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Driving concrete piling has generally been abandoned in USA/Canada/Western Europe due to the propensity of concrete to crack in tension during pile driving oper

by abduhl 10y ago

Driving concrete piling has generally been abandoned in USA/Canada/Western Europe due to the propensity of concrete to crack in tension during pile driving operations. Driven pile is typically steel now in most construction you will see unless you live in a place where concrete is extremely cheap compared to steel.

lobster_johnson 10y ago
In that case what I've observed was probably steel after all. Thanks.
Someone 10y ago
Wouldn't that be to crack in compression? Also, I don't see concrete piles being abandoned at all. Part of the reason may be that, where I live, many poles now are drilled, pressed or vibrated into the ground to decrease noise and potential impact on surrounding buildings. Thats is possible because there is no bedrock to build on where I live, so poles often go down easily for the first meters; I have seen wooden poles sink in five meters or so under their own weight. Traditional piling into the ground still is used, too. If necessary, a protective head cover on the pole (made from wood or, nowadays, plastic) softens the blows a bit, protecting the concrete from damage.
- abduhl 10y ago
  No, tension is what I meant. Imagine the pile hammer hitting the top of the pile. This impulse is transmitted down the length of the pile at the speed of sound as a wave. There exists a point where the wave gets to the end of the pile (this is at the pile tip) and the compression front attempts to continue which results in tension (eg - the pile tip is dragging itself forward with the energy). This is mostly seen with soft soils where end reaction is not sufficient to provide a hard "stop" on the pile. For hard ground, the opposite can occur where the driving energy reflects at the pile tip. This can result in huge compressive forces that crush (not crack) the concrete due to the two compressive waves (one new wave from the next hammer strike and the reflected wave from the previous hammer strike) stacking due to superposition. The reason that this failure mechanism wasn't noted by me is that steel piles suffer the same issue, so it is not a good reason to use steel over concrete piling. As you note, the solution to both issues is the use of a shoe and control of the hammer stroke. I should have been more clear, I guess. Driven concrete pile is not used in the USA/Canada in my experience. When deep concrete foundations are used they are typically drilled in, for the reasons cited above. There are obviously times when concrete piles are cheaper and will get the job done even with the risks above. This is most likely for smaller buildings where loadings are relatively light and pile lengths are therefore short.
  - PietdeVries 10y ago
    Not sure about your statement... In the Netherlands this is still done quite often because the soil is too unstable. Concrete piles are driven into the weak soil until it hits the sand. Houses are typically built on top. The pole can be protected with a wooden block that due to the friction can set fire. Amsterdam is known to be built on wooden piles that remain intact as long as they stand under water: pumping away the water will cause the piles to rot and the houses to sink away.
- cromulent 10y ago
  My understanding is that concrete resists the compression of the ram impact well, but the shock wave reflects back and causes tension which then triggers failure. This tension is the point that needs to be controlled.
astrodust 10y ago
The steel pile-driving process is also extremely loud and creates a lot of vibration, so it's all but extinct inside urban areas. All the projects I've seen here in recent years, and there are hundreds, use caisson holes, wide, bored holes going straight down, to create the basis of the foundation. Once drilled, they insert steel and fill it with concrete. The equipment resembles a very large-scale post-hole digger. It seems to be fairly quick and work quite well: http://www.rwhengineering.ca/?page_id=2518 http://www.rwhengineering.ca/?page_id=2518 Although the drilling machines are somewhat loud, they're an order of magnitude quieter than the pile driving machines. The amount of banging those machines would generate was absolutely nuts.

by abduhl 10y ago

lobster_johnson 10y ago

In that case what I've observed was probably steel after all. Thanks.

Someone 10y ago

Wouldn't that be to crack in compression? Also, I don't see concrete piles being abandoned at all. Part of the reason may be that, where I live, many poles now are drilled, pressed or vibrated into the ground to decrease noise and potential impact on surrounding buildings. Thats is possible because there is no bedrock to build on where I live, so poles often go down easily for the first meters; I have seen wooden poles sink in five meters or so under their own weight. Traditional piling into the ground still is used, too. If necessary, a protective head cover on the pole (made from wood or, nowadays, plastic) softens the blows a bit, protecting the concrete from damage.

abduhl 10y ago
No, tension is what I meant. Imagine the pile hammer hitting the top of the pile. This impulse is transmitted down the length of the pile at the speed of sound as a wave. There exists a point where the wave gets to the end of the pile (this is at the pile tip) and the compression front attempts to continue which results in tension (eg - the pile tip is dragging itself forward with the energy). This is mostly seen with soft soils where end reaction is not sufficient to provide a hard "stop" on the pile. For hard ground, the opposite can occur where the driving energy reflects at the pile tip. This can result in huge compressive forces that crush (not crack) the concrete due to the two compressive waves (one new wave from the next hammer strike and the reflected wave from the previous hammer strike) stacking due to superposition. The reason that this failure mechanism wasn't noted by me is that steel piles suffer the same issue, so it is not a good reason to use steel over concrete piling. As you note, the solution to both issues is the use of a shoe and control of the hammer stroke. I should have been more clear, I guess. Driven concrete pile is not used in the USA/Canada in my experience. When deep concrete foundations are used they are typically drilled in, for the reasons cited above. There are obviously times when concrete piles are cheaper and will get the job done even with the risks above. This is most likely for smaller buildings where loadings are relatively light and pile lengths are therefore short.
- PietdeVries 10y ago
  Not sure about your statement... In the Netherlands this is still done quite often because the soil is too unstable. Concrete piles are driven into the weak soil until it hits the sand. Houses are typically built on top. The pole can be protected with a wooden block that due to the friction can set fire. Amsterdam is known to be built on wooden piles that remain intact as long as they stand under water: pumping away the water will cause the piles to rot and the houses to sink away.
cromulent 10y ago
My understanding is that concrete resists the compression of the ram impact well, but the shock wave reflects back and causes tension which then triggers failure. This tension is the point that needs to be controlled.

astrodust 10y ago

The steel pile-driving process is also extremely loud and creates a lot of vibration, so it's all but extinct inside urban areas. All the projects I've seen here in recent years, and there are hundreds, use caisson holes, wide, bored holes going straight down, to create the basis of the foundation. Once drilled, they insert steel and fill it with concrete. The equipment resembles a very large-scale post-hole digger. It seems to be fairly quick and work quite well: http://www.rwhengineering.ca/?page_id=2518 http://www.rwhengineering.ca/?page_id=2518 Although the drilling machines are somewhat loud, they're an order of magnitude quieter than the pile driving machines. The amount of banging those machines would generate was absolutely nuts.