【作者】 王正；

【导师】 祝文化；

【作者基本信息】 武汉理工大学 ， 岩土工程， 2014， 硕士

【摘要】 岩爆是高地应力条件下地下工程开挖过程中硬脆性围岩因开挖卸荷扰动引起岩体局部应力集中，当应力集中程度超过极限平衡状态时，储存于岩体中的弹性应变能突然释放而引起的一种动力失稳破坏现象，已成为世界性的地下工程难题之一。目前，国内外对于岩爆的研究一般是基于现场监测和室内试验，现有室内试验主要存在两个主要方面的限制：一是小尺寸试件的均布加载试验，不能模拟岩体应力环境中的梯度荷载效应；二是试验加载过程中较少的考虑应力作用时间效应的影响。本文依托武汉理工大学与总参科研三所联合研制的YB-A型岩爆模拟试验装置，通过总结工程岩爆现象发生的时间和部位，提出了一种梯度荷载作用下的考虑应力作用时间效应的加载试验方法，进行了不同强度等级、不同侧压系数条件下的模型岩爆模拟试验，提出了岩爆烈度判断的依据，分析了岩爆产生的机理和声发射特性。主要研究成果：(1)基于石膏材料的室内岩爆模拟试验，分析试块破坏最大主应力σ与单轴抗压强度Rc之间的关系，得出在考虑应力作用时间效应下的岩爆烈度判别依据：σ/Rc=1.0-1.2；轻微岩爆，有清脆的响声，临空面有剥离、弹射的现象；σ/Rc=1.2-1.3；中等岩爆，清脆的响声，临空面出现较大面积的剥离、抛掷；σ/Rc≥1.3；强烈岩爆，剧烈的响声，靠近临空面的区域发生大面积的抛掷。(2)试验结果表明：岩爆的产生需要一个外荷载的扰动，当岩体未达到极限储能状态或者处于极限储能状态时，是不会发生岩爆的，而当达到了极限储能状态时，如果有一个外荷载继续对岩体施加能量，那么打破极限储能状态，使得多余的能量就会以破坏的形式释放出来，对于结构性完整、强度高、脆性好的岩体就可能是岩爆。(3)不同强度试验破坏情况表明，在其他条件一定的情况下，强度越高的岩体，释放的弹性应变能越多，发生岩爆的烈度就越大；多次加载-稳压试验表明，岩体发生第一次岩爆后，如果继续还有外荷载的施加，使得岩体再次储存弹性应变能，当能量再次超过极限平衡状态后，可能继续发生岩爆。将本次4组试验与以往未考虑应力作用时间效应的试样结果对比发现，应力作用时间效应是影响岩爆破坏形式的重要影响因素，在充分考虑应力作用时间效应的破坏多以拉压复合式破坏，这与工程岩爆现象类似，而未考虑的情况下破坏形式以剪切破坏为主。(4)分析了岩爆声发射特征参数、波形与声发射定位；声发射事件数能够作为岩爆发生前兆的依据，岩爆前，试件会产生大量的声发射事件数，且会有高能量和高幅值的波形产生。声发射频谱特性表明，在岩爆前声发射频谱特性为高频低幅，并且存在多个主频带，岩爆时声发射特性为低频高幅，主频带变为一个，频率范围为20Hz-40Hz，且有所变窄，岩爆后声发射频谱特性为低频中幅，主频带比岩爆时有所变宽；多组试验的比较发现，强度的不同会影响主频带的范围大小差异，强度越低其岩爆后的主频带就会越宽一点。利用声发射定位技术，分析了岩爆时裂纹的发育、扩展到贯通成宏观裂纹的过程，声发射定位图与室内现场试验的破坏图完全吻合，这对深入研究岩爆的破坏机理有着非常重要的作用。(5)运用flac3d软件，合理设置材料参数，选择与室内试验相同的应力边界和位移边界条件，跟踪特征点的位移，全程监控屈服破坏状态，对室内试验结果进行了验证和补充。模拟结果表明岩爆破坏是由于所受的拉应力超过极限抗拉能力，产生大量拉伸微裂纹，进而发生的拉裂失稳破坏，这与物理模型试验结果吻合。更多还原

