岩石临破裂前波速变化特征的实验研究
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摘要
为了提高波速的测量精度以便能观测到岩石临破裂前波速的微小变化,采用了波形的数值化,波的叠加,波的互相关和DTE(Subsample delay time estimate)方法和cosine插值,使时间分辨率提高到0.001μs,波速分辨率达到1m/s.在较小的应力增量(0.17MPa)下测量了波的延迟时间,进而得到速度随应力的变化规律.实验结果显示在0.98破裂强度时岩石波速最大,然后下降直到破裂,此期间的波速下降量约30m/s.同时对临破裂前波的主频能量进行了计算,其变化规律与波速相同,认为破裂前的有关变化与岩石膨胀有关.最后用涨落模型讨论了延迟时间的方差变化.
In order to measure the small change of velocity before rock fracture,the velocity measurement precision must be improved,the methods including digital wave form,the wave stacking,cross correlation and Subsample delay time estimate were used,the precision of time and velocity reached to 0.001 micro second and 1 m/s respectively.The delay time was measured as the stress increase with the interval of 0.17 MPa,then the rule of velocity as stress increase was obtained.Experimental results showed the velocity had the maximum value at the rock strength of 0.98,after that the velocity decreased about 30m/s to fracture.The power of wave at main frequency was calculated and had the same characteristic with velocity,it was considered the changes may be caused by rock dilation.The square error of delay time was discussed by using the fluctuation model.
In order to measure the small change of velocity before rock fracture,the velocity measurement precision must be improved,the methods including digital wave form,the wave stacking,cross correlation and Subsample delay time estimate were used,the precision of time and velocity reached to 0.001 micro second and 1 m/s respectively.The delay time was measured as the stress increase with the interval of 0.17 MPa,then the rule of velocity as stress increase was obtained.Experimental results showed the velocity had the maximum value at the rock strength of 0.98,after that the velocity decreased about 30m/s to fracture.The power of wave at main frequency was calculated and had the same characteristic with velocity,it was considered the changes may be caused by rock dilation.The square error of delay time was discussed by using the fluctuation model.
引文
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[10]Scheffer M,Bascompte J,Brock W A,et al.Early-warningsignals for critical transitions.Nature,2009,461(2):55-59.
[11]施行觉,赵闯,李成波.岩石蠕变破裂过程及其响应比变化的实验研究.地震学报,2010,32(3):332-339.Shi X J,Zhao C,Li C B.Experimental study on rock creepfracture and it′s Load/Unload respond ratio.ActaSeismologica Sinica(in Chinese),2010,32(3):332-339.
[12]吕培苓,吴开统,焦远碧等.岩石蠕变过程中声发射活动的实验研究.地震学报,1991,13(1):104-112.LüP L,Wu K T,Jiao Y B,et al.The experimental study ofacoustic emission during creep of Rock.Acta SeismologicaSinica(in Chinese),1991,13(1):104-112.
[13]许昭永,王彬,胡毅力等.试论岩石破裂和破坏的差异对地震模拟及前兆研究的响.地球物理学报,2009,52(3):712-718.Xu Z Y,Wang B,Hu Y L,et al.A discussion on theinfluence of the difference between the rock fracture andfailure to the earthquake simulation and the precursorstudies.Chinese Journal of Geophysics(in Chinese),2009,52(3):712-718.
[14]Crampin S,Gao Y.Earthquakes can be stress-forecast.Geophysical Journal International,2010,180(3):1124-1127.
[2]Silver P G,Daley T M,Niu F,et al.Active sourcemonitoring of cross-well,seismic travel time for stress-induced changes.Bull.Seismol.Soc.Am.,2007,97(1B):281-293.
[3]陈颙,黄庭芳,刘恩儒.岩石物理学.合肥:中国科学技术大学出版社,2009.Chen R,Huang T F,Liu E R.Rock Physics(in Chinese).Hefei:University of Science and Technology of China Press,2009.
[4]方华,伍向阳.温压条件下岩石破坏前后的力学性质与波速.地球物理学进展,1999,14(3):73-78.Fang H,Wu X Y.The mechanical properties and velocitiesof rocks pre-and post-failure under pressure and temperature.Progress in Geophysics(in Chinese),1999,14(3):73-78.
[5]刘晓红.岩石摩擦滑动失稳前断层区的波速变化.中国地震,1997,13(1):82-87.Liu X H.The change of wave velocity in fault zone beforelosing stability of rocks frictional sliding.Earthquake Research inChina(in Chinese),1997,13(1):82-87.
[6]赵晋明,胡毅力,杨润海等.岩石临破坏前波速奇异变化的再研究.地震研究,2001,24(2):136-139.Zhao J M,Hu Y L,Yang R H,et al.Further study onstrange variation of wave velocity before Rock Rupture.Journal of Seismological Research(in Chinese),2001,24(2):136-139.
[7]杨宏峰,施行觉.轴向压力下砂岩波速的实验研究.地球物理学进展,2004,19(2):481-485.Yang H F,Shi X J.Experimental research on wave velocityunder axial pressure.Progress in Geophysics(in Chinese),2004,19(2):481-485.
[8]De Jong P G M,Arts T,Hoeks A P G,et al.Determinationof tissue,motion velocity by correlation interpolation ofpulsed ultrasonic echo signals.Ultrason,1990,12:84-98.
[9]Cespedes I,Huang Y,Ophir J,et al.Methods for estimationof subsample,time delays of digitized echo signals.Ultrason,1995,17:142-171.
[10]Scheffer M,Bascompte J,Brock W A,et al.Early-warningsignals for critical transitions.Nature,2009,461(2):55-59.
[11]施行觉,赵闯,李成波.岩石蠕变破裂过程及其响应比变化的实验研究.地震学报,2010,32(3):332-339.Shi X J,Zhao C,Li C B.Experimental study on rock creepfracture and it′s Load/Unload respond ratio.ActaSeismologica Sinica(in Chinese),2010,32(3):332-339.
[12]吕培苓,吴开统,焦远碧等.岩石蠕变过程中声发射活动的实验研究.地震学报,1991,13(1):104-112.LüP L,Wu K T,Jiao Y B,et al.The experimental study ofacoustic emission during creep of Rock.Acta SeismologicaSinica(in Chinese),1991,13(1):104-112.
[13]许昭永,王彬,胡毅力等.试论岩石破裂和破坏的差异对地震模拟及前兆研究的响.地球物理学报,2009,52(3):712-718.Xu Z Y,Wang B,Hu Y L,et al.A discussion on theinfluence of the difference between the rock fracture andfailure to the earthquake simulation and the precursorstudies.Chinese Journal of Geophysics(in Chinese),2009,52(3):712-718.
[14]Crampin S,Gao Y.Earthquakes can be stress-forecast.Geophysical Journal International,2010,180(3):1124-1127.
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