Development and application of analogue testing system for floor confined water rise in coal mining

In order to deeply analyze the law of confined water conductivity and directly display the formation process of water inrush channels in coal seam floor,a simulation test system of confined water conductivity is developed based on the existing two-dimensional simulation test-bed of analogue materials. The system is composed of a two-dimensional simulation test-bed ( improved),a loading system of confined water,a system of confined water conductivity and a computer monitoring system. It has been applied into the laying, excavation and monitoring of the 1 900 mm× 220 mm×1 800 mm model. The test results show that the system combines flexible water sacs,water conductivity veins and water inrush nozzles as a whole,which avoids the phenomenon of unbalanced floor loading pressure in general models and solves the difficult sealing problem between the water tank and the model; under the condition of 0． 03 MPa water pressure,the height of confined water conductivity keeps on rising with the increase of working face distance and in the central gob the water yield is the largest and the height of the conductivity is the highest;the confined water bursts along the shortest route of the least resistance,and the formation process of water inrush channel is sudden and fast;the stress values show a changing trend of “negative-positive-negative” because of the compression- shear effect of the floor strata affected by mining pressure and confined water pressure.