Application of vacuum decay tester in measuring air permeability of loess in the Chinese Loess Plateau, northwest China

Abstract

Soil air permeability (k_a) is an important parameter to characterize gas transport and exchange in soil. In-situ air permeability tests of loess at different depths in three sites (Xi’an, Yan’an and Heifangtai) were carried out with a vacuum attenuation air permeometer in this study. Two sizes of sleeve probes (φ 8 × 4 cm and φ 6.18 × 4 cm) were tested in the laboratory on undisturbed loess samples to assess the dependence of air permeability on sample size. Results showed that the permeability of the three sites tested in-situ decreased when depth increased. Xi'an loess has the best air permeability, and Heifangtai has the worst. The influence of the initial state on in-situ air permeability was analyzed. Laboratory tests showed that the air permeability values of the two sizes are essentially the same, and the scale effect is small. In-situ and in-lab air permeability were compared, and results of the two probes have a good 1:1 relationship. We also evaluated the validity of the YO model for the determination of the permeability of undisturbed loess in the laboratory. The vacuum attenuation air permeameter can be used to measure the permeability of loess quickly and portable.

Keywords:

• air permeability
• vacuum decay
• undisturbed soil
• semi-spherical flow
• columnar flow
• scale effects

Disclosure statement

The authors declare that they have no conflict of interest.

Additional information

Funding

This research was funded by the Natural Science Foundation China (grant numbers 41572264 and 41877225), and the Fundamental Research Funds for the Central Universities, CHD (grant number 300102268717).