A Study Of Stability Of Underground Mining In Complex Conditions

The present paper, taking a typical mine-Jinshandian Iron Mine of Wuhan Steel and Iron Company as background engineering, adopts such methods as engineering geological analysis, field and lab tests, comprehensive in-situ cubic observation, theoretical and numerical analyses and analogue of projects etc to make studies of the stability of underground mining in complex conditions and discusses the research method and the correlated theoretical aspects for the stability problem of this kind. The major results are as follows:1. Makes clear the deformation failure mechanism of silt mining galleries. The primary roof collapse in construction and big gap between surrounding rocks and supports result in relaxation and failure of rocks surrounding gallery top and the falling blocks press on the arch crown to transfer loads to the surrounding rocks of the side wall, thus the pressure makes the wall rupture; with the advance of mining activities, this process takes place repeatedly, which leads to the extremely high roof collapse of the upward rocks and unceasing squeezing on the side wall; under the action of roof collapse and squeezing, the relaxation and final stability failure of galleries take place.2. Discusses the effects of supporting pattern and structure size on the stability of silt mining galleries. The stability can be improved greatly using the following method: change the straight wall into the curvature one, increase the wall thickness and improve steel reinforcement. The results have shown that bolts have no remarkable reinforcing effects on the rocks surrounding the galleries top but have an effect to a certent exten if reasonable parameters of bolts are selected.3. Puts forward measures to increase the galleries stability. For the structure of silty clay and mixed silt blocks, the supporting in advance such as pipe-shed and small-diameter-injection-tube can avoid too large primary roof collapse but for the clastic-like structure, the methods are suitable of changing blasting parameters to reduce disturbance and timely primary supporting of shotcrete; the initial voids that are produced between supports and surrounding rocks can be filled with concrete or mortar.4. In allusion to the roof-collapse failure character of the gallery surrounded by loosened rocks, establishes an earth-pressure theory and correlated formulation using the principle of limit equilibrium method. The theory is rigorous in theory and simple in form, compared with the traditional theory, it can more reasonably describe the effects of lithological character, superincumbent depth, gallery dimension and lateral pressure on the deformation failure of galleries. In...