真三轴单面卸荷条件下中间主应力对深埋洞室岩爆影响特征

Influence of intermediate principal stress on rockburst in deep cavern under true triaxial condition with single face unloading

岩爆灾害已成为国内外深埋洞室建设的重大安全隐患。利用新型真三轴岩爆试验系统,开展了不同中间主应力下“单面侧向卸荷-三向五面受力-竖向持续加载”的室内物理模拟试验,对比分析了不同中间主应力下岩样的弹射破坏过程、破坏形态特征、声发射特性、碎块特征以及弹射动能等变化规律;基于三维离散元理论和多晶建模技术(随机生成Voronoi矿物晶粒),研究了真三轴单面卸荷条件下岩爆“孕育—发生—发展—破坏”全过程及能量演化特征。研究结果表明:不同中间主应力下岩爆弹射破坏过程可概括为颗粒局部弹射、岩石劈裂成板、板折断裂成块及块片全面弹射;其中,岩石劈裂成板是岩爆孕育过程中必然经历的破坏现象。岩样临空面破坏形态具有相似的多元分区破坏特征,即邻近临空面区域产生以张拉破坏为主的劈裂裂缝,远离临空面区域产生以剪切破坏为主的贯穿性斜裂缝。声发射撞击数演化过程可分为相对平稳阶段、快速上升阶段、整体破坏阶段及平静期阶段。随着中间主应力的不断增大,碎块的弹射动能呈增大的变化趋势。岩爆碎块多以粗粒、中粒与细粒碎块为主,且随中间主应力的增加,微粒碎块质量基本不变,细粒、中粒与粗粒碎块质量则呈平稳增加的趋势。利用考虑颗粒矿物成分的晶体尺度精细仿真模型(CSFM)模拟了岩爆“孕育—发生—发展—破坏”全过程,获得了岩样的应力-应变曲线,其变化趋势与室内试验测试结果基本一致且曲线吻合度较好。弹性应变能的演化曲线大致可分为早期增长速率递增阶段、近似线性增长阶段、屈服平台期间增长速率递减阶段及峰后急剧下降阶段。

Rockburst disaster has become a major safety hazard for deep cavern construction worldwide.Using the new true triaxial rockburst test system,an indoor physical simulation test of“single face lateral unloading-three direction and five faces stress-vertical continuous loading”under different intermediate principal stresses was conducted.The ejection failure process,failure mode,acoustic emission characteristics,fragment characteristics and ejection kinetic energy of rock samples under different intermediate principal stresses were compared and analyzed.Based on the three-dimensional discrete element theory and the polycrystalline modeling technique(randomly generated Voronoi mineral grains),the entire process of rockburst inoculation-occurrence-development-failure as well as the energy evolution characteristics under true triaxial single face unloading conditions were studied.The results indicate that the ejection failure process of rockburst under different intermediate principal stresses can be summarized as four stages:grains ejection,rock spalling into plates,rock shearing into fragments,and rock fragments ejection.Among them,the rock spalling into plates is an inevitable failure phenomenon in the process of rockburst.The failure modes of free face of rock samples have similar multi-zone failure characteristics.That is,the splitting cracks dominated by tensile failure are generated near the free face,and the penetrating shear cracks dominated by shear failure are generated away from the free face.The evolution process of AE hits can be divided into four stages:relatively stable,rapid rising,overall failure stage and quiet period.As the intermediate principal stress increases,the ejection kinetic energy of the fragments increases.Rockburst fragments is mostly coarse-grained,medium-grained,and fine-grained fragments.With the increase of intermediate principal stress,the mass of fine particles is basically unchanged,while the mass of fine,medium and coarse particles shows a steady increase trend.The entire process of rockburst inoculation-occurrence-development-failure is successfully simulated using the crystal scale fine model(CSFM)considering the grain mineral composition.The variation trend of the stress-strain curve of the rock sample is basically consistent with the indoor test results and the curve is in good agreement.The evolution curve of elastic strain energy can be roughly divided into the early growth rate increasing stage,the approximate linear growth stage,the growth rate decreasing stage during the yield platform period and the post-peak sharp decline stage.