地球物理探测技术在成都市浅表地质结构调查中的应用研究

【研究目的】 查明城市浅表地质结构特征，对于城市地下空间规划、开发区建设、地质灾害评价等有着重要的指导意义，而无损、抗干扰能力强的地球物理探测技术在提供城市地区地下地质信息方面可以发挥关键作用。【研究方法】 为了支撑成都市浅表的三维地质填图工作，本文应用11种新、老地球物理探测技术，开展了成都市浅表地质结构的探测研究。【研究结果】 研究结果表明：（1）地质雷达对于近地表的地层结构成像、建筑结构识别分辨率较高；（2）瞬态面波、混合源面波、三分量频率谐振法对50 m以浅的地质结构识别能力强，分辨率很高，但探测深度有限；（3）微动勘探法和高密度电阻率法对50 m以浅的地质结构分辨率较高，但深部分辨率一般；（4）等值反磁通瞬变电磁抗干扰能力强，施工效率高，50 m以浅分辨率较高，50~200 m深度范围内分辨率一般，对膏岩泥岩有较好的识别能力；（5）半航空瞬变电磁可弥补了常规物探方法无法进入特殊场地施工的不足；（6）浅层地震勘探对于浅地表50～300 m深度范围内的砂泥岩互层的变化特征和断层结构特征效果较好，配合自然伽马曲线，可有效识别砂泥岩的岩性界面；（7）音频大地电磁可有效识别成都平原深大断裂的空间分布形态。【结论】 综合各种地球物理方法的优缺点，建立了成都市浅表地质结构的地球物理组合探测技术方案，以期能为今后的城市浅表地质结构调查提供参考。

Application research of geophysical exploration technology in the investigation of shallow geological structure in Chengdu

This paper is the result of the geological survey engineering. Objective] There is great significance to find out the characteristics of urban shallow geological structure for urban underground space planning, development zone construction, geological disaster evaluation. While the nondestructive and strong anti-interference geophysical exploration technology can play a key role in providing urban underground geological information. Method]In order to support the three-dimensional geological mapping of Chengdu City, 11 kinds of new and old geophysical exploration techniques are used to study the shallow geological structure of Chengdu City. Results]The results show that: (1) GPR has a high resolution for the formation structure imaging and human structure identification near the surface; (2) Transient surface wave, mixed source surface wave and three-component resonance method have a strong recognition ability for the geological structure with a shallow depth of 50m, although the resolution is very high, but the detection depth is limited; (3) Microtremor survey method and high- density resistivity method have a better resolution for the geological structure with a shallow depth of 50 m, but under the deep of 50 m, the resolution is general, especially the high-density electrical method is greatly disturbed by humanity, and the detection effect is not stable; (4) Opossing coils transient electromagnetic method anti-interference ability is strong, the construction efficiency is high, the resolution is better in the range of 0-15 m, and general in the range of 50-200 m, which has a good identification ability for gypsum mudstone; (5) The semi-airborne TEM method can effectively identify the base form of Chang''an landfill and make up for the lack of conventional geophysical methods that the special site for detection; (6) The shallow seismic exploration has a good effect on the variation characteristics and fault structure characteristics of the sand shale interbedding within the depth range of 50- 300 m underground, and can effectively identify the lithology interface of the sand shale in combination with the natural gamma curve; (7) The audio-frequency magnetotelluric method can effectively identify the deep fracture in Chengdu Plain. Conclusions]Based on the merits and demerits of various geophysical methods, a combined geophysical exploration scheme of shallow geological structure in Chengdu is established under conditions of multiple geological structures and complex working conditions, which is expected to provide a reference for the investigation of urban shallow geological structure in the future.