| According to exploration data, there are geothermal abnormal phenomena in eastern Huainan coalmine, and the heat problem is relatively serious. Taking Pansan mine in Huainan coalfield as the research object, through laboratory experiments, theoretical analysis, numerical simulation and other methods, this paper systematically analyzed the influence of groundwater movement on temperature field, and tried to provide a reference for coal mine heat damage control. Firstly, the geothermal distribution of regional and mine was systematically analyzed. Secondly, water chemical characteristics of aquifers in this minefield were studied. Then, this paper established mathematical models of horizontal movement and vertical migration of groundwater, and derived their analytical solutions. Base on the equations about convection and heat transfer, the influences of groundwater plane flow and vertical migration in mine geothermal field were analyzed. Finally, according to the geological and hydrogeological conditions of the study area, with the aid of FLAC software, the numerical simulation analysis of the temperature response characteristics of the floor water invasion under the mining condition was carried out. Through the above researches, this paper drew the following main conclusions:(l)In Pansan mine, the mean geothermal gradient was 3.08 ℃/hm, the earth thermal current value was 73.14mW/m2, and most areas belonged to geothermal positive anomalies. And the vertical geothermal distribution was dominated by thermal conduction, parts of area existed convection heat transfer phenomena.(2)The main water chemistry type of study area was Cl-Na+K type, and main recharge source was atmospheric precipitation. The mine was in a closed and semi closed hydrogeological environment, and the corrosion rate of water from limestone aquifers was small. In the abnormal geothermal area, water salinity and concentration of Ca2+, Na+, SO42- and Cl- had a certain positive correlation with temperature.(3)This paper established a mathematical model for the horizontal transport in a temperature field of porous media, and analyszed thermal effect of groundwater migration in Huainan mining area base on the analytical solution of the equation. The results showed that the influence of horizontal movement of groundwater on geothermal field was relatively obvious. In the process of groundwater flowing from the western part to the eastern part of the mine area, the water continued to absorb heat from rocks, and its temperature was gradually increased.(4)This paper established vertical temperature distribution equations of surrounding rocks on the slow vertical seepage in large area and fast vertical flow within faults. According to the situation of slow vertical seepage in large area, this paper established mathematical models composed of n-1 layers of conduction type temperature fields and 1 layer of conduction-convection type temperature field, and derived the analytical solutions.And the sections affected obviously by the vertical migration of groundwater were given, which were in the vicinity of 14-west 9 hole and 13-14E-1 hole.(5)The heat conduction could be neglected when the fluid was in a rapid vertical flow, the heat transfer equation was derived, and the analytical solution was given. Taking the pumping borehole of limestone as examples, the thermal storage temperature of limestone was calculated according to the measured water temperature.(6)In the numerical simulation of group A mining water inrush on temperature response, with the enlargement of the range of goaf, in the left and right ends appeared stress concentrated. And the roof and floor of goaf was the stress release. Before water inrush, the water pressure distribution was basically not affected by mining. And heat transfer in surrounding rock near the working face was dominated by heat conduction. When water inrush accident happened, the permeability coefficient ratio of top and bottom rock destruction belt reached 50; the bottom hot water inrushed into working surface along the mining fracture, and the temperature of the working face increased from 20 centigrade to 50 centigrade.(7)From the numerical simulation results, it was known that when the bottom hot water inrushed into working surface along the mining fracture, the floor rock mass appeared abnormal phenomenon of temperature rise. So monitoring the temperature of floor rock mass in the process of coal mining was feasible to water inrush prediction. |
