Check out Vibracore as well. This method may also be useful.

We have something like that but not quite as wet. We ended up using pushcore where the sample comes out essentially in-situ in rigid plastic tubes. It is quite expensive though and better for sg and perhaps twinning a few of your resource holes to confirm that you are getting a representative sample from the drilling method chosen. I think the deepest we got was about 18m. You could try a sonic rig which produces a sample in a sealed plastic bag essentially. They use it for brine deposits to capture the sediment and the brine so it would handle your material ok. We considered this method but because the plastic material is fairly loose it is not suitable for sg as you can get a lot of clay expansion but if you are not worried about volume changes then it would work for you.

You both are on the right approach. Your core system is a good one in Geotech sphere. But every tool has it optimal conditions and we rarely have the luxury and finance of being able to use all!

Since you are clearly there with a rock coring rig then tools must be appropriate. It's rare, impossible or very expensive to get a full 100% recovery for the entire hole so strategy comes into play; by sampling and testing appropriately you can get a reliable answer. Push samples will be easiest and cheapest. But be very careful in hole preparation; and in sample examination. You need to be selective and understand the impact of drilling processes. This I know is sometimes frowned upon in resource measurements but will give most reliable and honest results. You then multiple hole close by and offset samples. This then is proof of continuity. This is often a Geotech approach but I am aware that resource methods demand different. But accurate knowledge at this stage will at least enable confidence to apply new techniques later if findings are good.

Using of Geobor S on core drill rig like LF or SC is difficult due to the openings diameters of drill head and foot clamp are just 127 mm. As well as there is no guarantee that you get full volume of sample even using plastic liner and catcher. Better solutions for highly saturated formations will to use the Stationary piston sampler or the Hydraulic stationary piston sampler. You can make a choice for right diameter and use them with conventional drill string probably on any type of drill rigs.

It seems Geobor S works quite well on the muddy part of the tailings - not so good on the unconsolidated material near surface.