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Seal not holding on Consolidation Plate

Seal not holding on Consolidation Plate

Seal not holding on Consolidation Plate

Hi all,

Long shot , but wondering can someone help me with the problem above. I am doing some scaled physical modelling of stone columns. 20mm dia columns constructed in a 200x200x200mm deep consolidated Kaolin Clay bed.

I am mixing the Kaolin to its LL of 69% so it acts as a liquid. This is poured into the mould and consolidated using a piston and plate. Filter paper is placed beneath the drainage holes so only the water gets out and the Kaolin consolidates. I am aiming to do this to reach a shear strength of 15-20kPa. It has been done many times before based on the literature i have read.

The problem i am having is that the O-ring seal around the consolidation plate isnt holding, when the pressure is applied the clay leaks up the sides. I was expecting some leaking of clay but not this much. I put a sample under 50kPa for 24 hours and came in this morning and the piston had penetrated to the bottom of the mould so not consolidating it at all. I have tried packing it with filter paper but it just jams the piston. I am also looking to see if i can get a larger dia O ring than the 4mm dia that i am using.

Also, what are your thoughts on the size of the drainage holes. The are 2 1mm dia holes on top of the plate. I think these are too small or that there are not enough of them. From what i have read it can take up to 5 days to consolidate it, starting at 20kPa and increasing by 20kPa every 24 hours.

This is probably a very specific problem but i would be greatful for any advice.

Some pics attached. 1st pic of piston set up and top of consolidation plate. Second pic of top of consolidation plate with clay leaking around seal

RE: Seal not holding on Consolidation Plate

Your clay mixture is too soupy. Try lower moisture content for moulding. Start with halfway between liquid and plastic limits.

RE: Seal not holding on Consolidation Plate


That is something I am also considering. The mixture is the same consistency of fresh paint! That is the Kaolin powder mixed to its LL. But from what I have read researchers have mixed it at 1.2 and 1.5 times LL. It must have been practically water.

I am looking to get some O-rings at a larger diameter 5mm and 6mm and try those with the sample at its LL and see if the seal holds. If that doesnt work I will look to mix it between PL and LL as you suggested.

RE: Seal not holding on Consolidation Plate

Does your mold allow for drainage at the base? If so, you may have to allow the slurry to drain under no load until it reaches a consistency which will allow loading. You may also consider using a lower initial normal load as well. Are you using a porous stone under the top plate?

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