【Abstract】 Rock burst is a dynamic instability failure phenomeno， due to excavationunloading the rock mass of underground engineering under the condition of highstress will come into being stress concentration in the excavation process of hardbrittle rock, when the stress is more concentrated than the limit equilibrium state, theelastic strain energy stored in the rock will burst release, which has become one of theworld’s underground engineering problems. At present, the domestic and internationalresearch on rock burst is generally based on the field monitoring and laboratory test,the test has two main limitations: one is the small test sample size under evenlydistributed load, which can not simulate rock gradient stress environment; another isthat loading process is less concerned about the time influence of stress effect. Basedon the research of Wuhan University of Technology and three institute jointlydeveloped YB-A type rock burst simulation test device, summarizing the engineeringrock burst phenomenon according to the time and place, put forward a kind ofgradient loading test method which takes the time influence of stress effect intoconsideration, then do rock burst simulation test denpend on different strength gradeand different lateral pressure coefficients. Put forward a rock burst intensity judgmenton the basis of test, analyze the mechanism of rock burst and acoustic emissioncharacteristic. The main research results:(1) based on gypsum material rock burst simulation experiment, analysis therelationship between maximum principal stress (σ) and the uniaxial compressivestrength (Rc), it is concluded laboratory rock burst intensity discriminant basis whichconsidering the time influence of stress effect,as follows:σ/Rc=1.0-1.2;slight rock burst: a crisp sound, free surface peeling, launch，phenomena;σ/Rc=1.2-1.3; moderate rock burst: crisp sound, the free surface of large area ofstripping, throwing;σ/Rc≥1.3; strong rock burst: violent noise near the free face, throwing a largearea of the region(2) The tests’ result shows: rock burst need a disturbance of out load, when therock does not reach the ultimate energy state or in the ultimate energy state, which is not occurring rockburst, when reached the limit energy storage state, if there is anexternal loads continue to exert energy on the rock,then break the limit energy storagestate, the excess energy will be to destroy the release form, for the rock massstructural integrity, high strength, good brittleness may be rock burst.(3) Different strength of rock mass’ test shows, in certain conditions, the higherthe strength of rock mass, the more elastic strain energy release, the bigger rockburstintensity generate. Many times loading stress and holding stress shows, after firstrock burst, if it continues apply external load, the rock will stored elastic strain energyagain, when the energy exceeding the limit equilibrium state again, which maycontinue to generate rock burst again. Conparising the4groups of test with thesample results without considering the effect of stress time, we can know stress timeeffect are the important influence factors of rock burst failure form, the tension andcompression type failure is the main failure form if effect forces time was under fullconsideration, and this phenomenon is similar with engineering rock burst, and theshear failure is the main failure form without considering the circumstances.(4) Analysis the rock burst emission characteristic parameter, wave and formandlocation. Draw the following conclusions:AE can be used as the rockburst precursoryevent basedment, when rock burst happens, the specimen will generate a largenumber of acoustic emission events, and havehigh energy and high amplitudewaveform generation;From gypsum laboratory rock burst simulation test, before therock burst, acoustic emission frequency spectrum characteristic is high-frequency andlow-amplitude, and there are multiple frequency zone of acoustic emissioncharacteristics; during rock burst, acoustic emission frequency spectrum characteristicbecome low-frequency and high-amplitude, frequency zone become one and range20Hz to40Hz, and the zone change to narrow; after the rock burst, acousticemission frequency spectrum characteristic in low-frequency and middle-amplitude,frequency zone is wider than rock-burst’s; Comparison of multiple groups of testsfound that the strength of the different will affect the range of frequency zone sizedifferences, the lower the strength of the rock, then the more wide frequency zonewill become a little after rock burst.Through the test of the three groups of acousticemission location map,which can judge rock burst internal micro cracks developmen,extension and penetration process, is also a sample show of the evolution of internal stress. Acoustic emission location map is match with the failure diagram of laboratorytest perfect, which has a very important role in the deep study of the failuremechanism of rock burst.(5) Using the flac3dfinite difference software, make the correct parameters,select the same stress and displacement boundary conditions with indoor test, trackthe displacement feature point and monitor the whole process yield failure state,which can verify and make up the laboratory test results. The simulation results showthat the rock burst failure is due to the tensile stresses exceed the ultimate tensilecapacity, micro cracks generated a lot of tension, and then tensile failure, which agreewell with the test results.更多还原