Wang Haode's Activities

Thick Lining Specified in PLAXIS 3D Tutorial Example 6

Wang Haode — Fri, 20 Mar 2020 03:24:56 GMT

Dear Support Team,

I would like to clarify for PLAXIS 3D Tutorial Example 6, what is the thickness lining specified in the text?

Is it the distance between the internal diameter and the TBM excavation diameter or the internal diameter and the external diameter of the tunnel lining? Please let me know. Thank you very much!

PLAXIS 3D Tutorial Example 6

Wang Haode — Thu, 05 Nov 2020 04:56:33 GMT

Dear Technical Support Team,

I was attempting the volume contraction concept introduced in PLAXIS 3D Tutorial Example 6 with the C coefficient as shown in the Figure below. (adopted from PLAXIS 3D Manual)

Using the PLAXIS 3D tutorial file provided from the PLAXIS download website, the model does not work (convergence error) when I tried changing the calculation type from PLASTIC to CONSOLIDATION. May I know why it doesnt work in consolidation calculation type? Thank you very much!

Saving PLAXIS file without calculated output results

Wang Haode — Wed, 26 Aug 2020 22:37:32 GMT

Dear Sir/Mdm,

I would like to know if there is a way to save a PLAXIS file (that has been calculated) as a file with only input information. As it is a 3D PLAXIS file that I am working on, the output results occupy alot of space. I hope to just save the file with only the input portion. May I know if it is possible? Thank you very much!

Expert Command - Improve Command Loading Speed

Wang Haode — Sat, 15 Aug 2020 23:56:10 GMT

Dear Sir/Mdm,

I am currently running many commands through a p3d.log script using the command runner window in PLAXIS 3D. However, as I am running over 10 000 command lines, the time required for the file to finish running is quite long. May I know if there is any way for me to speed up the process? Thank you very much!

Error 204 in PLAXIS 3D

Wang Haode — Thu, 09 Apr 2020 14:06:14 GMT

Dear Sir/Mdm,

I was trying to simulate tunnel excavation in plaxis 3D model. The calculation type is chosen to be consolidation. During calculation, the error 204 (incorrect solution, show convergence) was encountered. I tried to refine the mesh and lower the time step in calculations but to no avail.

The tunnel was excavated in mixed soil layers: clay and sand. The clay is undrained with hydraulic conductivity of 3.5e-06 m/day and the sand with hydraulic conductivity of 3.0 m/d. A 2D simplified view is shown below:

The main questions I would like to have answered are:

1) Are there any other suggestions to resolve the error 204 other than refinement of mesh/optimizing time steps?

2) From the figure above, there is a large difference in hydraulic conductivities between clay and sand. Will this large difference affect the convergence? This is because I have attempted to increase the hydraulic conductivity of clay to 3.5e-05 m/d (1 order) and no error was resulted.

3) How can I determine the mesh quality based on quality spheres and quality SICN?

Please let me know. Thank you very much!

Assumptions of SoilTest for Triaxial PLAXIS 2D

Wang Haode — Wed, 01 Apr 2020 23:09:57 GMT

Hi,

I am wondering what sort of assumptions are used for the Triaxial SoilTest for PLAXIS 2D? I was not able to find it online.

Some questions I have include:

1) is it assumed that the end platens are frictionless?

2) What is the height to diameter ratio of the sample? 2 : 1?

3) boundary conditions as per the figure below?

Please let me know. Thank you very much!

Secant modulus reduction curve for Hardening soil model with small strain stiffness (HSS model)

Wang Haode — Tue, 31 Mar 2020 20:04:07 GMT

Based on PLAXIS material introduction, the tangent and secant modulus reductions vs shear strain satisfy:

To capture the strain hardening at plastic zone, a lower bound was introduced to HSS model, as with Figure 7.3 below.

In terms of tangent shear modulus reduction, there is a significant cut-off, at which Gur = Gt as per Figure 7.3 above.

I would like to know:

1) Could this cut-off be employed to secant modulus reduction?

2) What’s the equation for the “new secant modulus reduction curve” when we take this cut-off into consideration (for example, the results that I obtained from PLAXIS in the Data Example diagram?

Unfortunately, I was not able to find the equation for this “new secant modulus reduction curve” from PLAXIS material manual. Please let me know. Thank you very much!

Constant Head boundary conditions for model boundaries

Wang Haode — Tue, 31 Mar 2020 19:51:40 GMT

As I know, there are two options, i.e. open and closed, could be used to define groundwater flow condition for model boundary.

Based on my understanding, when we set open groundwater flow to model boundaries, the water outside the model is allowed to flow into model and the excess pore water pressure can be dissipated through “open” boundaries.

Does this “open boundary” imply that there is constant water head condition at the boundary since the boundaries are supposed to be far away from the construction such that it should not be affected? If it is not the case, how can I set constant head boundary conditions?

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Thu, 19 Mar 2020 01:09:04 GMT

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PLAXIS 3D Modelling of Tunnel Shield Pressure

Wang Haode — Thu, 19 Mar 2020 01:09:02 GMT

Hi,

I am trying to model the tunnel shield pressure in PLAXIS 3D that exerts outward from the tunnel on the surrounding soil. However, if I apply a line load on the tunnel, the load acts on the tunnel plate element instead of outward from the plate element onto the soil (which is what I want to achieve).

May I know if there is anyway I can model the shield pressure and keep the plate element intact in the model? Please let me know. Thank you very much.