A Comparative Study of Different Mechanism and Equipments Usable In Shear Testing of Soils |
Inorder to put subsequent discussions into proper perspective, it is convenient tolist the various kinds of apparatus that have been used to measure the shearingstrength and associated stress-strain properties of soils. More detailedattention will then be directed at the few types of tests that have achievedgeneral usage by consulting and testing firms. Basedon a detailed analysis of DEM simulation data, this paper provides new insightsinto the effects of boundary surface topography on the mobilized stress ratioand stress-displacement behavior in the interface shear test and the directshear test. The soil mechanics observed in the two types of tests are unifiedunder a novel perspective of boundary-induced soil behavior. It is shown thatthe principal direction of the contact force anisotropy developed at thesoil-surface boundary has an exclusive control over the peak stress ratiomeasured both at the boundary and inside the sampling window. However, a subtlechange in the roles of the principal direction and the magnitude of contactforce anisotropy is found as the contact force chains extend from the surfaceinto the interphase soil. ABSTRACT:A review and evaluation of the advantages and limitations of laboratoryequipment for measuring the shear strength of soils arc presented. Equipmentevaluated include direct shear, torsional shear, simple shear, triaxial.multiaxial (true triaxial), plane strain, hollow cylinder triaxial, anddirectional shear devices. The evaluation indicates that the impetus to obtainparameters for constitutive equations and modeling has resulted in thedevelopment of improved equipment and testing techniques; specifically, thedevelopment of multiaxial (true triaxial) and hollow cylinder triaxial testequipment. Although these devices are more versatile, the conventional solidcylinder triaxial test is still the most popular. The evaluation suggests thatdirect shear and simple shear devices are best utilized by designers who havegained experience applying the results from such tests to structures that havebehaved satisfactorily.