My next video is about drainage in sub-floor basement areas. After that, what would you like me to do a video about? Please comment! Matt Cornell

@fernandajade1268

2 жыл бұрын

I like to see your videos because I doing construction and your videos helps me a lot

@CornellEngineers

2 жыл бұрын

Thank you @@fernandajade1268. I appreciate you taking the time to leave a comment.

@landynvick6187

2 жыл бұрын

You should walk through a real life example with engineering analysis regarding soil parameters needed and best practice, buckling, up lift and how you determine and quantify the said design as per structural needs. Horizontal, vertical. Thanks for the great video.

I’m in Alaska where we also have to contend with frost heave. Additionally, in virtually all owner hired contractors its an imperative to be knowledgeable about what your buying to ensure the job is being done correctly. Your educational video is exactly what I’ve been looking for and appreciate the fact that you’ve taken the time to share in detail your knowledge and experience. I feel better armed going forward preparing a foundation for my log cabin.

The Euler's theory states that the stress in the column due to direct loads is small compared to the stress due to buckling failure. Basically long thin columns like the ones on screw piers with minimal support due to disturbed soil surrounding the column can fail in buckling.

Hi Matt - it is a good message about the reduction of load capacity with longer piles. Getting the foundations right is so important. Cheers Mark

@CornellEngineers

4 жыл бұрын

Thanks for your comment Mark. I know you're a keen advocate for getting the message out there too about doing foundations well.

Thanks for the video. Came here after seeing an advert from a company that uses this system.

@CornellEngineers

2 жыл бұрын

Very glad we could help.

Love the video guys, thanks of the shout out!

@129GympieStreet

Жыл бұрын

Idealcorp yours was a great video. Thanks for making it available to the good people of YT! Matt

Thank you for your post. I built a 16' x 32' foot Chapel in loose soil between two creeks 12" ×18" thick footing with regard. The ground has settled and am getting quotes for piers. This has been helpful

@CornellEngineers

2 жыл бұрын

Hi Richard Glad we could help. Matt

Hi Matt, thank you for making this video. We are going through some ground issues at our place in Nth Brisbane and found this to be very informative and will help us with working out a plan for our next move (which will possibly be a knock-down rebuild).

@CornellEngineers

4 жыл бұрын

Hi Tim. Thanks for checking out our videos. I hope we were able to help resolve your questions.

I have seen these used many times, and they are as good as the soil they are in. I've noticed that once the helix and shaft have displaced some soil at the surface they advance well if properly installed. Once several feet down the displaced soil almost compacts adjacent soils near the helix. In certain soils and depths , they are fantastic.

@CornellEngineers

2 жыл бұрын

Thanks for your comments Tommy.

@canonicaltom

Жыл бұрын

Yeah, once a good quality screw pile is driven a couple feet into the ground, into better soil, they don't require any downward force in order to be driven, only torque. Also when you do a pull test, you pull much harder than the weight of the soil in the hole, and if all that soil was just churned up into fluffy uncompressed fill the pile would just come right out. There would be essentially no uplift resistance. Suggesting that because the top layer of soil comes out, the bad soil that is the entire reason for using a screw pile in the first place, that the entire rest of the ground has been churned up all the way to the bottom, shows a deep misunderstanding of soil mechanics.

Thanks for sharing these experiences.

@CornellEngineers

4 жыл бұрын

It's a pleasure Bassem.

thanks for sharing your knowledge. Much appreciated

@CornellEngineers

4 жыл бұрын

You're welcome JR. Thanks for commenting.

Wonderful tutorial video, cheers mate! 👍

@CornellEngineers

4 жыл бұрын

Thanks Scott. Really appreciate your feedback.

great demonstration, love it!

@CornellEngineers

2 жыл бұрын

Thank you very much. Are you getting ready to have some screw piers installed?

Fascinating video Matt, thanks for sharing, I’m leaning so much. If my builder insists on a waffle slab, I would request, as suggested a perimeter strip footing + screw piers with pile caps across the whole slab. Apart from physically watching the pour & screw pier installation, are there procedures to ensure the slab is constructed to quoted & defined engineered specs? A poured slab looks the same to a homeowner unfortunately

Thank you Matt. I am considering screwed piles for my next build and I will incorporate your suggestions with a top concrete (reinforced) cap with a depth of about 3-4 feet.

