海底砂土中气体运移过程电阻率监测探针设计与实验

Design and experiment of resistivity monitoring probe for gas migration in marine sand

在浮力和动、静压力作用下,海底浅层气会在高渗透性土中发生垂直和水平方向的运移、聚集,诱发地层变形,甚至失稳破坏。为探索一种新型的气体运移过程原位监测技术,实现气致灾害实时监测预警,根据静电场测量原理,设计、制作了点状电极和环状电极两种形式电阻率探针。在分析了两种探针探测精度基础上,以砂土中气体扩散过程监测为例,利用其对3种速率气体运移过程进行连续监测实验。实验结果表明,两种探针电阻率测量误差均小于0.1%。点状电极探针测量灵敏度较高,可准确监测布设点含气量的变化、气体汇聚、消散过程及相应速率;环状电极探针测量灵敏度相对较低,但可监测气体在砂土中的时空运移过程。两种探针各有利弊,都可实现气体运移过程的有效监测。

Under the influence of buoyancy and static or dynamic pressure, submarine shallow gas stored on high penetrability soil aggregates and migrates in uprightness and horizontal direction, which inducing stratum deformation and failure. For the purpose of real-time monitoring geological hazard induced by gas as well as early warning,a new type of in situ gas migration monitoring technology is discussed. Two resistivity probes with point-shaped electrode and ring-shaped electrode were respectively designed and manufactured based on the electrostatic field measurement principle. On the basis of detection accuracy analysis, continuous gas diffusion monitoring experiments in sand with three dissimilar gas injection rate are performed. As a result, both resistivity measurement error of two probes are less than 0.1%. With a high measuring sensitivity, the point-shaped electrode probe is capable of monitoring the variation of gas content, gas accumulation, gas dispersing and corresponding rate. The ring-shaped electrode probe has a relatively low sensitivity measurement, while it could monitor the spatio-temporal gas migration in sand soil. Understanding the pros and cons, each probe is able to implement effectively monitoring gas migration.