爆破振动对不同埋深采空区稳定性影响研究

摘要

采空区在爆破振动荷载作用下极易发生坍塌事故,研究爆破振动对不同埋深采空区稳定性的影响规律对确保采空区安全具有重要意义.结合工程实际,采用有限元软件ANSYS/LS-DYNA分别建立了10 m、15 m和20 m不同埋深的采空区爆破数值模型,模拟分析了采空区在爆破荷载作用下的动态响应规律.分析结果表明:当采空区埋深为10 m时,其顶板的水平方向振速为23.41 cm/s,大于采空区中部及底板位置的振速,主要原因是爆破地震波在采空区顶板处发生反射和折射,使其振速发生叠加放大,随着采空区埋深的增加,其顶板的水平方向振速由23.41减小至16.94 cm/s,呈现出明显的衰减作用;爆破振动作用下采空区的顶板位置出现了拉应力集中现象,导致其应力远大于采空区其他位置,且当采空区埋深为10 m时,其顶板处的有效应力达到1.1 MPa,超过了岩体的极限抗拉强度,随着采空区埋深的增加,其顶板处单元的有效应力由1.1 MPa减小至0.25 MPa,呈现出明显的下降趋势.%A certain open-pit mine in Guizhou exist large scope of interpenetration mined-out areas,In order to ensure the stability of the mined-out areas,this paper has studied the influence of blasting vibration on the stability of different depths of mined-out areas. Combined with a certain open-pit mine blasting engineering in Guizhou,the finite element software ANSYS/LS-DYNA was used to establish 10 m,15 m,20 m different depths of mined-out areas blas-ting numerical model to discuss the changes of velocity and stress. The results showed that the velocity of roof of the mined-out areas is 23. 41 cm/s,which is greater than the middle(21. 18 cm/s)and bottom(16. 57 cm/s)position of the mined-out area,when the burial depth of the mined-out area is 10 m. It states that reflection and refraction of blasting seismic wave will take place in the roof of mined-out area,which leads to the superposition of amplification of vibrating velocity. With the increase of burial depth of the mined-out area,the vibrating velocity decrease from 23. 41 cm/s to 16. 94 cm/s,which show the obvious attenuation effect. Due to tensile stress concentration phenomenon oc-curring in the middle roof of the mined-out area,the stress of the roof of mined-out area is greater than other location of mined-out area under the influence of blasting vibration. The effective stress of the roof is 1. 1 MPa when the burial depth of the mined-out area is 10 m,exceed the ultimate tensile strength of rock mass. With the increase of depth of mined-out area,the effective stress of unit is of the significant decline,which decrease from 1. 1 MPa to 0. 25 MPa.