Encountering induced horizontal stress during simultaneous depillaring of thick and contiguous section below hilly terrain : a case study

After successful simultaneous depillaring of most of the panels of thick and contiguous sections of the Zero seam at Bartunga hill mine of Chirimiri Area, SECL under fast change in cover below hill cap, last few panels of the mine encountered strata control problems. Underground instrumentation and observations showed that the last phase depillaring of the property near free surface of the hill slope becomes challenging due to shearing of overlying strata along weak and incompetent layers. A simple study on simulated model also supported occurrence of th problem due to poor confinement of the rock mass. The shearing resulted high value of horizontal mining induced stress, which caused failure of the roof strata. Field and laboratory studies were conducted to identify the main horizons of lateral movement and, accordingly, a management plan for the induced horizontal stress was successfully executed in both, top and bottom sections of the seam, to overcome the strata control problem of the depillaring. The efficacy of the adopted strata management plan was visualized through field instrumentation