Thursday, April 26, 2012

hunting with a pencel

In an evolutionary scene, we engineers hunt with a pencil. We consulting engineers are the storehouse of designs, concepts, ideas, computing models, formulas, data, and some theories, and many approximations of the physical world as it was, which we pull off the shelf, add a bit of site specific data, adjust the model, turn the crank three times to the left, flick the accumulator switch, once to the right, put in a bit more data, or take some out, turn the crank a few more times, and come up with an answer (If you are old enough to remember the Curta Calculator).  The final step is to communicate the answer to the client. Before this can happen, we must know what we are hunting for, and where to find it.

We had better know the answer in a general way at least, or what data we will need and where to get it before we take on the project. If it is reclamation, we had better know the cause of the original failure, and how to avoid it, or if we are dealing with time and wear, what the clients current and expectations are.

Traffic loads are increasing, not only in volume, but the governments have and are increasing legal loads. This has a tremendous impact on the cost of roads, at public expense.  These legal loads come onto private property, and pavements must be thicker to support them. The equipment that loads and unloads them is large, more heavy pavements. The building that house them are large, heavier loads. Buildings  in general are large, heavier, and the clients are only looking at dollars in most decisions now.  

It has become a much more difficult struggle to operate a small firm. The specialization has made it difficult to find suitable replacement personnel. Burnout of senior people, myself in particular, is the issue.    

Sunday, April 8, 2012

Asphalt Pavements

How do we repair asphalt pavements that are in need of overlay and there is no money?
Well that is a hard question. Water is the main issue. Overlay patch anywhere that water stands after a shower. Truck dumped and grader leveled asphalt is the best solution, equivalent to a leveling course. Seal to prevent water ingress. Water softens the support and hastens failure.

Expect heavier overlays.

Cracking will continue at a faster rate. New cracks and old cracks growing in length and width will create additional issues, so annual sealing via spray chip seal is the best patching method, where water is draining.

It becomes repeat the truck dump patching and spray seal annually until the road/pavement has been evaluated, and a structural over lay has been applied.

Most of the roads that I have designed the pavement thickness on were constructed with less asphalt and gravel than I recommended. This reduces a 20 year design, that should be overlayed at 15 years, to something less. When the next government administration asks why it is failing at 10 years, all involved have mover on. Say la vie.