Grouted Pile-to-Sleeve Connection Tests

The ultimate axial strength of grouted pile-to-sleeve connections was investigated to determine the influence of moment, relative shear key location between pile and sleeve, eccentric pile and sleeve position and grout strength. A total of eighteen tests were conducted. These tests were divided into six series containing three replicates each.

The results showed that moment had no detrimental effect on the ultimate strength of a grouted pile-to-sleeve connection. The ultimate strength was not effected by extremes in the shear-key arrangements or by the variations in the thickness of the grout annulus. The strength of the connections varied with the square root of the grout strength.

The measured strengths were compared with empirical equations for the ultimate axial strength of a grouted pile-to-sleeve connection, recommended by the American Petroleum Institute (API) and the United Kingdom Department of Energy. The API equation was found to be more conservative in all cases. The United Kingdom Department of Energy formulation yielded strengths that were in better agreement with the measured values, although the solutions were not always conservative.

The behavior of the grouted pile-to-sleeve connection was examined in order to develop a simple analytical solution for ultimate strength. The empirical design equation yield reasonable estimates of ultimate strength but do not provide insight into the load-resisting mechanism of the connection. An examination of tested specimens revealed that one of the major load-resisting mechanisms of a grouted connection is the grout compression struts which develop throughout the length of the connection. Another significant component of load transfer was found to be friction that develops at the steel-grout interface.

A model based on classical plasticity was developed using the assumption that the tubes were infinitely stiff. By examining solutions based on different constitutive relations it was shown that the constitutive relations should include triaxial effects. Existing constitutive relations developed for normal strength grouts (3000- 5000 psi) may not be applicable to grout strengths exceeding 6000 psi.