Is the FEM any good for geotechnics?


Triggered by a topic raised some time ago, 'which geotechnical software is good for engineering', I raise a different question. Is a 'simple' method for solving partial differential equations (ie the FEM method), after it has been enhanced by commercial companies (ie they create the graphics) any good for the geotechnical community? An example: When you buy a program people will promise that you will save a lot of time and your results will be highly accurate. No more wasted money to overconservative design from the old and useless limit equilibrium methods. So you go home and try it. The screen has lots of bright colours and the program seems user friendly. So why do you need to read the manual and spoil the fun? You can design the embankment in no time. It is really easy to do inelastic analysis with the FEM also. All the program wants is an angle of dilation. Are you going to pay for the lab test to actually find its value? Probably not, but anyway the program has a default value equal to the angle of shearing resistance. Why not... You can also include anisotropy in the analysis. That 's amazing! You can 't do that with those simple methods. But what is even more amazing is the settlement evaluation. 2-D and also 3-D. You couldn 't do that with the Terzaghi 1-D. You may not have the required triaxials but you have some UU 's. Why not estimate the stifness from these? Press some more buttons and here you are. The embankment ready in no time. Now returning to my question: how can you possibly imagine that your FEM program is any better than a limit equilibrium calculation?

Soil Mechanics / Geotechnical Deep Foundations Education Analysis Shallow Foundations Software Soil Mechanics / Geotechnical

Asked 25/03/2005 04:52, updated: 14/03/2017 14:07
Johnjohn

10 Answers

Votes: 1

BauMarc

It is absolutely right: You have to take care by using geotechnical FEM programs. But on the other hand, you have possibilities to model problems, which are difficult to model without numerical analysis. Is the failure figure always a circle? No !! And what about soilpressure and displacements for a sheet pile wall calculation. You have always the full active and passive soil-pressure in your "old" calculation!? So, it is a fine thing tohave programs like PLAXIS or Tochnog, but handle with care!! Marc

Votes: 1

Redarmy

Numerical analysis can be very useful in research work, but don't count on them to be very accurate in geoengineering.

Votes: 1

Jakub Jacobjacob

Analytical methods of computation allow users to design and check structures quickly. In addition (e.g. by using GEO5 software http://www.finesoftware.eu/geotechnical-software/) the designed structure may be transferred into the FEM application where the general analysis of the structure is performed using the Finite Element Method. This not only saves designer


Votes: 1

Johnny Doe

I agree with everything you say but most of engineers abuse FEM analysis in that way that they think they know everything about it and there is where problems start. I would say that all of closed form solutions can give us some kind of value that can be used as reference but if you're good with FEM modeling you could see what will be the behavior of soil, rock or interaction of soil, rock and structure. Best regards

Votes: 1

Chrisadam12

The program can model a wide range of geotechnical problems including terrain settlement, sheet piling/diaphragm walls, underpinning of structures, slope stability, beams on foundation, excavation, etc. MATERIAL MODELS A reliable and accurate response of a given soil or rock mass can be obtained by using a suitable material model. The current release offers the following models: Linear elastic model Modified linear elastic model Mohr-Coulomb model Drucker-Prager model Cam Clay model BUILT-IN GEOMETRICAL MODEL CORRECTION, AUTOMATIC MESH GENERATION The program includes built-in correction of the input geometrical model. All material interfaces, new structures or construction stages (tunnel excavation, excavation of a foundation ditch) can be specified independently from each other. Before running the mesh generator the program automatically locates the intersections of all specified lines and all closed regions, creating a corresponding geometrical model. Introducing even a fairly complicated structure into the program thus becomes a relatively simple task. MESH GENERATOR The program contains a built-in automatic mesh generator that considerably simplifies construction of the finite element mesh. Both 3-node and 6-node triangular elements are available. The density of the finite elements mesh is assumed constant for the entire model but it can easily be refined in local areas as required. Preparing an effective mesh for a complex structure thus requires only a few minutes of the user

Votes: 1

Helans573

Yes this is good for some reason as long as you know how to use it. Its not that simple like other program that they used. As long as you worked for this or you have background I believe nothing problem will happen. and if there problem I know you can solve it.

Votes: 1

Jessem189

Yes it is very useful geoengineering analysis and research. One of the best in the market.

Votes: 1

Jessem189

Geotechnical software: talren 4, tunren, k-rea, galena 4, sv head laga systems is a leading scientific software distributor in USA. Here is a list of all products that the company distributes, with details-galena 4, talren 4, tunren, k-rea, sv. Software tagasoft is a leading supplier of software for geotechnical analysis and design

Votes: 1

Picajol

Guys one thing that always botherd me. When using all this fine softwares like PLAXIS, GEO5 one can simulate ground beheavior, calculate stress increasse in ground dou to the building, analyze settlements that will happen based on soil parametras. But how can I transfer all this data to my buliding design? If I get an settlement of 5cm ,from PLAXIS 3D or Geo5, under my raft slab , how can I design my slab for these displacements that will happen? Thanx in advance!

Votes: 1

AnaDesouza

I have to agree with Marc. Programs like Plaxis and GEO5 should be used, but should also be handled with care in order to get the best result.