Usually rigid retaining structures are used in civil works such as retaining walls, bridge abutments and foundations, among others. The design of these structures is based on thrust calculation, static and dynamic, exerted by the material retained on the structure. In the case of dynamic actions, internationally the Mononobe-Okabe (M-O) method is the most accepted for the calculation of dynamic thrusts. This paper presents an extension of M-O method, called M-O modified method (M-M-O), to obtain dynamic thrusts on nonyielding rigid retaining walls with a compressible inclusion of expanded polystyrene (EPS), between the structure and the retained material. Compressible inclusions provide thrust attenuation, static and dynamic, on the back of a nonyielding rigid retaining structure. The analytic method M-M-O is based on experimental results from shaking table tests of rigid retaining walls models 0.2m in height with sand backfill and Expanded Polystyrene compressible inclusions of different densities (between 10 and 32kg/m3) and variable thickness/height relation (4.7 and 7.8%). Sine wave-type motions with maximum accelerations of 0.05 and 0.10g and frequencies of 1, 2 and 3Hz were applied to the models.