Development and preliminary application of a microfriction load-transfer plate for triaxial tests in geotechnical engineering

In order to solve the problem of end restraint in triaxial tests on coarse-grained soils, based on a new friction reduction method in which the contact between soils and loading plates is changed from the integral contact to the distributed one and the sliding friction to the rolling one, a load-transfer plate with microfriction loads for triaxial compression tests in geotechnical engineering is developed. The development idea, structural principle and detailed structure of the apparatus are introduced, and the effects of the friction-reducing measures of the distributed contact instead of the integral one are further demonstrated by numerical calculation. By use of this apparatus and a large-scale stress-strain triaxial apparatus, the consolidated drainage triaxial shear tests on the conventional and end friction reduction of typical sand are carried out. The strength and deformation characteristics of sand under normal end restraint and end free (micro-friction) are studied, and the effects of end restraint on stress-strain characteristics of sand are analyzed. The results show that the end restraint is the basic reason for the swelling of the specimen, the peak strength of the specimen is overestimated by the conventional test method, the deviatoric stress-strain curve is softened easily, and the volumetric strain curve of the specimen shows more prominent dilatancy. The apparatus effectively solves the problem of end restraint in triaxial tests and improves the accuracy of triaxial tests.