双轴压力下岩样自电位变化实验的新结果
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摘要
利用伺服控制双轴加载系统 ,采用阵列式布局的应变、自电位测量方法 ,对岩石样品弹性变形阶段和破坏过程中的应变和自电位进行了实验研究 .结果表明 ,在突然加卸载、黏滑和岩样破裂几种特定情况下 ,自电位和应变场均出现了互相关联的脉冲状突然变化 ,且具有相当大的空间展布 .尽管有时应力σ值相当高 ,但当应力变化率γ =dσ dt为零 (恒载 )且保持正、负常数 (匀速加、卸载 )时 ,自电位始终没有异常出现 .反之 ,无论γ的增量Δγ为正值或负值 ,当γ突变 ,即对样品进行突然加卸载的时刻则出现了脉冲状自电位信号ΔV ,Δγ的正或负对ΔV的影响是相反的 .分析表明 ,应力突变时ΔV与Δγ的异常幅度成正比 .应力突变和岩石破裂过程中自电位明显的时空变化意味着 ,孕震区附近如果自电位有突变 ,就有可能观测到相关的自电位前兆和同震变化 ,并可能出现同步的应变变化 ,这给地震的自电位和应变前兆方法提供了实验证据
An experiment on self potential and strain changes during the elastic deformation and fracture of rock samples was conducted by means of a biaxial servo control loading machine and a detecting array of strain gauges and electrodes. Some correlated and widespread pulse like transient variations in self potential and strain field appeared at some special situations, including sudden loading/ unloading, stick slip and fracture of rocks. The results indicate that though sometimes the stress σ is rather high, there is no SP anomaly occurring if the stress change rate γ =d σ / d t equals zero or keeps positive or negative constants. On the contrary, at the moment γ changes suddenly the pulse like SP change Δ V will always arise no matter the increment Δ γ is positive or negative. The positive or negative sign of Δ γ gives opposite effect on Δ V . The anomalous amplitude of Δ V is proportional to that of Δ γ . The observed clear temporal and spatial self potential changes at sudden stress rate change and rock fracture mean that it is possible to detect the precursory and co seismic electric and corresponding strain variations if the above mentioned conditions can be met near a seismic generating zone. It is a support to the seismic precursory research of self potential and strain.
An experiment on self potential and strain changes during the elastic deformation and fracture of rock samples was conducted by means of a biaxial servo control loading machine and a detecting array of strain gauges and electrodes. Some correlated and widespread pulse like transient variations in self potential and strain field appeared at some special situations, including sudden loading/ unloading, stick slip and fracture of rocks. The results indicate that though sometimes the stress σ is rather high, there is no SP anomaly occurring if the stress change rate γ =d σ / d t equals zero or keeps positive or negative constants. On the contrary, at the moment γ changes suddenly the pulse like SP change Δ V will always arise no matter the increment Δ γ is positive or negative. The positive or negative sign of Δ γ gives opposite effect on Δ V . The anomalous amplitude of Δ V is proportional to that of Δ γ . The observed clear temporal and spatial self potential changes at sudden stress rate change and rock fracture mean that it is possible to detect the precursory and co seismic electric and corresponding strain variations if the above mentioned conditions can be met near a seismic generating zone. It is a support to the seismic precursory research of self potential and strain.
引文
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[5] 赵玉林,卢军,张洪魁等.电测量在中国地震预报中的应用.地震地质,2001,23(2):277～285ZhaoYL ,LuJ,ZhangHK ,etal.Theapplicationofelectricalmea surementstoearthquakepredictioninChina.SeismologyandGeology(inChinese),2001,23(2):277～285
[6] 郝锦绮,钱书清,高金田等.岩石破裂过程中的超低频电磁异常.地震学报,2003,25(1):102～111HaoJQ ,QianSQ ,GaoJT ,etal.ULFelectricandmagneticanomaliesaccompanyingthecrackingofrocksample.ActaSeismolog icaSinica(inChinese),2003,16(1):113～123
[7] TakeuchiA ,NagahamaH .Voltagechangesinducedbystick slipofgranites.GeophysicalResearchLetters,2001,28(17):3365～3368
[8] 钱书清,郝锦绮,周建国等.岩石受压破裂的ULF和LF电磁前兆信号.中国地震,2003,19(2):109～116QianSQ ,HaoJQ ,ZhouJG ,etal.Precursoryelectricandmagnet icsignalsatULFandLFbandsduringthefractureofrocksunderpres sure.EarthquakeResearchinChina(inChinese),2003,19(2):109～116
[9] HadjicontisV ,MavromatouC .Electricsignalsrecordedduringuniax ialcompressionofrocksamples:theirpossiblecorrelationwithpre seismicelectricsignals.ActaGeophysicaPolonica,1995,43(1):49～61
[10] MizutaniH ,IshidoT ,YokokuraT ,etal.Electrokineticphenomenaassociatedwithearthquakes.Geophys.Res.Lett.,1976,3:365～368
[11] SlifkinL .Seismicelectricsignalsfromdisplacementofchargeddislo cations.Tectonophysics,1993,224:149～152
[12] 郭自强,周大庄,施行觉等.岩石破裂中的电子发射.地球物理学报,1988,31(5):566～571GuoZQ ,ZhouDZ ,ShiXJ ,etal.Electronemissionduringrockfracture.ChineseJ .Geophys.(ActaGeophysicaSinica)(inChi nese),1988,31(5):566～571