基于观测系统布置优化与角度域逆时偏移的隧道超前探测方法

Tunnel Advanced Detection Method Based on Observation System Optimization and Angle-Domain Reverse Time Migration

  • 摘要: 受隧道狭小空间限制,地震采集观测系统布置困难,导致超前探测成像结果易出现伪影和假象,降低不良地质体探测精度。为此,通过建立典型隧道地质模型,采用逆时偏移成像方法,分析不同观测系统布置对隧道超前探测成像精度的影响,提出炮检同点观测系统布置方式,即在掌子面附近两侧边墙布置检波点,并在掌子面及检波器位置放置震源,从而提升对掌子面前方地质信息的辨识能力。针对隧道逆时偏移成像中存在的低波数干扰和大倾角构造成像不足问题,提出基于Poynting矢量的角度域逆时偏移方法,通过角度分解压制噪声,改善成像质量。研究表明,所提出的炮检同点观测系统、角度域成像方法可有效减少成像干扰,提升成像精度。

     

    Abstract: Due to space constraints in the narrow tunnel, it is difficult to arrange the seismic acquisition and observation system. This makes the advanced detection imaging results prone to artifacts and false images, which reduce the detection accuracy of unfavorable geological bodies. Therefore, by establishing a typical tunnel geological model and adopting the reverse time migration (RTM) imaging method, analyze the influence of different observation system arrangements on the imaging accuracy of tunnel advanced detection . A coincident source and geophone observation system layout method is proposed, geophones are arranged on the side walls on both sides near the tunnel face, and seismic sources are placed on the tunnel face and at the geophone positions, Thus improving the ability to identify geological information ahead of the face. To address the issues of low-wavenumber noise interference and insufficient imaging of steeply dipping structures in tunnel RTM, proposed an angle-domain reverse time migration method based on the Poynting vector. This method decomposed seismic wavefields by angle to suppress noise and enhance the imaging accuracy of advanced detection. The study indicates that the proposing coincident source and geophone observation system and angle-domain imaging method effectively reduce imaging interference and improve imaging precision.

     

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