Nonuniformities imposed by simple shear apparatus

Abstract

Two types of simple shear apparatus are in use — one developed at Cambridge, which is elaborately instrumented and accepts a cuboidal sample, and the other developed at the Norwegian Geotechnical Institute (NGI), which is attractively simple and accepts a cylindrical sample, and in which only shear and normal loads applied to the horizontal surface of the sample are measured.Results of drained monotonic and repeated shear straining tests in the Cambridge and an NGI type simple shear apparatus, both elaborately instrumented, show that nonuniformities of stress and strain develop in monotonic loading and grow with the number of cycles of shear straining. The rigid boundaries of the Cambridge type apparatus impose a definite simple shear configuration to the sample. The flexible boundary of the Norwegian Geotechnical Institute type apparatus provides less restraint allowing out-of-plane movements to occur. The characteristic responses of similarly prepared sand samples are different in the two apparatus because the conditions imposed are not exactly the same.The Cambridge apparatus can be expected to give an accurate estimate of the behavior of sand in monotonic loading if stress measurements are taken at the centre of the sample. Keywords: simple shear apparatus, NGI, Cambridge, monotonic and cyclic loading, dense sand, nonuniformities.