EGU2020-10334
https://doi.org/10.5194/egusphere-egu2020-10334
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Joint Acoustic and Electrical Measurements for Unfrozen Water Saturation of Frozen Saline Soil

Chuangxin Lyu1, Thomas Ingeman-Nielsen2, Seyed Ali Ghoreishian Amiri1, Gudmund Reidar Eiksund1, and Gustav Grimstad1
Chuangxin Lyu et al.
  • 1NTNU, Department of civil and environmental engineering, Norway (chuangxin.lyu@ntnu.no)
  • 2Department of Civil Engineering, Technical University of Denmark (DTU), 2800 Kgs. Lyngby Denmark

Abstract. The climate change has aroused great concern on the stability and durability of the infrastructure installed on permafrost, especially for frozen saline clay with a large amount of unfrozen water content at subzero temperature. The joint electrical resistivity and acoustic velocity measurements are conducted for frozen saline sand and onsøy clay with 50% clay content and 20~40 g/L salinity in order to determine the unfrozen water content. A systematic program of tests involves the saline sand with different salinity, natural onsøy clay with the variable of temperature and freezing-thawing cycles and reconstituted onsøy clay with distinctive density and salinity. The data analysis of measurement results in combination with previous joint measurements for frozen soil resolves the effect of temperature, salinity, soil type and freezing-thawing cycles on the acoustic and electrical properties. An increase of temperature, fine content and salinity results in a decrease of both acoustic velocity and electrical resistivity. Electrical resistivity is sensitive to salinity, while acoustic velocity changes substantially near thawing temperature. We also find that both natural and reconstituted clay with similar water content and salinity show quite different acoustic velocity and electrical resistivity, which indicates that ice crystal structures are distinctive between natural and reconstituted samples. Besides, P-wave velocity is much more sensitive to the fabric change or induced cracks than electrical resistance during freezing-thawing cycles.  In the end, acoustic models like the weighted equation (Lee et al., 1996), Zimmerman and King’s model (King et al., 1988) and BGTL (Lee, 2002) are applied to the UWS estimates based on P-wave velocity and electrical models like Archine’s law are adopted based on electrical resistance. Both estimated UWS from different methods is not always consistent. The difference can be up to 20%.

Keywords: Frozen Saline Clay, Acoustic Velocity, Electrical Resistance, Unfrozen Water Saturation

References:

King, M. S., Zimmerman, R. W., & Corwin, R. F. (1988, May). Seismic and Electrical-Properties of Unconsolidated Permafrost. Geophysical Prospecting, 36(4), 349-364. https://doi.org/10.1111/j.1365-2478.1988.tb02168.x

Lee, J. S. (2002). Biot–Gassmann theory for velocities of gas hydrate-bearing sediments.

Lee, M. W., Hutchinson, D. R., Collett, T. S., & Dillon, W. P. (1996). Seismic velocities for hydrate-bearing sediments using weighted equation. Journal of Geophysical Research: Solid Earth, 101(B9), 20347-20358. https://doi.org/10.1029/96jb01886

 

How to cite: Lyu, C., Ingeman-Nielsen, T., Ali Ghoreishian Amiri, S., Reidar Eiksund, G., and Grimstad, G.: Joint Acoustic and Electrical Measurements for Unfrozen Water Saturation of Frozen Saline Soil, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10334, https://doi.org/10.5194/egusphere-egu2020-10334, 2020