NinerStruct
Structural
- Nov 5, 2012
- 36
When is one more beneficial than the other? I have specified helical piers on several recent projects and contractors often call asking if they can use push piers instead. All of my projects are in the Midwest (Iowa), where we generally have glacial till soils with clays, sand, and gravel, or loess soils over deeper bedrock (can be up to 80 ft. depending on where you are).
The last few projects have been areas of an existing building that we're putting an addition onto, but are not any areas directly related to the addition. These areas have also been brought to our attention during the design phase, so the decision to use these anchors comes after the soil borings have been done, which limits the soils information to what can be extrapolated from borings that may not be as deep as had we known we'd have to use deeper foundations in the first place.
Maybe this is my own misconception, but in my head, helicals are generally a better solution for a retrofit application when the bearing is typically still within cohesive soils, especially when you have less information about the soils below. Push piers are typically better if they can achieve end bearing on bedrock. Around here, it seems that can be much further than required for a helical, which would be more expensive. Both systems claim they can achieve the specified capacity with required factor of safety.
Some of my concern comes from the fact that I'm just not as familiar with push piers, and maybe my thought process is completely backwards. I just want to make sure that I'm making a sound decision, while not avoiding a perfectly good, possibly more economical, solution for clients.
Is there any general rule of thumb that others used in deciding between the two, or is one system more prone to problems than the other?
Thanks in adavance for any and all input.
The last few projects have been areas of an existing building that we're putting an addition onto, but are not any areas directly related to the addition. These areas have also been brought to our attention during the design phase, so the decision to use these anchors comes after the soil borings have been done, which limits the soils information to what can be extrapolated from borings that may not be as deep as had we known we'd have to use deeper foundations in the first place.
Maybe this is my own misconception, but in my head, helicals are generally a better solution for a retrofit application when the bearing is typically still within cohesive soils, especially when you have less information about the soils below. Push piers are typically better if they can achieve end bearing on bedrock. Around here, it seems that can be much further than required for a helical, which would be more expensive. Both systems claim they can achieve the specified capacity with required factor of safety.
Some of my concern comes from the fact that I'm just not as familiar with push piers, and maybe my thought process is completely backwards. I just want to make sure that I'm making a sound decision, while not avoiding a perfectly good, possibly more economical, solution for clients.
Is there any general rule of thumb that others used in deciding between the two, or is one system more prone to problems than the other?
Thanks in adavance for any and all input.
