Deformation and Damage Law of Coal–Concrete Materials with Additional Moisture

Abstract

The hydrological conditions in deep mines are complex, with coal and concrete structures exposed to prolonged water immersion. This alters their mechanical properties and causes damage, posing a significant threat to mine safety. Therefore, this study conducted uniaxial and triaxial compression tests on coal, concrete materials, and their combinations under water immersion to investigate deformation and damage patterns. The experimental results show that as water immersion time increases, the specimen’s moisture content goes through three stages—rapid growth, slow growth, and stabilization—following a logarithmic relationship with time. Under uniaxial compression, higher moisture content flattens the stress–strain curve during the compression and elastic deformation stages, reduces crack development, and increases plastic and ductile characteristics. Compressive strength negatively linearly correlates with moisture content, whereas the modulus of elasticity has a negative exponential relationship. As moisture content increases, the deterioration of compressive strength and elasticity modulus intensifies, although at a decreasing rate over time. Under triaxial compression at 4 MPa of peripheral pressure, the compaction stage was shorter than under uniaxial compression. The subsequent stages were more clearly characterized and exhibited stress residuals. As peripheral pressure increased, peak stress, peak strain, and postpeak residual stress of saturated specimens notably increased.