GEOLOGICAL FORMATION AND THAW-SETTLEMENT CHARACTERISTICS OF FROZEN SOIL IN SULIJIAN GULLY, SOUTHERN TIANSHAN MOUNTAINS

Climate warming introduces increasing uncertainty to engineering construction in the cryosphere. It is crucial to accurately determine the geological formation and thaw-settlement characteristics of frozen soils when selecting project sites and construction methods. This paper investigated the mountainous frozen soil distributed in the Sulijian Gully in the southern Tianshan region and used the methods of drilling,high-density electrical tomography,and ground temperature monitoring. It clarified the spatial distribution of the frozen soil in the region and summarized the formation conditions and mechanisms of the frozen soil. Then,it revealed the thawing-settlement characteristics and their influencing factors with laboratory tests. The results show that both permafrost and seasonally frozen soils are distributed in the Sulijian Gully. The seasonally frozen soils and discontinuous permafrost are mainly distributed at the toe of the left bank(the sunny slope),while continuous permafrost is mainly distributed at the toe of the right bank(shady slope). The depth and thickness distributions of the permafrost layer are uneven,which are mostly distributed below the 1.9~2.7m-thick topsoil,with a thickness range of 1.5~6m. The geological formation mode of permafrost can be divided into two types: the formation mode of rich water and low temperature on the shady slope,and the formation mode of convergence on the sunny slope. The thaw-settlement coefficient of the Sulijian Gully permafrost area ranges from 0.39% to 91.25%,while the multiple value range of the continuous permafrost area is between 42.5% and 68.75%,with an average value of 55.62%. The thaw-settlement coefficient of the Sulijian Gully permafrost is highly correlated with total water content,natural density,dry density,natural void ratio,and liquid index,with the Pearson correlation coefficients exceeding 0.8.