Solid element is often used to simulate soil and rock in geotechnical engineering. Other structures such as pile

cut-off wall and concrete panel are also often simulated with solid element when then are embedded in soils. Internal force and bending moment are important for design of these structures

so it is necessary to calculate bending moment with stress and displacement obtained by finite element method(FEM). This problem is studied by analyzing a cantilever beam. It shows that enough elements are necessary when bending moment is calculated with stress

whereas oscillation occurs and leads to unreliable results when bending moment is calculated with displacement. Shear locking and its influence is also investigated herein.