Author Topic: SpaceX Texas launch site Discussion and Updates - Thread 3  (Read 850987 times)

Offline Nomadd

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Re: SpaceX Texas launch site Discussion and Updates - Thread 3
« Reply #2340 on: 08/23/2016 02:36 AM »
Those tubes have got to be just to line the hole until they get it filled with concrete and rebar. Been watching a similar process used to make foundations for the new HV power lines along US 52 in MN (CAPX-2020 project) -- those were just a lot larger, some as much as 6' across and about 30' tall. Pipes were removed from the outside after the concrete got poured and set. Of course here you won't have issues with having to drill/blast limestone out of the way like they did here in MN...
That's what I guessed. They have the built up area on one end that the types you pull back out of the ground have. I see them around the wet areas of Louisiana a lot doing concrete elevation piling. I guess they pull them out while the concrete is still soft until the bottom of the tube is just below the surface. I'll see if I can find an umbrella and a cooler full of something and go watch for a while.
« Last Edit: 08/25/2016 03:59 PM by Nomadd »

Offline Nomadd

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Re: SpaceX Texas launch site Discussion and Updates - Thread 3
« Reply #2341 on: 08/25/2016 12:20 AM »
 49 feet of those 50 foot tubes at the Stargate site are underground now. I've heard 50 to 60 feet to hit centuries undisturbed ground around here, so it makes sense if you need a base that won't move.

Offline IainMcClatchie

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Re: SpaceX Texas launch site Discussion and Updates - Thread 3
« Reply #2342 on: 08/25/2016 05:39 AM »
Concrete, even with a lot of rebar in it, is just 2.4 g/cc.  A 1 foot diameter pipe will hold the concrete in it so long as the concrete to steel bond has at least 1800 Pa shear strength.  That's a quarter psi.  Greasy pasta sticks better than that.

Assuming they coat the steel pipe interior with grease, it seems really difficult to pull it up off the piling.  And even if they did, they'd lose all the side friction between the piling and the undisturbed soil.  That side friction is a major component of how pilings work.

Something doesn't seem right here.

Offline xpete

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Re: SpaceX Texas launch site Discussion and Updates - Thread 3
« Reply #2343 on: 08/25/2016 08:50 AM »
"SpaceX said the first ground station antenna will arrive at Boca Chica via tractor-trailer in October. A thick concrete foundation will have to be poured first and allowed to cure for at least one month before the antenna is installed, the company said.

The antenna’s heavy hydraulics will be removed prior to shipping and replaced by electronics once at Boca Chica.

According to the contract, SpaceX must have the first antenna installed before the end of the year and “qualified” (certified by NASA as being installed correctly) by spring, SpaceX said. No date has been set for shipment of the second antenna, the company said."

http://www.brownsvilleherald.com/premium/article_d8b149a2-61b3-11e6-bfa1-8b38c37d8d4c.html

Offline rsdavis9

I've seen a lot of pilings poured for bridges in portsmouth nh. They always leave the steel tubes around the pilings. They just rust away. They may cut some of the tubing above the water line. It makes it look better.
With ELV best efficiency was the paradigm. The new paradigm is reusable, good enough, and commonality of design.
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Offline acsawdey

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Re: SpaceX Texas launch site Discussion and Updates - Thread 3
« Reply #2345 on: 08/25/2016 12:36 PM »
Concrete, even with a lot of rebar in it, is just 2.4 g/cc.  A 1 foot diameter pipe will hold the concrete in it so long as the concrete to steel bond has at least 1800 Pa shear strength.  That's a quarter psi.  Greasy pasta sticks better than that.

Assuming they coat the steel pipe interior with grease, it seems really difficult to pull it up off the piling.  And even if they did, they'd lose all the side friction between the piling and the undisturbed soil.  That side friction is a major component of how pilings work.

Something doesn't seem right here.

Well, seemed like the most plausible explanation for why they had only 2 pipes and a whole pile of rebar.