@CornellEngineers

2 жыл бұрын

Hope it goes well, Mike. Feel free to share some photos/videos of the installation!

thank you for this video. could you talk more about the construction of the ground beams? would you concrete them at the same time as the piles?

Great video, very informative

@CornellEngineers

3 жыл бұрын

Glad it was helpful!

hi love you info on the channel keep up the good work

@CornellEngineers

3 жыл бұрын

Thank you, Bill. Thanks for taking time out of your busy schedule to stop by.

So from what I have read, the guys in the video were... 1.) Spinning the screwpiles to fast, the US engineering standard is about 1.5" (40mm) of down travel per one revolution 2.) putting to much down force on the screw This is what caused all the uplift and loosening of the soil pack. I have seen these piles run into all types of soils and when done right never push loose dirt back up the bore.

@CornellEngineers

2 жыл бұрын

Thanks for the comments, Richard.

Hi Matt, great video. I am currently about to build a house on a class P site on a waffle slab and my engineering specifies that I can have the screw piles in the beams or under the beams with support caps. Which method would you recommend?

What about the type which resemble a wood screw? The diameter of the tube is constant after the threaded portion, so no soil is displaced. The diameter of the hole being the same diameter of the screw pier. Therefore side loading will be minimised. I've seen the "pull" being tested by hydraulic lift to over two tonnes.....

@CornellEngineers

2 жыл бұрын

Hi Martin. Good question. Are the type you are talking about used for residential and commercial buildings? I can only find them for solar panel installations. Can you give me a link o check out? Matt Cornell

Awesome!

@CornellEngineers

2 жыл бұрын

Thank you Godfrido Gomapas. Screw piers are awesome!!

Thanks for the very informative video. When the engineer designs for screw piers I'm assuming they just specify the rotational torque that needs to be reached when insallting the screw pier? Is this enough to determine that the pier is in 'solid' enough ground? Each screw goes down as far as it needs to to reach that resistive torque?

@CornellEngineers

9 ай бұрын

Hi Mark Sometimes - but from my involvement with the guys designing screw piers their assessment of the torque requirement is tied to the soil testing carried out at design stage rather than blind trust that somewhere down there the screw pier will stop spinning. Torque then becomes the way the installer shows they have achieved the screw pier designer's requirements. Load testing can be carried out on installed screw piers in case there is uncertainty. Matt Cornell

@markharwood

9 ай бұрын

Understood. Thanks.

Instead of a pile cap that might try to lift the pile with surface frost, how about a collar with radial fins, that is pressed into the surface?

@CornellEngineers

3 ай бұрын

Hi Dan Sounds like an option for lateral stability without being affected too much by frost heave (clay heave in Australia). However The collar and radial fins would have to be protected from corrosion and somehow transfer enough lateral load through the fins into the adjacent ground without pushing into the ground. Then the whole assembly needs to not ever be damaged by homeowners, mowers and future renovations. Solve those issues and you might have a plan!

When there is high wind load on a particular axis, I suppose grade beams may be also advisable... something to check with NL FEA maybe. :+ )

How about not removing the soil that comes up around the screw pile, & following up with a vibratory compactor after each pile is installed?

@CornellEngineers

3 ай бұрын

Hi Dan Maybe. That would recompact the soil - but the screw pile steel shafts are quite narrow meaning that if they push sideways from bracing loads or buckling, the stresses into the surface level soils would be very high. Some good thoughts Dan. But I'm not a fan of compacted soil as the answer! Matt Cornell

One additional comment. Would it make any sense at all to ram the dirt churned up by the helix down to the end, and simply add cement to the now clear part of the hole? I'm assuming it might not, as your cap is probably larger in diameter to greater horizontal movement resistance?

In my area we have 5 feet of frost lifting in winter

@CornellEngineers

2 жыл бұрын

Wow Paul. it must get cold there. Where are you from?

