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

The room-pillar mining technology of underground gypsum resources results in numerous gypsum rock pillars for controlling and supporting mined gobs, which forms a large area of roof hanging gobs. Owing to weathering and mining activities, gypsum rock pillar damage and failure will occur, thereby inducing a large area of gypsum mined-gob collapse accidents and disasters. Blasting is vital to the stability of gypsum rock pillars and is indispensable in mining engineering. Based on field blasting tests and using wave velocity as the basic parameter to characterise the integrity of gypsum rock, the damage mechanism of gypsum rock pillars subjected to blasting disturbance is investigated. With ten blasting tests, the maximum damage rate is 7.82% along the horizontal direction of pillar, and 3.52% along the vertical direction. The FLAC numerical simulation calculation software is used to analyse the stress distribution law of gypsum rock pillars with disturbances of different strengths from different distances. As the disturbance strength increased, the stress increased with no clear linear relationship; as the disturbance distance increased, the stress decreased gradually with a linear relationship. All stress after disturbance is greater than the original static stress, and lower than the ultimate compressive strength. However, the correlation between blasting tests results and numerical simulation results is poor and is discussed for many factors. The results can provide important guidance and reference for clarifying the damage mechanism of gypsum rock pillars subjected to blasting disturbance, as well as reveal the collapse mechanism of gypsum mined gobs.