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作者试验研究了在不同三轴应力条件下,饱水砂岩的电阻率变化与施加应力的方式及应变积累速率的关系.试验方式为开始在一定的静水压力下,保持最小主应力(σ_3)不变,考察了两种应力积累过程:1.以快速—慢速—最快速三种加载速率施加最大主应力(σ_1),中间主应力(σ_2)称之谓 Ⅰ 型;2.以慢速—快速—恒压—最快速四种加载速率施加σ_1、σ_2称之谓Ⅱ型.两种应力过程的σ_1、σ_2,均加至破强度的80—90%后,再快速卸载至原静水压.同时,其应变速率控制在10~(-6)—10~(-7)/秒范围内.实验结果与某些大地震前后的一些地电变化的实测记录相吻合.从而揭示了地震前后视电阻率异常的阶段性变化特征,可能与地震在孕育过程中应变能的积累方式、应变速率、能量释放(地震活动)等因素相关联.为实测电阻率的前兆现象(地电异常)的理论解释提供了实验基础.
The authors experimentally studied the relationship between the resistivity change and the mode of stress application and the rate of strain accumulation of saturated sandstone under different triaxial stress conditions. The test method is to start with a certain hydrostatic pressure to maintain the minimum principal stress (σ_3) The main stress (σ_1) is applied at three fast-slow-fast loading rates. The middle principal stress (σ_2) is called type I. 2. The slow- Fast - constant pressure - the fastest four kinds of loading rate imposed σ_1, σ_2 known as Type Ⅱ Both stress process σ_1, σ_2, are added to the breaking strength of 80-90%, and then quickly unloaded to the original hydrostatic pressure At the same time, the strain rate is controlled in the range of 10 -6 -6 -10 -7 / s.The experimental results are in good agreement with the measured records of some geoelectric changes before and after some major earthquakes, The characteristics of the phase change of apparent resistivity anomaly may be related to the factors such as the accumulation of strain energy during earthquake, strain rate, energy release (seismic activity), etc. For the purpose of measuring the precursor phenomenon of resistivity (geoelectric anomaly) Theoretical explanation provides the experimental basis.