共查询到17条相似文献，搜索用时 499 毫秒
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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
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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
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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
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煤炭变形破裂电磁辐射的实验研究 总被引：13，自引：3，他引：10
对受载煤体变形破裂产生电磁辐射地实验研究及规律分析,并对煤炭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,电磁辐射信号罗声发射信号丰富,电磁辐射与煤盎体的变形破裂过程密切相关。煤炭电在辐射技术在揭示煤岩变形破裂机理,预测、预报地震、矿山煤炭灾害动力现象及岩石混凝土稳定性方面有着非常广泛的应用前景。 相似文献
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《世界地震译丛》2016,(2)
应用电磁辐射(EME)和声发射(AE)信号检测研究了机械应力加载条件下脆性、介电性材料的断裂。对环氧树脂样品采用3点弯曲实验装置施加应力使之破裂,同时监测破裂引起的电磁辐射和声发射信号。本次研究的重点是裂纹面的走向及距离对检测到的电磁辐射信号的影响。由于采用的电磁辐射传感器是电容式传感器,我们利用人工检测源测试了传感器、连接的放大器、数据采集卡以及内置带通滤波器的系统响应特征。基于在破裂面位置上模拟的表面电荷密度,我们提出了一种电磁辐射信号的源。将电磁辐射源的有限元方法模拟结果与实验结果进行比较,显示出较好的一致性。实验结果显示辐射出的电磁场优势方向明显,检测到的信号幅值显著依赖于信号源到传感器的距离,并发现测量链对检测到的电磁信号带宽具有显著影响。进一步研究表明电磁信号由3部分构成,分别产生于不同机制,即裂纹生长过程中电荷的分离和弛豫,以及带电裂纹面的振动。 相似文献
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在单轴加压下进行了有预制裂纹的岩石板在裂纹扩展过程中声发射时b值的实验。发现b值的变化与岩石裂纹的扩展过程有密切关系,并且不同岩石介质的相互作用可影响b值的变化。通常裂纹扩展时,b值下降,但扩展受阻时,b值又有所回升,因此,有预制裂纹的岩石板在破裂过程中,b值呈起伏变化。 相似文献
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本文以共线剪切裂纹的归并为例,研究裂纹系的动态相互作用．实验结果表明：在张破裂的意义上,小间距共线剪切裂纹的内端部实际上是阻碍结构,通过迂回弯曲的张破裂归并．本文提出一种估计张破裂扩展途径的近似方法,利用张应力破裂判据找出了潜在的破裂扩展途径的第一近似,较好地模拟了共线裂纹的破裂途径,和现有的数值模拟方法比较,可以大大缩短机时,简化计算程序,保证精确度．本研究结出了岩石剪切破裂“隧道效应”（即破裂跳过障碍体,而障碍体本身不破坏）的机理,还给出了脆性介质在摩擦、磨损过程中碎屑产生的机理． 相似文献
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This paper discusses the applicability of the tension-softening model in the determination of the fracture toughness of rocks,
where the fracture toughness evaluated based on the tension-softening model is compared with the crack growth resistance deduced
from laboratory-scale hydraulic fracturing tests. It is generally accepted that the fracture process is dominated by the growth
of a fracture process zone for most types of rocks. In this study, the J-integral based technique is employed to determine the fracture toughness of Iidate granite on the basis of the tension-softening
model, where compact tension specimens of different dimensions were tested in order to examine the specimen size effect on
the measured fracture toughness. It was shown that the tension-softening relation deduced from the J-integral based technique allowed us to determine the specimen size independent fracture toughness Kc of Iidate granite. Laboratory-scale hydraulic fracturing tests were performed on cubic specimens (up to a 10 m sized specimen),
where cyclic pressurization was conducted using a rubber-made straddle packer to observe the extent of the hydraulically induced
crack. The experimental results of pressure and crack length were then used to construct the crack growth resistance curve
based on the stress intensity factor K. The crack growth resistance obtained from the hydraulic fracturing tests was observed to initially increase and then level
off, giving a constant K value for a long crack extension stage. The plateau K value in the crack growth resistance curve was found to be in reasonable agreement with the fracture toughness Kc deduced from the tension-softening relation. It was demonstrated that the tension-softening model provides a useful tool
to determine the appropriate fracture toughness of rocks, which may be applicable for the analysis of the process of large-scale
crack extension in rock masses. 相似文献
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Crack widths and rock temperatures were monitored on an andestic bedrock cliff in the summit area of the Daisetsu Mountains, Hokkaido, northern Japan. Sequential data recorded the gradual widening of a crack to the point of critical crack extension, which resulted in catastrophic rock breakage. The data indicate that a combination of liquid water in?ltration into crack tip and subsequent freezing is the most signi?cant factor contributing to critical crack extension. The recorded sub‐critical crack movements involved a number of minor crack extensions and contractions, the timing of which correlates well with the magnitude of the reconstructed thermal stresses at the crack tip derived from thermal deformation of the plate‐shaped rock fragment. Larger crack extensions occurred when stress at the crack tip exceeded a threshold value, possibly re?ecting the control of rock fracture mechanics by which cracks are thought to propagate when the stress intensity factor at the crack tip exceeds the threshold values for stress corrosion cracking and the fracture toughness of the material. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
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Geoeiectromagnetic signals related to earthquakes have been detected in China and many other countries.Problems concerning the mechanism of the electromagnetic emission and transportation still remain unsolved,although several models have been proposed.We consider that the theory of "electromagnetic missile emission" may be used to solve this problem,and thus develops the basic ideal of the Electro Magnetic Missile Emission(EMME)model of the emission of electromagnetic signals before earthquakes:pulse variation of the stress state causes the emission of electrons,or sudden flow of the fluid,in a certain direction along or near the fault which is located at the focus of an earthquake,forming a pulse electric current; this current accordingly produces a kind of slowly attenuated EM Wave(electromagnetic missile,which may be observed on the surface of the earth)in the perpendicular direction.In other directions these EM waves vanish quickly and cannot reach ground level. 相似文献