Hi Thanks for a very informative video, what about a situation where we prefer to instal a concrete slab over the site supported by screw piers. Soil is Wealden clay under 1.5m of consolidated made ground ?

@CornellEngineers

3 жыл бұрын

Hi Nick. Thanks for your comment and question. Local knowledge of the local conditions (and engaging with a local engineer) is our recommendation for any tricky sites. Hope your projects are going well. Matt Cornell

Hi Matt we would love u to explain interpreting engineer drawings including deepened edge beams,clay plugs etc

@CornellEngineers

2 жыл бұрын

Great idea. What are some more engineering terms you are struggling with?

Hi Matt, thanks for you very informative video. curiously how do you guys deal with a screw pier takes some bending?

@CornellEngineers

2 жыл бұрын

Hi Ning Chen I'm not sure whether you mean that the below ground portion of the screw pier is being subject to lateral load somehow? Or do you mean that the screw pier continues up out of the ground to become a column for a building that is laterally loaded by wind? Screw piers are typically designed by the supplier - so this might be a great question for Mark from Katana Foundations. Matt Cornell

@ningchen6242

2 жыл бұрын

@@CornellEngineers Hi Matt, very much appreciated your reply. Maybe I should say do you ususlly design screw pile for lateral load? Yes you are right in your video the soil around the shaft could be very soft, once it has some lateral load, at the end of the pile shaft could have big moment...not sure if im correct. thanks

@CornellEngineers

2 жыл бұрын

Hi@@ningchen6242 Again, I'll defer to Mark's expertise on pile design, but for our designs of the other aspects, I don't think we would expect to cantilever a screw pile from the bottom of the footing and expect it to resist lateral loads without a pile cap.

@oldtimefarmboy617

2 жыл бұрын

@@ningchen6242 If the soil was actually loosened to the point that the rod could bend then a lot more soil would have come out of the hole. Helical piers work like screws in wood. Like wood, once the screw gets a little below the surface, the screw and the pole displace the soil to the side and actually becomes more compacted so bending will not be a problem. Also, helical piers are designed to be used in conjunction with the building's foundation, wither a solid slab on grade or pier and beam. If you are doing a pier and beam foundation you would dig around the helical pier as deep as you normally would and put you forms around it and then put the cap plate on top of the pole, install rebar like normal except for attaching it to the cap plate, and then pour the concrete. The helical pier would then become part of the concrete pier and provide the extra resistance from ground heaving that being in denser soil deeper down will provide. On a slab on grade foundation you would dig out the trenches for the foundation for your load bearing walls like normal with the helical piers installed where those foundation trenches are dug and make the helical pier part of the foundation just like you would above. Either way you are tying the foundation of the building to the denser soil deeper in the ground for the extra stability it provides. Otherwise you would have to dig a hole that deep and install rebar in the hole and pour concrete. Helical piers do the same thing without displacing a lot of soil and without the cost of concrete or waiting for it to cure so you can continue with the rest of the foundation.

it appears to be going in at an angle? Potential issues later?

Every year soil move or lift up that will cause crack the house.

Hi Matt, Enjoying your videos. I'm about to do an owner build. Any thought on screwpiles vs using Surefoot?

@CornellEngineers

2 жыл бұрын

Hi Peter Thanks for the question. I am not familiar with the reticulated micropile system you mentioned so I read the engineering report on #reticulatedmicropilesystems that was undertaken by Swinburne #University of Technology (available at this link): www.researchgate.net/publication/307905816_Static_Load_Testing_of_Concrete_Free_Reticulated_Micropiles_System My comments are as follows: - The reticulated micropile system relies on engaging the soil that the micropiles are driven into. This tends to be the surface layers of soil rather than the deeper soil that a screw pier is driven into. Maybe a reticulated micropile system would be affected by slab heave more than a screw pier. - Since a reticulated micropile system relies on surface soils the system would be affected by the full reactive ground movement of the site. A screw pier system could be considered to be founded into soils below the reactive ground movement zone (Hs) depending on the designer. Perhaps a slight win for screw piers? - A reticulated micropile seems to have creep/displacement near ultimate loads that could be outside the tolerance of the building depending on the situation. ie the footing might get loose after being loaded to more than 50% ultimate loads. - A reticulated micropile system may not be suitable for lateral loads or cantilevered posts without further testing. I'm not sure that a house on stumps and cross-braces could be founded such a system. Screw piles also need concrete pile caps for these situations so no clear winner in this regard. It will come down to aligning your building design to your site conditions, your structural engineer's knowledge and experience, your risk appetite and the consequence of footing movement (up/down or lateral). Best of luck with your owner/builder project.

@peter9117

2 жыл бұрын

@@CornellEngineers Thanks for that Matt. I'm on a sloping site so a raised floor is the way to go. Reading the report it suggests Surefoot needs more time to be proven. One positive is any heaving or subsidence could be rectified by adjusting post height. So bored concrete piers are a safer bet than these or helical piers?

@CornellEngineers

2 жыл бұрын

@@peter9117 It still comes down to the site classification and reactivity of the site. Raised floor = steel or timber stumps. Steel stumps can be bought with adjustable heads (still needs a handyperson to adjust them from time to time) but stairs, slabs and plumbing are all a little less tolerant. I'd think that screw piers wouldn't be ruled out so long as they incorporate pile caps. Bored piers would be ok if you have diggable soil and are able to found all footings into a rocky layer. Depending on the slope you might also need to comply with slope stability requirements - but that is a whole other story/video/problem! Matt Cornell

🤔good 👍

@CornellEngineers

11 ай бұрын

I appreciate your comment. Thanks!

If you have two or three helixes that have progressive smaller pitches in relation to each other, would that compress the loose soil between the helixes as it goes down?

@CornellEngineers

10 ай бұрын

Actually I have no idea if this would work. Let me defer to the gents that actually design and certify screw pier installations if any of them would like to comment!?!

Once the screw pile is installed, is it possible to then fill it with cement / concrete giving them a little more strength and possibly preventing them from buckling, if the earth around them is loose? Thanks for the educational video, very enlightening!

@CornellEngineers

2 жыл бұрын

Hi Pauly Perhaps. The ground is not normally so loose that concrete will flow down the shaft to the bottom where the screws are. So I think the screw pier designer has to take into account the total length of the screw pier when designing the shaft diameter and a concrete pile cap placed around the top of the shaft for the reason we suggest -> lateral stability.

@elfillari

10 ай бұрын

I've done the digging in two stages, just because my crowler arm is too short for screwing the 2m long pile with one shot at the time!😂 So, first I dig the hole like one meter only, then bring the soil up from the hole. Then pouring wet cement to the hole, then penetrate the screw pole in between the wet cement in the hole. Then twisting the rest of the pole to the solid ground beneath the cemented hole. I think it's the just right method done similar principle as you teached on your video!😊

Great content Not a fan of waffle slabs. Never heard of E classifications.

@CornellEngineers

3 жыл бұрын

Thanks for stopping by, watching and commenting.

Do you recommend any book or online reading regarding residential footings systems?

@CornellEngineers

4 жыл бұрын

Hi gabrielbobmarley Actually, I do. I strongly recommend all engineers read these books: infostore.saiglobal.com/en-au/Standards/HB-28-1997-131073_SAIG_AS_AS_277659/ psengineering.com.au/wp-content/uploads/2018/03/BDPSNewsletter_Issue50_waffle-slab.pdf www.ccaa.com.au/imis_prod/documents/Library%20Documents/CCAA%20Technical%20Publications/CCAA%20Guides/CCAAGUIDE2007-T53-HousingWEB.pdf and finally, find and attend a course on AS2870.

@CornellEngineers

4 жыл бұрын

Also, we have a list of reference guides on our website that you might find handy. www.cornellengineers.com.au/design-guides/

Mate, I'm no engineer but 🤣 if the soil surrounding the pier was less dense (as you infer), than you would have continuing expulsions of soil through the whole 5 metres out the top. Could I argue that as the auger/helical travels, it is compressing the soil behind it ? The initial expulsion would be due to lack of resistance. Indeed if this ceases after the initial expulsion, surely the volume of the pipe is further compressing the soil ?

@CornellEngineers

2 жыл бұрын

Hi Brian Dirou It is a legitimate argument that the top of the screw pier is compressing the soil it leaves behind as it travels down the hole. I just wouldn't rely on it to prevent lateral buckling of a 5m long pipe buried in the ground. That's why some screw pile contractors install mid-height screws in deep embedment piers - to improve lateral buckling capacity. The design of the screw pier is up to the screw pile engineer and in that regard I fully trust them. The design of the superstructure is the responsibility of the building's structural engineer and in that regard we all need do the very best we can to provide a (laterally and vertically) stable building. Matt Cornell

60t concrete swimming pool. 4mx8, 2m deep end. Mid 1.2m deep. Shallow end 1.5m deep. 150mm wall concrete walls with 60mm of polystyrene panels inside and outside. 300mm thick slab, hd12 rebar 200mm centres verticals 300mm centres horizontals. Double caged 2m deep end deep end with Hd16 200mm centres. With a 900mm by 4m coverpit. The cover pit filled with water, and 1'3 of the pool filled. And the swimming pool floated in this recent float in Auckland..... how did it happen.. and how do we remedy it? Just out of curiosity. I really dig your channel. Cheers brotha Wolfgang

@CornellEngineers

Жыл бұрын

Cheers Wolfgang! Glad to hear from you. Sounds like a beautiful pool. In comparison to your pool, Royal Carribean's cruise liner "Wonder of the Seas" weighs 236,857 gross tonnes and it floats as well as a rubber ducky in the bathtub. Big and heavy does not equal not buoyant. Buoyancy comes from displacing more weight of water than your vessel weighs. Stopping a big, heavy concrete pool from floating could be as simple (but expensive) as making the pool so heavy that it weighs more than the water it dsiplaces. The better option is to ensure the pool is never surrounded by water by improving drainage around the pool surface and improving subsoil drainage around the walls of the pool (ie gravel backfill that drains freely to somehwere lower than the pool). The final alternative is to anchor the pool into the ground with big concrete blobs or steel bars that activate the weight of the soil around the pool (thereby increasing the weight of the pool to more than the weight of the water displaced). Good drainage is pretty much the most economic solution top preventing a pool popping out of the ground when it floods. Best of luck getting that baby back into the hole. Matt Cornell

Your mistake: the tip of the pile underneath the helix is compressing the ground. The ground displacement is bigger than the disturbing forces from the helix. The end result is completely different from what you discribe here and even better than the ground was before. It's this compression that creates the dirt at the start of the job. Creating dirt is far from continuous. I agrree the advantage of concrete at the top in case of huge lateral forces to resist.

@CornellEngineers

Жыл бұрын

Thanks for your comment! I'd be happy to review your reference material relating to the positive effect of the tip of the pile and the soil compression effect - even if it is in Dutch. Have you seen this Practice Note from the Institution of Professional Enigneers New Zealand? d2rjvl4n5h2b61.cloudfront.net/media/documents/Practice_Note_28_Screw_Piles_Guidelines_for_Design_Construction_and_Installation.pdf Or the guide by Mark Armstrong at Katana Foundations? www.youtube.com/@katanafoundations3790/ Looking forward to hearing from you. Matt Cornell

I have only ever built using Flight Auger Piles and never had a problem, these screw piles look mickey mouse to me.

If you're going to go through the trouble of performing this installation why wouldn't you just use an auger and pour a pier or set a post? What is the benefit?

@CornellEngineers

2 жыл бұрын

Hi Steve So a couple of benefits stand out. - Screw piers can be installed through wet/loose sloppy soils that would ordinarily collapse into a bored pier excavation. - They are a one-step, faster operation in lieu of digging a hole, keeping it safe, covering it, tamping the bottom and removing cave-ins and filling it with concrete. - They are a D&C item that allows the builder to offload the design and installation. I'm sure the screw pier installers following along have some additional benefits? Matt

@boots7859

2 жыл бұрын

Because you can arrive on site with a small work crew of 2-3, and have 15-20 post done by late lunch time. And, you can then start framing after lunch. And, if you price how much it actually costs to install piers...

How long till they rust?

