addition on pile/existing structure on strip footings
addition on pile/existing structure on strip footings
(OP)
Hello, this is my first post but I've read a lot of posts and really like this forum.
I would just like to get some feedback from this forum on additions on piles. Project: Addition to Existing fire station founded on strip footings on very loose to loose sand down to depth of about 42 ft (where dense till was encountered). Preliminary liquefaction analyses based on SPT indicates sand is susceptible to liquefaction and settlements could be in range of 300 to 400 mm.
1) If we recommend piles for addition, I'm worried about the performance of the existing building connected to the addition on piles during earthquakes. If there is an earthquake, won't the two structure behave differently and wont it make it worst that the addition is on piles?
2) If so, would recommending pilling the whole structure the only solution or is it excessive?
3) i have the same question for additions to building founded on soft clays (where major settlement cracks were observed on the existing building), Do you have experience with pilled additions? I have seen structure with soft clay consolidation settlements damages being partially underpinned (piles to rock) and have performed well but I'm always worried about performance during an earthquake. I would like feedback because I have seen some projects (where we were not involved) where additions were built on piles and existing structure most likely on superficial foundations as settlement cracks were observed. I'm wondering if our way thinking is excessive.
thanks
I would just like to get some feedback from this forum on additions on piles. Project: Addition to Existing fire station founded on strip footings on very loose to loose sand down to depth of about 42 ft (where dense till was encountered). Preliminary liquefaction analyses based on SPT indicates sand is susceptible to liquefaction and settlements could be in range of 300 to 400 mm.
1) If we recommend piles for addition, I'm worried about the performance of the existing building connected to the addition on piles during earthquakes. If there is an earthquake, won't the two structure behave differently and wont it make it worst that the addition is on piles?
2) If so, would recommending pilling the whole structure the only solution or is it excessive?
3) i have the same question for additions to building founded on soft clays (where major settlement cracks were observed on the existing building), Do you have experience with pilled additions? I have seen structure with soft clay consolidation settlements damages being partially underpinned (piles to rock) and have performed well but I'm always worried about performance during an earthquake. I would like feedback because I have seen some projects (where we were not involved) where additions were built on piles and existing structure most likely on superficial foundations as settlement cracks were observed. I'm wondering if our way thinking is excessive.
thanks





RE: addition on pile/existing structure on strip footings
There may be other alternatives, such as improving the density or settlement potential of that sand under old and then treating new areas, and no piles driven.
RE: addition on pile/existing structure on strip footings
RE: addition on pile/existing structure on strip footings
RE: addition on pile/existing structure on strip footings
Chemical injection soil improvement
RE: addition on pile/existing structure on strip footings
http://www.haywardbaker.com/WhatWeDo/Techniques/Gr...
RE: addition on pile/existing structure on strip footings
RE: addition on pile/existing structure on strip footings
Given this is a fire station and a building of high importance, there is most likely scope to future proof the structure. Low Mobility Grout columns (LMG) are one option which can be installed with minimal disruption (i.e. removing floor coverings etc) with the existing building in place, however they have divided opinion in ChCh as some people say that there isn't enough confining pressure at the surface to provide compaction. Essentially the columns expand at the surface and push the soil away causing some heave at the surface and little compaction. This was an issue for green field sites however less of an issue with retro fitting existing buildings. They are also used to re-level existing buildings which have settled. I understand that buildings which have settled by 350mm have been re-levelled to within normal building tolerances. Two companies which have good information on the topic are RE-LEVEL and URETEK.
Good Luck.
RE: addition on pile/existing structure on strip footings
I believe deep foundations such as helical piles are the only solutions here but to minimize differential settlement, you may need to drive piles to rock. If driving piles is a vibration concern, then choose mini piles.