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1.
V. A. Gavrilov L. M. Bogomolov A. S. Zakupin 《Izvestiya Physics of the Solid Earth》2011,47(11):1009-1019
The data of borehole geoacoustic and electromagnetic measurements in Kamchatka are compared with the results of laboratory
and field experiments on electromagnetic excitation of rocks. A noticeable similarity in the responses of the natural geological
medium and rock specimens is observed. The field experiments with controlled electromagnetic sources show that the geophones
placed in boreholes are capable of reliably detecting the responses of rocks in situ to electric impacts as low as 0.5 mV/m.
The obtained results provide the experimental evidence in favor of the previously proposed hypothesis of modulation of geoacoustic
emission in rocks in situ by the ULF atmospheric electromagnetic field. 相似文献
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《地震学报(英文版)》1996,9(3):447-454
In order to investigate the physical mechanism of seismo-electromagnetic signals, many scholars from China and other countries
have carried out laboratory and field experiments of rock samples by loading them up to fracture in recent ten-odd years.
In each of these experiments, the phenomenon of electromagnetic radiation was observed during the process of rock sample fracture.
However, the experimental results can not explain the non-synchronous electromagnetic radiation in actual observation records.
In these records, some stations displayed anomalies but some others did not, and the signals of different frequency bands
observed by the same station did not occur simultaneously. This has brought about many difficulties to the application of
electromagnetic radiation in earthquake prediction. The experimental result of this paper can explain the phenomenon of non-synchronous
electromagnetic radiation. In the experiment of this paper, rock samples are uniaxially compressed up to fracture. The antennas
of different frequency bands are installed two meters away from the rock sample in different directions. The electromagnetic
signals during the whole process of rock sample fracture are recorded synchronously by a 14-channel tape recorder. The experimental
results are as follows: (1) signals of the four frequency bands: VLF, MF, HF and VHF, are all recorded during the main fracturing
process of rock samples, but signals of different frequencies may somtimes occur non-synchronously; (2) the intensity of electromagnetic
radiation is the highest at the moment when the main fracture occurs, but signals in different directions are of different
intensities. The above results are consistent with the non-synchronous electromagnetic radiation observed in real earthquakes.
It seems possible to predict the orientation of future seismic source by the electromagnetic method of the LF or VLF frequency
bands.
Contribution No. 95A0075, Institute of Geophysics, SSB, China.
The paper is translated by Prof.Jie-Fan HUANG, Peking University from the Chinese into English version. 相似文献
3.
The influencing factors and mechanisms of the electromagnetic radiation during rock fracture 总被引:4,自引:0,他引:4
TheinfluencingfactorsandmechanismsoftheelectromagneticradiationduringrockfractureYU-ZHONLIU1)(刘煜洲)YINLIU1)(刘因)YIN-SHENGWANG2... 相似文献
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Introduction Earthquake is a kind of severe natural disaster. In order to predict earthquake effectively, thegeoscientists at home and abroad have carried out a great deal of studies on seismicity. For exam-ple,Willis, (1924) and Tocher (1959) made some early investigations on seismicity before largeearthquake. Chinese geoscientists performed even more studies in this field (CHEN, et al, 1981;HUANG, FENG, 1981; LIU, 1982; LU, 1985; LU, et al, 2001; MA, et al, 1982; MEI, 1960; … 相似文献
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Yu Huai-zhong Yin Xiang-chu Xia Meng-fen Xu Zhao-yong Li Min Liang Nai-gang Peng Ke-yin Victor Kukshenko Wu Zhi-shen Li Qi Surguei Elizarov 《地震学报(英文版)》2004,17(1):129-137
According to the critical point hypothesis (CPH), energy release would accelerate in power law before occurrence of large
earthquakes or failure of brittle materials. In the paper, CPH was studied by acoustic emission experiments of large-scale
rock samples. Three kinds of rock samples were used in the experiments. The tri-axial loading condition was applied under
different loading histories. The released elastic energy (Acoustic emission) was recorded with acoustic emission technique
as microcracks emerged and developed inside the rock samples. The experimental results gave a further verification on the
CPH. The elastic energy release of rock samples would accelerate before the failure even under different experimental conditions.
