Seismic Testing Methods for Evaluation of Deep Foundation Improvement by Compaction Grouting

Abstract

Improvement of subsurface soils by the injection of grout inclusions, termed compaction grouting, has been used since the mid 1950's. For improvement verification, past practice has generally been to test the compaction grouted area with SPT or CPT methods. However, since these procedures test only a single point: too little testing may not accurately represent the non-homogeneous nature of the improved soils while testing in sufficient numbers for accurate statistical evaluation may be uneconomic. An alternative to these methods is direct transmission seismic testing. This technique is particularly well suited to evaluate inclusion-improved soils since the seismic velocity is measured throughout the zone of improvement. To date, little information has been published on this method. The purpose of this paper, therefore, is to demonstrate the use of seismic test procedures, to evaluate data accumulated from two test sites and to present recommended guidelines for the use of these methods.