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1.
岩石破裂电磁辐射频率与岩石属性参数的关系   总被引:1,自引:0,他引:1       下载免费PDF全文
为进一步明确岩石破裂电磁辐射频率特征,基于岩石破裂电磁辐射是由岩石破裂时传播裂纹引起原子扰动产生的假说, 通过断裂力学理论中小范围屈服条件下张开位移法计算岩石破裂时的裂纹宽度,由单脉冲电磁辐射频率与裂纹宽度之间的关系,研究电磁辐射频率与岩石属性参数之间的关系,并给出了它们之间的关系表达式;单独讨论了不同属性参数对电磁辐射频率的影响.结果表明,电磁辐射频率随弹性模量增大而增大,随岩样尺寸和强度增大而减小,随泊松比的变化、岩石弹模的不同电磁辐射频率有变化;当弹模较小时,泊松比的影响也较小,而当弹模很大,即岩石刚度很大时,泊松比的增大会导致频率的增大;裂纹初始长度的变化受试件尺寸的影响,进而影响频率,当尺寸较大时,裂纹长度对频率影响较小,当尺寸较小时,频率随裂纹长度增大而增大.通过计算几种常见岩石破裂时电磁辐射频率值发现,岩石破裂时电磁辐射频率达到105 Hz量级,这与现有的实验结果相吻合.  相似文献   

2.
岩石破裂电磁辐射频率与弹性参数的关系   总被引:3,自引:0,他引:3       下载免费PDF全文
为进一步研究岩石破裂电磁辐射特征,本文根据岩石破裂电磁辐射是由岩石破裂时产生带电粒子扰动引起的假说,通过断裂力学理论中的张开位移法计算岩石破裂过程中的裂纹宽度,由电磁辐射频率与破裂宽度之间的关系,研究电磁辐射频率与弹性参数之间的关系,并给出了它们之间的关系表达式.通过建立具有中心贯穿裂纹的无限大平板模型,根据破裂宽度计算了在该模型条件下几种岩石破裂过程中产生电磁辐射频率范围.理论模型计算出来的频率范围主要集中在实验观测的中高频段,并体现出频率随弹性参数的变化.  相似文献   

3.
岩石破裂时电磁辐射的机理研究   总被引:21,自引:6,他引:21  
本文提出了岩石破裂时的电磁辐射是裂纹尖端电荷随着裂纹加速扩展运动所产生的假说.应用断裂力学方法推导了岩石破裂时初始裂纹长度与裂纹扩展加速度的关系,并计算了其速度和加速度值.根据破裂岩石的电子发射理论,解释了裂纹尖端带电荷的现象.利用岩石在单轴压缩致裂过程中记录到的近场电磁辐射的实验结果,计算了裂纹扩展时裂纹尖端的电荷量和远场电磁辐射强度.通过对电磁辐射波谱分析的研究,得到岩石破裂时电磁辐射频率上限的估计值.最后对岩石破裂时出现的声光电磁现象在理论上作了统一的定性的解释.  相似文献   

4.
岩石破裂中多裂纹辐射模型   总被引:4,自引:0,他引:4       下载免费PDF全文
以往有关岩石破裂过程中产生的电磁辐射(EM)理论均建立在单裂纹模型之上,但实验表明,岩石破裂中存在着多裂纹同步扩展的现象,因而存在多裂纹同步扩展产生的电磁辐射。根据实验结果,提出了多裂纹同步扩展的简化辐射模型,计算了电磁辐射场的特性。结果表明,这种电磁辐射比单裂纹辐射场强振幅大N倍和具有更强的方向性,用实验测量值与该模型的计算值进行了比较,二者基本吻合。  相似文献   

5.
岩石破裂系分形及分维数测定   总被引:1,自引:3,他引:1  
花岗岩在固体围压三轴压缩下破裂,然后沿主破裂面摩擦滑动(粘滑或稳滑),实际后我们将样品从围压介质铅中剥出来,做成显微薄片。在20倍显微投影仪下观测其主破裂及裂纹系分布,用尺度法统计并计算裂纹系分维。结果表明,8个样品的无标度区(R)都相同,但是随尺度变化,分维值表现出分段线性的特征。当0.05〈R〈0.15mm时,裂纹系分维在1.12-1.41之间,主破裂分维在1.08-1.15之间;当0.15〈  相似文献   

