Extraction and analysis of saline soil deformation in the Qarhan Salt Lake region (in Qinghai, China) by the sentinel SBAS-InSAR technique

The instability of saline soil foundation affects the safety of artificial construction, and may cause ground collapse, building destruction and road damage. It is fundamental to reduce the potential engineering geological disasters by exploring the dynamic evolution of saline soil. Most of the previous researches of saline soil were conducted by simulated experiments and traditional geodetic surveying methods. Restricted to the limited sampling points, the spatiotemporal evolution characteristics of saline soil were difficult to find out in a large scale. This paper exploited SBAS-InSAR method to extract the deformation of the Qarhan Salt Lake (in Qinghai, China) section along Qinghai-Tibet railway, based on 119 image data acquired by Sentinel-1A from 2015 to 2020. The results showed that the deformation trends varied frequently in this saline mud flat. Between the adjacent areas with different deformation trends along Qinghai-Tibet railway, discontinuities caused by uplift and subsidence were very obvious. Besides, among the areas with brine exploitation or artificial construction, the maximum subsidence rate reached50 mm/yr, and the maximum cumulative subsidence exceeded 320 mm in the latest 5 years. In the saline mud flat closed to the rivers and lakes, the deformation trend was continuous uplift. Nevertheless, there were obvious seasonal deformation characteristics in those areas far away from the water body. Further analysis found out a sharply subsidence caused by the salt collapsibility appeared in rainy seasons. While an uplift trend induced by the salt swelling or frost heave was remarkable in dry seasons. Subsequently, the relationships were analyzed between the time series deformation and external environmental factors. Furthermore, the deformation mechanism of saline soilin the Qarhan Salt Lake region was interpreted then. In general, this study provides complete spatiotemporal evolution information of saline soil, and demonstrates the deformation characteristics of saline soil in the Qarhan Salt Lake region successfully. Related results would contribute to the safety monitoring for large-scale infrastructure construction in the saline soil areas.