Parameterization of a ventilation network model for the analysis of mine working emergency ventilation modes

Digital simulation of mine fires and explosions is an important stage in the process of developing technical solutions and measures aimed at improving the safety of personnel involved in underground mining. Correct simulation results determine the effectiveness of decisions in the event of an actual emergency situation. In this regard, due attention should be paid to each stage of the simulation, and especially to the initial stage of model parameterization. This study formulates a general principle for determining the parameters of mine fire and explosion models, in order to assess their development using the AeroNetwork analytical package. Such parameters in the event of a fire are heat and gas (afterdamp) releases. In the event of an explosion, excessive pressure at the shock front in the explosion origin. It has been established that when simulating a fire, it is advisable to use equivalent heat and gas releases determined by the content of combustible components in the combustion origin. In the event of burning mining equipment, these parameters can be calculated on the basis of the technical characteristics of a machine. Furthermore, when simulating an unauthorized explosion of explosives, the excess pressure determined by the dimensionless length of the active combustion area is calculated taking into account the weight and specific heat of an explosive, as well as the geometric parameters of a mine working. When simulating an explosion of a methane-air mixture (firedamp), the excess pressure is calculated taking into account the gas content of rocks in terms of free combustible gases, the length of a blast cut, the size of the area of increased fracturing, and the lower explosive limit of methane. Based on the proposed principle of the parameterization of emergency models, as an example, a model of fire and explosion development in existing extended dead-end workings (more than 1000 m long) passing coaxially to each other at different heights was developed. The numerical simulation of different emergency situations in workings was carried out, taking into account performing mining in difficult mining conditions

Method for solvig inverse Stefan problem to control ice wall state during shaft excavation

Mathematical statement of direct and inverse problem of Stefan for horizontal layer of rock massif with homogenous and isotropic thermophysical properties is presented. It is assumed as a hypothesis that heat transfer in vertical direction is negligible compared to heat exchange in horizontal plane. At the initial moment, the rock massif has a uniform temperature and the temperature on surfaces of freezing columns was the same for all columns and constant in time. A method proposed allows getting an approximate solution of the direct Stefan problem for a single freezing column with a small consumption of computational resources. Based on a proposed method, a high-speed algorithm for solving inverse Stefan problem for the case of a single freezing column is built. An algorithm is based on the gradient descent method. The effect on the solution of different types of functions used is analyzed. Functions approximate the temperature field in a cooling zone. It is established that time dependence of the radius of a phase transition front essentially depends on the type of an approximation function. The most preferable is an integral exponential function that is a solution to the one-dimensional heat equation in cylindrical coordinates. Then, proposed technique and algorithm are considered for the case of variety of freezing columns that form circle counter and random number of control wells. Results of the calculation of inverse Stefan problem for conditions of the shaft No. 1 of the mine being under construction at the Petrikovsky ore mining and processing enterprise are presented. The calculation included well inclinometry based on geological data. It was studied how measurements of the temperature made at different wells can affect obtaining solution. Options of interpretation of inconsistency of temperatures measured in control wells are offered. Probabilistic analysis of ice wall thickness is carried out

Features of the thermal regime formation in the downcast shafts in the cold period of the year

In the cold period of the year, to ensure the required thermal regime in underground mine workings, the air supplied to the mine is heated using air handling systems. In future, the thermodynamic state of the prepared air flow when it is lowered along the mine shaft changes due to the influence of a number of factors. At the same time, the processes of heat and mass exchange between the incoming air and its environment are of particular interest. These processes directly depend on the initial parameters of the heated air, the downcast shaft depth and the presence of water flows into the mine shaft. Based on the obtained experimental data and theoretical studies, the analysis of the influence of various heat and mass transfer factors on the formation of microclimatic parameters of air in the downcast shafts of the Norilsk industrial district mines is carried out. It is shown that in the presence of external water flows from the flooded rocks behind the shaft lining, the microclimatic parameters of the air in the shaft are determined by the heat transfer from the incoming air flow to the underground water flowing down the downcast shaft lining. The research results made it possible to describe and explain the effect of lowering the air temperature entering the underground workings of deep mine