Aurélien PACE's Communities Activities

Consolidation - Structure settlements

Aurélien PACE — Tue, 11 Jul 2023 09:34:12 GMT

Good morning,

I made a 3D model with an earthwork about 3 m deep on which I put a building. I am founded on soft clays. After consolidation, I notice differences in the results of the settlements (uz) in the output if I look directly at the settlements of the ground on the bottom of the excavation or if I look at the settlements of the foundation slab. Why are there differences in results? I should normally have the same displacements between the slab and the ground?

I attach the images of the differences in results.

Thanks for your help.

Aurélien

Dismantling of sheet piling curtains - reinstatement of water pressure

Aurélien PACE — Tue, 06 Jun 2023 13:34:03 GMT

Good morning,
I have a plaxis 3D model with an earthwork inside a sheet pile wall. Once the earthwork has been completed with the groundwater level lowered under the bottom of the excavation, I construct the building in reinforced concrete with interfaces that are fully impermeable. The problem is when I carry out a phase with the dismantling of my sheet pile wall. In the results, I have water pressure everywhere inside my basement while the water table should remain around the concrete walls?
My goal is to simulate the effect of Archimedes thrust on my building. So I have to bring the level of the water table back to normal, but the water must not enter my basement. Could you help me ?
Cordially

Aurelien P

Node-to-node anchors in several elements

Aurélien PACE — Tue, 13 Jun 2023 07:39:26 GMT

Hello, as you can see in the attached image, I have to dig an excavation with a strut type shoring system. The problem is that the butons are bi-pods. I tried to use a central beam connected to two node-to-node to attach a sheet pile curtain to the plate. The calculation fails. Do you have a technique for modeling these shoring in several elements?

Best regards

Aurélien

Piles parameters - Embedded beam PLAXIS 3D

Aurélien PACE — Thu, 09 Feb 2023 09:18:54 GMT

Hello PLAXIS Community, 

I have a few questions regarding pile modeling in plaxis. I made a first simple 3D plaxis model to simulate a concrete pile. 
So I created a circle that I extruded to have a ground volume representing the pile. 
I then assigned a concrete floor model in linear elastic. I also created interfaces at the tip of the pile but also on the skin of the pile. 
Then I added a surface load on the diameter of the pile. Do you think this is a good method to see the behavior of a pile? 
I tried doing this method to an entire model but the meshing doesn't seem to work because there are too many piles done this way. 
I therefore think that the method with the embedded beams is much less cumbersome for the 3D model.
In the Output results, what is the right parameter to see the strength of the skin and also the tip strength of the pile?

For a simpler model with embedded beams, when we choose parameters, he unit weights must be deducted from the volume of soil in place? 
For example for concrete at 25 kN/m3, we take 25-19.5 = 5.5 kN/m3?
In mechanical parameters, when we want that plaxis calculate the axial skin resistance automatically depending on soil parameters, we need to choose "layer depend"?
But why we need to choose Tmax ? Where can we fin this value without pile test ?
Same question for base resistance, how can we best approach the value of the base resistance in function of the soil parameters calculated automatically by plaxis?
The value of these parameters are of great importance, especially in a 3D model with piles located in soft clay without hard bed rock. I would therefore like to know the most reliable way to enter these parameters to calculate the most real settlements.

Best regards

Aurélien PACE

Consolidation analysis

Aurélien PACE — Thu, 09 Feb 2023 08:42:36 GMT


I am currently making a 3D model for a 7 story building on one basement level founded in soft clays.
My project is surrounded by sheet piles driven into the clay to retain the water table which circulates in the sands in the upper part.
So I have major settling issues. I chose to improve the soils with preloading associated with vertical drains to accelerate consolidation. 
As the floors are built, I carry out consolidations in staged construction. 
At the end of the construction, I carry out a consolidation analysis with "minimum exess pressure" in order to dissipate the pore pressures as much as possible and thus determine the settlements due to long-term consolidation.
The soil model is in HSM with clay in undrained A.
My questions are: 
- When carrying out several consolidations from phase to phase, the results of the consolidation time in the Output seem to add up. Is it possible to display the consolidation time only of the phase?
- When we want to compare the consolidation time with the degree of consolidation U(%), the consolidation time does not seems correct in the Output... 
Is it possible to see the consolidation time when doing an analysis with the degree of consolidation?
- During my modelling, experts in plaxis my adviser to simulate as close as possible to reality the pore pressures to do the following phases: 
1. Initialization in k0 procedure 
2. Initialization phase by checking "ignore undrained behavior" 
3. Earthworks of the project 
4. Installation of the foundation raft with small loads and reset of the displacements in order to measure the settlements from this phase 
5. Consolidation mininum exess pressure: this seems to allow the interstitial pressures to be well balanced with reality 
6. Construction of the building 
7. Minimum consolidation exess pressure: used to determine the settlements after long-term consolidation.

Could you explain to me why it is necessary to do all these manipulations in order to better calibrate the pore pressures in the clays?

Thank you all in advance for your answers


Aurélien PACE

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Thu, 09 Feb 2023 01:01:41 GMT

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