Posted on 01/25/2010 10:22:53 AM PST by NormsRevenge
SAN ANTONIO – Dozens of homes were evacuated in San Antonio after the ground below began shifting, creating crevices up to 15 feet deep and nearly splitting a nearby retaining wall in half, officials said.
About 80 homes were first evacuated on Sunday after residents in a northwest side subdivision reported that the ground was caving behind several houses. No one was injured.
The large crack in the retaining wall sent soil tumbling out below. Fences were tossed askew and crumpled like accordions, and aerial photos showed land had given way near the foundations of several homes.
Engineers at the scene Monday were trying to determine why the ground was shifting and how much damage it could cause.
(Excerpt) Read more at news.yahoo.com ...
I just get a kick out of the technical terms “alluvial fill” and “retreating scarp!”
All scarps erode back or "retreat." If you build on a deposit near one, you better be sure that the rates of scarp retreat are longer than human lifespans.
The World According to Scarp.
Holy Cow! Those are some pretty tall ‘retaining walls’.
I’ve seen many developments like this ... the developers find it easier to do monumental terracing in order to build their cookie-cutter desig slab-on-grade houses (designed for flat lots) than to work with the natural terrain and build homes actually designed for non-flat lots.
Looks like the plan is not working out so well.
It is always good to learn something new everyday!
Must be an intriguing profession. I genuinely appreciate the interesting facts.
What he said was they were built on dirt that was hauled in. That is why there is a retaining wall that "is supposed" to keep the alluvial fill (dirt) from slumping down the hill.
Now the short version:
Bad construction and engineering.
“Value engineering” is probably closer to the truth.
Talk about internal conflict. Like a dog that's a Chow/Lab mix. Doesn't know whether to lick you to death or rip your face off.
No, not any underground mines in San Antonio - We are on top of old limestone here, and all quarries are open pit.
Fiesta Texas, for example, is built inside an old gravel pit.
Good old San Antonio again. A few years ago in another subdivision home foundations were cracking a emitting fumes from an old dump they built the development over.
You’re all mistaken, when they checked with o-bow-man he said it was all Bush’s fault.
There that mystery is solved by the chosen one.
It may not have been hauled in -- they could have just used a bulldozer to sculpt out house sites without doing a thorough geological study. I'm sensing big-time lawsuits a'comin'
Bad construction and engineering.
Spot on.
I think I caused it when I buried my life savings in the backyard where the interest rate happens to be higher than at the bank. I just didn’t expect such a small hole to cause such a big problem.
That retaining wall appears to be about 20 feet tall. If the fill was not properly compacted and becomes wet with rain it will behave like a very thick fluid. Assuming the specific gravity of the fill is 2.0 you could easily have 25 psi at the bottom of the retaining wall pushing out. That would mean a force of over 3000 lbs on each square foot.
Can't help but notice what looks like a residential development of some sort in the picture?
Looking a couple of photos and this description it appears the slope of the hill is moving downward. Sounds like poor planning/etc in the developmental stages.
http://www.mysanantonio.com/news/local_news/Sinkhole_prompts_evacuation_on_Northwest_Side.html
Authorities evacuated about 80 homes in a Northwest Side neighborhood Sunday when ground caved in behind several houses, pushing earth down a 30-foot hill and into two retaining walls that cracked and threatened residences below.
No one was injured, and agencies acted quickly to address the endangered homes near West Hausman Road and Loop 1604.
Describing the collapse as a “slope failure,” authorities at a Sunday night meeting told residents from The Hills at Rivermist subdivision that in some areas the crevices grew to 12 to 15 feet deep and 6 to 8 feet wide. But they didn’t know the cause.
end snip
a home vid but very shaky shows the slope;
http://www.ustream.tv/recorded/4200736
A better view showing the area and homes: Note Oak Water that is where some of them were supposedly: Note retaining walls.
or a Geoengineologist
Not even close dude, in Armageddon Bruce Willis and a crew of misfits had to blow up a huge asteroid before it hit Earth. This is a lot more like Earthquake, where Charlton Heston and Ava Gardner try to survive after a huge earthquake hits Los Angeles.
I feel that I was denied CRITICAL, Need-to-Know Information.
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