爆破作用下岩溶对边坡稳定性的数值模拟研究

Numerical Simulation of Karst Effect on Slope Stability under Blasting

露天矿山在爆破过程中势必会给边坡稳定性造成影响,特别是边坡处于岩溶发育区时更容易造成边坡失稳,为了研究在爆破作用下岩溶对边坡稳定性的影响,本文依托塘垭石灰岩矿山边坡工程,以该矿山+1014 m平台出露岩溶为研究对象,利用ANSYS/LS-DYNA有限元分析软件进行数值模拟,考虑爆破振动效应影响,得到了围岩的应力分布,重点对比分析了有无溶洞条件下,爆破对边坡应力、爆破振速、边坡岩体损伤以及边坡有效应力产生影响的差异。研究结果表明:在台阶爆破时,由于溶洞的存在,使得台阶出现受力改变,出现多次应力集中现象,但台阶受力产生的应力值仅有7.6 MPa,仍无法达到破坏岩体的程度;不同空间位置的监测点,由于溶洞的存在,振动速度的差值变大,且垂直方向比水平方向的振动速度变化更大,尤其是空间位置靠近边坡坡面的监测点,对这种情况的反应更加明显,边坡坡面的监测点振动速度差值最大约1 cm/s,未超过安全允许振速;在爆破次数不断增加的过程中,岩体内部的损伤也在逐步加剧,且损伤在有溶洞的影响下更为明显,岩溶区半径越大,爆破次数越多,损伤就更为严重;对比前期开展的岩石单轴抗压强度实验得知,尽管溶洞的存在会造成应力值的改变和应力集中现象,但产生的有效应力峰值总体均远低于岩体的单轴抗压强度。针对爆破过程对边坡稳定性造成的影响,提出岩溶区边坡的支护处理措施,可为类似边坡爆破工程提供参考。

The slope stability is bound to be affected in the blasting process of open-pit mine,especially when the slope is in the karst area.In order to study the influence of karst on slope stability under blasting and based on Tangya limestone mine slope project,this paper takes the exposed karst at the 1014 m platform of the mine as the research object,and uses ANSYS/LS-DYNA finite element analysis software to conduct numerical simulation.Considering the effect of blasting vibration,the stress distribution of the surrounding rock is obtained,and the effects of blasting on slope stress,vibration velocity,rock damage and effective stress of slope with or without karst cave are compared.The results show that the force of the bench changes and stress concentration occurs for several times due to the existence of karst caves,but the stress value generated by the bench loads is only 7.6 MPa,which still cannot reach the degree of rock mass destruction.For monitoring points at different spatial locations,the difference of vibration velocity becomes larger due to the existence of karst caves,and the vibration velocity in the vertical direction changes more than that in the horizontal direction.In particular,the spatial locations of the monitoring points near the slope edge are more sensitive to this situation.The vibration velocity difference of the monitoring points on the slope edge is about 1 cm/s at most,which does not exceed the allowable vibration velocity.In the process of increasing blasting times,the damage inside the rock mass is also gradually increasing,and the damage is more obvious under the influence of karst caves.The larger the radius of karst area,the more blasting times,the more serious the damage.Compared with previous uniaxial compressive strength experiments,it is found that although the existence of karst caves will cause the change of stress value and stress concentration phenomenon,the peak effective stress generated is far lower than the uniaxial compressive strength of rock mass.In view of the influence of blasting process on slope stability,the support treatment measures of slope in karst area are put forward.