进路充填法爆破扰动诱发充填体破坏规律研究

Study on the Failure Law of Backfill Induced by Blasting Disturbance During Cut and Fill Mining Process

针对焦家金矿进路充填法爆破扰动诱发充填体破坏严重的问题,基于Mises屈服准则确定充填体破坏阈值,采用LS-DYNA软件对炮孔距充填体距离、充填体养护龄期与充填体破坏范围之间的关系进行了数值模拟研究。结果表明:充填体的破坏范围与炮孔距充填体距离(孔边距)呈线性关系,随着孔边距的增加,充填体的破坏范围逐渐减小;充填体的破坏范围与其养护龄期密切相关,随着养护龄期的增加,充填体的破坏范围逐渐减小,且超过7d养护龄期后,充填体的破坏范围受爆破扰动影响明显减弱。该研究成果为现场爆破参数优化和回采时间的确定提供了理论依据。

During the mining process by using cut and fill method in Jiaojia gold mine,the blasting compensation space is obtained by squeezing the backfill to avoid cutting holes and improve the mining efficiency. As a result,the strength and self-reliance of backfill are obviously reduced.In addition,due to the heavy production task,the stopes are usually mined while backfill be cured only two or three days.As the insufficient curing,the strength of backfill cannot reached its designed value.Therefore,large scale collapses of backfill are easily occurred during mining process,which impact the safety of operators and equipment.At the same time,the backfill mixed into the ore that results in ore dilution and higher processing cost.To resolve the problems of backfill serious damaged by blasting disturbance and unreasonable design of blasting parameters, numerical studies were carried out by use of LS-DYNA software.The influence factors of backfill damage, including the layout of blast holes and the curing age of backfill,have been analyzed. Mises yield criterion was used to determine the threshold of backfill damage by analyzing Mises effective stress distribution in backfill body. The results show that the damage area of backfill determined by comparing the dynamic tensile strength of backfill with the effective peak stress is feasible. The backfill damage area is closely related with the position of blast holes,and show a negative linear relationship between them,i.e.,the closer of the blast holes to the backfill,the greater damage of the backfill. When the distances between blast hole and backfill increased from 0.2 m to 0.8 m,the damage area of backfill decreased from 1.48 m 2 to 0.74 m 2 . Based on the blasting theory,the process of fracture zone induced by blasting can be divided into two phases. First,the shock wave energy would cause cracks generated around the hole. Then,the quasi-static pressure from the gaseous explosive energy result in the propagation of cracks. The reasonable distance between blast hole and backfill obtained from blasting theory is consistent with the result obtained by numerical simulation. The curing age is deeply influence the backfill damage characteristics. With the curing age prolongs,the damage range of the backfill gradually decreases. Seven days is an important time to influence the strength of backfill. When the curing age of backfill is more than 7 days,the damage zone of backfill remarkably decrease,and vice versa.Take the distance of blast hole is 0.5 m from backfill as an example,backfill damage areas decreased from 2.94 m 2 to 0.93 m 2 with its curing age prolonged from 3 days to 28 days. According to the above research results,the blast holes arranged from 0.3 m to 0.6 m to backfill and the backfill cured at least 7 days are recommended.