The application effect of geophysical method in fine exploration of urban geological structure and study of optimal combination method: A case study of Tianfu New Area in Chengdu, Sichuan Province

This paper is the result of urban geological survey engineering.

Objective Tianfu New Area (TNA) of Chengdu is characterized by a typical red stratigraphy in southwest China, including interbed sedimentary rocks of mudstone, silty mudstone, argillaceous siltstone and sandstone. The difference of physical property among the above rocks is minor. Clarifying the shallow geological structure by geophysical method is favor for constructing the fine three-dimensional geological model of TNA.

Methods This paper attempts to image fine geological structure in 4 typical sites of TNA through a variety of new and traditional geophysical methods.

Results Ground penetrating radar (GPR) and three component frequency resonance (TCFR) have higher imaging resolution than that of shallow seismic exploration (SSE), electrical resistivity tomography (ERT), opposing coils transient electromagnetic (OCTEM) and microtremor exploration (ME). Urban noise tends to affect field data quality in SSE, TCFR and ME, but not in GPR and OCTEM. Fine geological structure from shallow to deep depth can be obtained by method assembly for GPR, TCFR, ERT, OCTEM, SSE and ME.

Conclusions Under comparing and analyzing the detection depth, resolution, anti-urban noise level, construction efficiency, and economic cost of the above methods, the optimal geophysical method assembly to detect fine geological structure with different construction conditions and exploration depths in TNA of Chengdu is summarized.