Primary studies were also made on medium-term earthquake prediction by using accelerating energy release (AER) in the paper.
Foundation item: Project of Natural Sciences Foundation of China (10232050), Project of State Key Basic Research (2002CB412706) and Project
of Computer Network Information Center, Chinese Academy of Sciences (2002CB412706). 相似文献
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On the theory of radio frequency emission from macroscopic hypervelocity impacts and rock fracturing
We suggest that the non-Maxwellian plasma produced during the catastrophic collapse of a rock (following, e.g., the impulsive momentum transfer in a collision between a hypervelocity projectile and a target rock, or the sudden failure of a rock specimen under stress) may satisfy the conditions for the onset of an ion-acoustic instability. If these fairly loose conditions are satisfied, the plasma may be the source of the electromagnetic RF radiation which has been detected in several laboratory experiments. The relevance of these results to the RF emissions which are know to accompany some earthquakes is discussed. 相似文献
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An up-to-date laboratory investigation complex for testing rock samples under controlled uniaxial and triaxial compression is designed. A wide range of loading modes of samples allows one to simulate various natural seismic regimes. The complex is equipped with systems intended for measuring and recording service and physical parameters, namely, axial, uniform, and pore pressure, axial and radial deformation, velocities of longitudinal waves along 16 travel paths, and waveforms of separate acoustic events, recorded by 16 sensors. The system ensures the continuous recording of the acoustic emission stream. Data of all measuring systems are synchronized with time. The rock samples are tested in the automatic mode, which can be optionally corrected during experiments. The experimental results are stored in a single database, which contains both raw and processed data (loading history, catalogs and bulletins of acoustic events, 3D graphic visualizations of pressure-wave velocity distributions in the sample volume, etc.). The application of the complex for the laboratory modeling of the seismic regime is illustrated by a number of practical examples. 相似文献
10.
加卸载响应比(LURR)理论的实验研究 总被引:13,自引:1,他引:13
利用大尺度岩石试件破坏声发射实验,对加卸载响应比(Load/Unload Response Ratio)理论进行了实验研究。实验采用的加载条件力求能够模拟地下岩石的复杂受力过程。在加载过程中,岩石试件内部出现的损伤用声发射技术进行了记录。实验数据经过分析之后所得的结论与加卸载响应比理论预测的结果相符合。把加卸载响应比值Y的变化情况与声发射事件定位的过程相对比,也可以进一步看出岩石材料内部的损伤发展过程与加卸载响应比Y值的变化具有一致性。而高Y值的异常情况出现,又是在材料发生最终破坏之前,所以,可以用加卸载响应比理论定量地分析岩石试件损伤演化情况,从而对岩石材料的破坏及地震做出预测。实验结果再一次验证了加卸载响应比理论。 相似文献
11.
