Risk Assessment of Permafrost Thawing along Qinghai-Tibet Engineering Corridor Integration Ground Deformation

Under the combined influence of global climate warming and human activities, permafrost within the Qinghai-Tibet Engineering Corridor (QTEC) has significantly degraded, posing threats to human safety, the ecological environment, and the secure operation of permafrost engineering facilities. Consequently, it is urgent to assess the risks of permafrost thaw settlement along QTEC. Traditional permafrost settlement assessment indices are mostly static, neglecting dynamic factors. To address this, an Analytic Hierarchy Process (AHP)-based multifactor assessment index (Im) was proposed in this paper, which integrates ground dynamic deformation data and three geo-hazard indices: the allowable bearing capacity index, the risk zone index, and the settlement index. The SBAS-InSAR technique can overcome atmospheric delay and spatiotemporal decorrelation issues. The allowable bearing capacity index considers MAGT (Mean Annual Ground Temperature) and soil type. The risk zone index incorporates factors such as bare rock, soil properties, ALT (Active Layer Thickness), and VIC (Volumetric Ice Content). The thaw settlement index is based on VIC and AδALT, with AδALT derived using the Stefan formula. The allowable bearing capacity index is calculated using a formula based on MAGT and soil type. The risk zone index is determined through hazard zone assessment. The VIC in the thaw settlement index is calculated using MAGT, soil type, NDVI, and slope, while the AδALT is obtained through the Stefan formula. The evaluation results of the three different geological hazard indices were calculated and analyzed individually, and then compared to the multi-factor analysis results to verify the reliability of the proposed method. The correlation between the geological hazard index and ground deformation was also explored. The ground deformation rate was derived using time-series interferometric SAR (InSAR), ranging from -60 mm/year to 43 mm/year, with an average surface deformation rate of -7 mm/year across the entire study area. The Im results show that the permafrost regions along QTEC are predominantly low-risk, accounting for nearly 60% of the area. High-risk areas make up roughly 22%, with the most concentrated high-risk regions located between Chumaerhe and Fenghuoshan. By combining static geological hazard indices with dynamic deformation information, this method provides a more accurate assessment of permafrost thaw settlement risk for the Qinghai-Tibet Railway project. A comparison with existing research validates the effectiveness of the proposed method, particularly in the Tanggula and Chumaerhe regions. These findings offer valuable guidelines for permafrost engineering design and construction in other permafrost regions. © 2024 Science Press. All rights reserved.