Pressure-injected anchors in sand: load and creep behaviour

This paper presents the results of recent research into the behaviour of pressure-injected anchors in sand. During the injection process, which was simulated by an anchor unit expanding radially as in a pressuremeter test, radial expansion was measured. In general there was a linear relationship between expansion pressure and static pull-out resistance. The creep coefficient was a function of the expansion pressure and the level of the applied load. The application of a small overload caused a significant reduction in creep. The reapplication of the expansion pressure resulted in an increase in pull-out capacity. The significance of these trends with respect to the control of anchor performance is discussed and the justification for some rules of thumb currently used during anchor construction are confirmed. Key words: anchors, sand, creep, testing, radial stress, relaxation, injection pressure, pressuremeter.