# Undrained shear strength using Undrained A check

Dear Support Team,

In PLAXIS Reference Manual, section 9.3.3 (i. e. PLAXIS 2D CE manual) we can find the hint:

Particularly when the soil strength has been defined by means of effective strength parameters (Undrained (A) it is useful to plot the mobilised shear strength τmob in a vertical cross section and to check this against a known shear strength profile.

So the results for Undrained A should be checked by comparing the mobilised strength, τmob.

On the other hand, in Tips and Tricks (https://communities.bentley.com/products/geotechnical1/w/wiki/46010/how-to-check-undrained-shear-strength-using-undrained-a) we can see the picture with circles that refer to the limit line, which means that it is the maximum strength, τmax, not τmob:

Could you please inform us which strength should be used for checking: maximum or minimum?

Best regards,
Rushan Gizzatullin