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The influence of thermophysical properties of frozen soil on the temperature of the cast-in-place concrete pile in a negative temperature environment

Liu Ziying, Yu Tianlai, Yan Ning, Gu Lipeng

Archives of Thermodynamics

2023

Vol. 44, no 2

21--48

Thermophysical properties of frozen soil have a great influence on the quality of cast-in-place concrete piles. In this paper, the embedded concrete temperature monitoring system is used to test the variation law of the concrete temperature during the construction of the bored pile. Thermophysical properties of permafrost around piles are tested. Based on the theory of three-phase unsteady heat conduction of soil, the influence of specific heat capacity, thermal conductivity, thermal diffusivity, and latent heat of phase transformation on the temperature change of a concrete pile is systematically studied. The thermal parameter is obtained which exerts the most significant influence on the temperature field. According to the influence degree of frozen soil on pile temperature, the order from high to low is thermal conductivity, thermal diffusivity, latent heat of phase change, and specific heat capacity. The changes in pile wall temperature caused by the change of these properties range between 2.60–10.97◦C, 1.49– 9.39◦C, 2.16–2.36◦C, and 0.24–3.45◦C, respectively. The change percentages of parameters vary between 35.77–47.12%, 12.22–40.20%, 12.46–32.25%, and 3.83–20.31%, respectively. Therefore, when designing and constructing concrete foundation piles, the influence of the thermal conductivity of frozen soil on concrete pile temperature should be considered first. The differences between the simulated and measured temperature along the concrete pile in the frozen soil varying with the respective thermal properties are: –2.99– 7.98◦C, –1.89–4.99◦C, –1.20–1.99◦C, and –1.76–1.27◦C. Polyurethane foam and other materials with small thermal conductivity can be added around the pile to achieve pile insulation.

Actinobacterial Communities of Chosen Extreme Habitats in China

Jia Pengli, Li Miao, Feng Haiyan, Ma Mutian, Gai Jingping, Yang Zhongfang

Polish Journal of Ecology

2020

Vol. 68, nr 3

181--194

Actinobacteria living in frozen soils which potentially could be producers of valuable and biologically active metabolites, remain still largely unexplored. Therefore, the diversity of culturable actinobacteria in the six frozen soil samples collected from the high-latitude and the high-altitude regions in China was investigated by using the culture-dependent method and 16S rRNA gene analysis. A total of 184 culturable actinobacterial isolates (morphotypes) were obtained. The abundance of culturable actinobacteria was 6.20 × 103–3.49 × 105 colony forming units (CFU) per gram of soil (dry weight). The actinobacteria isolated from the high-latitude region in China belong to five genera: Streptacidiphilus, Kitasatospora, Streptomyces, Arthrobacter, and Rhodococcus. The strains belonging to Arthrobacter were dominant, the 19 strains were closely related to Arthrobacter globiformis in terms of evolutionary distance. The actinobacterial isolates from the high-altitude region, from 2,813 m to 4,775 m in elevation, in China could be grouped into six genera (Arthrobacter, Microbacterium, Streptomyces, Rhodococcus, Nocardia, and Nocardiopsis), with dominant Streptomyces and Arthrobacter strains. The 4 strains were closely related to Rhodococcus fascians and one strain was closely with Microbacterium hydrocarbonoxydans in terms of evolutionary distance. Three genera of Arthrobacter, Streptomyces, and Rhodococcus were found in both areas. Our research provides new insight into the characteristics of the distribution of actinobacteria associated with frozen soils, which help us gain a better understanding of the potential of the cryogenic environments – the potential source of actinobacterial antibiotics.