Weathering reduces the strength of rocks and so is a key control on the stability of rock slopes. Recent research suggests that the geotechnical response of rocks to weathering varies with ambient stress conditions resulting from overburden loading and/or stress concentrations driven by near-surface topography. In addition, the stress history experienced by the rock can influence the degree to which current weathering processes cause rock breakdown. To address the combined effect of these potential controls, we conducted a set of weathering experiments on two sedimentary lithologies in laboratory and field conditions. We firstly defined the baseline geotechnical behaviour of each lithology, characterising surface hardness and stress–strain behaviour in unconfined compression. Weathering significantly reduced intact rock strength, but this was not evident in measurements of surface hardness. The ambient compressive stress applied to samples throughout the experiments did not cause any observable differences in the geotechnical behaviour of the samples. We created a stress history effect in sub-sets of samples by generating a population of microcracks that could be exploited by weathering processes. We also geometrically modified groups of samples to cause near-surface stress concentrations that may allow greater weathering efficacy. However, even these pronounced sample modifications resulted in insignificant changes in geotechnical behaviour when compared to unmodified samples. The observed reduction in rock strength changed the nature of failure of the samples, which developed post-peak strength and underwent multiple stages of brittle failure. Although weakened, these samples could sustain greater stress and strain following exceedance of peak strength. On this basis, the multi-stage failure style exhibited by weaker weathered rock may permit smaller-magnitude, higher-frequency events to trigger fracture through intact rock bridges as well as influencing the characteristics of pre-failure deformation. These findings are consistent with patterns of behaviour observed in field monitoring results. © 2019 John Wiley & Sons, Ltd. 相似文献
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Henryk Marcak 《Journal of Applied Geophysics》1994,31(1-4)
The essential conditions for effective and ecologically safe exploitation of underground waste storage are maintenance, prevention, and monitoring of tightness of rock masses covering and surrounding the reservoir rock complex. This monitoring can be realized by a especially designed acoustic measurement system.The reservoir rock complexes - without leakage - are supposed to be in physical equilibrium; without changes of rock dynamic properties the acoustic emission vanishes. In contrast, as is shown, the results of the field tests carried out in coal mines proved that there was a correlation between the stresses and the acoustic emission ratio. The laboratory experiments also showed correlation between changes of permeability of coal samples and acoustic emission.the explanation of the observed results is based on the development of inelastic deformation of a rock skeleton. The plastic strains in the porous rock appear after overcoming the yield point. The yield point value can be extended by increase of shear stresses, effective stresses and interstitial pressure.In particular, there are three kinds of dynamic phases which may appear preceding the failure of leak tightness:
- 1. (1) breaking of the rock masses due to stress (Griffith criterion of stability may be expressed in terms of the acoustic emission parameters),
- 2. (2) the dilatant corrosion of pressure plasticity resulting from chemical, physical and thermal activities, and
- 3. (3) the destructive increase of pressure in rock pores.
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本文研究了在不同的应力途径下岩石破坏的条件和破裂的前兆.选定了三种应力途径进行研究:在一定应力状态下增加最大主应力σ1, 保持σ2, σ3不变, 使岩石破坏(A 型);减小最小主应力使岩石破坏(B 型);增加最小主应力岩石不破坏(C 型).通过实验得到了济南辉长岩和昌平花岗岩 A 型途径和 B 型途径破裂强度的比较.对三种途径岩石的体应变、声发射和波速Vp, 进行了对比研究.A 型途径的破裂前兆表现与许多作者的结果相符合.B 型途径岩石断裂前处于"过密"状态, 与此相联系的声发射增加和波速Vp下降出现得很晚.C 型途径岩石处于超膨胀状态, 出现了声发射增加和波速Vp下降而岩石并未破坏的现象. 相似文献
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Yu Huaizhong Yin Xiangchu Liang Naigang Xia Mengfen Li Min Xu Zhaoyong Peng Keyin Victor Kukshenko Wu Zhishen Qi Li Surguei Elizarov 《中国地震研究》2003,17(3):227-235
