GROUND PENETRATING RADAR DETECTION OF SUBGRADE PERMAFROST ALONG THE QINGHAI-TIBET HIGHWAY WITH REVERSE TIME MIGRATION

摘要

The distribution of the Qinghai-Tibet (QT) Plateau's permafrost has dramatically changed, expressed as increasing permafrost degradation, thawing depth deepening and the disappearance of island permafrost. These changes have serious impact on the local ecological environment and the stability of engineering infrastructures. Ground penetrating radar (GPR) is used to detect permafrost active layer depth, the upper limit of permafrost and the thawing of permafrost with seasonal changes. Due to the influence of complex structure in the permafrost layer, it is difficult to effectively reflect the accurate structure within the permafrost on the radar profile. In order to get high resolution GPR profile along the QT highway, reverse time migration (RTM) imaging method in applied to GPR real data. The RTM algorithm is first validated through application to a synthetic data set generated from a groove model, then is applied to the real data acquired on the permafrost layer in the region of Beilu River along the QT highway. The results bear great significance for the study of complex structures and freezing and thawing process of permafrost.