石碌铁矿北一采区露天转地下开采沉陷机理研究

Study on the Subsidence Mechanism of Open-Pit Underground Mining in the Beiyi Mining Area of Shilu Iron Mine

露天转地下开采过程伴随着强烈的岩体移动及变形特征,引发开采沉陷问题,是露天转地下矿山安全管理方面的重点研究内容。以海南石碌铁矿北一采区为研究对象,采用FLAC3D数值模拟方法,建立考虑开采扰动的露天转地下力学分析模型,分析不同开采阶段下采区围岩、边坡岩体及地表岩层的位移、应力分布特征,根据塑性区变化特征和现场地表塌陷现象,揭示露天转地下开采沉陷机理。研究表明:边坡岩体中最大拉应力区主要集中在采场回采区与坡顶区域,并随着开采深度增加持续扩展,这将降低岩体稳定性。开采扰动下北帮、西帮处的边坡整体位移值相对较小,南帮东部、东帮至小英山区域岩体位移值随着开采深度增加而显著增大,尤其在开采-90 m至-105 m时,位移值急剧增加。塑性区主要出现在回采区围岩和东帮上方坡面及其部分坡顶后方区域。回采区围岩的塌陷进一步引起了崩落区和变形区岩体位移,沿塑性区边缘形成采坑裂缝,小英山后方区域拉伸破坏进而形成地表拉伸型裂缝,坡脚沉陷及岩体裂隙发育造成东帮边坡滑坡。整体上看,露天转地下工况下开采沉陷表现出强烈的向坡体临空面方向的水平位移特征。

The process of open-pit to underground mining is accompanied by strong rock movement and deformation characteristics,which triggers mining subsidence problems.It is a key research element in the safety management of open-pit to underground mines.Based on FLAC3D numerical simulation method,a mechanical analysis model considering mining disturbance was established in the Beiyi mining area of Shilu Iron Mine in Hainan.The displacement and stress distribution characteristics of surrounding rock,slope rock and surface rock in different mining stages were analyzed.The subsidence mechanism of open-pit to underground mining was revealed according to the change characteristics of the plastic zone and the surface subsidence phenomenon in the field.The results indicated that the maximum tensile stress zone in slope rock mass mainly existed in the stope mining area and slope top area,and continued to expand with the increase of mining depth,which reduced the stability of rock mass.The rock displacement values of the slope at the north and west sides of the open-pit under mining disturbance were relatively small,while the rock displacement values of the eastern part of the south and the east part of Xiaoyingshan area increased significantly with the increase of mining depth.The displacement value increased sharply when the mining depth was from-90 m to-105 m.The plastic zone mainly appeared in the surrounding rock of the mining area,the slope above the east slope and the area behind part of the slope top.The collapse of surrounding rock in the mining area further caused the displacement of rock mass in the caving area and deformation area,and formed mining pit cracks along the edge of the plastic area.Surface tensile cracks were formed by tensile failure in the area behind Xiaoyingshan.The eastern slope landslide was caused by the subsidence of slope toe and the development of rock cracks.On the whole,the mining subsidence under the open-pit to underground working condition exhibits a strong horizontal displacement feature toward the slope prograde direction.