探头安装偏心对钻孔应变观测影响的分析  

Analysis of eccentric impact borehole strain observation probe installation

作　　者：李进武[1,2] 邱泽华[2] 

机构地区：[1]中国地震局第一监测中心,天津300180 [2]中国地震局地壳应力研究所,北京100085

出　　处：《地球物理学进展》2016年第1期433-441,共9页Progress in Geophysics

基　　金：地震行业科研专项(201108009);中国大陆现代垂直形变图集的编制与资料整编(2015FY210400)联合资助

摘　　要：钻孔应变仪安装时出现的探头偏心现象会使观测数据质量受到影响.四分量钻孔应变仪设计独特,第一、三组元件观测值之和与第二、四组观测值之和相等,此为钻孔应变观测自洽.钻孔应变观测质量可由观测值能否自洽进行检测.本文将有限元数值计算和钻孔应变观测理论模型相结合,主要分析应变仪安装探头偏心是否造成观测数据不自洽,并讨论造成不自洽的原因.考虑仪器不同程度偏心,结果显示偏心引起观测数据不自洽,偏心尺度越大,不自洽越明显.本文也发现仪器不偏心时,耦合系数为常数,一旦仪器偏心,耦合系数随着元件方位角改变而变化,这与通常总将耦合系数看作常数是不一致的.而引起不自洽的原因是探头偏心导致耦合系数随着元件方位角发生改变.此外,耦合系数A,B和加载载荷无关.本文对偏心情形下的数据进行校正,通过校正去除了偏心对结果的影响,同时也分析了钻孔应变观测相对标定的合理性和有效性.The borehole deviation problem affects the observation after borehole strainmeter install. The four-gauge borehole strainmeter own unique design. The four gauges in the four-gauge borehole strainmeter are arranged at 45° intervals to bring about a self-consistency equation,which serves as a means of checking that the measurements obtained from the four-gauge borehole strainmeter are correct. In the paper,we combine the finite element numerical calculation and theoretical model of borehole strain observation. We analyze whether the borehole deviation is a reason for the observation not to exhibit a self-consistency. Considering the different degree of eccentricity,we find the borehole deviation is a reason for the observation not to exhibit a self-consistency. The bigger the deviation,not self-consistent. At the same time,we find When the instrument is not eccentric,coupling coefficient is constant,once the instrument is eccentric,coupling coefficient varies with the sensor azimuth. But,we general consider coupling coefficient is constant. The reason of the observation not to exhibit a selfconsistency is coupling coefficient varies with the sensor azimuth. In addition,the coupling coefficient A、B has nothing to do with the loading. We calibrate the observations as the borehole deviation,removing influence of the borehole deviation. Final,we analyze the rationality and effectiveness of relative in situ calibration.

关 键 词：偏心 数值模拟 自洽 耦合系数 钻孔应变仪 

分 类 号：P631[天文地球—地质矿产勘探]