Hello Everyone,

I have been trying to simulate the cyclic triaxial test using the SANISAND04 subroutine. When I plotting the stress path (p-q plot), I am getting only the positive value of q. Maybe because the definition of q i.e; sqrt(J2) always gives a positive value. How to get the negative values of q?. Am I missing something in modeling in Abaqus?. Please help me to figure things out. I have attached the exact figure in which I am getting the values below the p axis.

Thanking you

SAQIB

According to the code qq =statev(31) is always possitive

qq=dsqrt(onept5*trs2)

if you want negative q as well then take q=S11-S33

S11 and S33 is abaqus output include waterpressure assume S33 is vertical

because waterpressure in 1 and 3 is the same it is not in q.

@Arie, Thanks, if we add water pressure it will cancel automatically right ?. i.e: q=(S11-u)-(S33-u). I did the way you suggest but there is not much variation inS11 and S33 which leads to the very small value of q=(S11-S33).