I was intrigued to run across your 2008 study regarding a question I've had for a while.
Road bumps after bridges: in my long cross-country drives, I can't help but notice that every bridge over a creek or road or railway, no matter how small the bridge is, tends to develop a small depression in the road right as the road material transitions from bridge back to highway. With the equivalent of ten-thousand pound rubber hammers hitting them thousands of times a day, and the pliability of asphalt, they become accentuated over time.
Do you think a flexible bladder full of, say, vegetable oil, could be placed where the depression inevitably occurs, and could be pumped back up to bridge level as the depression worsens? It would have to contain an environmentally friendly liquid that didn't freeze, in a bladder that could withstand the high pressure needed to raise the road and wouldn't be damaged by traffic vibrations, burrowing rodents, earthquakes and so on. But the amount that they would need to raise the road might be merely an inch or two if it was caught early before traffic pounded the depression too deep.
Perhaps the answer you'll give me is that the cost would be way more than just filling the depression and re-paving periodically when it gets bad.
Your study found that "geosynthetic reinforced fill" and "flowable fill (controlled low strength material)" were more expensive and didn't help. Bridges needed 5-7 foot-deep "granular foundation" to prevent subsidence.
https://www.google.com/url?sa=t&source=web&rct=j&url=http://wisconsindot.gov/documents2/research/00-13bridgesettlement-b.pdf&ved=0ahUKEwj7gKLS1sPVAhVK2mMKHfGNAK8QFgglMAA&usg=AFQjCNFNEUD5q21AhmPXvfkREw3t2iuCqA
-Tom Elwood
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