are becoming more and more difficult with each day as mining extends to deeper horizons, resulting in more adverse geo-mining Conditions. This situation obviously demands more and more sophisticated and advanced instruments in checking and monitoring the ground control parameters (Mandal et al., 2000).
Hydraulic leg pressures are the results of a continually changing interaction between the shield and the roof strata. As such, it can be used to analyze the past and Current roof conditions and predict roof conditions Prior to mining. When the shearer passes, an additional Unsupported roof is expected in front of the shield canopy causing the leg pressure to increase slightly, but rapidly; When the adjacent shields are released in sequence for advancement toward the shield of interest after the shearer passes), the leg pressure continues to rise until the immediately adjacent shield is released for advancement, which causes a sharp and sudden rise in the leg pressure. A normal mining cycle lasts 30 to 60miutes. The pressure change within the mining cycle varies from cycle to cycle (Peng, 1998).
Longwall shields provide essential ground control in longwall mining, yet a high percentage of shields are operating at less than peak capacity and many well below the rated support capacity, due to defective cylinders or malfunctions in other hydraulic components. Leg pressure data are currently collected on state-of-the-art longwall shields, but typically are not analyzed to evaluate shield performance. Many hydraulic problems go undetected since the leaks are internal and there are no visible signs of fluid loss associated with these events. Shields play a vital role in achieving successful, safe and productive longwall mining. Although shield design has improved considerably through the years, hydraulic leakages and other problems that degrade the support performance are still prevalent, particularly on the aging supports that have been in service for several years (Barczak & Conover, 2002).
To augment the coal production from deep underground mines in India, adoption of longwall technology is a must. The coal industry has already taken steps in this direction.