Another plausible explanation. I didn't see a good picture of the boring tool but if it's the type that can expand after it clear the end of the tube, maybe these aren't friction piles but have a bulbed end. Another method a quick search turned up is this:

http://theconstructor.org/geotechnical/driven-cast-in-situ-concrete-piles-construction-process/7088/

Which looks like exactly what we have here. The tube is removed while the concrete is wet, which ought to result in an irregular shape and increase friction.


Offline Beittil

Is the terrain unsuitable for driving in prefab pilings?

Offline rsdavis9

I've seen a lot of pilings poured for bridges in portsmouth nh. They always leave the steel tubes around the pilings. They just rust away. They may cut some of the tubing above the water line. It makes it look better.

also all the pilings in portsmouth nh hit bedrock pretty quickly. :-)
With ELV best efficiency was the paradigm. The new paradigm is reusable, good enough, and commonality of design.
Same engines. Design once. Same vehicle. Design once. Reusable. Build once.

Offline Nomadd

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Re: SpaceX Texas launch site Discussion and Updates - Thread 3
« Reply #2348 on: 08/25/2016 03:21 PM »
Concrete, even with a lot of rebar in it, is just 2.4 g/cc.  A 1 foot diameter pipe will hold the concrete in it so long as the concrete to steel bond has at least 1800 Pa shear strength.  That's a quarter psi.  Greasy pasta sticks better than that.

Assuming they coat the steel pipe interior with grease, it seems really difficult to pull it up off the piling.  And even if they did, they'd lose all the side friction between the piling and the undisturbed soil.  That side friction is a major component of how pilings work.

Something doesn't seem right here.
All they have to do is pull the pipe as they pour the concrete. We'll know shortly.
« Last Edit: 08/25/2016 03:24 PM by Nomadd »

Offline Johnnyhinbos

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SpaceX Texas launch site Discussion and Updates - Thread 3
« Reply #2349 on: 08/25/2016 03:32 PM »
Living in the heart of Boston I watch a LOT of very large scale construction and have watched just about every sort of foundation work - from driven piles to slurry walls to drilled footings. The gear shown in Nomad's pics is pretty small stuff and it looks like they're only vibrating in small circular sleeves. Is there a drill on site for excavating out the soil within the sleeves? Typically the rebar inserts are already preformed into the proper diameter cages and dropped into the excavated hole. Is the rebar in site straight runs or preformed cages?
« Last Edit: 08/25/2016 03:33 PM by Johnnyhinbos »
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Offline Nomadd

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Re: SpaceX Texas launch site Discussion and Updates - Thread 3
« Reply #2350 on: 08/25/2016 04:01 PM »
Living in the heart of Boston I watch a LOT of very large scale construction and have watched just about every sort of foundation work - from driven piles to slurry walls to drilled footings. The gear shown in Nomad's pics is pretty small stuff and it looks like they're only vibrating in small circular sleeves. Is there a drill on site for excavating out the soil within the sleeves? Typically the rebar inserts are already preformed into the proper diameter cages and dropped into the excavated hole. Is the rebar in site straight runs or preformed cages?
You can see the drill and rebar cages in the photos.

Offline Dave G

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Re: SpaceX Texas launch site Discussion and Updates - Thread 3
« Reply #2351 on: 08/25/2016 06:53 PM »
Living in the heart of Boston I watch a LOT of very large scale construction and have watched just about every sort of foundation work - from driven piles to slurry walls to drilled footings. The gear shown in Nomad's pics is pretty small stuff and it looks like they're only vibrating in small circular sleeves. Is there a drill on site for excavating out the soil within the sleeves? Typically the rebar inserts are already preformed into the proper diameter cages and dropped into the excavated hole. Is the rebar in site straight runs or preformed cages?
You can see the drill and rebar cages in the photos.
« Last Edit: 08/25/2016 07:17 PM by Dave G »

Offline Nomadd

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Re: SpaceX Texas launch site Discussion and Updates - Thread 3
« Reply #2352 on: 08/25/2016 07:36 PM »
 They're pulling the pipes out, dropping the cages in and pumping concrete. (They might be dropping the cages first. I missed that part) I guess the pipes were drill guides and keep the hole from deforming overnight.

