Experimental study on evolution of pore structure of inclined layered cemented tailings backfill based on X-ray CT

In underground backfill mining, the stope usually needs to be filled several times, the cured backfill contains several inclined layered surfaces inside, which leads to the reduction of the overall stability of the backfill due to the existence of layered contact surfaces(LCS). In order to study the influence of inclined layered contact surface on the stability of backfill and its internal macroscopic and microscopic structure evolution law under loading conditions, the specimens of backfill with no layer, two layers, three layers and layered angle of 5° were prepared. Uniaxial compression tests of specimens with the different number of layers and CT real-time scanning tests of three-layered specimen were carried out to quantitatively analyze the porosity and density of layered cemented tailings backfill(LCTB) during compression by the gray value of CT scanning images and other parameters. The results showed that the load-bearing capacity of LCTB decreases with the appearance of the LCS; the higher the number of layers, the lower the uniaxial compressive strength, and all kind of LCTB specimens manifested as tensile failure. Before the compression reaches 70% of the peak stress, the pore and density changes mainly occur at the LCS and middle layer of LCTB, and show the same trend. That is, the porosity increases first and then decreases, and the density decreases and then increases.