Stresses in Solid element

Question

Hi there, 
 I am looking for some guidance on the interpretation of stresses when tunnel lining is modelled as a solid element. Plaxis manual suggests that the largest compression is Sigma 1 whereas the largest tension is Sigma 3. If I am looking to find out maximum tension and compression stress on the tunnel lining should I take the tension Principal Stress Sigma 3 and compression as Principal Stress Sigma 1? Please advise. 
 
 thanks

Stefanos Papavasileiou · Answer

Dear Nadeem, 
 Indeed, the &sigma;1 would be the largest compressive stress and &sigma;3 the largest tensile stress, as you correctly pointed in the manual. 
 Note that if you are using PLAXIS 2D, and you want to check the structural forces on a tunnel lining you can also use the option Structural forces in volume plates.