Effects of Drift Width of Non-pillar Sublevel Caving Method on Stability of Surrounding Rock
Increasing the drift width can improve the ore-drawing effect of non-pillar sublevel caving method,but it also has the risk of reducing the stability of the surrounding rock of drift.The distribution law of surrounding rock stress,the varia-tion of displacement and the distribution characteristics of plastic zone under 5 groups of drift width in the west section of an i-ron mine are analyzed,and the effects of drift width on the stability of surrounding rock is studied on the basis of using numeri-cal analysis methods.The results show that:① The maximum and minimum principal stresses in the surrounding rock are dis-tributed in different forms in the stress concentration area in the roof,the bottom and the side wall of the drifts,and their ranges are also different,and there is a"rounded rectangle"stress concentration area between the two adjacent drifts due to the effect of stress superposition;② With the increase of the drift width and the depth of surrounding rock,the maximum and minimum principal stresses in surrounding rock also increase,and the stress concentration areas vary in different sizes.Among which the stress concentration areas at the roof and bottom floor increase greatly,and the roof surrounding rock of the 5 groups of drifts width is prone to tensile failure;③ When the drift width is at 7 m and 8 m,the side wall surrounding rock of the drifts may have tensile failure due to the change of the minimum principal stress which affected by the superposition of stress in the sur-rounding rock of the adjacent drifts;④ The roof displacement of the drifts present the characteristics of"large in the middle,small on the both sides".The displacement of the roof and its increase rate are much greater than that of the side wall,the in-creasing the drift width is easy to cause the roof collapse accident;⑤ The mixed zone of shear plastic zone and tensile plastic zone is dominant in the surrounding rock of the roof and bottom floor,and the shear plastic zone is dominant in the surrounding rock of the two side walls.The larger the drift width,the faster the growth of the total volume of the plastic zone.The increasing the drift width is not conducive to the stability of the drift roof.It is suggested that the drift width in the west section of the mine should be at 6 m with certain supporting measures.If the drift width is greater than 6 m,appropriate support measures should be taken for the roof surrounding rock.
drift widthsurrounding rockstress distributiondisplacementplastic zone distributionstability
NETL
NSTL
万方数据
