VULNERABILITY OF UNDERGROUND COAL MINE LIFE DUE TO DUPITILA AQUIFER WATER SYSTEM IN BARAPUKURIA, BANGLADESH

Barapukuria is the first and only coal mine in Bangladesh. This work deals with the groundwater monitoring and mine subsidence with its practical applications to recognize the mining related geo-environmental hazards associated with the Gondwana Barapukuria Coal Basin of northwest Bangladesh. It is apparent from the fracture heights that large amounts of caving have been occurred towards the roof due to the multi-slice extraction of coal, and finally it is apprehensiveh that it may be linked with the water-bearing DupiTila Formation. If this may happen, it would ultimately cause a major water inflow hazard in the mine. The study also reveals that the hydraulic gradient and the general direction of groundwater flow are almost at right angles with the trends of faults Fb and Fb1, which could act as barriers to groundwater flow into the mines.

It was observed that the water inflow rate increased simultaneously with the mining within the mining tunnels in Barapukuria. The water inflow rate in August 1998 was about 620 m3/hr when the underground mine tunnel length was about 1200 m. In November 2004, it increased up to about 1300 m3/hr, while the developed tunnel length was about 19,000 m At present, the total inflow rate is about 1750 m3/hr (ref: Monthly Progress Report, Barapukuria Coal Mining Co. Ltd, December 2010). Initially water inrushes were predicted to be 500 m3/hr inside the mine. But over the time with high production rate of coal, caving propagated the fracture to the direct roof and indirect roofs and which may be reached up to lower Dupi Tila and upper Dupi Tila formations which have caused of the water inrush volume almost tripled.

From the analysis of data we conclude that the whole mine subsidence zone is divided into three types: a) fractured zone (Gondwana formation) b) Aquiclude zone (lower Dupi Tila formation) and c) Surface zone (upper Dupi Tila formation). On the continuation of this work, we want to describe how this fractured rock and permeable DupiTila rock formation allow the contaminated mine water in the aquifer system. It will be the study to understand how the mine wash water can contaminate local aquifer system.