SIF for an edge crack in mode III

Hi everyone,

I am working on the propagation of an edge crack in semi-infinite plate under antiplane loading.

I need to estimate the stress intensity factor KIII at the front of the crack but I can't find a theoretical formula for this purpose. For an embedded crack of length l in an infinite plate under shear stress sigma_23 I can use KIII = sigma23*sqrt(pi*l). But I don't know what I must use in the case of an edge crack.

I searched in the Stress Intensity Factor and Limit Load Handbook by Dr. Laham, but I can't find something useful for the edge crack in mode III .

Can someone, please, help me ?

Thank you.