Experimental Study on Strength Weakening of Gypsum Rock with Effect of Long-Term Overlying Strata Pressure

A long time lag is the main characteristic of gypsum mined gob collapse disasters. With coring a rock specimen from supporting pillars in gob, which formed over several years, strength weakening effect with long-term overlying strata pressure revealed by experimentation. The results show that: uniaxial compression stress–strain curves represent major differences different lateral depths same pillar. increase depth, peak increases and corresponding strain decreases, becomes more obvious as age increases. As function time, decreases shallow part pillar Peak fluctuates middle deep part; parts, but demonstrates opposite changing law. Finally, reason for above law was comprehensively thoroughly researched demonstrated. maximum rate 0.5 m depth 21.06% year 1996. slow essential why collapses occur subsequent years or even decades.