Although compaction grouting has been developed empirically with little technical understanding of the associated grouting mechanisms and improvements, its applications are numerous. Compaction grout piles, usually formed by a volume-controlled staging up method, have been extensively used in many applications especially to improve the ground resistance against liquefaction. This paper presents the results of a field test in which 37 compaction grout piles were injected. Grouting records, ground surface displacements, as well as CPT and SPT results are used herein to investigate the performance of compaction grout piles. An important finding is the correlation between the tip resistance measured by cone penetration test and the maximum pressure during injecting a given grout volume. The results show a good potential of this correlation for understanding the performance of compaction grout piles and evaluating the development of improvement with injection. Conclusions are drawn concerning the effect of soil properties and injection sequence on the performance and their implications for the design of compaction grouting operations.
Among grouting techniques, compaction grouting represents an extreme of the range in which the stiffest mortars are injected. Description of the procedure, material and equipment of compaction grouting is well documented in the literature (e.g., Warner and Brown 1974; Graf 1992). The grout material is normally injected as a globular bulb into discrete soil zones under high pressures, using the top-down or bottom-up procedure, to densify the surrounding soil. Compaction grout piles are natural development of the bottom-up procedure. The pile is formed in steps along the desired treatment depth. An assumed uniform diameter of the piles is controlled by the step length, normally one foot (30 cm) plus or minus, and the injected volume of grout. Despite the numerous applications of the technique, its practice is empirical and depends mainly on the observations of the practitioners.