 Four done and enough parts for 18 more. It looks like they're just using the 3/4" cages in the top half of the hole and running a single 1" rebar all the way down. I guess you don't have to worry so much about off vertical hurricane loads more than 24 feet down.

 The portable building east of the control center has been emptied and gutted down to the studs.

 This may be enough posts and pictures of pilings. I need to save myself for really important stuff like wiring and grounding systems. That's the good part about building in muck. You don't have to sink a 300 foot well for a decent ground.
« Last Edit: 08/27/2016 03:09 AM by Nomadd »

Offline Nomadd

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Re: SpaceX Texas launch site Discussion and Updates - Thread 3
« Reply #2353 on: 08/26/2016 12:32 AM »
Is the terrain unsuitable for driving in prefab pilings?
It's mostly sand and no bedrock for something like 1,000 feet. I'm not sure what's going where, but 150 mph hurricane winds can make for some pretty serious loads, and poured concrete is probably the most immovable type of piling they could have here.
 I'm getting to be an expert on soil here. (For the first 4 feet at least) I finally figured out my drain problems were because some genius put the leach field 16 inches higher than the sewer line from the house. I've spent the last week digging a 4'x4'x13' hole for some Home Depot leach chambers. There was only one 8" layer of hard clay and the rest was sand.
« Last Edit: 08/26/2016 06:08 AM by Nomadd »

Offline IainMcClatchie

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Re: SpaceX Texas launch site Discussion and Updates - Thread 3
« Reply #2354 on: 08/26/2016 06:55 AM »
I'm not saying it's unusual, but those piling tops look terribly dirty to me.  When they pour the concrete that goes over the top, they'll have to dig out around the top of that poured piling, and then blast it clean.  What a pain in the butt.  And they'll never completely seal the joint between the two pours.

I'm impressed they were able to pull 50' long 1' diameter pipes out of the ground.  I would have expected that to take a huge amount of hammering, basically a pile driver running in reverse.

Offline Nomadd

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Re: SpaceX Texas launch site Discussion and Updates - Thread 3
« Reply #2355 on: 08/26/2016 07:48 AM »
I'm not saying it's unusual, but those piling tops look terribly dirty to me.  When they pour the concrete that goes over the top, they'll have to dig out around the top of that poured piling, and then blast it clean.  What a pain in the butt.  And they'll never completely seal the joint between the two pours.

I'm impressed they were able to pull 50' long 1' diameter pipes out of the ground.  I would have expected that to take a huge amount of hammering, basically a pile driver running in reverse.
Those are 2' diameter pipes. The vibrating whatchamacallit should make pulling the pipes a lot easier than just hammering them out. There's no rock at all in the ground here so it's a lot easier than in some places.
 Sometimes they throw dirt on top of fresh concrete to keep it from drying too fast while it cures. That doesn't seem like it would be a factor here, but I'm not all that well versed in cementology.
« Last Edit: 08/26/2016 03:22 PM by Nomadd »

Offline woods170

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Re: SpaceX Texas launch site Discussion and Updates - Thread 3
« Reply #2356 on: 08/26/2016 08:47 AM »
I'm not saying it's unusual, but those piling tops look terribly dirty to me.  When they pour the concrete that goes over the top, they'll have to dig out around the top of that poured piling, and then blast it clean.  What a pain in the butt.  And they'll never completely seal the joint between the two pours.

I'm impressed they were able to pull 50' long 1' diameter pipes out of the ground.  I would have expected that to take a huge amount of hammering, basically a pile driver running in reverse.
Not quite a pain in the butt. I see that happening around here all the time with regards to poured concrete pilings. The top is dug out and blasted clean with high-pressure water. The joint between the two pours does not need to be perfectly sealed. The pilings are just there to make sure the actual foundation does not sink into the ground. It just basically 'sits' on top of the pilings. The level of rigidity between the pilings and the rest of the foundation only needs to be capable of preventing the foundation of 'sliding off' the piles when the building is exposed to lateral forces (such as wind). To achieve this, the interface between the top of a pile and the foundation beams is often 'over-poured'.
« Last Edit: 08/26/2016 08:49 AM by woods170 »


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