冲击地压矿井安全性研究

Study on safety of rockburst mine

针对当前冲击地压矿井缺少对防冲设计的可靠性和对自身防冲能力综合评判的环节,导致一些冲击地压矿井虽然采取了防冲措施,但依然发生冲击地压这一现状。参考了岩土工程中采用安全系数来评价安全程度这种办法,提出了冲击地压矿井安全性的基本理念。通过调研发现:冲击地压造成的破坏范围占所在工作面总的作业范围比例是有限的;矿井巷道围岩应力集中大小是有限的,应力集中系数基本介于1~6;冲击地压事故释放的能量都不大于109 J级,即冲击地压释放的能量是有限的;冲击地压矿井的安全性评价可以转化为巷道安全性评价,即保证了巷道安全就保证了整个矿井安全;冲击地压发生后控制巷道断面收缩率在20%以内基本可以避免人员伤亡。因此,指出冲击地压是可防可控的。进而提出冲击地压不发生的条件和发生不造成人员伤亡的条件,即分别为:巷道围岩变形系统的实际受载应力低于巷道失稳发生冲击地压的临界应力;围岩变形系统失稳释放能量低于围岩−支护系统可吸收能量。并提出矿井在进行冲击危险性评价、划分危险等级以及防冲设计后,还需要进行安全性评价,包括临界条件、安全系数的计算和划分安全等级。基于冲击地压扰动响应失稳理论,给出安全性评价需要考虑的2个方面:应力安全性和能量安全性。其中,应力安全性由围岩变形系统的实际受载应力与失稳临界应力的比值(即应力安全系数)来判断;能量安全性由围岩变形系统失稳释放能量与围岩−支护系统可吸收能量的比值(即能量安全系数)来判断。进而将矿井安全性划分为A、B、C三级,分别对应:安全、基本安全和不安全。其中,应力安全系数大于1.5且能量安全系数大于1.0,为A级安全矿井,矿井具备防冲能力,可以正常进行开采;应力安全系数大于1.0且能量安全系数大于1.5,为B级基本安全矿井,矿井具备防冲能力,可以正常进行开采;安全系数非A级和非B级,则为C级不安全矿井,矿井不具备防冲能力或应暂停开采活动。以某矿为例,给出了矿井安全性计算的完整流程和评价结果。最后给出了全国部分冲击地压矿井的应力安全系数和能量安全系数,并结合这些矿井的实际冲击地压发生情况,验证了安全系数计算结果的可参考性,从而说明安全性评价方法具备一定的可靠性和实用性。

Because of the lack of comprehensive evaluation on the control design reliability and their control ability of rockburst in current rockburst mines,the rockburst still occurs in some mines although the rockburst control measures have been taken.Based on the method of evaluating the safety degree by safety factor in geotechnical engineering,the basic idea of rockburst mine safety is put forward.Through site investigations,it is found that the damage area caused by rockburst is limited in proportion to the total working area of the working face.The stress concentration in the surrounding rock of mine roadway is limited,ranging from 1 to 6.The energy released by rockburst accidents is no more than 109 J level,that is,the energy released by rockburst is limited.The safety evaluation of rockburst mine can be transformed into roadway safety evaluation,that is,the safety of roadway can ensure the safety of the whole mine.After rock burst occurs,controlling the shrinkage rate of roadway section within 20%can basically avoid casualties.Therefore,it is pointed out that rockburst can be prevented and controlled.Therefore,the conditions of non-occurrence of rockburst and occurrence of no casualties are put forward,that is,the actual load stress of roadway surrounding rock deformation system is lower than the critical stress of rockburst when roadway instability occurs and the energy released by the instability of the surrounding rock deformation system is lower than that absorbed by the surrounding rock support system.Safety evaluation should be carried out after impact risk evaluation,hazard classification and control design of rockburst,which includes critical condition,calculation of safety factor and classification of safety grade.Based on the instability theory of rockburst disturbance response,two aspects that need to be considered in safety evaluation are given:stress safety and energy safety.The stress safety is determined by the ratio of the actual stress under load to the critical stress of buckling in the surrounding rock deformation system(i.e.the stress safety factor).The energy safety is determined by the ratio of energy released from the instability of surrounding rock deformation system to the energy absorbed by surrounding rock supporting system(i.e.energy safety factor).Furthermore,the mine safety is divided into three levels:A,B and C,corresponding to safety,basic safety and unsafe respectively.Among them,if the stress safety factor is greater than 1.5 and the energy safety factor is greater than 1.0,it is a Grade A safe mine.The mine has control ability of rockburst and can be mined normally.If the stress safety factor is greater than 1.0 and the energy safety factor is greater than 1.5,it is a Grade B basic safety mine.The mine has control ability of rockburst and can be mined normally.If the safety factor is not Grade A or Grade B,it is classified as Grade C unsafe mine.The mine does not have control capability of rockburst or mining activities should be suspended.Taking a mine as an example,the complete flow of mine safety calculation and evaluation results are given.Finally,the stress safety factor and energy safety factor of some coal mines in China are given.Combined with the actual occurrence of rockburst in these mines,the reference of the calculation results of safety factor is verified,which shows that the safety evaluation method has certain reliability and practicability.