The modulus of elasticity differs in various conditions of foundation soil. I am struggling with defining modulus of elasticity of geosynthetic reinforced sand foundation beneath a shallow strip footing.
The modulus of elasticity of sand increases with increase in depth. You need to perform triaxial test for sand to know the true value of modulus of elasticity by varying confining pressure and test conditions. Test condition in triaxial test includes UU, CU and CD test. For foundation related problem, you can use CU test for obtaining the true value of modulus. Also, you may refer to literature mainly the principles of foundation engineering authored by J.E. Bowles. How to give modulus as input in PLAXIS. You will get enough information from PLAXIS scientific and tutorial manual itself. So, i suggest you to read PLAXIS manual or the already published research work related to the topic using PLAXIS software. You will find lot of literature related to your topic.
Your question is actually not clear. Are you struggling with finding the modulus of elasticity of sand or struggling with inputting these values in plaxis? You usually need bulk modulus, shear modulus, cohesion (if any), density, friction angle, dilation angle etc. of sand and elastic modulus of geosynthetic, its poisson ratio. You may also need the interface parameters, such as stiffness per unit area, soil-geosynthetic interface friction angle, etc. Typical values for these parameters are available in the literature and if you are simulating the real problems, then you have to carry out tests to obtain these parameters.
You can obtain the value of E lastic modulus of sand by conduction CD triaxial test on the same. Typical values are available in literature including Plaxis manual and also correlation with SPT N value. Whereas the the interface parameters can be obtained again by conducting interface shear test on dry sand. Hope that helps
Shadi, try defining the geosynthetic materials as element embedded in the soil. Also, use different layers for soils with different values of elastic modulus. You can download any of my papers on prediction or evaluation of foundation settlement and bearing capacity here on researchgate.
Good luck.
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