Physical and mechanical properties of thermal insulation materials for in-situ temperature-preserved coring of deep rocks

High temperature affects deep coal mining and other engineering activities. However, conventional coring methods for terrestrial hard rocks lack temperature-preserved measures, ignoring the effects of temperature on the physical and mechanical properties of rocks. Consequently, the parameters obtained are subjected to distortion, affecting the safe and efficient mining of resources such as deep coals. To make breakthroughs in the development of in-situ temperature-preserved coring technologies for deep rocks, this study proposed using the hollow glass microsphere/epoxy resin (HGM/EP) as thermal insulation materials and the physical and mechanical properties. The results are as follows: (1) With an increase in the HGM content, the thermal conductivity of the thermal insulation materials showed a significant downward trend, and the mechanical properties of the materials weakened. (2) The increase in the content of HGM with different strengths led to changes in the load-bearing objects. As a result, inflection points occurred at different volume fractions when mechanical properties decreased. (3) There is a contradiction between the thermal conductivity and strength, which compete with each other as the HGM content increases. To quantitatively evaluate the performance of thermal insulation materials, this study defined the strength-to-thermal conductivity ratio, discovering that thermal insulation materials with 30%, 40%, and 50% volume fractions of S60HS HGM had comprehensive strength-to-thermal conductivity ratios of 1.796, 1.719 and 1.737, respectively. These materials, outperforming similar materials, were preliminarily determined as thermal insulation materials for deep rock coring. The test results of this study make it possible to achieve in-situ temperature-preserved coring of deep rocks, further supporting the mining of resources such as deep coals.