关于在土层中进行钻孔应变观测的可行性问题
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摘要
在土层中开展钻孔应变观测实验是地球动力学以及地震预报研究的需要。能否观测到固体潮对该实验的成功与否起决定作用。土层与岩层的主要区别是其疏松性。由此造成的压密永久变形问题,可以通过在适当深处以下安装探头来解决。同时,因为土在小变形动态载荷下呈现弹性,而固体潮应变变化量级为10-8左右,所以探头并不需要安装在太深的地方。理论分析的结果是,虽然钻孔应变仪在土层中观测应变变化的灵敏度小于岩层,但是因为在相同的应力下,土层弹性变形比岩层大得多,所以在整体效果上是有利于在土层中观测到固体潮的。孔隙水的变化会给钻孔应变观测带来严重干扰,钻孔应变探头的深度应该避开地下水位变动范围。如何能在土层中观测到固体潮,最终需要通过实验来说明。
Tests for observing strain changes in soil with borehole strainmeters are needed in researches of earthquake forecast as well as geodynamics.The observation can be testified if solid earth tides will be clearly recognized.The difference of observation in soil from in rocks lies on the looseness of the medium.Therefore,the strainmeter should be placed significantly deeper in order to solve the problem of permanent deformation.Meanwhile,since soil responds elastically to small dynamic deformation,and the tides of strain are on the order of 10-8,the placement may not be necessarily very deep.Results of theoretic analysis indicate that,although resolution of borehole strainmeter for observation in soil is lower than in rocks,soil deforms much larger than rocks for same stress changes will benefit the observation of tides in soil.Existence of pore liquid will bring about disturbance to borehole strain observation and the sensor should be placed beyond the depth close to water table.It will eventually be checked through practical tests.Whether the present borehole strainmeters can record earth tides.
Tests for observing strain changes in soil with borehole strainmeters are needed in researches of earthquake forecast as well as geodynamics.The observation can be testified if solid earth tides will be clearly recognized.The difference of observation in soil from in rocks lies on the looseness of the medium.Therefore,the strainmeter should be placed significantly deeper in order to solve the problem of permanent deformation.Meanwhile,since soil responds elastically to small dynamic deformation,and the tides of strain are on the order of 10-8,the placement may not be necessarily very deep.Results of theoretic analysis indicate that,although resolution of borehole strainmeter for observation in soil is lower than in rocks,soil deforms much larger than rocks for same stress changes will benefit the observation of tides in soil.Existence of pore liquid will bring about disturbance to borehole strain observation and the sensor should be placed beyond the depth close to water table.It will eventually be checked through practical tests.Whether the present borehole strainmeters can record earth tides.
引文
1邱泽华,石耀霖.地震造成远距离应力阶变的观测实例[J].中国科学,2003,33(增刊):60-64.
2邱泽华,石耀霖.国际钻孔应变观测的发展现状[J].地震学报,2004,26(增刊):162-168.
3邱泽华,石耀霖.观测应变阶在地震应力触发研究中的应用[J].地震学报,2004,26(5):481-488.
4邱泽华,等.钻孔差应变仪观测的苏门答腊大地震激发的地球环形自由振荡[J].地球物理学报,2007,50(3):797-805.
5 Gladwin M T.A report on the Gladwin tensor strainmeter[R].CSIRO xploration and Mining,2002.
6 Gladwin M TE,et al.A medium term precursor to the LomaPrieta earthquake?[J].Geophy.Res.Lett.,1991,18(8):1 377-1 380.
7 Gwyther R L,et al.Anomalous tensor strain at Parkfield dur-ing 1993-1994[J].Geophys.Res.Lett.,1996,23:2 425-2 428.
8 Langbein J,et al.Slip rate increase at Parkfield in 1993 de-tected by high-precision EDM and borehole tensor strainme-ters[J].Geophys.Res.Lett.,1999,26:2 529-2 532.
9 Linde AT,et al.Aslowearthquake sequence on the San An-dreas fault[J].Nature,1996,383:65-68.
10 Roeloffs E and Quilty E.Water level and strain changespreceding and following the August 4,1985 KettlemanHills,California,Earthquake[J].Pure Appl.Geophys.,1997,149:21-60.
11 Sakata S and Sato H.Borehole-type tiltmeter and three-component strainmeter for earthquake prediction[J].J.Phys.Earth,1986,34(Sup.):129-140.
12 Segall P,Jonsson S and Agustsson K.When is the strain inthe meter the same as the strain in the rock?[J].Geo-phys.Res.Lett.,2003,30(19):1 990-1 994.
13邱泽华.地面应变场变化图像的观测[J].国际地震动态,2006,(6):7-11.
14苏恺之.液位型体积式应变仪的工作原理[J].地震科学研究,1982,(4):57-62.
