Exploration on the Development Characteristics of"Three Zones"in Thick Loose Layer Strip Goaf of Coal Mines
Exploration of the development characteristics of the"three zones"of overlying strata in the thick loose layer strip goaf is an important task in the comprehensive management of coal mining subsidence areas in the eastern part of China.In order to determine the development height and residual porosity distribution characteristics of the"three zones"of overlying strata in the goaf,taking the thick loose layer strip mining area of a certain mine in Jining as the background,theoretical research,on-site detection and qualitative analysis were conducted comprehensively using high-density three-dimensional seismic,transient electromagnetic method,geological drilling,coalfield logging,borehole television and calculation formulas.The research results show that in the deep and thick loose layer goaf,when the ratio of mining depth to thickness is greater than 190,the main key layer is not broken,the development characteristics of the"three zones"of the overlying strata are significant,and the bending deformation zone has developed to the surface.Under the action of a large load on a loose layer with a thickness of over 260 m,the roof of the goaf with a mining retention ratio of 1:2(Mining 50 m leaving 100 m)basically collapsed completely.The first weighting step of the old roof is 23 m,and the periodic weighting step is 10 m.Geological exploration shows that there is no large-scale voids in the goaf.The height of the water conducting crack zone is 18.9～77.7 m,with an average of 50.8 m,which is 18.2 times the mining height.The height of the collapse zone is 8.00～9.58 m,with an average of 8.19 m,which is 2.9 times the mining height.The height of the main water conducting cracks in the overlying strata is 40 m.The residual porosity of the caving zone is 15％,the residual porosity in the fractured zone is 2.7％,and the residual porosity in the coal pillar affected by mining is 9％.Based on this,the volume of residual voids in goaf can be quantitatively calculated,in order to provide accurate data for grouting design in goaf.
thick loose layerstrip goafwater conducting fracture zonevoid distribution characteristicsgoaf treatment
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