  We consider the 3-manifold obtained by the 0-surgery along a double twist
knot. We construct a candidate for a generalized torsion element in the
fundamental group of the surged manifold, and see that there exists the cases
where the candidate is actually a generalized torsion element. For a proof, we
use the JSJ-decomposition of the surged manifold. We also prove that the
fundamental group of the 3-manifold obtained from the 0-surgery along a double
twist knot is bi-orderable if and only if it admits no generalized torsion
elements. We also list some examples of the surged manifolds whose fundamental
groups admit generalized torsion elements.
