Research on New Solid Waste Heat Insulation Material for Deep Mining

Abstract

The global demand for mineral resources has led to the gradual transformation of the mining industry from the traditional shallow, small-scale mining mode to the high-intensity mining of deep underground mines. Due to the high stress, high temperature, high permeability, and easy disturbance of deep mines, new challenges have been brought to the mining of materials. Some scholars have improved the thermal insulation performance of concrete by adding low thermal conductivity materials such as ceramsite, shell, and natural fiber to traditional shotcrete, but there are still high costs, insufficient support strength, and unsatisfactory thermal insulation effects. Given the background related to the fact that it is still not possible to fully recycle the large amount of solid waste generated by mining activities, this paper, with traditional shotcrete as its basis, uses coal fly ash to replace part of the cement and tailings to replace part of the sand and gravel aggregate. In addition, it adds basalt fiber to reduce thermal conductivity and restore strength. An orthogonal experiment of three factors and three levels was designed to explore a new type of solid waste-based thermal insulation support shotcrete material. Through the testing and analysis of the mechanical and thermal properties of the specimens, it was concluded that the optimal ratio of the materials was 45% fly ash, 50% tailings, and 25% basalt fiber (the percentage of the total mass of fly ash and cement). The compressive strength of the specimens after curing for 28 days could reach 16.26 MPa, and the thermal conductivity and apparent density were 0.228561 W/(m·k) and 1544.00 kg/m3, respectively. By using COMSOL Multiphysics multi-physics coupling software to analyze the coupling of the stress field and temperature field, it was concluded that the optimum thickness of the thermal insulation layer of this material was 150 mm. The field application in a mine in Shandong Province proved that it met the effects of thermal insulation (the ability to isolate heat conduction) and support. The successful trial of this material provides a new idea for the solving of the problem of heat damage and solid waste utilization in deep mines, which has a certain practical significance.