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Introduction The study of acoustic emission evidenced by rock fracture experiments is the most important field of seismology. By means of the rock fracture technique system, many researchers tried to prove the possible relationship between some parameters such as b value and the stress variation prior to rock fracture using the acoustic emission results from different types of rock fracture ex-periments (MA et al, 2004a, b; Lockner, 1993; JIANG and ZHANG, 1998). In order to investigate th… 相似文献
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Jianping Xiang N.B. Jones Daizhan Cheng F.S. Schlindwein 《Geophysical Prospecting》2002,50(6):565-576
The problem of discrimination between a valid induced polarization (IP) response and electromagnetic (EM) coupling effects is considered and an effective solution is provided. First, a finite dimensional approximation to the Cole‐Cole model is investigated. Using the least‐squares approach, the parameters of the approximate model are obtained. Next, based on the analysis of overvoltage, a finite dimensional structure of the IP model is produced. Using this overvoltage‐based structure, a specific finite dimensional approximation of the Cole‐Cole model is proposed. Summarizing the analysis of the finite dimensional IP model, it is concluded that the proposed IP model, which fits the field data much better than the traditional Cole‐Cole model, is essentially an RC‐circuit. From a circuit‐analysis point of view, it is well known that an electromagnetic effect can be described by an RL‐circuit. The simulation results on experimental data support this conception. According to this observation, a new method to discriminate between a valid IP response and EM coupling effects is proposed as follows: (i) use a special finite dimensional model for IP–EM systems; (ii) obtain the parameters for the model using a least‐squares approach; (iii) separate RC‐type terms and RL‐type terms – the first models the IP behaviour, the latter represents the EM part. Simulation on experimental data shows that the method is very simple and effective. 相似文献
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As the economy of China develops, an increasing number of key traffic projects have been undertaken in the west of China, where there are high, steep rock slopes. The collapse of dangerous rock masses, especially following a strong earthquake, is one of common geological disasters known in rock slope engineering. Therefore, it is important to study the collapse mechanism of dangerous rock masses induced by an earthquake and the analysis approach of its stability. This study provides a simple and convenient method to determine the collapse mechanisms of two types of dangerous rock masses (i.e. cantilever and upright) associated with the definition and calculation of the safety factor, which is based on the flexure theory of a constant-section beam by combining with the maximum tensile-stress criterion to depict the process of crack propagation caused by seismic waves. The calculation results show that there are critical crack depths in each form of the dangerous rock masses. Once the accumulated depth of the crack growth during an earthquake exceeds the critical depth, the collapse will occur. It is also demonstrated that the crack extension amount of each step is not a constant value, and is closely associated with the current accumulated crack depth. The greater the cumulative crack depth, the more easily the crack propagates. Finally, the validity and applicability of the proposed method are verified through two actual engineering examples. 相似文献
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The results of hardware and methodological developments for recording of electromagnetic emission (EME) generated by rock
samples under loading in laboratory experiments are presented. The results of experiments with the instruments developed are
described. The facilities developed made it possible to measure reliably the electromagnetic emission under conditions of
high background of electromagnetic noise and to reduce the level of reliably recorded signals as compared with previous experiments.
The results of observation of the appearance of electromagnetic emission in the experiments with the rock samples under laboratory
conditions showed a high correlation of the time instants of generation of the electromagnetic emission and the changes of
its parameters with the changes in the reactive resistivity of the rock sample and seismoacoustic emission activity in the
controlled area of the sample. It is revealed that electromagnetic emission occurs and reaches its maximum on the descending
branch of the plot of polarizability during rock destruction. 相似文献