Research On Thermal Environment Characteristics And Heat Control Technology In Ultra-deep Mine

With the development of deep mining in China,the problem of heat stress becomes more and more severely and also seriously limit the normal production in mines.Due to the long distance of ventilating route,large exposed area of roadways and strong effects of the high in-suit ground rock temperature in the deep mines,the airflow temperature is generally very high.In order to effectively control the thermal stress of deep mines,it is necessary to conduct researches of thermal environment characteristics and to study the mechanism of heat control and cooling in deep mines.In this paper,methods including theoretical analysis,physical experiment,numerical simulation and field test are used to finish the tasks,such as prediction of ventilation airflow temperature,temperature field of surrounding rock in deep mine roadways,the heat conduction and exchange characteristics of rock,the preliminary design and evaluation of cooling scheme.A mathematical model for the prediction of airflow temperature along the ventilation route is established,a basis for evaluating the thermal environment of deep mining is provided,a fast trial solution of "hypothesis-correction" is given;The field measurement on the temperature distribution of the surrounding rock in the high temperature roadway is carried out,and the evolution of the range and the temperature distribution of the heat adjusting circle in the roadway is revealed;A series of experiments are desiged to study the influenceial parameters on the distribution characteristics of the heat adjusting circle and their effects are revealed by using simulating experimental device for heat conduction and heat adjusting of roadway surrounding rock.The mathematical model of heat adjusting and energy storage in the roadway surrounding rock is given,which could be used to calculate the theoretical heat(cold)energy storage in the alternation time between winter and summer;A numerical model is also established to simulate the unsteady temperature field of roadway surrounding rock,and the evolution of the temperature field of the surrounding rock under the condition of seasonal air temperature is further discussed;On the basis of the above analyses,the equivalent air conditioning method is used to evaluate the temperature regulation ability of the surrounding rock heat adjusting circle.The main research results are as follows:(1)A mathematical model for prediction of airflow temperature along the roadway in deep mine is established.By studying the characteristics of various heat sources in deep mines,based on the basic heat theory and method,the heat release calculation model of heat sources and heat transfer model of unsteady heat conduction and convection in the surrounding rock of deep mine roadway are summarized and analyzed;A mathematical model for the prediction of airflow temperature in deep mine roadway is established,and the "hypothesis-correction" iterative calculation method is used to derive the solutions with a fast convergence way.The corresponding software program is developed.In the practical application of deep mining in Sanhejian coal mine,the accuracy of the airflow temperature prediction model is verified.(2)The dynamic law of periodic variation of surrounding rock heat adjusting circle in the Sahejian mine is studied in detail,and the evolution characteristics of the physical range and the distribution of temperature field in the roadway are revealed through the measurement of temperature field in mine roadways.Based on the measured data,the following conclusions are obtained: The distribution patterns of five modes of typical roadway surrounding rock heat adjusting circle are summarized;The mechanism of the occurrence and development of the five types of surrounding rock are analyzed and explained by comprehensive consideration of rock physical property,the formation of hot environment and the boundary conditions and so on.According to the analyses of various types of roadway surrounding rock heat adjusting circle,the key thermal physical parameters could decide the different forms,different physical scope,different change regulation and the basic characteristic of roadway that is suitable to be used as high temperature transfer roadway are summed up,which provided a reference for the future engineering design of cooling.(3)A simulation experiment device for the thermal conductivity and heat adjusting of roadway surrounding rock is designed and manufactured based on the similarity theory,and the influence of different thermal physical parameters on the temperature field of the surrounding rock and its dynamic variation are analyzed quantitatively by this device.The experimental results show that: There is a strong correlation between the airflow velocity and the temperature field of the surrounding rock,but the effect of ventilation velocity on the temperature distribution of the surrounding rock is weak;The thermal diffusivity of surrounding rock had an important effect on the stability of the temperature curve of the surrounding rock,but it had little effects on the shape of the curve and the steady state after the stability;Changing water content of the surrounding rock had an important influence on the range of the temperature field,but the duration time of the influence is limited;The roadway with heat resisting circle structure had a great influence on heat adjusting,which is equivalent to the increase of the total thermal resistance of the medium and led to the time of the surrounding rock to reach a new stable equilibrium state increase;The mathematical model of heat adjusting and energy storage in the roadway surrounding rock is put forward.(4)The numerical model of unsteady temperature field of roadway surrounding rock was established,the roadway numerical simulation of temperature field of heat adjusting circle is developed based on the actual situation of Sanhejian mine.The results are as follows: Taking a 3 km length roadway in Sanhejian mine as the research object,associate with the mathematical model of heat transfer and energy storage in surrounding rock heat adjusting circle,the numerical model of airflow temperature and the unsteady temperature field of the surrounding rock are established based on the transient heat conduction theory of finite element method,the finite element method is used to solve the problem,the evolution law of the temperature distribution in the surrounding rock of the roadway under the influence of seasonal airflow is obtained,the results of physical simulation experiments are further verified.At the same time,the cold storage in roadway is estimated.Finally,the economic efficiency of utilization of cooling capacity in heat adjusting circle is analyzed.The technology of self regulating temperature of mine based on heat adjusting circle in roadway is put forward.