陈大元1, 陈峰1, 贺国玉2. 1987: 岩石受压过程中应力反复对电阻率的影响. 地震学报, 9(3): 303-311.
引用本文: 陈大元1, 陈峰1, 贺国玉2. 1987: 岩石受压过程中应力反复对电阻率的影响. 地震学报, 9(3): 303-311.
CHEN DAYUANup, CHEN FENGup, HE GUOYUup2. 1987: INFLUNCES OF STRESS REVERSAL ON ROCK RESISTIVITY DURING LOADING PROCEDURE. Acta Seismologica Sinica, 9(3): 303-311.
Citation: CHEN DAYUANup, CHEN FENGup, HE GUOYUup2. 1987: INFLUNCES OF STRESS REVERSAL ON ROCK RESISTIVITY DURING LOADING PROCEDURE. Acta Seismologica Sinica, 9(3): 303-311.

岩石受压过程中应力反复对电阻率的影响

INFLUNCES OF STRESS REVERSAL ON ROCK RESISTIVITY DURING LOADING PROCEDURE

  • 摘要: 在岩石电阻率随压力变化的不同阶段,部份地减低轴向压力后再加压(每回总压降约为破坏应力的10%).研究这种特殊的加载方式下,即所谓应力反复对电阻率的影响.结果如下:(1)对高水饱和度岩石,随压力不断增加电阻率变化的总趋势为上升——平稳——下降的变化形态(包括饱和度为100——70%).对低饱和度岩石(实验中饱和度为70%和50%),电阻率变化的总趋势已改变.(2)对高饱和度岩石共作了十一次应力反复实验.除了水饱和度为71%的岩石在压力为30MPa 处,应力反复时电阻率无明显变化外,其余均呈现电阻率的负异常(下降幅度约2%左右),我国地电台在震前观测到的地电阻率变化以负异常为主.实验结果为解释这种负异常提供一种新的可能机制.(3)在电阻率随压力变化的下降段,特别是接近岩石破坏时,应力反复所引起的电阻率负异常与一般情况下出现的负异常相比,有以下三个特征:a)负异常的幅度要大一个数量级(约-20%);b)不仅应力下降时电阻率下降,而且应力恢复时电阻率仍然下降;c)各个方向电阻率变化的差别很大(约10%).以上这三个特征可作为岩石临近破坏的标志.而一般的电阻率负异常可能只与应力反复有关,并不意味着岩石处于临近破裂的危险状态.(4)低饱和度岩石,应力反复可能引起电阻率的正异常.作者还用

     

    Abstract: The properties of rock resistivity were studied under pressure, particularly with stress reversal procedure, in which the applied pressure was increased, decreased, and increased again.It was observed that, 1) with pressure increasing, the main feature of the resistivity changes was increase-steady-decrease for high saturation rock samples (saturation 71-100%). But the main feature for low saturation samples was different (resistivity increased). 2) In 10 out of 11 cases for high saturation samples the resistivities droped remarkably (about 2%). These drops could explain the negative anomalies commonly observed in geoelectricity surveys, before earthquakes in China. 3) It was also observed shortly before rock failure that, a) The resistivity drops much more dramatically in the stress reversal period, about 20% more than ordinary drops, b) These drops occured not only during stress decrease but also during stress increase, c) The anisotropic property of resistivity change is enhanced. 4) Resittivity increase was observed during the stress reversal period for low saturation rock samples.The results mentioned above were explained with the effect of water flowing in and out of the cracks of rocks. Temporary factors, which bring about a reduction of the main stress, may enhance the possibility of earthquake occurrence.

     

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