Characterization of Subsurface Structure in Different Landforms based on GPR Profiles along the Qinghai-Tibet Highway on Permafrost region

摘要

Ground-penetrating radar was applied at Beiluhe and Xieshuihe region along the Qlnghai-Tlbet Highway (QTH) to investigate the permafrost active layer thickness (ALT) and shallow subsurface internal structure. It has obviously differences for ALT and characteristic of shallow internal structure in different soil types and vegetation coverage. For the GPR data in different soil types and vegetation coverage, we analyzed the characteristic of reflection and diffraction and processed data using different migration method, respectively. From the analysis results, we summarize as follows: 1) the permafrost active layer was about 0.8 m in June 2015 in Beiluhe region. Due to have influence on the stratigraphy and soil moisture content, GPR profile have obviously lateral variations in Beiluhe region. It's shown the characteristic of graben-like structure from reverse time migration (RTM) profile, which may be related to the cycle of freezing and thawing on the roadbed. 2) The closer to the highway, the deeper the stratigraphy layer thickness near the north side of highway in Xieshuihe region, which may be related to compaction in highway construction. We can find out the characteristic of multi-stage internal structure of paleo-channel from GPR profile. The paleo-channel is 57.5 m wide and 3 m depth. 3) The characteristic of internal structure of shallow ground surface have obviously differences in the different landform and vegetation. The vegetation coverage is key factor to permafrost active layer. GPR can be used to analyze the lateral changes rule and internal structure of permafrost active layer in different soil types and vegetation coverage. It is very important to clearly reveal ALT and shallow ground internal structure for engineering construction and safeguard. Our work will provide a new foundation for the future detection work.