Pulled intact blocks near Trondheim testing at about 60 kPa undrained, then a quick remold and they flowed — what geologic process sets up that fragile structure, and how do you reflect it in foundation selection? I’ve defaulted to displacement piles and preload to build shear strength, but I’d like to hear if anyone’s had success with in situ mixing in those marine layers.
Leached marine clay — ‘salt‑stripped house‑of‑cards’ — gives you that about 60 kPa su intact near Trondheim and soup on remold. If you try in‑situ mixing, run EC/Cl and organics first and do quick binder box tests; lime‑cement columns can work where organics are low, but design for brittleness, setup time, and negative skin friction on your displacement piles. Otherwise, wick drains with staged preload remain the safer baseline in those marine layers.
If you try in-situ mixing there, make it lime–cement with a binder trial first: fall-cone remold su and UCS at 7/28 days, and bail out if LOI > about 3% or SO4 is elevated, otherwise quick clay columns won’t gain enough. Given your about 60 kPa UU near Trondheim, I’d still favor displacement piles to rock but drive in low-energy stages with rests to bleed pore pressure, and keep any preload and PVDs outside the suspected quick-clay prism. @peter_taylor66 did you get CPTu (Bq/u2) or a quick fall-cone sensitivity map before committing to mixing?
Glaciomarine clay fabric formed in saltwater then de‑bonded by freshwater leaching near Trondheim; if you go mixing, per @lgrant92’s binder note, do a brine pre‑flush on the first pass so the blend holds together until the cement sets. If you stick with displacement piles and preload, allow for downdrag and sleeve the upper few meters to limit negative skin friction.