  The radial (penny-shaped) model of hydraulic fracture is considered. The
tangential traction on the fracture walls is incorporated, including an updated
evaluation of the energy release rate (fracture criterion), system asymptotics
and the need to account for stagnant zone formation near the injection point.
The impact of incorporating the shear stress on the construction of solvers,
and the effectiveness of approximating system parameters using the first term
of the crack tip asymptotics, is discussed. A full quantitative investigation
of the impact of tangential traction on solution is undertaken, utilizing an
extremely effective (in-house build) adaptive time-space solver.
