Thermo-seismic performance of the novel thermal anchor pipe frame (TAPF) structure for supporting slope in earthquake-prone permafrost regions

Abstract

The thermal anchor pipe frame (TAPF) structure is a new type of permafrost slope support technology, but its thermo-seismic characteristics are still unclear. In this paper, the coupled hydro-thermal-dynamic model of the thermal anchor pipe frame permafrost slope system is established. The cooling performance of the TAPF structure is investigated and the seismic responses are comparatively analyzed for different freeze-thaw periods. Results show that the presence of “elliptical” freezing cores with lower temperatures (which ranged from −3.94 to −5.36 °C) near the active layer at the end of the thawing period, which raised the permafrost table. The strip-shaped unfrozen moisture accumulation layer appears near the upper part of the thawing front at the highest temperature in the warm season. The peak acceleration response is the largest on October 15, 52.3% greater than the peak acceleration on April 15. The peak axial force of the thermal anchor pipe during the freezing period was 119 kN, which was 32.2% greater than that during the thawing period, and the peak total axial force after the earthquake appeared at the location of the freeze-thaw interface, and the axial force of the heat-transfer free section is greater than that of the anchored section. The frame structure is sensitive to earthquakes during the freezing period, and plastic bending damage may occur, especially at connection locations with thermal anchor pipes. Seasonal effects also have a strong influence on the shape of the acceleration response spectrum. The results can provide useful references for the maintenance and safe operation of permafrost slopes along the Qinghai-Tibet Project as well as for the seismic design of the new structure.