The groundwater model of pre-mining subsidence predicted an accurate hydraulic heads compared with the observation of water wells during the pre-mining periods.
However, the post-subsidence
groundwater models predicted much different water tables from
observations in wells W1S, W2S and W1D.
The longwall face in panel B6 passed through the water wells on
11 September 2008. The water in wells W2S, W2I and W2D was
totally lost after the longwall face passed. Thewater table recovered
to 1090 ft on 10 February 2009. The water table in well W3I
declined slightly and substantially restored to 1110 ft.
There existed an aquifer layer or a low-permeability layer to
prevent the water level in intermediate well from dropping below
the underlying aquifers. The post-mining water level in well W2I
was higher than the pre-mining one. This phenomenon indicated
that the effective porosity and storativity were increased, enlarging
the vertical connection between the surface aquifers and intermediate
well. Surface water recharged the underlying aquifers.
The wells W3D and W4D were located in the panel B5, and they
were apparently affected by longwall subsidence in panels B5 and
B6. After the panel B6 was mined, the fracture zone above the panel
B5 developed higher than that above the panel B6. So the water in
both deep wellswas totally lost and never recharged afterward. It is
better to find away to control the development of fracture zone and
protect the groundwater resource, just like increasing the velocity
of face advance.
The groundwater model of pre-mining subsidence predicted an accurate hydraulic heads compared with the observation of water wells during the pre-mining periods. However, the post-subsidencegroundwater models predicted much different water tables fromobservations in wells W1S, W2S and W1D.The longwall face in panel B6 passed through the water wells on11 September 2008. The water in wells W2S, W2I and W2D wastotally lost after the longwall face passed. Thewater table recoveredto 1090 ft on 10 February 2009. The water table in well W3Ideclined slightly and substantially restored to 1110 ft.There existed an aquifer layer or a low-permeability layer toprevent the water level in intermediate well from dropping belowthe underlying aquifers. The post-mining water level in well W2Iwas higher than the pre-mining one. This phenomenon indicatedthat the effective porosity and storativity were increased, enlargingthe vertical connection between the surface aquifers and intermediatewell. Surface water recharged the underlying aquifers.The wells W3D and W4D were located in the panel B5, and theywere apparently affected by longwall subsidence in panels B5 andB6. After the panel B6 was mined, the fracture zone above the panelB5 developed higher than that above the panel B6. So the water inboth deep wellswas totally lost and never recharged afterward. It isbetter to find away to control the development of fracture zone andprotect the groundwater resource, just like increasing the velocity
of face advance.
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