Risk Zoning of Permafrost Thaw Settlement in the Qinghai–Tibet Engineering Corridor

Abstract

The Qinghai–Tibet Plateau is the highest and largest permafrost area in the middle and low latitudes of China. In this region, permafrost thaw settlement is the main form of expressway subgrade disaster. Therefore, the quantitative analysis and regionalization study of permafrost thaw settlement deformation are of great significance for expressway construction and maintenance in the Qinghai–Tibet region. This paper establishes a thaw settlement prediction model using the thaw settlement coefficient and thaw depth. The thaw depth was predicted by the mean annual ground temperatures and active-layer thicknesses using the Radial Basis Function (RBF) neural network model, and the thaw settlement coefficient was determined according to the type of ice content. Further, the distribution characteristics of thaw settlement risk of the permafrost subgrade in the study region were mapped and analyzed. The results showed that the thaw settlement risk was able to be divided into four risk levels, namely significant risk, high risk, medium risk and low risk levels, with the areas of these four risk levels covering 3868.67 km2, 1594.21 km2, 2456.10 km2 and 558.78 km2, respectively, of the total study region. The significant risk level had the highest proportion among all the risk levels and was mainly distributed across the Chumar River Basin, Beiluhe River Basin and Gaerqu River Basin regions. Moreover, ice content was found to be the main factor affecting thaw settlement, with thaw settlement found to increase as the ice content increased.

Prediction of Permafrost Subgrade Thawing Settlement in the Qinghai–Tibet Engineering Corridor under Climate Warming

“…The distribution of ice content in the QTEC was obtained by field drilling survey method. Utilizing the permafrost ice content survey results, the subgrade thawing settlement coefficient of permafrost along the QTEC was classified and valued [31], as shown in Table 1. The thawing depth of permafrost subgrade is influenced by various factors such as surface conditions and vegetation environment.…”

“…The thawing depth of permafrost subgrade is influenced by various factors such as surface conditions and vegetation environment. In the previous research results [31], a The subgrade thawing settlement was calculated by combining the subgrade thawing depth and the subgrade thawing settlement coefficient, as follows:…”

“…The thawing depth of permafrost subgrade is influenced by various factors such as surface conditions and vegetation environment. In the previous research results [31], a calculation formula between the permafrost subgrade thawing depth and the GMAT and ALT was established by combining numerical calculation and radial basis function (RBF) neural networks methods. The distribution of GMAT, ALT, and subgrade thawing depth of permafrost in the QTEC was analyzed separately.…”

Study on the Damage Characteristics and Internal Variable Modeling of Single-Fracture Sandstone under the Coupling Effect of Freeze–Thaw and Fatigue Load

“…However, the frost heaving, thermal shrinkage, damage, and deterioration of rocks in the freezing and thawing environment have caused great harm to engineering construction in cold areas. The stability evaluation of rock mass engineering in cold areas and the prevention and control of freeze-thaw disasters have become key scientific issues that need to be urgently solved [1][2][3][4][5][6]. The essence of freeze-thaw damage in fractured sandstone in cold regions is fatigue damage induced by repeated freeze expansion force and unloading [7].…”