Research To Miao Gou Iron Mine Slope Instability During Turning Open Pit Into Underground Mining

With the development of stirp mining, there has been a dramatic decrease in shallow resource. If we continue strip mining, there will be some difficulty in money and mining technology, consequently,a transformation is urgently needed from strip mining to undergroup mining. But during this transformation, the stability of open pit slope is so extremely complicated that it is critical to the successful transformation and the production safety of the entire mine, therefore, the research is significantly meaningful.We carry out field investigation, investigate and analyse the engineering geological conditions of Miaogou iron ore to determine the fundamental physical parameters of rock mass. Based on the prior geological investigetion and the rock quality evaluation, and in accordance with the principle of simulitude, we conduct the similar physical experiment to explicitly simulate and analyse the changes of open pit slope during the transformation from strip mining to underground mining. By means of PLAXIS simulation software, we make a comparative research of numerical simulation, analyse the stability of the open pit slope, and authenticate with the similar physical model experiment.Experimental study by physical similar model, discoving that underground mining make the slope rock lose their supporting of original ore body, stress balance is broken and stress occurs continuously adjusting. In the adjustment process, when the stress exceeds its carrying limit, then appear ingdamage microfissure. As the underground mining, the micro-cracks expand continue and developing deep and the upper slope, when mining to a depth, the rock slope can not continue to bear the impact of mine and gravity, making the micro cracks rapid expansion, making the rock slope appear destruction. Due to the impact of faults F2 in east, fissures and the extent of damage produced substantially along the fault F2, and the fault prevented the crack develop possible to up and deep.Through the analysis of PLAXIS software, we discover that during the process of underground mining, the main damage occur in the west slope, mainly including tensile failure in the surface of slope, shear failure in the goaf and shear failureinthe inner part of slope rock. As we mine deeper and deeper, the scattered shear failure develop and expand, and it results in the slope failure; The damage in the east side appear mainly along the F2 fault, and the fault prevent the damage of rock in the upper and deep part of slope.