洼克阿莫公路隧道中的小江断裂电性特征

Conductivity characteristics of the Xiaojiang fault in highway tunnel of wakeamo

中国西部山区地形条件和地质构造复杂,为满足高速公路设计要求,路线在山岭重丘区不可避免地要采用深埋特长隧道设计通过。若公路隧道必需通过断层构造,如结构、基础形式选择不当,容易在施工时出现塌方、结构失稳等现象,所以在勘察过程中,应查明断层的基本性质及特征,提供较为准确的资料,避免出现后续问题。本研究区域发生地震的频率和震级都很高,且从现有资料表明小江断裂在第四纪全新世时期仍有活动,属地震高危地段。因此,地质调查,地质钻探、地球物理勘探等一整套综合技术用于识别断层及其特征,以直观地显示一定深度范围内的地下信息。在这项研究中,地球物理勘探大地电磁法被用来分析公路隧道的电性特征及电性结构,重点讨论了小江断裂的电性特征及电性结构,经地质调查及钻探验证了其反演解释等研究成果的正确性,并进一步提出采用波阻抗张量极化图长轴倾角统计结果修正断层倾角的处理解释方法,故可有效获取隧址区大量地质信息以进行预测评价小江断裂,为公路隧道设计及运营提供强有力的技术支撑,也为以后的物探处理解释提供有意义的经验和参考。

The terrain conditions and geological structure of the mountainous areas in western China are complex.To meet the design requirements for the expressway,the route adopts the design of deep-buried super-long tunnels in hilly areas.If the highway tunnel passes through faulty structures,such as improper selection of structure and foundation form,it can cause collapse and structural instability during construction.Therefore,basic characteristics of faults and information that is more accurate should be provided during the survey process to avoid subsequent problems.The frequency and magnitude of earthquakes in this study area are high and available data show that the Xiaojiang fault was still active during the Quaternary Holocene period,which is a high-risk area for earthquakes.Therefore,a set of comprehensive technologies,such as geophysical prospecting,geological survey,and drilling,and was used to identify faults and their characteristics and to visually display underground information within a certain depth range.Here,the magnetotelluric method was used to analyze the electrical characteristics and structure of the highway tunnel.In addition,the electrical characteristics and structure of the Xiaojiang fault were discussed.Geological surveys and drilling agree well with the analysis and interpretation of the research results and further proposed a processing and interpretation method for correcting the dip angle of the fault using the statistical results from the long axis dip angle of the tensor polarization map for the wave impedance.Thus,a large amount of information in the tunnel site can be effectively obtained for predicting and evaluating the Xiaojiang fault.Furthermore,our results provide strong technical support for designing and operating highway tunnels,with meaningful experience and reference for future geophysical processing and interpretation.