Reference temperature for the soil parameters and parameters depend on this

Question

Dear All, 
 Maybe the following questions are the basic ones but I couldn't figure them out correctly so need your help to solve my doubt. 
 
 Questions => 
 1. Why soil parameters that are inserted in any checking or Plaxis analysis should be measured at the 20 deg celsius? 
 2. What are the soil parameters which are dependent on the temperature changes and need to be corrected to 20 deg celsius before inputting? 
 3. Any sources where I can find the correction factor values for every parameter? 
 
 Thanks.

Stefanos Papavasileiou · Answer

Dear Nitharshan, 
 No worries, that is why Fora like this exist. 
 
 I assume you refer to the Tref property in the Project properties > Constants tab. This is just a default value for the temperature which is editable. Typically a temperature of 20&ordm;C (=293.15 K) is considered a reference level but users can adjust this depending on the data they have. 
 This affects only projects that consider the temperature (thermal analyses). This is considered the reference temperature at the ground level when no other specific thermal condition is given. You can also see this in the Climate air temperature option under Model conditions in Staged construction mode. For more information please check our Reference manual. 
 Typically material properties are defined for a reference temperature. Therefore, I would first check what data I have and adjust the PLAXIS defaults. I am not sure how I can answer that further, but I am certain that you can find information online and in publications. Maybe other fellow geotechnical engineers in this forum can share their views on this.

Stefanos Papavasileiou · Answer

Hello again, 
 In general, PLAXIS has collected the properties necessary for a thermal analysis in the Thermal tabsheet. You can find relevant information in our Reference manual, too. 
 Again, the Tref property is a reference value used as a default when nothing else is defined. After all, we need to have a reference level to start with. 
 If you are running a Thermal analysis the Tref will be considered as the reference temperature for the Climate condition. That would be the temperature considered as an initial condition if nothing else is defined. 
 Naturally, if you are not running a Thermal analysis, then the Tref value is not relevant.