Implementing acoustic emission experiments with large rock samples, LURR (Load/Unload Response Ratio) theory was studied. The loading conditions in the experiments were designed to simulate the complicated loading process of underground rocks. The damages emerging inside the rock samples were recorded by the acoustic emission technique during the loading process. The experimental results were consistent with prediction by LURR theory. Integrating the changing processes of LURR value Y and the location process of acoustic emission events showed agreement between the variation of LURR value Y and the damage evolution inside the rocks. Furthermore, the high value of Y emerged before the complete breakdown of materials. Therefore, the damage evolution of rock specimen can be quantitatively analyzed with LURR theory, thus the failure of the rock materials and the earthquake occurrence may be predicted. The experimental results gave a further verification of LURR theory. 相似文献
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本文介绍了对岩石在不同应力途径下的体积变化进行的实验研究。主要的应力途径有三种,并且都是首先把岩石加载到破裂前一定的应力状态,再分别三种类型加载。实验用电阻应变片测量纵向和横向应变以计算体应变。实验表明:同一种岩石在不同应力途径下膨胀效应有显著的不同。文中用辉长岩的实验数据对过密量和超膨胀量进行了估算。研究表明,过密与膨胀是应力途径变化时岩石体积变化的滞后效应。研究了B型实验过密状态出现的条件。从强度80%左右开始减小最小主应力的B型实验明显表现经历过密状态。从低应力状态(强度50%左右)和高应力状态(强度92%以上)开始减小最小应力的B型实验,岩石均未经历过密状态。最后联系地震预报问题进行了简单的讨论 相似文献
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A review of rock mechanics studies in the United States pertinent to earthquake prediction 总被引:1,自引:0,他引:1
J. Byerlee 《Pure and Applied Geophysics》1978,116(4-5):586-602
Premonitory phenomena such as dilatancy, creep, acoustic emission, and changes in seismic velocity and attenuation, electrical resistivity, magnetic moment, and gas emission, which occur before fracture of initially intact rock and before stick-slip on faults or between finely ground surfaces of rock, have been reviewed and discussed in relation to earthquake prediction. This review is restricted to the results of laboratory experiments that have been carried out in the United States of America. 相似文献
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为了从实验角度探索低渗砂岩是否存在很小的ESCK值及重新认识低渗砂岩ESCK的变化规律,用两种修正的析因设计方案开展了塔巴庙低渗致密砂岩渗透率有效应力定律实验研究.一种方案包含了3个循环,每个循环是在孔隙流体压力不变,通过加载和卸载围压完成的;另一种方案包含4个循环,每个循环是在围压不变,通过降低和增加孔隙流体压力完成的.采用稳态法采集每个测点的渗透率值,并选择合适的经验模型拟合实验数据.为了使模型更好地拟合实验数据,本文采用最大似然函数法确定的转换系数转换实验得到的渗透率数据,使拟合得到的经验模型计算的渗透率值与实验值偏差的联合概率密度趋于极大值且残余平方和最小.拟合得到的经验模型可以用渗透率-围压-内压响应面直观地表示,再用Bernabe的ESCK计算式将这一响应面转换成渗透率有效应力系数ESCK-围压-内压响应面.ESCK响应面的响应特征表明,ESCK随围压和孔隙流体压力的变化而变化,随围压的增加而降低,随内压的增加而增加,反之亦然;实验研究还表明,ESCK的变化范围在0.0~1.02之间,这一变化范围和以往实验的结果存在巨大的差异,为此,文中分析了产生这一差异原因,同时提出一新的机理模型解释了实验获取的ESCK的变化规律是低渗岩石中微裂缝和孔隙变形共同作用的结果. 相似文献
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Peter Herzsprung Elke Bozau Olaf Büttner Anja Duffek Kurt Friese Matthias Koschorreck Martin Schultze Wolf v. Tümpling Katrin Wendt‐Potthoff 《洁净——土壤、空气、水》2006,34(6):593-607
Pore water of sediments plays an important role in aquatic systems as mediator and as the reactive zone between the sediment and surface water. Sediment pore waters with high ionic strength from acidified pit lakes were investigated to obtain information about the influence on the lake water quality. The analysis of soluble reactive phosphorus, nitrate, ammonium, silica, dissolved organic carbon, ferrous iron, sulfate, chloride, sodium, potassium, calcium, magnesium, manganese, and total dissolved iron was predetermined as the dataset required for evaluation of water quality. The data collection procedure was optimised by designing a methodology for stabilisation, dilution of pore water samples and adaptation of analytical methods. The developed methodology was evaluated with respect to the effort required in the laboratory under routine conditions. In the first round of analyses, 72% of 638 individual analyses from a random selection of pore water profiles were found to be within the calibration ranges. Remedial actions to handle the remaining 28% of invalid analytical results are exemplified. Differences between comparative analyses of some ions by continuous flow analysis, ion chromatography, and atomic emission spectroscopy were evaluated. The majority of results measured by ion chromatography differed on a highly significant level from results measured by atomic emission spectroscopy. Possible reasons, originating from the extreme sample matrix, are discussed. Finally, the designed methodology and the results of the method comparison are used to recommend the selection of analytical methods under specific conditions. 相似文献