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Changsha City is the political, economic and cultural centre of Hunan Province. In recent years, because of large-scale urban construction and special geological structure, land subsidence has become one of the main geological disasters in Changsha City, which seriously threatens the health of buildings and infrastructure. To solve this problem, this paper monitored the land subsidence in Changsha City from 2015 to 2021 using the Point Target (PT) based Small Baseline Subset InSAR (SBAS-InSAR), revealed the spatial distribution characteristics of land subsidence in the study area, studied the causes of subsidence, and carried out geological disaster risk assessment. The results show that the overall stability of Changsha City is dominated by uneven subsidence. The subsidence areas are mainly distributed in the north of Kaifu District, Moon Island, Malan Mountain Chuangzhi Park and the periphery of the main urban area. The maximum settlement rate is about 87 mm/year, and the cumulative settlement reaches 250 mm. The settlement monitoring results are basically consistent with the actual situation at the same time, which is mainly caused by engineering construction. [ABSTRACT FROM AUTHOR]

The unique architectural style of Western Hunan traditional dwellings must be protected, and their poor indoor thermal environment should also be improved. This investigation sought to determine the optimal passive retrofitting methods for such timber-structure dwellings. An analysis of the thermal environment of a typical traditional dwelling in Western Hunan was carried out by field study and indoor thermal evaluation on the typically coldest and hottest days. Based on the test results, this study calculated the predicted mean vote (PMV) linear fit and the acceptable temperature ranges. Then, the optimum thicknesses of the envelope insulation layer and window-to-wall ratio were evaluated by numerical simulation software based on the thermal performance of different strategies. Finally, according to the thermal performance results of the orthogonal experiments and the calculated acceptable temperature, a final comprehensive retrofitting strategy, using ordinary insulating glass units (12-mm hollow layer), a 0.2 window-to-wall ratio improvement, a polyurethane foam insulation layer (10 mm) for the double-fir external wall envelope, and reed foil (80 mm) for the clay insulation layer roof, was optimized for the existing vernacular dwellings in rural areas of Western Hunan, which can decrease the annual load from 188.38 to 65.99 kW·h/m2 and increase the acceptable temperature by 1,159 h over the whole year. [ABSTRACT FROM AUTHOR]