Against the background of global warming, permafrost areas are facing increasing thawing, and the threat to the surface of the Qinghai–Tibet Engineering Corridor (QTEC) is serious. It is imperative to understand the current surface deformation and analyze the changes spatiotemporal characteristics for future warnings. At present, observation of a long time series and overall coverage of vertical ground deformation in QTEC are lacking. This paper takes the permafrost deformation of the QTEC as its research object. It uses the pretreated LiCSAR product and combines it with the LiCSBAS package to obtain monitoring results of the long time series deformation of the engineering corridor’s surface. The SAR image acquisition date is taken as the constraint, the results covering the whole processing area are selected, and then the vertical deformation information covering the entire engineering corridor area by ignoring the north–south displacement is calculated. The results show that the surface of the study area, as a whole, slightly subsided between May 2017 and March 2022, and the vertical deformation rate was mostly distributed at −27.068 mm/yr − 18.586 mm/yr, with an average of −1.06 mm/yr. Vertical deformation dominated at 52.84 percent of the study area, of which settlement accounted for 27.57 percent and uplift accounted for 25.27 percent. According to the statistics of the normal distribution of deformation velocity per pixel, a total of 77% of the engineering corridor was stable, with a vertical deformation rate between −6.964 mm/yr and −4.844 mm/yr, and 17.7% of the region was sub-stable, with a settling rate of −12.868 mm/yr − –6.964 mm/yr. The unstable regions included areas with settlement rates greater than 12.868 mm/yr and uplift rates greater than 10.748 mm/yr, representing 4.4 percent and 0.9 percent of the total area, respectively, for a total of 5.3 percent. The results of this paper can be used as the theoretical basis and as basic data for decision making and scientific research in various departments, and they are of great significance for surface stability assessment and early warnings along engineering corridors and traffic projects.

Diatomite is a siliceous sedimentary rock containing amorphous silica, which can be used as a green mineral admixture to improve the properties of concrete. This study investigates the affecting mechanism of diatomite on concrete performance by macro and micro tests. The results indicate that diatomite can reduce the fluidity of concrete mixture and change its water absorption, compressive strength, resistance to chloride penetration (RCP), porosity, and microstructure. The low fluidity of concrete mixture containing diatomite can reduce workability. With increasing diatomite as partial replacement for cement in concrete, water absorption of concrete decreases before increasing, while compressive strength and RCP rise first and then drop. When diatomite is added to the cement at a content of 5% by weight, the concrete has the lowest water absorption and the highest compressive strength and RCP. Through the mercury intrusion porosimetry (MIP) test, we determined that the addition of 5% diatomite reduces the porosity of concrete from 12.68% to 10.82% and changes the proportion of pores with different sizes in concrete, the proportion of harmless and less harmful pores increases, and the proportion of harmful pores reduces. Based on the microstructure analysis, the SiO₂ in diatomite can react with CH and produce C-S-H. C-S-H is responsible for developing concrete because it fills pores and cracks, forms a platy structure, and makes the concrete much denser, thereby improving its macroscopic performance and microstructure.

Meteorological characteristics and freeze-thaw processes are crucial indicators guiding regional economic development and practical production. The Da Xing’anling Mountains, serving as a transitional zone between continuous permafrost and seasonal frozen ground in northeastern China’s high latitudes, understanding the meteorological parameters and freeze-thaw development patterns in this region can significantly enhance the accuracy of permafrost zoning maps and validate climate simulation models. Based on meteorological and ground temperature monitoring data from 2022–2023, this study analyzed the meteorological characteristics and seasonal freeze-thaw processes of Jagdaqi (southern Da Xing’anling Mountains), which is located at the boundary between permafrost and seasonally frozen soil. The results indicate: (1) At a height of 5 m, the annual average temperature is 1.04°C. The air-freezing index and air-thawing index are −2318.95°Cd and 2698.52°Cd, respectively, categorizing it as a severe cold region. (2) The total annual precipitation is 397.1 mm, with summer rainfall accounting for 77.4% and winter rainfall only 11.3%. (3) The prevailing wind direction is from the northwest, accounting for approximately 47% of the total annual wind direction frequency. Annual wind speeds range from 0.045 to 10.33 m/s, with an average speed of 1.51 m/s. (4) At heights of 5 m and 10 m, the annual average relative humidity is 63.49% and 62.1%, respectively, reaching its lowest in May at 44.58% and 43.38%. (5) The study area is located in a seasonal frozen ground region, with maximum frost depths occurring in early to mid-March, ranging between 1.93–1.99 m, classified as middle-thick seasonally frozen ground. These findings hold valuable implications for ecological conservation, resource management, and engineering construction, enhancing the accuracy and applicability of models and permafrost zoning maps in this region.

The China–Russia crude oil pipeline (CRCOP) has been in operation for over ten years. Field observation results have shown that a thaw bulb has developed around the CRCOP which expands at a rate of more than 0.8 m∙a⁻¹ in depth. In view of the deficits of existing measures in mitigating permafrost thaw, a new control method is proposed based on active cooling. According to the relationship between total pressure loss and the driving force of natural ventilation, the wind speed in a U-shaped air-ventilation pipe around the CRCOP is calculated. By analyzing the theoretical calculation and numerical analysis results, it is found that the influence of thermal pressure difference on the natural ventilation of the structure can be negligible, and the influences of resistance loss along the pipe and local resistance loss in the pipe are similarly negligible. Exhaust elbows greatly improve the ventilation performance of the U-shaped air-ventilated pipe. This study developed a novel structure around warm-oil pipelines in permafrost for mitigating thaw settlement along the CRCOP and other similar projects across the world.