> I wonder how those things happen.
You are forgetting post-construction settlement as a cause, which I think probably accounts for a large percentage.
In my experience taking time to check the calcs and the match line is the most productive use of my "on site quality control time allowance".
But I agree that it is the bigger blunder to find because if it is the hundredth you are looking for, which do you hold, the side shot from a loop that closed 0.015 or the coordinate shot that checked a bench 0.014?
I had a old timer tell me that they used to lay out a base line for the lot and then come off of that with a Rt. Angle prism, rag tape and p-gun. I would be interested in hearing more about that methodology.
> When I'm going to the grocery store or a restaurant after some rain or melting snow,, I am constantly noticing large puddles along some curb and gutter that was obviously the result of either a poor design, surveyors blindly spraying hubs in, or carpenters blindly building forms to hubs set by a survey crew in error .
> I wonder how those things happen.
I take great offense to your post. It's always the surveyors fault, huh? You see a result and automatically infer the cause. How is it you wonder how those things happen yet precede that statement with all of the causes?
How much experience do you have in the way roads are constructed? It is a rarity that the subgrade under a curb is compacted to the spec of the pavement. Have you heard the term "slump?" There is a difference between hand rolled curb and slip formed curb. Surveyors do screw up. We have a tolerance, the materials have a tolerance, the contractor has a tolerance. If everything is in error, and still within tolerance, problems may arise.
So it's Moe, Larry and Curly
I couldn't resist.
If it's my robot then I'm using the numbers it gives. Of course, there are a bunch of errors that can occur when you mark stakes. So I layout all the stakes and mark them, then go through them a second time with a different robot set-up and make sure the numbers I shoot the second time match what's on the stake. Usually I find one or two on a job that got written wrong on a stake.
> I've never done a bridge, so maybe I'd change my tune, but hopefully I never have to!
Using a level for a bridge is a little insane also 😉
We run digital levels through our control but after that, if something needs to be tight,the robot is the tool to use.
I have been involved in hundreds and hundreds of miles of roadway paving and have yet to see anybody able to place and finish concrete on a 0.5% and it drain correctly. If I see it on a plan I usually do everyone a favor and adjust it where I can.
"I take great offense to your post." - [sarcasm]No need to be greatly offended. I hadn't realized you worked on that particular project, otherwise I wouldn't have brought it up in a public forum. 😉
[/sarcasm]
I was not referring to minor puddling. I'm talking ponding i.e. .5' deep.
The kind that makes you wonder if someone forgot a D.I.
I did elude to the fact that it may have been the result of poor engineering.
My point is - how do blunders like this not get caught at some point during construction?
I feel I am fairly knowledgeable about construction and how roads are designed and built. The relative compaction requirements for soils range from 90% to 95%. Even at 90% (which is easy to obtain), you should not see any settling that causes ponding at finish grade.
The use of "choker sections" stopped quite awhile ago in my part of the country. Our roads are typically built full width with the same amount of effort.
"Have you heard the term "slump?" "
[sarcasm]"slump"? Yes that is what I do in my easy chair at 5:00...[/sarcasm]
oh, your talking about concrete - sorry.
Any curb contractor that knowingly places curb with a 0.5' birdbath in it is irresponsible and partly responsible. They should be notifying either the inspector, engineer, or surveyor PRIOR to pouring said section of curb.
Yes, it could be design, staking, or both. But when they put that string line up, and it doesn't flow - they need to blow the whistle ASAP. If not then they are negligent.
I know I've written "C - 0.25'" on a hub, when my numbers say "F - 0.25'". Opps, sorry ma'am. There is your 6" bird bath. My dumbness - yuppers. If he doesn't blow the whistle - negligent workmanship IMO.
Unlike cars and other moving machinery, that is one instance where you definitely "FIX IT BEFORE it's broke".
$0.02
No.
I agree
I had a crew make some blunders on a section of curb (this is why I do NOT rely on doing calcs in my head.) We left the site, the contractor set the string. The contractor stood back and didn't think it looked right. (It was wrong due to our stakes) The contractor then proceeded to adjust the string to what he thought is correct. (his "corrections" made things worse) The DOT was supposed to do a final inspection of the string before the curb went in. It was Saturday and the inspector wasn't around. The curb got poured. We didn't get the call until a few weeks later when a string line got pulled across the road to check proposed asphalt depths.
Yes we were wrong, but all could have been avoided if the contractor would have made a phone call as soon he even thought there was a problem.
The Answer to most of these problems.....
...can be solved by using Machine Control or at least building a surface to use for staking purposes.
Building a surface first, you find design errors BEFORE ever going on-site.