Simulating the membrane contact patterns of triaxial sand specimens

Abstract

Listen

Translate article

One of the common sources of error in triaxial tests is the penetration of the latex membrane into the peripheral voids of the specimen as confining pressure is applied. Existing analytical solutions developed to predict the magnitude of this membrane penetration have all assumed that the peripheral sand particles in contact with the surrounding membrane are arranged so that the centroids of the sand–membrane contact areas form a square pattern of side length D50 on a plane parallel to the undeflected membrane. Measurements made on digital images of sand–membrane contact patterns for triaxial specimens of varying characteristics have shown this assumption to be inadequate. The analysis presented herein shows how actual contact pattern can be reasonably replicated by simulated patterns. These simulated patterns are generated by adding randomly selected distances to the centroid co-ordinates of contact areas initially placed in a systematic grid pattern. The results indicate that it is possible to systematically model sand–membrane contact patterns as a function of triaxial specimen characteristics such as relative density and preparation method. The ability to simulate the real patterns eliminates the reliance of existing analytical solutions on a single assumed square contact pattern and hence can serve as the basis for improving the accuracy of future solutions to account for the effects of membrane penetration. Copyright © 2000 John Wiley & Sons, Ltd.