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工程降水对钻孔应变的干扰特征及干扰机制研究

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抽水干扰在钻孔应变观测中常见且影响显著,为了能真实捕捉到地震前兆信息,须对其干扰机制进行研究.随着城市化进程,基坑工程及其伴随的工程降水逐步增多,工程降水对钻孔应变的干扰比普通单井抽水干扰更为严重.工程降水对钻孔应变观测有何干扰特征、干扰机制如何、干扰数据能否修复等问题对地震异常的探测具有重要意义.本文基于莱阳体应变受到附近御龙湾项目工程降水干扰的观测案例,研究了工程降水的干扰特征,修复了干扰畸变,通过数值模拟确定了干扰机制.结果表明:(1)工程降水在干扰体应变趋势变化的基础上叠加了方向明确、量级稳定的固体潮畸变,可以通过一阶差分逆运算进行修复.修复固体潮畸变并扣除背景速率后,工程降水干扰量级达-15.65×10-9/d;(2)通过建立基于集中载荷模型的网格算法,模拟出工程降水在体应变异常初期和后期分别产生6.61×109 N和1.73×1010 N的集中力载荷,干扰量级明显大于常见的单井抽水干扰,压性干扰集中于体应变仪与抽水井连线的垂直方向;(3)通过固体潮畸变特征及力学机制分析确定了工程降水造成固体潮畸变的干扰机制为"抽水引起压性趋势下降—抽水暂停引起张性台阶上升—抽水引起压性趋势下降"周期行为,固体潮畸变时间间隔(频次)和钻孔水位之间呈显著同步特征,线性系数为0.737.
The study of interference characteristics and mechanism of engineering dewatering on borehole volume strainmeter
The interference of pumping is common and significant on borehole strain observations,to detect true seismic precursor information from borehole strain strainmeter,the mechanisms of the disturbances generated by pumping must be studied.With the development of urbanization,foundation pit engineering and its associated engineering dewatering gradually increases.It is easy to understand that the interference magnitude of engineering dewatering to borehole strainmeter is more severely than ordinary single-well pumping since more wells are pumping.Studying how the engineering dewatering interferes with the borehole strain observation,what the interference mechanism is,and whether the interference data can be corrected,are of great significance for the detecting of seismic precursor anomalies.In this paper,based on an observation case of TJ-2 volume strainmeter at Laiyang seismic station(short for Laiyang volume strainmeter),which is interfered by engineering dewatering of nearby Yulongwan housing project,the interference characteristics are studied,the disturbed solid tide distortion is corrected,and the interference mechanism is determined by numerical simulation.The results show that:(1)Based on the trend change of Laiyang volume strainmeter caused by the engineering dewatering,solid tide distortion with definite direction and stable magnitude has been superimposed,and we find that the solid tide distortion can be corrected by inverse operation of first-order difference.After correcting the solid tide distortion and deducting the long-term background rate,the interference magnitude caused by engineering dewatering reaches-15.65 × 10-9/d;(2)We used a concentrated load model and meshed the research area to simulate the volume strain field of the surrounding area caused by the engineering dewatering.The simulation results show that the concentrated force loads of 6.61 × 109 N and 1.73 × 1010 N are generated respectively in the early and late period of the volume strain anomaly caused by the engineering dewatering,which is significantly greater than that of single pumping well.The compressive interference concentrates on the vertical direction of the line between the volume strainmeter and the pumping well;(3)Through the analysis of solid tide distortion characteristics and mechanical mechanisms,we found the periodic behavior characteristics of the volume strain observation generated by engineering dewatering.The period can be divided into three stages,the first stage is the decreasing trend of compression caused by pumping of dewatering,the second stage is the increasing tension step caused by suspension of pumping,and the last stage is the decreasing trend of compression caused by resumption of pumping.It shows obviously synchronization between the solid tide distortion time interval(frequency)and borehole water level,where the linear coefficient is 0.737.

Borehole strainEngineering dewateringSolid tide distortionConcentrated load modelInterference mechanismData correcting

朱成林、甘卫军、贾媛、徐芳芳、张正帅、鞠佳斌、冯志军、刘克辉

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山东省地震局,济南 250014

中国地震局地质研究所地震动力学国家重点实验室,北京 100029

吉林地震监测中心站,吉林 132108

钻孔应变 工程降水 固体潮畸变 集中载荷模型 干扰机制 数据修复

中国地震局地震科技星火计划中国地震局地震科技星火计划国家自然科学基金山东省地震局构造变形与地震动力学、基于人工智能的地震预测研究科技创新团队项目

XH21018XH21019Y41974105

2024

10.6038/cjg2023Q0629

地球物理学报
中国地球物理学会 中国科学院地质与地球物理研究所

地球物理学报

CSTPCD北大核心
影响因子：3.703
ISSN：0001-5733
年,卷(期)：2024.67(4)
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