6.
许多国内外学者观测到伴随岩石破裂的电磁辐射现象,但实验结果不能解释实际观测记录的不同步现象,即有的台有异常,有的台没有异常;同一个观测台不同频段的信号也不同时出现.给地震预报工作带来不少困难.本实验结果可以解释不同步现象.实验采用单轴加压岩样直至破裂.不同频段的天线安置在远离岩样2m的不同方位上.采用14道磁带机同步记录岩样破裂全过程的电磁信号.实验结果表明:①岩样在主破裂过程中,4种频段都记录到了信号,但不同频率出现的时间有时不同步;②主破裂发生时刻电磁辐射强度最大,但不同方位信号的强度不同  相似文献   

7.
通过实验力学方法研究了几种典型组合裂纹非共面破裂特征.实验结果表明,在双轴加载条件下,脆性材料内部的初始不闭合裂纹在受力闭合之前出现新裂纹,扩展裂纹中不仅有张性裂纹,而且有剪切裂纹,部分甚至还出现逆向剪切裂纹.对单轴加载和双轴加载两种条件下裂纹的破坏规律作了比较.  相似文献   

8.
岩石破裂时电磁辐射的影响因素和机理   总被引:12,自引:0,他引:12       下载免费PDF全文
刘煜洲  王寅生 《地震学报》1997,19(4):418-425
根据实验提出,岩石破裂时产生电磁辐射的影响因素主要是岩石力学性质和矿物组成.脆性破裂的样品和含石英、黄铁矿、黄铜矿等的样品易产生电磁辐射.存在3种破裂-辐射效应:晶体破裂效应、压电效应和天然半导体效应,分别是产生高频信号、低频信号和具有独特波形的中频信号的主要机理.   相似文献   

9.
钱书清  任克新 《地震学报》1996,18(3):346-351
许多国内外学者观测到伴随岩石破裂的电磁辐射现象,但实验结果不能解释实际观测记录的不同步现象,即有的台有异常,有的台没有异常;同一个观测台不同频段的信号也不同时出现.给地震预报工作带来不少困难.本实验结果可以解释不同步现象.实验采用单轴加压岩样直至破裂.不同频段的天线安置在远离岩样2 m的不同方位上.采用14道磁带机同步记录岩样破裂全过程的电磁信号. 实验结果表明:① 岩样在主破裂过程中,4种频段都记录到了信号,但不同频率出现的时间有时不同步;② 主破裂发生时刻电磁辐射强度最大,但不同方位信号的强度不同.   相似文献   

10.
裂纹系微破裂集结和动态扩展的实验研究   总被引:3,自引:0,他引:3  
研究了裂纹系的动态破裂,重点考察了裂纹系相互作用.选用大理石、玻璃为实验材料,将其加工成薄板状,并在板内预制各种不同形态的裂纹系,在单轴压下用可见光透视观察裂纹系动态相互作用的破裂过程.实验中发现,岩石的动态破裂过程和玻璃有很大差别,岩石的裂纹系动态相互作用后期是通过微破裂演化来实现的,而在玻璃中观察不到.裂纹系的不均匀应力场分布是破裂演化的初始原因.通过实验,给出大理石材料中各种不同形态裂纹系的动态破裂演化的全场过程图像,直观地揭示了含裂纹系岩石变形破坏的实质.实验显示了不同几何形态的裂纹系的破裂发育过程有明显区别.在微破裂集结时,周围的破裂部分闭合.因此,用二维模型描述的微破裂图像和实际有很大出入.为了消除这个差距,必须研究三维破裂.本文的实验结果表明,裂纹(断层)不能起到阻碍破裂扩展的作月;裂纹(断层)作为障碍体,和预存裂纹之间存在强烈的相互作用,使得样品的强度降低几乎一个量级.讨论了上述结论对于认识地震(包括矿震)断层行为的意义.  相似文献   

11.
ApossibleULFseismicelectro-magneticemissionXing-CaiLI;(李兴才)Hui-XinCAO;(曹惠馨)Tie-HongYU;(俞铁宏)andZhi-YongCHEN;(@2陈智勇)(Instituteo...  相似文献   

