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RnR
Senior Nomad
Posts: 836
Registered: 5-1-2010
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| Quote: | | Quote: | Originally posted by rts551
A local friend told us that so many bridges wash out because of the way the approach from the highway joins the bridge---the builders often short cut
the process and use nothing but dirt fill. Then with the first big rains and floods, the dirts washed away and undermines the bridge.
I certainly am no engineer, but we started looking at the bridges along highway 1 that were washed out last year and it does look like they had dirt
filled approaches.
Hope one of the engneers around here comments one way or another. |
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Here goes:
The bridges are built with sacrificial dirt approaches by design. Ninety percent or more of the cost of the crossing is in the concrete portion of
the bridge so the designers strive to protect the major investment while minimizing the overall cost of the structure.
The bridges are built with the concrete sections in the deepest part of the arroyos. When the arroyo starts to flow it first passes under the
concrete span section of the bridge. If the water flow exceeds the capacity of the concrete section, it washes out the dirt approach and increases
the channel width. When the flow starts to recede, the water retreats back to the concrete section of the bridge allowing the dirt approach area to
be dewatered and rapidly repaired.
That is why the road was back in operation at three of the four bridges in about a week after last Februaury's storms. The fourth bridge, at El
Rosario, really exceeded the channel capacity and dropped a span into the arroyo in addition to washing out the approaches. That is why the bridge is
still out of service. It takes a long time to repair the concrete sections.
This design theory is very evident on several bridges near Santa Maria and El Cien. The approches are built of dirt and are up to five feet lower in
elevation than the concrete decks.
This design theory is also used on small dam spillways in the US. A portion of the embankment is built lower than the remaining crest of the dam in
order to allow for a controlled breaching of the embankment and iniciation of flow down the spillway. It's called a "fuse plug" spillway.
Whew!
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DianaT
Select Nomad
Posts: 10020
Registered: 12-17-2004
Member Is Offline
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| Quote: | | Quote: | Originally posted by RnR
| Quote: | Originally posted by rts551
A local friend told us that so many bridges wash out because of the way the approach from the highway joins the bridge---the builders often short cut
the process and use nothing but dirt fill. Then with the first big rains and floods, the dirts washed away and undermines the bridge.
I certainly am no engineer, but we started looking at the bridges along highway 1 that were washed out last year and it does look like they had dirt
filled approaches.
Hope one of the engneers around here comments one way or another. |
|
Here goes:
The bridges are built with sacrificial dirt approaches by design. Ninety percent or more of the cost of the crossing is in the concrete portion of
the bridge so the designers strive to protect the major investment while minimizing the overall cost of the structure.
The bridges are built with the concrete sections in the deepest part of the arroyos. When the arroyo starts to flow it first passes under the
concrete span section of the bridge. If the water flow exceeds the capacity of the concrete section, it washes out the dirt approach and increases
the channel width. When the flow starts to recede, the water retreats back to the concrete section of the bridge allowing the dirt approach area to
be dewatered and rapidly repaired.
That is why the road was back in operation at three of the four bridges in about a week after last Februaury's storms. The fourth bridge, at El
Rosario, really exceeded the channel capacity and dropped a span into the arroyo in addition to washing out the approaches. That is why the bridge is
still out of service. It takes a long time to repair the concrete sections.
This design theory is very evident on several bridges near Santa Maria and El Cien. The approches are built of dirt and are up to five feet lower in
elevation than the concrete decks.
This design theory is also used on small dam spillways in the US. A portion of the embankment is built lower than the remaining crest of the dam in
order to allow for a controlled breaching of the embankment and iniciation of flow down the spillway. It's called a "fuse plug" spillway.
Whew! |
Thank you VERY much for taking the time to explain the design---always good to learn something new. Good to know there is a good reason for that
design.
