Plumbing Trench Collapse Before Backfill

[JamesW]

You probably need to talk to the engineer or an engineer who can answer your questions better than we can.

They can review what was specified and compare it to what was actually used.

They can advise you about the suitability of the actual concrete used and if there are any reasons to be concerned or if any tests are appropriate.

 

[Ktm41]

You probably need to talk to the engineer or an engineer who can answer your questions better than we can.

They can review what was specified and compare it to what was actually used.

They can advise you about the suitability of the actual concrete used and if there are any reasons to be concerned or if any tests are appropriate.

Perfect that will be our next step, appreciate you guys taking the time!

 

[.ben]

These are the sections that refer to PSI on the approved plans. The contract states 4500 PSI which is what we discussed so when we saw 3500 on the ticket from the shotcrete sub it raised a question. We don’t know how to read the water content information from the ticket or how to interpret “28 day compressive strength” vs the psi they shot with.

There is a discrepancy in 28-day compressive strength (f'c) between the contract (4,500 psi) and Structural note #5 (2,500 psi).

I think it's very safe to assume that the 3500 from the ticket refers to the concrete f'c. So, the strength meets engineering specifications, but does not meet the contract. (I recommend contacting the structural engineer to verify. It's possible a higher strength is called out elsewhere). How this is rectified is a negotiation between the builder and you.

Water/cement ratio is simply the weight of water divided by the weight of concrete (plus cementitious material; none based on the ticket). So,
w/c = 236.3-gal x 8.34 #/gal) / 6570 # = 0.3. This meets the structural specification of less than or equal to 0.45

 

[AQUA~HOLICS]

If the shell is being properly hydrated for the proper amount of time it stands a good chance that it will be at or higher than 4,500 PSI after 28 days, but this can only be validated by a lab.

 

[Ktm41]

There is a discrepancy in 28-day compressive strength (f'c) between the contract (4,500 psi) and Structural note #5 (2,500 psi).

I think it's very safe to assume that the 3500 from the ticket refers to the concrete f'c. So, the strength meets engineering specifications, but does not meet the contract. (I recommend contacting the structural engineer to verify. It's possible a higher strength is called out elsewhere). How this is rectified is a negotiation between the builder and you.

Water/cement ratio is simply the weight of water divided by the weight of concrete (plus cementitious material; none based on the ticket). So,
w/c = 236.3-gal x 8.34 #/gal) / 6570 # = 0.3. This meets the structural specification of less than or equal to 0.45

Thanks for your expertise!

 

[Ktm41]

Looking for advice. We have to decide if we want the sheer descents a) on the center wall and pillars or b) centered on the three walls. See photos. PB points out that the pillars will be taller than the center wall and it might not look right having the outside sheer descents higher than the middle one. It would also leave a lot of empty wall space. My biggest concern is going with option B will place a 24” sheer descent at the foot of our baja step. Will it be too noisy and “splashy” or a nice water addition to that space? It’s a large 15x7’ baja step so presumably you wouldn’t have to sit right next to the fountain. Advice appreciated!

 

[Hotbobcool]

Looking for advice. We have to decide if we want the sheer descents a) on the center wall and pillars or b) centered on the three walls. See photos. PB points out that the pillars will be taller than the center wall and it might not look right having the outside sheer descents higher than the middle one. It would also leave a lot of empty wall space. My biggest concern is going with option B will place a 24” sheer descent at the foot of our baja step. Will it be too noisy and “splashy” or a nice water addition to that space? It’s a large 15x7’ baja step so presumably you wouldn’t have to sit right next to the fountain. Advice appreciated!

Curious about this because I have the same conundrum!

What are the dimensions of your wall and columns?

 

[AQUA~HOLICS]

An elevated spillway over a Baja shelf may have two negatives, one being that it will take away from surface/useable area of the shelf due to the falling water, second if the shelf is too shallow, over time it may erode the plaster surface.

 

[Ktm41]

Curious about this because I have the same conundrum!

What are the dimensions of your wall and columns?

Our wall is 38’ total. The pillars are 24”x24”. The walls are 12” on the sides and 18” in the center. I’ve attached a rendering! I think we are going to go for the sheers centered on each segment of wall which will put one near the baja. It will only be a 12” wall so hoping it’s a nice addition and not too splashy.

 

[Ktm41]

An elevated spillway over a Baja shelf may have two negatives, one being that it will take away from surface/useable area of the shelf due to the falling water, second if the shelf is too shallow, over time it may erode the plaster surface.

That’s something to consider, thanks for mentioning it.

 

[proavia]

Be sure each sheer has its own valve (NOT ball valves) to control the output.
This allows much better balancing and also shutting one or more off while others remain running.

 

[Ktm41]

Be sure each sheer has its own valve (NOT ball valves) to control the output.
This allows much better balancing and also shutting one or more off while others remain running.

So glad you mentioned this, will definitely ask the PB about it. Is this pretty standard or something they’d likely say is more cost / labor?

 

[proavia]

So glad you mentioned this, will definitely ask the PB about it. Is this pretty standard or something they’d likely say is more cost / labor?

It isn't standard at all. PB will do it the easy way - one line to the pool for all sheers and no valves to control independently.
Ideally, I'd want each sheer to have a separate plumbing line all the way back to the pad and Jandy 2-way valves on each line to control them independently. I like all the valves to be at the equipment pad.

 

[Hotbobcool]

Our wall is 38’ total. The pillars are 24”x24”. The walls are 12” on the sides and 18” in the center. I’ve attached a rendering! I think we are going to go for the sheers centered on each segment of wall which will put one near the baja. It will only be a 12” wall so hoping it’s a nice addition and not too splashy.

Thank you! Extremely similar to what we were doing, but ours is 36' long. 24 on the sides, 30 in the center, and 36" high columns. Yours makes me wonder if I should do a little less height.

 

[Ktm41]

Thank you! Extremely similar to what we were doing, but ours is 36' long. 24 on the sides, 30 in the center, and 36" high columns. Yours makes me wonder if I should do a little less height.

Yours sounds lovely! I’ve been worried 12” might seem a little underwhelming, but ours is purely for aesthetics, it’s not a retaining wall or serving any structural purpose. Since it’s sticking up above grade we thought we would keep it on shorter side.