Energy evolution and water immersion-induced weakening in sandstone roof of coal mines

Autor: Wenjie Liu, Ke Yang, Shuai Zhang, Zhainan Zhang, Rijie Xu
Jazyk: angličtina
Rok vydání: 2022
Předmět:
Zdroj: International Journal of Coal Science & Technology, Vol 9, Iss 1, Pp 1-14 (2022)
Druh dokumentu: article
ISSN: 2095-8293
2198-7823
DOI: 10.1007/s40789-022-00529-6
Popis: Abstract The instability of underground spaces in abandoned coal mines with water-immersed rocks is one of the main hazards hindering the geothermal energy use and ecological restoration of post-mining areas. This study conducted graded cyclic loading–unloading tests of five groups of sandstone samples with different water contents. The evolution of input, elastic, dissipated, damping, and plastic energies were explored, considering the damping effect. The normalized plastic energy serves to characterize the damage evolution of sandstone samples, whose failure characteristics were analyzed from both the macroscopic and microscopic perspectives. X-ray diffraction technique and scanning electron microscopy were used to reveal the softening mechanism of sandstone. The results show that under graded cyclic loading, input energy, elastic energy, and dissipated energy all increase gradually, and the fraction of elastic energy increases gradually at first and then tends to stabilize. The variation in the fraction of dissipated energy is opposite to that of elastic energy. In each cycle, the input energy is stored primarily in the form of elastic energy, whereas the dissipated energy is used primarily to overcome the damping of sandstone. When the normalized number of cycles approached unity, the plastic energy fraction sharply increases, while that of the dampening energy drops abruptly. With increasing water content, the effect of pore water on the lubrication, the water wedge, and dissolution of mineral particles becomes more obvious, reducing the elastic-storage limit of sandstone, meanwhile the sandstone damage factor increases significantly under the same cycle and the failure mode changes from brittle to ductile.
Databáze: Directory of Open Access Journals
Externí odkaz: