Temperature response of magnetic susceptibility and pore structure of white Bleached sandstone

Bleached sandstone is prevalent in the coal fire area of northern Shaanxi with abundant coal resources. The frequent occurrence of coal fire roasting has influenced the properties of upper Bleached sandstone. This study selected white Bleached sandstone near the Shenmu fire-burned area as the object. After high-temperature baking of samples, nitrogen adsorption experiments, scanning electron microscopy experiments, and fractal dimension theory were used to analyze the micropore structure and its complexity. Simultaneously, its mass magnetization was analyzed. The experimental results demonstrated that the adsorption and desorption isotherms of rocks exhibited a reverse ‘S’ shape, with the pore structure exhibiting signs of homogenization. At temperatures exceeding 600 °C, the specific surface area of the samples was lower than that of the Protolith. The microstructure variations in the sample were significantly influenced by temperature, with the internal pores of the sample increasing or enlarging with increasing temperatures, eventually leading to an increase in the sample pore volume. The sample quality magnetization was significantly affected by temperature, and the variation in sample magnetization was divided into three stages, with the degree of temperature influence increasing stepwise at each stage. The third stage was most affected by temperature, and the magnetization rapidly increased with temperature. The higher temperature indicated a lower complexity of the pore structure. The research results can support disaster prevention arising from structural instability and collapse in coal mine roofs caused by fracture development in coal mine roofs from burning rock.