Excavation is one of the most important basic steps in civil engineering projects. A successful excavation requires the stability of trench, providing safe conditions for construction, safety of people and adjacent buildings. Excavation could cause large displacement in the wall of the trench and adjacent grounds that may harm people, buildings and adjacent equipments. Therefore permanent and temporary excavation supports are built in order to prevent such damages. Volume of soil mass increases or decreases during shear deformation which is demonstrated by dilation angle. Dilation angle is one of the factors which can affects the stability of trench and excavation analyses. Generally, the dilation angle is smaller than internal friction angle. Dilation angle of a homogenous is variable parameter and depends on mobilized shear strain and induced stress level. In the conventional analyses, dilation angle is equal to internal friction angle of soil. Therefore, in order to simulate of the soil behavior as accurate as possible, dilation angle should be considered smaller than internal friction angle in the analyses, which results in more accurate and applying lower safety factors in the analyses. In this study, the effect of dilation angle on analyses of the excavation has been studied by the softwares PLAXIS and ZSoil. The analyses were performed for anchorage, nailing, and truss construction. At the beginning, anchorage, nailing, and truss construction elements have been defined and methods for their implementation have been described. Then, for each of them, numerical models have been verified. To simulate soil behavior, Mohr - Coulomb and hardening soil models were used in the presence and absence of water. Then, the results were analyzed and evaluated. The effect of dilation angle on several parameters, including surface vertical displacement, wall horizontal displacement, bending moment in wall, axial force in anchor in and in nail, axial force in vertical and inclined members in the truss, heaving, and safety factor after last stage of excavation was evaluated. To verify the analyses performed by PLAXIS and ZSoil the results compared with the ones of the other researchers. Since the angle of dilation is a soil strength parameter, assumption of associated flow rule provides non-conservative results for safety factor in comparison to non-associated flow rule, as expected. One of the approaches of applying angle of dilation in the calculations is equivalent associated flow rule concept. For evaluate the accuracy of this approach the results of the non-associated flow rule were compared with equivalent associated flow rule. For anchorage, nailing, and truss construction, the results of equivalent associated flow rule for safety factor are conservative in comparison to non-associated flow rule. Large amount of errors have been observed between equivalent associated flow rule and non-associated flow rule for especially small value of dilation angle. This is due to excessive reduction in cohesion and internal friction angle for smaller values of dilation angles. Key words: Excavation support, dilation angle, anchorage, nailing, truss construction, flow rule