hobo_ist
Civil/Environmental
- Sep 19, 2023
- 11
Hi all,
First and foremost apologies for the length of this post. Please see the attached mark-ups to clarify what I'm going to try to explain. Not a geotech engineer so rusty in this department.
Clients contractor wants me to explore a way in which he can excavate (passive side) along 6 metres of a 30m length secant pile wall without using props. The excavation will be sloped at 45 degrees from top of capping beam to formation level (approx. 3mbgl). I won't bore you with the details of why it needs to be done this way.
A small section of the secant piles and capping beam will cantilever as a result (conservatively assumed as the full 6m length of excavation, even though the passive soil level varies due to the slope). The pile designer has confirmed the piles can cantilever to full excavation depth but deflections will exceed maximum allowable (obviously).
The pile designers calcs, done in WALLAP, do not account for the additional stiffness provided by the capping beam to tie together the piles, which should be beneficial for deflections. Consequently I'm having to assess if it's possible with a capping beam that's heavily reinforced so that it's stiff enough to rein in the deflections a little bit.
This is the approach I'm considering (see the mark-up drawing if clarification is needed). Please let me know if I'm way off the mark!
To model the 24m long section of "restrained" capping beam, I'm considering defining the support condition at each structural pile location as a spring with stiffness corresponding to the modulus of horizontal reaction of the passive soil.
Question:
What would be the best way to model the "cantilevering" section of the capping beam seeing as they're not failing while in cantilever(according to the pile designer) and providing some degree of restraint?
Thanks.
First and foremost apologies for the length of this post. Please see the attached mark-ups to clarify what I'm going to try to explain. Not a geotech engineer so rusty in this department.
Clients contractor wants me to explore a way in which he can excavate (passive side) along 6 metres of a 30m length secant pile wall without using props. The excavation will be sloped at 45 degrees from top of capping beam to formation level (approx. 3mbgl). I won't bore you with the details of why it needs to be done this way.
A small section of the secant piles and capping beam will cantilever as a result (conservatively assumed as the full 6m length of excavation, even though the passive soil level varies due to the slope). The pile designer has confirmed the piles can cantilever to full excavation depth but deflections will exceed maximum allowable (obviously).
The pile designers calcs, done in WALLAP, do not account for the additional stiffness provided by the capping beam to tie together the piles, which should be beneficial for deflections. Consequently I'm having to assess if it's possible with a capping beam that's heavily reinforced so that it's stiff enough to rein in the deflections a little bit.
This is the approach I'm considering (see the mark-up drawing if clarification is needed). Please let me know if I'm way off the mark!
To model the 24m long section of "restrained" capping beam, I'm considering defining the support condition at each structural pile location as a spring with stiffness corresponding to the modulus of horizontal reaction of the passive soil.
Question:
What would be the best way to model the "cantilevering" section of the capping beam seeing as they're not failing while in cantilever(according to the pile designer) and providing some degree of restraint?
Thanks.
