The increased popularity of using reinforcement in embankment fills and slopes has created a need for studies of the interaction between the reinforcement and surrounding soil to provide an improved basis for limit equilibrium design methods. The purpose of this study was to develop a plane strain triaxial apparatus and associated equipment to study the interaction of soil and reinforcement. The plane strain apparatus was designed to model an element of soil situated along a slip surface in a reinforced embankment. The device constructed is capable of testing a sample 9.4 inches square and 23 inches high with full-size reinforcing materials included. A 30,000-pound capacity load frame and a 20,000-pound capacity electric load cell were also constructed during this study. Drawings of the equipment constructed and a design method for the load cell are included. Preliminary tests on unreinforced and reinforced samples under a confining pressure of 10 psi were performed to check the equipment operation. These tests show that the equipment functions as planned. Modifications desirable to improve the performance of the equipment are given. / M.S.