Frost Heave

[colinc]

Hello

I have just taken on a new role and found frost heave in some of the door ways at our cold stores. This is due to having rapid roller doors fitted outside the cold store and leaving the slidding doors open 24/7. Whats the best and quickest way of getting the slab back down obviously closing the sliding door when not used but some sites are 24/7. Should the insulation extend past the store wall line?

I have also found heave in another cold store this inside the room. I have checked the air flow and installed a heater and also had a camera put down the vent pipes. Some have collapsed - whats the best way to re instate these vent pipes? Core drill and back fill with copper pipes?

Any suggestions would be greatfully appreciated

[US Iceman]

Oh boy. You have a mess you have inherited.

The only way to get the ice lens to melt is:

a) shut off the refrigeration system and wait years for it to melt (probably not much of an exaggeration).

or,

b) you have to put more heat into the affected area than that which is being removed.

I have only seen this once or twice and both times the affected place was shut down.

One story I have heard from a close associate who had first hand information on this subject.... What they did was use a portable welder and connected the leads to the re-bar in the floor. Of course the re-bar mat has to be tied together to make contact, but apparently they turned the re-bar mat into an induction heater.

[gwapa]

colinc
Could you be more precise in the size of the room. Also inform what you have outside of each wall.
Is the the facility rised in order to have the dock at seme level as trailer?
what kind of heater do you have under floor?
regards
gwapa

[nh3wizard]

We had a similar problem at a facility, we found the approx area where the worst of the heaving was and core drilled the concrete floor and installed an electric heater into the dirt and refilled, I dont remember what size and type heater, but it took approx 1 year for the ice to melt and lower the floor. What we have done on new constructions is install 2 glycol loops outside of the freezers on the docks to prevent this from happening again.

Hope this helps.

[colinc]

The store hold's approx 3000 pallets 50x35mtr and we have no capacity spur to emty the site.

The slab is raised about 1.2mtr with forced draft air pushed down the centre of the building with vent pipes 100mm at each side of the tunnel expelling outside. All vent pipes are clear of debris If I could core drill the holes back out and reinstate the pipe and increse air temp this should start to drop the slab? I hope

[nh3wizard]

Could you put heat trace in the tubes where the heaving is occuring, and cap off the ends to keep the heat in the vent tubes, we have done this also, this way there is no core drilling.

[Peter_1]

Or installing an air curtain

[keepitcool]

Oh boy, What a mess. To fix this properly you will probably have to cut the floor up and excavate the frost. Back fill and add electric heat mats or extend the glycol loops. If you simply thaw this and go on your way you probably will not have proper soil compaction.

[Josip]

Hi, colinc

something similar happened 20+ years but in freezing tunnel.... suddenly the slab rised for 25-35 cm (10"-14") ... they had to stop with freezing tunnel .... and excavate layer of frozen soil .... came to unfrozen soil after 4m.... then refill all with gravel ... of course reinstall new heating, vapour barrier... etc...etc... big job...

.... hope that is not scenario of your case...

.... try to examine soil temperature under every ventilation pipe.... fast...

Best regards, Josip

[old gas bottle]

also when it gets heated up it will more than likely blow the slab big time,think its get the big disc cutter out and get digging with a pick axe come out about a metre from the doorway asswell,then i would fit some heater mats,thats if it will work out with the existing underfloor pipework arrangement, thats a bad un!!!

[gwapa]

COLINC
As you mentioned you already have a air heating system installed.

are this pipes free contected with the ambient? or they are forced air with a fan?

How wide are the 100 mm pipes installed?
Are those slopped?

What could be the level of water en the zone? Freatic level