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[RC] I-40 slide & the SF - Oakland bridge - Lynn White

As one who works as a pavement/geotech engineer for a highway department in a 
mountainous state I am actually qualified to make a comment on this.? Truck 
tires only affect the top four feet of a pavement structure.? So basically, 
anything deeper than four feet will not be "felt" by a truck tire.

POE or weigh stations do enforce weight limits, and for interstate highways 
they are somewhat uniform.? The locations are placed so that it is not cost 
effective for long haulers to go around them.? Time is money for these drivers 
and they can't afford to be stopped.

The thing that drives me crazy is that I'll design a pavement for a certain 
number of trucks at a certain weight and then the legislature will raise the 
weight limit.? So a section designed for 20 years will last about 15. 

The only complaint I have about trucks is that the caps of the tires tend to 
come off in one peice during a blow-out.? I almost got hit by one years ago and 
when I stopped to pick it up I was suprised at how heavy the thing was. If that 
cap had landed on my windsheild I'd be dead.? I stay away from trucks for this 
very reason. In fact, if I can get to a ride without ever having to hit the 
interstate I'm tickled. 

As for vibrations caused by trucks, the side of a mountain is more likely to 
experience naturally occuring vibrations generated from the earth itself. 

The general public is always quick to want fixes but hesitant about actually 
paying for them.? Uniformly fractured rock with random joint orientation on a 
face steeper than 1:1 will always be prone to freeze/thaw failures.? To fix 
something like the slope on I-40 would be very expensive and require the 
consturction of anchored wire or shot-crete well up the slope along with a 
possible dewatering system. It all depends on the joint orientation. But just 
waiting for the enviornmental clearances would take years. 

Now for all you people thinking about traveling through the Bay area:  The San 
Francisco - Oakland Bridge got closed today.  Glad I don't have to commute 
there!


Lynn







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