Thread: Bell shaped holes?

Bell bottoms have fallen out of favour because the bell cutter must be retracted into the bucket to withdraw the bucket for soil disposal. This increases the complexity of the bucket design and its maintenance requirements, as well as slowing production. For end bearing, it's usually easier to just increase the depth to achieve adequate bearing capacity at the smaller diameter.

I suppose the bell bottom as shown could provide some uplift resistance in lightly-loaded situations. Concrete is notoriuosly deficient in tension capacity, though. For very significant loads, I'd prefer to see some reo anchoring the bell into the rest of the shaft, as well as in the shaft itself.

North Atlantic hurricanes are substantially the same as South Pacific cyclones, except for the direction of rotation. In Florida, the preferred method of providing uplift resistance for small structures such as sheds and mobile homes, is to use soil anchors - a helical steel plate at the end of a long steel shaft, screwed into the ground. I think there was a discussion here (WWF) a year or so ago, and they weren't a mystery to the congregation.

Please read my comments in light of my limited familiarity with small structures. IIRC, the smallest drilled shaft I've ever used was 8 feet (2.4m) in diameter. Several in the foundations for a drawbridge, with each leaf weighing about 1,000,000 pounds - equal to the maximum takeoff weight of a Boeing 747.

Joe

Uplift resistance and download support are very different and I don't know where you are building and the design intent so will leave that.

As far as the drain pipe goes, find out if it is storm water or sewerage.
Be careful about making long or short roundabout routes around the hole. You will probably loose grade (slope) and liquid (whatever it is) will not flow properly which may cause more problems.

If storm water, it may be better to encase it in concrete and leave it as it is. BUt check with council or an engineer would be my suggestion. THe little bit of concrete needed for this is not really going to be that much. If sewerage then move it. (not under the carport) I'd replace a longer section so that there is slope and the "stuff" will actually drain away. Best to get a professional to do this job.

All up it may be better to ask the council and take their advice as they are the ones who will OK it or not anyway.

It's definitely storm water, it's directly in line (and the same shape) with the downpipe from the house and the exit at the street. I started to dig around today to re-route it, geez it'll be a big job. Well, big for me anyway. I'll call council tomorrow and see what they have to say, but I suspect they'll want me to re-route it...

Carport kit arrived today. I think it's rather beyond my level of strength or expertise... And the guy who offered to help me appears to have piked (well, he piked on helping me dig the holes, and is now sort of uncontactable...). Might call Titan tomorrow and see how much it would cost to get them to put it up for me... Or maybe someone here?

Originally Posted by joe greiner

Bell bottoms have fallen out of favour...........

I've still got several pairs in my wardrobe, do you reckon they might come back into fashion some time soon?

Mick

Originally Posted by journeyman Mick

I've still got several pairs in my wardrobe, do you reckon they might come back into fashion some time soon?

Mick

If they still fit, more power to ya.

Joe

Originally Posted by journeyman Mick

I've still got several pairs in my wardrobe, do you reckon they might come back into fashion some time soon?

Mick

The Mardi Gras was the other night Mick, so you will have to wait till next year.

Called up Council, they said not to worry about the storm water pipe (yay), just put some flexible material around it so it doesn't bind to the concrete (yay). So the inspector is coming out tomorrow to inspect the holes, hopefully they pass.

I asked about the plumbing for the gutter, specifically about a gravel pit so I wouldn't need to cut the storm water pipe, and they mentioned that if I have enough fall then I should plumb it to the storm water. Hmm, so I'll still need to cut the pipe anyway... (unless they meant something else?)

The pipe doesn't appear to be a standard 90mm round pipe, it's more of a flat shape (like a 90mm pipe that's been squashed flat). Not square, it's round'ish. I haven't seen this sort of pipe before, where do I get connectors for it?

Originally Posted by demuire

.............The pipe doesn't appear to be a standard 90mm round pipe, it's more of a flat shape (like a 90mm pipe that's been squashed flat). Not square, it's round'ish. I haven't seen this sort of pipe before, where do I get connectors for it?

It is in fact, 90mm pipe that's been squashed by the weight of the backfill. Just use your standard connectors. You may need to use a bit of heat to get the pipe round again.

Mick

Oh right. YAY Oh well, I guess assuming the holes are approved today, I can dig the hole out a little to get proper access to the pipe and cut it and put a T-piece in it...

so like... is there anyone in Ipswich who would like to help me put up a carport this weekend?

... and it passed YAY. Dug around the pipe today to have a closer look at it and yes, it is indeed a 90mm pipe that's been squashed flat. Will buy a Y-piece and 45 degree bend and throw that in...

Thinking about concrete for these footings - am I right in calculating that I would need approx 0.2 square meters of concrete? ((0.15 * 0.15 * 3.142) * 0.6) x 4, with a little bit more for the bell...? Someone has suggested to me to get it from a landscaping place, maybe 2 bags of cement and some premix gravel + sand, mixed in with 1:6 ratio? Does that sound about right?

Also, would it be safe to put up the frame of the carport by itself (not concreted in) and have it left for a week or so before pouring the footings in? It's just that I doubt we'd have time to square and level it all up properly this weekend after we put it up... I'm thinking that it's sort of like a big table (without the top so the wind shouldn't blow it away), and as long as the bolts are done up it should just stand there by itself and not fall over...?

That volume (0.2m3) sounds about right.

From memory you need about 16 bags of concrete (20kg) per m3, so you will need 4 bags. Also when using all in mix (sand and gravel already mixed) you should use 5:1 or even better 4:1.

Is more concrete to sand better? (I'm assuming 4:1 means 4 parts mix to 1 part cement)? How much water goes in this? I sort of know what consistency it's meant to look like but it's always reassuring to know I haven't added too little or too much water...

Originally Posted by demuire

Is more concrete to sand better?

Yes generally, although the water to cement ratio also effects the strength.

(I'm assuming 4:1 means 4 parts mix to 1 part cement)?

Yep, that is correct.

How much water goes in this?

I try and stick to about 0.7:1 i.e. if you put in 10lt bucket of cement you put in about 7 litres of water. The more water the weaker the mix. Being post holes you could probably get away with a dryer mix (less water).