I am not aware of any "exact" analytical two phase flow shock tube problem. This might be a numerical solution of a 1-D model, as commonly used as test case for compressible flow solvers. By the way do you consider bubbly liquids or mist flow?
The "exact" solution assumes initial conditions with on the high pressure side pure liquid water and at the low pressure side a perfect gas. The solution is an expansion fan in the water, which can be calculated using a linearised theory (because of the limited compressibility, we have an acoustical behaviour) and in the gas a shock wave (which you can calculate using the Rankine Hugoniot shock adiabatic). The final solution is found because at the contact between the two phases the pressure should be continuous. So this is not a "two phase solution), but two single phase solutions glued to each other at the contact surface.