青岛地震台钻孔体应变异常变化因素分析

分时段研究降雨、钻孔水位、工程施工等因素对青岛地震台体应变的影响,研究结果表明:钻孔水位反映区域地下水主要由降雨补给,降雨下渗改变地下水状态,并影响体应变观测;青岛体应变与钻孔水位的相关性及其周期特性均在2015年前后出现变化,可能与2015—2016年降雨偏少及工程施工有关;2018年1月17日台站钻孔施工很可能改变了体应变周围岩石孔隙环境,并扩大孔隙压力作用系数,可解释2018年3月以来水位小幅上升引起的体应变显著压性上升现象,受钻孔施工的影响,体应变与钻孔水位相关性的滞后特征明显减弱。

Analysis of the Abnormal Variation Factors of the Borehole Volumetric Strain at Qingdao Seismic Station

This paper studied the influence of factors such as rainfall, borehole water level, engineering construction on the borehole volumetric strain at Qingdao seismic station. The results show that the groundwater level at Qingdao seismic station reflected by borehole water level is mainly recharged by rainfall, and the rainfall infiltration affects the volumetric strain observation by changing the groundwater state. The correlation between the volumetric strain and borehole water level, as well as the periodic characteristics have changed around 2015, which might be related to the lack of rainfall and engineering construction from 2015 to 2016. The drilling construction at Qingdao seismic station on January 17, 2018 changed the pore environment of rocks around the volumetric strain, and expanded the action coefficient of pore pressure, which can explain the phenomenon of significant increase of the volumetric strain due to the slight rise of water level since March, 2018. Under the influence of drilling construction, the hysteretic characteristic of the correlation between the volumetric strain and borehole water level is obviously weakened.