Infrared radiation characteristics and statistical damage model for failure of water-bearing sandstone

The presence of water significantly decreases the strength of sandstone. This highlights the need for accurate and effective monitoring and prediction of the instability and failure of water-bearing rock formations. In this work, sandstones with different water contents were subjected to infrared radiation (IR) under uniaxial loading. The mechanical and IR characteristics during the failure process of dry and water-bearing sandstones were examined. The results show a negative correlation between the uniaxial compressive strength, elastic modulus, and water content of the rock. The innovative introduction of a new index, the Jaccard distance (d_J), as a pre-warning indicator for rock instability failure. The rate of increase in d_J for water-bearing rock is significantly greater than that for dry rock during the compaction stage. Rocks with various water contents exhibited a brief steady stage in d_J before a sudden increase prior to reaching the peak stress, corresponding to the complete failure of the rock. In terms of fracture patterns, dry rock primarily exhibited tensile failure, whereas the failure mode of water-bearing rock shifted to combined tensile-shear composite failure. Furthermore, a segmented constitutive model based on IR for rock uniaxial loading was established, incorporating modifications for water content. This model enables the calculation of stress variations through monitoring the infrared temperature field. The resulting model shows a high degree of agreement with the experimental results, significantly outperforming the unmodified model. These findings provide a valuable reference for IR-based monitoring of the engineering stability of water-bearing rock masses.