There are some closed form solutions available to estimate the virtual anchor length for a buried pipeline that is unrestrained at one end, and is subjected to internal pressure and temperature differential. However, these approximations assume the axial soil reistance is fully mobilized along the virtual anchor length (which is not exactly correct). The virtual anchor length calculation is a function of many variables such as pipeline diameter, thermal expansion corficient, soil type, internal pressure, and the change in temperature that the buried pipeline experiences between installation (i.e. temperature at which the line was buried-restrained) and operation. P.J. Schnackenberg (Pipe Line Industry, Nov. 1976, pp. 53-56)presents a simplified solution for virtual anchor length.

However, if you use CAESAR II, just keep increasing the buried pipline segment length until the nodal displacemnts go to zero at some point along the buried pipeline segment. By definition, this is the point at which the virtual anchor occurs.