Field Investigation into Effectiveness of Compaction Grouting

The common design approach of compaction grouting for ground improvement works is oversimplified and does not account for the effects of soil properties and grouting variables. The obtained improvements therefore appear inconsistent with the predicted ones. This paper presents the results of a field test conducted at Tokyo International Airport to evaluate the effectiveness of compaction grouting under well-controlled conditions. The test consisted of 87 compaction grout piles injected in three cases of different pile diameters and spacings. The paper also discusses the effects of soil properties, replacement ratio, and injection sequence on the effectiveness that is evaluated in terms of the standard penetration test N-value and cone penetration test tip resistance, and the variation of effectiveness with depth. A new design procedure that accounts for the effects of initial soil properties is introduced. It has been found that the injection sequence has a significant effect on the grouting mechanisms and effectiveness; this effect is discussed for both high and low compressibility soils. Significant observations are also made on relatively shallow treatments, the associated ground surface heave, and the corresponding improvement. DOI: 10.1061/(ASCE)GT.1943-5606.0000540. (C) 2012 American Society of Civil Engineers.