12.
煤岩变形破裂电磁辐射的实验研究   总被引:68,自引:3,他引:65       下载免费PDF全文
对受载煤体变形破裂产生电磁辐射进行了实验研究及规律分析,并对煤岩变形破裂电磁辐射的机理进行了探讨分析.研究结果表明,煤体变形破裂时能够产生电磁辐射,电磁辐射信号与声发射信号并非严格同步,电磁辐射信号较声发射信号丰富,电磁辐射与煤岩体的变形破裂过程密切相关.煤岩电磁辐射技术在揭示煤岩变形破裂机理,预测、预报地震,矿山煤岩灾害动力现象及岩石混凝土建筑稳定性方面有着非常广泛的应用前景.  相似文献   

13.
冲击矿压危险预测的电磁辐射原理   总被引:11,自引:2,他引:11       下载免费PDF全文
由于煤岩冲击破裂过程中,裂缝的形成和颗粒的摩擦会产生电磁辐射,因此,可采用电磁辐射技术来预测煤矿的冲击矿压危险.研究表明,电磁辐射基本上随着加载及变形速率的增加而增强;在发生冲击性破坏以前,电磁辐射强度一般在某个值以下,而在冲击破坏时,电磁辐射强度突然增加;煤体应力越大,变形破裂越强烈,电磁辐射信号也越强.煤岩变形破坏的弹塑脆性模型分析表明,煤岩体的损伤速度与电磁辐射脉冲数、声发射事件数成正比,与瞬间释放的能量、变形速度成正比.对具有强冲击危险工作面进行的研究表明,电磁辐射完全可以预测煤矿冲击矿压危险,检验卸压爆破效果,而且准确率高,效果明显.  相似文献   

14.
煤岩变形破坏电磁辐射记忆效应的力电耦合规律   总被引:1,自引:0,他引:1       下载免费PDF全文
理论分析了煤岩变形破坏过程中电磁辐射脉冲数与损伤之间的关系,探讨了煤岩变形破坏电磁辐射产生机制及电磁辐射记忆效应的力电耦合规律,建立了等围压三轴应力状态下含瓦斯煤岩变形破坏电磁辐射记忆效应的力电耦合模型,实验测定并分析了单轴压缩状况下含瓦斯煤岩变形破坏电磁辐射记忆效应的力电耦合规律.结果表明,含瓦斯煤岩变形破坏电磁辐射记忆效应力电耦合模型很好地反映了煤岩变形破坏电磁辐射记忆效应特征规律和微观损伤机理.  相似文献   

15.
—?Unique data from microseismic (MS) and acoustic emission (AE) systems monitoring a common rock volume have been analyzed from the Underground Research Laboratory in Canada. The two 16 sensor systems were installed to investigate stress-induced microcracking around clay and concrete bulkheads as part of the Tunnel Sealing Experiment. Single and double MS events are found to be spatially associated with clusters of between 19–86 higher frequency AE events. Each AE cluster is elongated with the longest axis between 15 and 50?cm. The AE events occurring before the associated MS event are termed foreshocks, and for two of the three analyzed AE clusters an acceleration in the AE frequency and cumulative magnitude occurs upto the time of the MS event, however with one AE cluster very few foreshocks are recorded, possibly indicating a more homogeneous failure plane. Time independent moment tensors were determined with the MS events showing significant deviatoric sources. The majority of the AE events have deviatoric mechanisms with a few crack opening and crack closure type events also determined. This study highlights the benefits of using small-scale seismic systems to investigate the temporal fracture mechanics of microcrack formation, and allows comparisons with larger more damaging seismicity.  相似文献   

16.
岩石裂纹扩展微观机制声发射定量反演   总被引:1,自引:0,他引:1       下载免费PDF全文
岩石受载内部微裂纹扩展及其震源机制反演有助于认识宏观裂纹扩展过程的非线性断裂力学行为.借助声发射监测手段,本文建立了仅涉及微裂纹张开/闭合和剪切滑移的位移不连续震源模型,通过各位置处传感器耦合质量标定及点源远场P波矩张量反演获得了含预制裂纹砂岩受载过程的震源机制解及时变响应特征,在全局坐标系下分析了微裂纹的三种断裂力学行为.结果表明:在位移不连续模型中,震源矩张量特征值与试样泊松比之间必须满足特定约束条件,该约束条件下的优化问题可采用拉格朗日乘子和Levenberg-Marquardt迭代法求解;受载砂岩裂纹扩展过程中,声发射震源以剪切滑移机制占优,微裂纹空间取向及运动方向与试样宏观主裂纹夹角平均值分别为40.9°和17.7°;对微裂纹体积分解表明岩体微观破裂机制以沿X方向I型张开为主,而沿Y方向的II型断裂滑移方向与试样全局变形方向相一致,由于试样内部晶粒分布非均质性造成了少量沿Z方向的III型平面外微裂纹滑移行为;受载砂岩裂纹扩展过程中微裂纹模式角与震源极性值变化趋势一致、利用震源震级评估的局部应力降值与实验观测结果相吻合,这两者均表明了位移不连续模型在震源机制定量反演中的适用性.  相似文献   

