  In this paper, we develop an arbitrary-order locking-free enriched Galerkin
method for the linear elasticity problem using the stress-displacement
formulation in both two and three dimensions. The method is based on the mixed
discontinuous Galerkin method in [30], but with a different stress
approximation space that enriches the arbitrary order continuous Galerkin space
with some piecewise symmetric-matrix valued polynomials. We prove that the
method is well-posed and provide a parameter-robust error estimate, which
confirms the locking-free property of the EG method. We present some numerical
examples in two and three dimensions to demonstrate the effectiveness of the
proposed method.
