The application of modified total sounding techniques in frozen ground

Abstract

The intention of this study was to find an efficient way to perform mechanical rotary soundings in permafrost. This was done by modifying the already known total sounding method.

Literature surveys did not result in information of previous research within the subject. The modification is mainly based on experiences from soil investigations at Svalbard, especially from SINTEF geotechnical group.

The modified total sounding method was tested by performing several soundings in a limited area. In addition to soundings core samples were extracted in the whole boring depth. The soil samples were identified visually and with laboratory tests. An assumed soil layering was found from the soilidentification. The modified total sounding profiles were interpreted and compared with the results from the soil identification and with each other. Maximum sounding depth was around 9 meter. All field work was conducted in Longyearbyen, Svalbard during the spring 2011.

Modified total sounding was found to be a workable method. The modified total sounding procedure achieved enough pressure to penetrate through the frozen ground. Due to limited time and resources the procedure was performed in a small area with saline marine sediments, clay and sandswith fines. This means that the method workability for other soil types is not known. The tested procedure appeared to work well in frozen permafrost and not well in unfrozen permafrost.

Interpretation of the modified total sounding profiles turned out to be complicated. The method appeared to indicate layering, but did not identify the different layers. Ice layers could not be detected from the sounding results. Soil identification from sampling gave an idea about ice layer occurrences in between the different soil layers. This means that ice layers may be assumed from the modified total sounding, as separators when the penetration rate change trends.

Modified total sounding method needs further development. It is not possible to use the method for consultancy purposes today. This study has shown the potential of the method in detecting layers,and more research can decide if it is possible to identify soil types from the sounding profiles.