应力松弛岩爆试验及演化模型研究

Study on Test and Evolution Model of Stress Relaxation Rock Burst

针对硬岩应力松弛特性及岩爆研究的不足,对具有岩爆倾向性的辉长岩开展了单轴压缩应力松弛岩爆试验,得出了两类应力松弛规律和岩爆演化过程,建立了应力松弛模型,定义了应力松弛损伤变量,分析了应力松弛岩爆过程与机理。结果表明,应力松弛岩爆过程可分为两类:第一类经过迅速衰减、逐渐衰减和稳定3个演化阶段,此类可能发生轻微到中等的局部岩爆,且集中在衰减阶段出现,最终趋于稳定;第二类经过逐渐衰减、迅速衰减和丧失3个演化阶段,全过程均伴随有轻微到中等岩爆发生,最终发生强岩爆或整体爆裂。整个应力松弛岩爆经历了裂纹萌生、扩展、贯通、爆开、颗粒和岩片弹射等复杂过程,直至最终发生整体爆裂。分数阶模型能较好反映第一类松弛演化阶段,其对预测分析符合此应力松弛规律的轻微到中等岩爆是适合的,但不能反映第二类松弛岩爆演化过程。依据定义的应力松弛损伤变量,第一类应力松弛岩爆过程经过加速损伤、缓慢损伤和稳定3个演化阶段,第二类经过缓慢损伤、加速损伤和失稳岩爆3个演化阶段。研究结果对岩爆机理、预测预警及硬岩长期稳定性分析等具有很好的指导作用。

Aimed at the shortages in the research of hard rock stress relaxation characteristics and rock burst, uniaxial compression stress relaxation rock burst tests were carried out on gabbro samples with rock burst tendencies. Two kinds of stress relaxation rules and rock burst evolution processes were obtained. Then, a stress relaxation model was established, the stress relaxation damage variable was defined, and the mechanism of stress relaxation rock burst was analyzed. Results show that the process of stress relaxation rock burst can be divided into two types. For the first type, gabbro samples undergo three stages of evolution, including rapid attenuation, gradual attenuation and stabilization. This type of specimen may have a slight to moderate local rock burst, which appears in the attenuation stages and finally tends to be stable. For the second type, gabbro samples undergo three stages of evolution, including gradual decay, rapid decay and loss. The whole process can be accompanied by a slight to moderate rock burst, and eventually a strong rock burst or a whole burst. The whole stress relaxation rock burst will go through the complex process of crack initiation, propagation, penetration, explosion, particle and rock fragment ejection until it finally burst. The fractional calculus model can well reflect the first type of relaxation evolution stage, which is suitable for predicting and analyzing slight to medium rock burst in line with this stress relaxation law, but it can not reflect the evolution process of the second type of relaxation rock burst. According to the defined stress relaxation damage variable, the first type of stress relaxation rock burst undergo three evolution stages, including accelerated damage, slow damage and stabilization, and the second type goes through three evolution stages, including slow damage, accelerated damage and unstable rock burst. The study results have a good guidance for the mechanism, the prediction and warning of rock burst, as well as the analysis of long-term stability of hard rock.