Influence of underground mining on surface open-pit in Dahongshan Iron Mine under the action of F₂ fault control barrier effect

In order to guarantee the stability of open-pit, FALC^3D is used to simulate and investigate the influence of stoping the overlain deep orebody in the northern part on the stability of the upper open-pit under F₂ fault barrier effect, and the expansion range of the plastic zone of overlying strata after the excavation of the orebody was deduced.The simulation results and the site survey indicate that F₂ fault exerts obvious barrier effect on the rock mass of both sides, and the surface plasticity disturbance zone in the northern part is still more than 70 meters away from the top of the open-pit mining slope; the collapse displacement in the south of F₂ fault becomes increasingly large, while the subsidence deformation of strata near the open-pit mining slope of the northern part is very small.Up to now, the damage caused by the subsidence and roof falling of the overlying strata due to underground mining has not exceeded the impact of F₂ fault on the open-pit slope.And thus the northern open-pit slope is currently safe and stable, indicating that F₂ fault, to some extent, exerts barrier effect on the ground cracking deformation caused by caving collapse zone and it objectively plays a role in protecting and isolating the upper slope of open-pit.