survey and control techniques to ensure pile installment accuracy
survey and control techniques to ensure pile installment accuracy
(OP)
To All the experts,
I am a new starter in the construction industry. The project that I am now working on is upon the completion of diaphram walls, structural auger piles are now required - positioning and vertical accuracy is very much required at this stage. What surveying and control techniques can be used to ensure that pile installment is as planned?? Previous marking may be distorted as a result of the diaphragm wall construction and heavy machineries that are used.
Please advise.
Thanx... :)
I am a new starter in the construction industry. The project that I am now working on is upon the completion of diaphram walls, structural auger piles are now required - positioning and vertical accuracy is very much required at this stage. What surveying and control techniques can be used to ensure that pile installment is as planned?? Previous marking may be distorted as a result of the diaphragm wall construction and heavy machineries that are used.
Please advise.
Thanx... :)





RE: survey and control techniques to ensure pile installment accuracy
To ensure alignment, I've seen a number of methods used and most are nothing more than developed barnyard devices. Moreover, most methods were based on a sounding line (really heavy weight on a tape). The weight on the sounding line should be heavy as you may encounter water or the process may use drillers mud. Anyway the weight usually will have some known distance from the center to the outside edge and based on this distance and the distance the line reads (depending how much line you lower in to the hole) will give you an idea of plunbness.
RE: survey and control techniques to ensure pile installment accuracy
ur suggestions are helpful, but I still hav a few guerries:
would the hubs disrupt the machinery movement / or be destroyed by machineries? (as this site invovles 100+ piles)
what would you suggest the site engineer to ensure the accuracy of the marking since the ground may shift. (i.e. check points required and system)
Tnx
RE: survey and control techniques to ensure pile installment accuracy
RE: survey and control techniques to ensure pile installment accuracy
During the operation, you'll want to set "tattletales" or benchmarks that will allow you to make a quick check (usually within a 6' distance for a 6' folding rule) for location checks. So in other words you have a mark for the center of pile and two offsets from that mark in each orthogonal direction to make quick measurements. However, please keep in mind that once the pile or auger begins there is little you can do to check anything which is why it is critical to place it right the first time. Moreover, you don't want to make the crew move a pile for anything less than allowed tolerance! Too much fight!
Suggest that if you can get a copy of Engineering of Pile Installations by Fredrick Merrit. This reference discusses all the steps and mostly from the inspector's viewpoint.
By the way, never set hubs where the contractor may run equipment over them. If this is the case then too many operations are going on to accurately set the hubs. Tell the contractor this and ask him to watch out or you won't set another hub and that if a pile is located incorrectly it will come out of his pocket. That has always burned me up. The contractor asking way too soon to have some type of control set only to have it run-over by an earthmover!
RE: survey and control techniques to ensure pile installment accuracy
Since you are new to the construction realm, I'm going to offer something outside the technical question you asked but is included in your question...
The term "ensure" has been used several times in this discourse. While I certainly understand the context in which you are using the term, let me offer that this is one of those words that attorneys just love to hang engineers with! While it is not quite as bad as "insure", it is quite close in meaning and is used synonymously in many instances. In short, it implies certification and guarantee, both of which are taboo in the liability lexicon of engineering.
As Qshake pointed out, this is not and does not have to be an exact location exercise. Tolerances are permitted and necessary. If you tie the term ensure to this, you tend to negate the effect of having tolerances, thus locking yourself into an accuracy that you probably cannot control nor deliver. "Down the road" it could become an issue, relevant or not, but nonetheless and issue. Issues often become problems.
Be careful of the use of words in our business. We often mean them in a different light than they will be interpreted by others.
RE: survey and control techniques to ensure pile installment accuracy
RE: survey and control techniques to ensure pile installment accuracy
RE: survey and control techniques to ensure pile installment accuracy
RE: survey and control techniques to ensure pile installment accuracy
RE: survey and control techniques to ensure pile installment accuracy
some distance, say 10 ft and 5 ft. He will ussually set hubs past the end of the line. This will allow him to quickly set up and restablish the line if some of the offsets are destroyed. Often times a hub or paint mark will be set at the actual pile location. If the actual pile location is not set or destroyed, the pile drilling foreman can hold his tape at the 10 ft offset, line it up over the 5 ft ofset ( to ensure line) and mark the pile at 10 ft. from the outside hub.
First a comment on destroyed markout - Hubs will be lost durring construction. Some projects it is tough to find places where the wont be lost. Some contractors do not have much regard for mark out, but that is rare. Most contractors do recognize the importance of trying to maintain stakes, however, some amount of remarkig will be inevitable. The trick is to establish control to allow remarking with a minimum of rework.
Second, If you are checking in installation of the piles is what do you check? tolerances for piles are typcally 1-2 inches for a pile that may have a diameter of 6 to 12 inches. On the plans, the piles are a perfect cile with an eaisly defined center. In the field th tops of the piles are anything but round (unless they are cased) making the center impossible to find. This brings into question the need for exact tolerances when you can't define what must be in tolerance. However, the best way I think, is to confirm the off set locations and the drill marks so that you know the drill was in tolerance to start. Note that obstructions, especcially near the surface may move the drill, and obstructions may or may not be the contractors responsibility.
Third, with auger cast piles, especcially uncased, the concern is not the tolerance usually, but the shape of the pile in the ground. GRL has equipment that can give you the pile shape in the ground. (www.pile.com for more information)
Finally if you are doing the inspection, it is a lot easier to correct a pile location prior to installing it than after, so get involved in the layout and be sure it is what you want. Also talk to the drillers and understand what it is that they are doing. If you have a good relationship with the crew, it will be easier to resolve problems when they arise.
RE: survey and control techniques to ensure pile installment accuracy