THE STUDY OF THE FEATURES OF INCREASING OF PLASTIC DEFORMATIONS IN SOILS
In soils under the application of load that exceeds the bearing capacity, vertical compression and horizontal extension deformation are developed, which leads to the failure. The aim of investigations was to study the stress-strain state in the stage of plastic deformations immediately preceding the destruction of soil specimens. Tests were carried out on the triaxial device in the chamber of type A. Specimens of sand, clay and sand reinforced with randomly oriented polypropylene fibers were investigated. Specimens of reinforced and non-reinforced sand were formed by dry layer-by-layer filling. Specimens of clay were molded from clay paste with predetermined characteristics of moisture. The method of specimen formation is described. Physical characteristics of soils are given. Tests were carried out according to the consolidated-drained scheme. Triaxial tests were carried out in kinematic and static modes, kinematic - with a given strain rate and static in steps of 50 kPa. Hydrostatic compression has been adopted 100 kPa for all tests. Strength characteristics of the specimens were determined by the results of triaxial tests. Destruction of clay and non-reinforced sand specimens was achieved. The destruction of fiber sand was not achieved at relative deformations of 20 %. For clay and non-reinforced sand specimens with continuous deformation, the lateral deformation and the maximum vertical pressure are lower than when applying a step load, and for sand containing polypropylene fibers, this dependence is the opposite. For sand reinforced with polypropylene fibres, it was found that dependence between the intensities of the tangential stresses and shear deformations close to a linear function. The angles of dilatancy were determined. The results of experimental studies are planned to be used as input data for numerical simulation.