Performance of composite thermal-insulating concrete for integrated thermal – mechanical performance in deep metal mine tunnels

Abstract

As shallow resources deplete, mining progresses to greater depths, intensifying high-temperature thermal hazards. Deep high-temperature conditions reduce equipment efficiency, pose significant health and safety risks, and exacerbate surrounding rock instability, increasing mine disaster risks. Heat released from surrounding rock is the main source of thermal hazards in deep mines. To control this, this study proposes tunnel wall insulation as an active cooling solution. A multi-component insulating composite, including straw fibers, SiO₂ aerogel, clay ceramsite, and steel fibers, was developed. Through orthogonal experiments, multi-objective optimization was conducted via range and variance analyses and principal component analysis. Small-scale heat conduction tests validated the thermal performance of various mixtures under high temperatures. Results show that straw fibers and SiO₂ aerogel combined adjustment enhances insulation, steel fibers improve tensile strength with minimal thermal impact, and clay ceramsite improves the tensile–compressive ratio. The optimal mix—6% straw fiber, 3% SiO₂ aerogel, 10% clay ceramsite, and 0.9% steel fiber—achieves a compressive strength of 43.07 MPa, tensile strength of 5.43 MPa, and thermal conductivity of 0.1998 W/m · K. This study offers an effective solution for integrated insulation and support materials in tunnels under deep, high-temperature, high-stress conditions.

Keywords

thermal-insulating concrete / tunnel support / SiO₂ aerogel / straw fiber / principal component analysis

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