Study On The Magma Intrusion Thermal Effect On Temperature Field Of Coalmine

China is a big country with a huge of coal resources. But along with the constant extension of the mining depth, the heat hazard in mine is increasingly outstanding and the safty mining is seriously affected. Huainan area of Anhui is the high temperature abnormality area, especially the Pansan coal mine whose character is deep embed coal seam, high ground temperature, high ground pressure and great heat hazard area. Along with the constant extension of the mining depth, the temperature of virgin rock is increased uninterrupted and the high temperature heat-harm of extracting coal face is increasingly serious. The safety production in mine is seriously threatened.We know that the earth temperature distribution law in coal mine was affected by many factors including the faults, fold, groundwater activity, thickness of losses bed, magma intrusion and so on. But the influence of the magma intrusion on the temperature fields was little. So based on the analysis and research on the characteristics ground temperature distributionand geothermal anomaly, the distribution law, invasion form, invasion age, lithology and chemical composition of the magmatic rock in Pansan coal mine, this paper studied the magma intrusion and its thermal effect on the temperature field in surrounding rock using the theoretical analysis and ANSYS numerical simulation.Throughout the study, the main conclusions are made as follows:(1)The depth of constant temperature zone in Pansan was31.13m. The geothermal gradient was higher than3.0℃/hm in most region and it was belongs to normal geothermal anomaly.The temperature distribution was much higher. The temperature increased gradually with increasing depth from the northeast to the southwestward in Pansan coal. The depth of the First ordert hermal damage and order thermal damage were530m and850m respectively. The geothermal disaster was relatively serious.(2)Intrusions are widespread in Pansan coal mine. The highest level which deteriorated by the magma corroding was the8coal and the magmatic intrusion range was gradually bigger from top to bottom. The age of magma intrusion was118Ma, to the third intrusion of Yanshanian. It made intrusion in coal measure strata along seam and fault fracture zone which main were sill. Its lithology was masanaga lamprophyre, syenite porphyry and so on. (3)The result of theoretical analysis and numerical analysis show that it would lead to the utmost imbalance of heat after the invasion of magmatic hydrothermal solution of high temperature and the heat transfer of intrusive mass from center to circumambience would cause the temperature increasing of surrounding rock and the formation of temperature fields.The temperature of the part which was in direct contact with intrusive mass would be higher than others and the temperature would decrease gradually with increasing distance from the intrusive mass. It would form a temperature field which taking the intrusive mass as center.At the prophase of magma intrusion, the temperature decreasefd gradually, but the rate was lower later. After100thousand years, the temperature of surrounding rock recovered to its primal temperature and the influence from magmatic intrusions with high temperature would disappere. In addition, the influence on the temperature fields of surrounding rock was controlled by many factors, such as the magma intrusion’ initial temperature,shape,thickness,the duration after intrusion,the thickness of unconsolidated layers and so on.But synthesizing the above researches indicated:the factors only affected the temperature fields after magma intrusion in a short time and it would disappear by enough time.(4)Through the analysis according to the actual boring data, we can get that the area of Geothermal Anomaly was inconsistent with the area of magma intrusion in Pansan coal mine. At the same time, the result of theoretical analysis and numerical analysis showed that, from a long span of geological time, the magma intrusion’s influence on present-day geothermal field in the coal mine would disappear. But also,the test results of the U,Th,40K and thermal conductivity of magmatic rock in the study area show that it’s low and the value of conductivity is3.0W/(m.K) which are close to surrounding rock. So the radioactive thermal of magmatic rock and the change to thermal conductivity of surrounding rock have no influence on the temperature field of the surrounding rock. In view of the effect of three researches and the age of the magma intrusion, we can get that magma intrusion formed in late Yanshanian period has no effects on the distribution of present-day geothermal field in Pansan coal mine.