Mechanism of dynamic mine pressure occurring below adjacent upper chamber mining goaf with shallow cover depth

The underground catastrophic incidents,such as dynamic mine pressure and support failure,are prone to oc- cur when longwall faces are mined below the upper chamber mining goaf in shallow cover coal seams. Based on a typi- cal case of dynamic mine pressure occurring below the chamber mining goaf in longwall 31201 of Shigetai Mine,the mechanism of this type of dynamic mine pressure has been investigated through field observation,theoretical analysis, experimental and numerical simulations. It is showed that the chamber coal pillar is prone to fail than the concentrated coal pillar;under the influence of mining abutment pressure,the sudden and large-scale failure of chamber coal pillar will break the key strata. The reverse rotation of key blocks transmits the considerable strata load to the lower rock strata structure,resulting in the sliding down of key blocks,which is the primary culprit of the strong dynamic mine pressure occurring in longwall face. Aiming at the similar potential conditions where the dynamic mine pressure is easi- ly to occur,several targeted measures have been proposed from the perspectives of preventing or transferring the upper rock strata load. The effectiveness and practicality of the proposed measures have been demonstrated by their application in longwall 31201.