Pile integrity testing—a misunderstood technology: 37539 Ellway, K. Ground Engineering, Vol. 20, No. 6, pp. 2, 6 (Sep. 1987)

Abstract

This article outlines the capabilities and limitations of hammer or vibration based integrity tests. Some practical implications to be considered when specifying tests are discussed. The tests can identify the base of the pile, locate constrictions and bulbs and detect major changes in concrete strength. It is possible to derive the dynamic shear moduli of soils surrounding a pile. Tests can only penetrate to a depth of about 30 pile diameters in chalk and about 20 diameters in London clay. Tests cannot be carried out beyond major changes in pile section or material property and they can detect relative changes in pile section or material property only. The axial extent of irregularities cannot be determined generally and there is no difference in the response from changes in cross section and changes in material properties. Proper preparation of test specimens is essential -pile heads must be sound and have adequate mounting surfaces for sensors. Integrity tests are acoustical, and identify acoustic anomolies. This does not necessarily indicate a significant structural defect, and the results of integrity testing must always be used in conjunction with other tests or examinations. (TRRL)