Diana
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mcfez
Elite Nomad
Posts: 8678
Registered: 12-2-2009
Location: aka BN yankeeirishman
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| Quote: | Originally posted by wilderone
the road to nowhere - now really - how many people drive that road in a year? Most people in Gonzaga fly in don't they? politics, waste, folly
I'm beginning to think Calderon is in cahoots with the drug cartels to launder money. that's how Panama City was built. |
We be driving that new road so much...we'll wear the asphalt down! Gonzaga Bay has got to be the top ten places in Baja...we love it there. Great
beaches....snorkeling...FISHING is awful though 
Old people are like the old cars, made of some tough stuff. May show a little rust, but good as gold on the inside.
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David K
Honored Nomad
Posts: 64852
Registered: 8-30-2002
Location: San Diego County
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Mood: Have Baja Fever
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Sadly, we heard the new highway alignment south of Gonzaga will not pass in front of Coco's Corner... It will be about a mile west, closer to the old
(pre-1982) road to Laguna Chapala.
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k-rico
Super Nomad
Posts: 2079
Registered: 7-10-2008
Location: Playas de Tijuana
Member Is Offline
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| Quote: | Originally posted by wilderone
the road to nowhere - now really - how many people drive that road in a year? Most people in Gonzaga fly in don't they? |
Hmmmmm, I wonder if folks fly in because there's no road to speak of and if a good road is put in, folks will drive there.
Waddya think? Maybe? 
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desertcpl
Super Nomad
Posts: 2396
Registered: 10-26-2008
Location: yuma,az
Member Is Offline
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| Quote: | Originally posted by David K
Sadly, we heard the new highway alignment south of Gonzaga will not pass in front of Coco's Corner... It will be about a mile west, closer to the old
(pre-1982) road to Laguna Chapala. |
maybe we all could do some thing about this,, like move Coco closer to the new highway
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elgatoloco
Ultra Nomad
Posts: 4332
Registered: 11-19-2002
Location: Yes
Member Is Offline
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| Quote: | Originally posted by desertcpl
| Quote: | Originally posted by David K
Sadly, we heard the new highway alignment south of Gonzaga will not pass in front of Coco's Corner... It will be about a mile west, closer to the old
(pre-1982) road to Laguna Chapala. |
maybe we all could do some thing about this,, like move Coco closer to the new highway |
Coco's Offramp! 
MAGA
Making Attorneys Get Attorneys
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David K
Honored Nomad
Posts: 64852
Registered: 8-30-2002
Location: San Diego County
Member Is Offline
Mood: Have Baja Fever
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Yah.... maybe Coco will prefer to not hear the roar of semis and their jake brakes... and stay on the dirt track to Calamajue for the off roaders...
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SFLowTide
Junior Nomad
Posts: 30
Registered: 5-6-2010
Location: Elk Grove, CA/Km 31
Member Is Offline
Mood: Waiting On The Sun
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I think you hit the nail right on the head, David. We were through a couple of weeks ago and asked him about the highway coming by his place. He, in
his "infamously candid" way, expressed to us that there is no way that he will be next to that NOISY &%$# ROAD! Besides, it would take lifetime
to move all of those beer cans and underwear...lol
Have you heard where the Main Hwy. 5 is to meet up with the Puertecitos road? The word is that they plan on bypassing San Felipe just north of town
(keeping the large trucks off of the city streets), but nobody seems to know where it will re-connect.
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David K
Honored Nomad
Posts: 64852
Registered: 8-30-2002
Location: San Diego County
Member Is Offline
Mood: Have Baja Fever
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| Quote: | Originally posted by SFLowTide
I think you hit the nail right on the head, David. We were through a couple of weeks ago and asked him about the highway coming by his place. He, in
his "infamously candid" way, expressed to us that there is no way that he will be next to that NOISY &%$# ROAD! Besides, it would take lifetime
to move all of those beer cans and underwear...lol
Have you heard where the Main Hwy. 5 is to meet up with the Puertecitos road? The word is that they plan on bypassing San Felipe just north of town
(keeping the large trucks off of the city streets), but nobody seems to know where it will re-connect. |
The old road south from San Felipe junctions with the new road just a couple miles south of Coloradito's road... that would be close to my guess as
the mountains would limit the route from being any more inland... ???
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