Evaluation of safety and deformation characteristics of the secondary stope sandwiched between backfills in underground iron mines

In a large underground iron mine (over 2000, 000 t/a) in China, volume of mined void could not be filled time, which posed threat to the working face. Physical and numerical models were used investigate stability sandwiched between backfills. Digital image correlation (DIC) method was employed physical model calculate deformation field roof Stress meters multi-point borehole extensometers installed observe change vertical stress horizontal displacement real Principal component analysis (PCA) cluster applied classify state around void. The exhibited by contour curves displacement, consistent simulation. indicated that highly deformed zones ellipse-shaped wedge-shaped backfills respectively. process classified into three states (stable state, transition unstable state) using density-based clustering. data obtained from situ monitoring showed increased 60–80 kPa small close Classification (temporary opening) remained stable during production plan.