@CornellEngineers

3 жыл бұрын

Great question. I admit I don't know the answer. My thoughts are the corrosion process on steel screw piers depends on a complicated combination of the availability of air, availability of moisture and damage to the corrosion protection system. Being installed below ground they are very difficult to monitor. There are of course various opinions and studies that have been done on this subject: piletechscrewfiles.blogspot.com/2016/05/stripping-down-corrosion.html www.researchgate.net/publication/237576562_Introduction_to_Corrosion_and_Galvanizing_of_Helix_Foundations www.helicalpilebook.com/Files/corrosion%20of%20helix%20piers.pdf

My porches have 12 inch concrete tubes resting on 24 by 24 footings with rebar in footing bent into vertical tube same depth as basement footings, I can’t See these small screws being reliable.

@CornellEngineers

2 жыл бұрын

Hi Paul That porch of yours doesn't sound like it is going to fall down in a hurry. Thanks for your comment. Hope all is well in your part of the world.

@boots7859

2 жыл бұрын

A lot of citys are built with these. The nice thing is unlike concrete footings, you know what the pressure is on these as they are installed, what they can bear, and much less worry about them occasionally sinking for some odd reason.

Can we install this type of pile by hand?

@CornellEngineers

3 жыл бұрын

Apparently, Yes. kzread.info/dash/bejne/lmeoxNqrebXTmLw.html

Great photo of a screw pier pile cap exposed by erosion. Nice work supporting this house on screw piers. Reinstatement work will be a bit tricky!! www.abc.net.au/cm/rimage/12465576-3x2-xlarge.jpg?v=2

@elfillari

10 ай бұрын

No picture opened?

Matt, fantastic video explaining the subject and pitfalls. I doubt I'm going to have much problem with a 48x16' deck, however I'd had some concerns when looking at helical piles with that unsupported area along the shaft. I just came across another screw pile manf., and its really is just a large screw. They are apparently IRC compliant in the US, and they do seem to avoid that pitfall of common helical piles. With your expertise, could you take a look at these? kzread.info/dash/bejne/no6I0MSbf9ywmcY.html I'm thinking if they are IRC compliant, they seem to have fewer potential issues. Cheers!

@CornellEngineers

2 жыл бұрын

Ahh yes. I think I've seen these used on a home renovation show. www.americangroundscrew.com/code-compliance/ They give the capacity of the steel section but no real comment on capacity in the ground so I'm thinking site-specific soil testing and design by a geotechnical engineer. The savings in residential construction would maybe be offset by the specialist advice? They look like they target solar installations and lightweight structures. I think they look cool but that's not a structural opinion.

@boots7859

2 жыл бұрын

@@CornellEngineers Matt, thanks very, very much for your time and considered opinion. In looking at their specs for soil bearing capacity (Table 5) in clay soil they show 8129 lbs bearing/axial compression. This is very close to the large Canadian helical pier manf's like Goliath that I've been looking at. And yes, this is for a deck not residence.

Waffle pods & screw piers ? Do you wear 2 condoms ? I hardly think lateral forces would be a problem. As an engineer, surely control of reactive soils is best achieved via adequate drainage of prevailing ground waters ? Grouting in uneven levels sounds foolhardy.

@CornellEngineers

2 жыл бұрын

Hi Brian Dirou You're right. Waffle slabs and screw piers are not a lateral load problem. Lateral loads are more of a problem when a house is on steel stumps and screw piers and the house relies on the screw pier footing only (without a pile cap) to resist and transfer lateral wind loads. Reactive soils and site drainage are the subject of this video: kzread.info/dash/bejne/Z3epmrKRfpa9nJc.html Regards Matt Cornell

@boots7859

2 жыл бұрын

So snarky, and yet many people buy a house only to later encounter these problems.

temporary accommodation construction 😅😅😅😅😅😅😅😅😅😅😅😅😅😅😅

Y don’t the Builder lean how to build a house that doesn’t sink……🤔🤔🤔

@CornellEngineers

Жыл бұрын

It takes a few things to go wrong for a house to sink. It's a team effort!

:)

@CornellEngineers

2 жыл бұрын

Cheers Sam