Study on Tensile Strength and Damage Evolution Law of Sandy Mudstones with Different Sedimentary Ages in Dongsheng Coalfield in China

摘要

Sandy mudstones of various sedimentary ages are deposited in the Dongsheng Coalfield in China. Studying the tensile mechanical properties of these sandy mudstones would provide a reference for underground construction in this area. Four sets of sandy mudstones with different sedimentary ages from Dongsheng Coalfield in China were selected as the research objects. First, the mineral composition and microstructure of the 4 sets of Brazilian disc specimens were obtained by X-ray diffraction and scanning electron microscope. With the increase of sedimentary age, the microstructure of sandy mudstone becomes denser. Then the deformation and acoustic emission (AE) characteristics of the specimens during the Brazilian tests were observed. The indirect tensile strength, peak strain, total strain and pre-peak energy accumulation of sandy mudstones showed an approximate increasing trend with sedimentary age increasing. AE hit rate of the specimens with longer sedimentary age was higher, and the AE signals of these specimens with longer sedimentary age were released more severely after the peak tensile strength. The influence of sedimentary age on the properties of sandy mudstones was discussed from three aspects: the main mineral components, the geostress environment of sandy mudstone, microscopic morphology and granular structure.