17.
Physical mechanisms of man-made influences on the magnetosphere   总被引:3,自引:0,他引:3  
Since the discovery of the Luxembourg effect in the 1930s, it is clear that man-made activities can perturb the ionosphere and the magnetosphere. The anthropogenic effects are mainly due to different kinds of waves coming from the Earth's surface. Acoustic-gravity waves are generated by large explosions, spacecraft launches, or flight of supersonic planes. Electromagnetic waves are active in different frequency ranges. Power line harmonic radiation which is radiated in the ELF range by electrical power systems can be observed over industrial areas. At VLF and HF, the ground-based transmitters used for communications or radio-navigation heat the ionosphere and change the natural parameters. A large variety of phenomena is observed: wave-particle interaction, precipitation of radiation belt electrons, parametric coupling of EM whistler waves, triggered emissions, frequency shift, and whistler spectrum broadening. This paper will review the different physical mechanisms which are relevant to such perturbations. The possibility of direct chemical pollution in the ionosphere due to gas releases is also discussed.  相似文献   

18.
Results of the spectral measurements of ionospheric noise in the meter band are presented. The events lasting several milliseconds (the emission maximum of which drifts upward (in frequency), is reflected (stops), and drifts downward) have been distinguished. Moreover, multiple harmonics are observed. The frequency-time structure of such events have been considered from the viewpoint of registration of the electron beam synchrotron emission harmonics at ionospheric altitudes in the geomagnetic field. The model calculations of the frequency-time structure of ionospheric radio noise bursts drifting in frequency have been performed taking into account the measurement conditions. It has been indicated that the model electron radio noise bursts agree with the measured bursts reflecting from the ionosphere at altitudes of 100–180 km. The model of the monoenergetic beam of electrons precipitating from the radiation belt (L ~ 2.0–2.8) into the ionosphere has been proposed.  相似文献   

19.
The mechanism and dynamics of the deformation and fracture of quartz, granite, and marble samples under the striker blow on their surface and electric discharge inside them are studied by the fractoluminescence (FL), electromagnetic (EME), and acoustic emission (AE) methods with 10-ns resolution. The impact excites a forced deformation wave with a velocity within 0.8 to 2 km/s depending on the mineral. The atomic bonds rupture and microcracks are formed at the nodes of the wave, which leads to the emergence of the FL flashes and disruption of the time dependences of EME. Based on the intensity of the flashes, the dimensions of microcracks are estimated to vary from 2 to 70 µm depending on the mineral. In turn, the emergence of microcracks initiates additional deformation waves.The discharge inside the studied samples excites a pressure shock wave which transforms into the tension wave after reflection from the surface. According to the analysis of FL spectra, this leads to the breakdown of the rocks into positively charged ions and electrons. The shock wave velocity in granites is measured at 4.8 km/s, which is close to the velocity of the longitudinal acoustic vibrations ~5 km/s. The microcracks in the rock have not enough time to form with this loading velocity. It is supposed that the shock wave stretches the deformed interatomic bonds at the dislocation nuclei in the crystal lattices of the minerals up to their breakdown into positively charged ions.  相似文献   

20.
A numerical solution of the dispersion equation for electromagnetic waves in a hot magnetized collisionless plasma has shown that, in a current-free ionospheric plasma, the distortion of the electron distribution function reproducing the downward flow of a thermal electron component and the compensating upward flow of the suprathermal electrons, which are responsible for the resulting heat flux, can destabilize quasi-electrostatic ion sound waves. The numerical analysis, performed with ion densities and electron temperature taken from the data recorded by the Interkosmos-24 (IK-24, Aktivny) satellite, is compared with a VLF spectrum registered at the same time on board. This spectrum shows a wide frequency band emission below the local ion plasma frequency. The direction of the electron heat flux inherent to the assumed model of VLF emission generation is discussed.  相似文献   

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