地球物理学进展 ›› 2017, Vol. 32 ›› Issue (4): 1525-1531.doi: 10.6038/pg20170415

• 空间与固体地球物理 • 上一篇    下一篇

基于双衬套理论求解地壳岩石应变传递系数的探讨

张凌空, 牛安福   

  1. 中国地震台网中心, 北京 100045
  • 收稿日期:2016-10-22 修回日期:2017-06-17 出版日期:2017-08-20 发布日期:2017-08-20
  • 作者简介:张凌空,男,1962年生,吉林长春市人,学士,高级工程师,长期从事钻孔应变和地形变等地震前兆方法的观测研究.(E-mail:zhll1023@163.com)
  • 基金资助:

    国家自然科学基金(41330314)资助.

Discussion on solution of crustal rock strain transfer coefficient based on double bush theory

ZHANG Ling-kong, NIU An-fu   

  1. China Earthquake Networks Center, Beijing 100045, China
  • Received:2016-10-22 Revised:2017-06-17 Online:2017-08-20 Published:2017-08-20

摘要:

分量式钻孔应变观测,是当今国际上地壳岩石应变相对测量的主流方法,由于应变需在岩石、水泥和仪器钢筒等三层介质中传递,故与无孔岩石不同,观测系统存在附加应变场,测得的面应变与剪应变并不等于钻孔围岩的真实应变,分别需要一个传递系数与之关联,所以分析外加应变向探头的传递过程很有必要.根据双衬套理论,首先推导出平面应力作用下岩石面应变与剪应变传递系数(βmβj)的计算公式,分别对其影响机制进行讨论,并给出有关变化规律曲线和定量指标.继续给出三维空间应力作用下面应变传递系数(βm3)的计算公式,并讨论了βm3βm的关系及适用范围;剪应变因不受垂直向应力的影响,传递系数仍为βj.通过观测值和求解传递系数,最终可以确定地壳岩石的真实应变量.该项工作对观测数据的物理解释和仪器设计、安装参数的优化也能提供帮助.

Abstract:

Component borehole strain observation is the main method for strain relative measurement of crustal rocks in today's world. Due to strain should be transferred in three layers of media, such as rock, cement and instrument steel tube, herefore, it is different from the non porous rock. Additional strain field exists in the observation system. The measured area strain and shear strain are not equal to the true strain of the surrounding rock. The correlation of a transfer coefficient is required. So it is very necessary to analyze the transfer process of the external strain to the probe. Firstly, according to the double bushing theory, the calculation formulas of rock area strain and shear strain transfer coefficients(βm, βj)are derived under the action of plane stress. Respectively, the influence mechanism is discussed. And give the relevant change rule curve and quantitative index. The calculation formula of area strain transfer coefficient(βm3)under three-dimensional stress is given. The relationship between βm3 and βm and its application range are discussed. The shear strain is not affected by the vertical stress. Transfer coefficient is still βj. Through the observation value and the solution transfer coefficient, finally, the real stress variables of crustal rocks can be determined. This work provides help for the physical interpretation of the observed data and the optimization of the instrument design and installation parameters.

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