15王启民,冯先水,马鸿钧.一种弦频式钻孔应变仪[J].地震学报,1983,5(3):370-376.
16欧阳祖熙,等.一种钻井式地应力测量系统[A].地壳构造与地壳应力文集(2)[C].北京:地震出版社,1988,1-47.
17池顺良.一种浅孔安装的YRY-2型钻孔应变仪在中国华北地区8个台站试验观测的结果[J].地震学报,1993,15(2):224-231.
18 HA崔托维奇.吴光输译.土力学(重译本)[M].北京:地质出版社,1956.
19刘成宇主编.土力学(第二版)[M].北京:中国铁道出版社,1999.
20张克绪,谢君斐.土动力学[M].北京:地震出版社,1989.
21潘立宙.测量地应力的钻孔变形法[A].见:中国地质科学院地质力学研究所和国家地震局地震地质大队编,地应力测量的原理和应用[C].北京:地质出版社,1981,1-47.
22潘立宙.与地应力测量的几个公式的推导和讨论[A].见:中国地质科学院地质力学研究所和国家地震局地震地质大队编,地应力测量的原理和应用[C].北京:地质出版社,1981,163-203.
23苏恺之,等.钻孔地应变观测新进展[M].北京:地震出版社,2003.
24邱泽华.钻孔应变观测地面载荷干扰源最小“安静”距离的理论分析[J].岩石力学与工程学报,2004,23(23):4 063-4 067.
2邱泽华,石耀霖.国际钻孔应变观测的发展现状[J].地震学报,2004,26(增刊):162-168.
3邱泽华,石耀霖.观测应变阶在地震应力触发研究中的应用[J].地震学报,2004,26(5):481-488.
4邱泽华,等.钻孔差应变仪观测的苏门答腊大地震激发的地球环形自由振荡[J].地球物理学报,2007,50(3):797-805.
5 Gladwin M T.A report on the Gladwin tensor strainmeter[R].CSIRO xploration and Mining,2002.
6 Gladwin M TE,et al.A medium term precursor to the LomaPrieta earthquake?[J].Geophy.Res.Lett.,1991,18(8):1 377-1 380.
7 Gwyther R L,et al.Anomalous tensor strain at Parkfield dur-ing 1993-1994[J].Geophys.Res.Lett.,1996,23:2 425-2 428.
8 Langbein J,et al.Slip rate increase at Parkfield in 1993 de-tected by high-precision EDM and borehole tensor strainme-ters[J].Geophys.Res.Lett.,1999,26:2 529-2 532.
9 Linde AT,et al.Aslowearthquake sequence on the San An-dreas fault[J].Nature,1996,383:65-68.
10 Roeloffs E and Quilty E.Water level and strain changespreceding and following the August 4,1985 KettlemanHills,California,Earthquake[J].Pure Appl.Geophys.,1997,149:21-60.
11 Sakata S and Sato H.Borehole-type tiltmeter and three-component strainmeter for earthquake prediction[J].J.Phys.Earth,1986,34(Sup.):129-140.
12 Segall P,Jonsson S and Agustsson K.When is the strain inthe meter the same as the strain in the rock?[J].Geo-phys.Res.Lett.,2003,30(19):1 990-1 994.
13邱泽华.地面应变场变化图像的观测[J].国际地震动态,2006,(6):7-11.
14苏恺之.液位型体积式应变仪的工作原理[J].地震科学研究,1982,(4):57-62.
15王启民,冯先水,马鸿钧.一种弦频式钻孔应变仪[J].地震学报,1983,5(3):370-376.
16欧阳祖熙,等.一种钻井式地应力测量系统[A].地壳构造与地壳应力文集(2)[C].北京:地震出版社,1988,1-47.
17池顺良.一种浅孔安装的YRY-2型钻孔应变仪在中国华北地区8个台站试验观测的结果[J].地震学报,1993,15(2):224-231.
18 HA崔托维奇.吴光输译.土力学(重译本)[M].北京:地质出版社,1956.
19刘成宇主编.土力学(第二版)[M].北京:中国铁道出版社,1999.
20张克绪,谢君斐.土动力学[M].北京:地震出版社,1989.
21潘立宙.测量地应力的钻孔变形法[A].见:中国地质科学院地质力学研究所和国家地震局地震地质大队编,地应力测量的原理和应用[C].北京:地质出版社,1981,1-47.
22潘立宙.与地应力测量的几个公式的推导和讨论[A].见:中国地质科学院地质力学研究所和国家地震局地震地质大队编,地应力测量的原理和应用[C].北京:地质出版社,1981,163-203.
23苏恺之,等.钻孔地应变观测新进展[M].北京:地震出版社,2003.
24邱泽华.钻孔应变观测地面载荷干扰源最小“安静”距离的理论分析[J].岩石力学与工程学报,2004,23(23):4 063-4 067.
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