Effectiveness of resistivity cone penetration tests in salt-treated highly sensitive clay

Abstract

Salt wells filled with potassium chloride may be used as landslide mitigation in highly sensitive quick clays, as the changed pore-water composition permanently improves the remoulded shear strength. To verify improvements, resistivity cone penetration tests were conducted around salt wells installed at Dragvoll, Trondheim, Norway. The cone-test measurements for electric resistivity (or conductivity), tip resistance and pore pressure were combined with the results from laboratory tests on piston-core samples extracted around the wells. Salt content, soil and pore-water conductivity, pore-water composition and geotechnical properties were studied. Quick clay is defined as that having a remoulded shear strength of <0•5 kPa, and the soil conductivity is often <100 mS/m. Increased tip resistance was detected at soil conductivities exceeding 200 mS/m as a result of increased salt content, corresponding to a laboratory determined remoulded shear strength of 3•5 kPa. At Dragvoll, improved non-quick clay is detected by a normalised tip resistance of 3•5 and a pore-pressure parameter of 0•9. Improved geotechnical properties around salt wells may be verified by cone testing, but a site-specific interpretation model based on geotechnical properties from laboratory tests correlated to conetest results may be needed.

Biogas desaturation and bio-gelation methods for mitigation of sand liquefaction

“…In RCPTu, the conventional penetration cone was installed with electrical resistivity probe which allows the measurement of soil resistivity together with the conventional cone penetration test (Campanella & Kokan, 1993). Still, site-specific interpretation model is required to link between the geotechnical properties and RCPTu results (Helle et al, 2017). Another way is to combine the electrical resistivity and induced polarization measurement together.…”