Using Ground Penetrating Radar Technology To Study The Active Layer Thickness And Its Influencing Factors Of Qinghai-Tibet Plateau

Compared with other permafrost zones of the same latitude in the northern hemisphere,the permafrost zone on the Qinghai-Tibet Plateau has the characteristics of higher temperature,thinner thickness,poor thermal stability,limited distribution and unevenness,so it is more susceptible to climate change and engineering disturbance The sensitivity makes the thickness of the active layer change in recent years.In the application of ground penetrating radar to detect permafrost,due to the influence of objective factors such as the complexity of the nature of the frozen ground,the non-uniformity of the medium and the multi-solution of geophysical prospecting,the interpretation of the ground penetrating radar is uncertain.The Beiluhe is located under the warm and ice-rich permafrost,the vegetation and soil have the characteristics of the Qinghai-Tibet Plateau,and the permafrost region is in a sensitive zone for climate change response.Five major projects have passed in parallel.It is one of the most fragile and sensitive areas of the ecosystem in the world,so it is a suitable area to study the permafrost active layer thickness and the local environmental factors or climate changes on the permafrost active layer.In this study,GPR technology is used to study the thickness of permafrost active layer and the influence of local factors on the active layer in the Tibetan Plateau,the area around 175 m on both sides of the Qinghai-Tibet Highway on the northern foothills of the Qinghai-Tibet Plateau was selected as the research area.GSSI SIR 30 ground penetrating radar was used to detect the area to obtain radar profiles on both sides of the road and on the road surface,and the CMP method was used to obtain speed information in this area.After processing the collected data and analyzing the problems,we use the collected 2D profile,the reflection time contour map of the active layer extracted from the radar data,and multiple 2D parallel profiles to build the 3D data volume to comprehensively analyze the thickness of the active layer in the study area and the change in the horizontal direction.The results show that the average reflection time of the active layer is 20 ns,and the average thickness of the active layer is-0.8 m to-1.0 m;the reflection time of the active layer is higher near roads and water.The overall active layer thickness decreases from north to south within the acquisition area,and the active layer thickness deepens in the middle survey line of the acquisition.According to the field survey,data collection records and data of the Beiluhe Research Area on the Qinghai-Tibet Plateau,vegetation,engineering activities(Qinghai-Tibet Highway and fiber optic cable),water and surface media were selected as the influencing factors to study the active layer.in the acquisition of the radar data,frequency and energy attributes in the analysis of results show that: engineering activities(Qinghai-Tibet Highway and optical cable)caused the active layer to deepen.The construction of the highway changed the vegetation coverage and surface medium in the area,and also indirectly deepened the active layer thickness.The warm season water melted It also deepens the thickness of the active layer in a small area.Studying the thickness of the permafrost active layer and the local factors affecting the active layer is of great significance to the local surface energy balance,cultural cycle,soil,ecology,engineering construction and climate feedback.It also provides more constraints and more objective suggestions for the infrastructure construction of the Qinghai-Tibet Plateau.