Abstract
The insulating concrete can be effectively reduced heat exchange between surrounding rock and ventilation air, which is of positive significance to mine cooling and energy conservation. The law of the mixing amount of insulation material on thermal conductivity and strength was discovered through testing 75 specimens of insulating concrete used for mine. Based on new effective medium theory, calculation model of coefficient of heat conductivity is deduced, and its parameters are acquired with the surface regression analysis method, then the mixing threshold of insulation material is determined. The resulting experimental data and calculational results make up data sample, and then the nomogram of thermal conductivity and strength of insulating concrete is plotted. The nomogram curve can be divided into regions with the main intensity and heat insulation as the auxiliary, the mutual influence region and the main intensity and heat insulation as the auxiliary. The constructed nomogram would not only provide the basis for determining porosity of compound concrete, but also determine thermal conductivity and strength according to porosity. It can simplify calculation step for the engineering and technical staffs, and help to guide design of insulating concrete.
Highlights
Mine high temperature is an irreversible thermodynamic process under the action of complex engineering geological environment
It has been confirmed that thermal conductivity and compressive strength of concrete incorporation with mineral admixtures[4-6].Combined with the basic theories of classical fluid mechanics and heat transfer, the rock-soil mass is simplified as a continuous medium with solid, liquid and gas threephase composition, uniform distribution and isotropy, and the mathematical model of heat transfer are established[7-10]
The nomogram can be used in two ways: (1)If the amount of heat insulation material is known, the porosity of heat insulation concrete can be converted, so that the thermal conductivity and compressive strength range of heat insulation concrete can be directly obtained according to the porosity
Summary
Mine high temperature is an irreversible thermodynamic process under the action of complex engineering geological environment. Factors affecting thermal conductivity are studied such as material structure, damage evolution, water-cement ratio, aggregate, porosity[15-19]. It can be seen that the calculation of thermal conductivity parameters involves many factors and the calculation process is complex, so it is necessary to establish a simple and feasible determination method to meet the needs of the engineering practice. The supporting concrete used in high-temperature mine roadway is different from ordinary insulating concrete, which requires both the strength to meet the needs of the project and the lowest thermal conductivity. This article uses the method of combining the experimental research and model calculation, the change rule of coefficient of thermal conductivity and strength of the insulating concrete are studied under the condition of different heat insulation material and mixing amount. Research results can provide basis for engineering application of heat insulation concrete support technology in high temperature mine
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