ABSTRACT

Intermittent compaction grout piles were used to improve foundation soils of Tokyo International Airport against liquefaction at the intersection area of the two runways A and B. The compaction grouting works were performed in five working stages. The grouting works of the fifth stage are described in this paper. The effectiveness of treatment is discussed in terms of the increase in N-value of the SPT test and the increase in the coefficient of earth pressure at rest (K0) as measured by the self-boring pressuremeter test. Observations are made on the improvements at the boundaries of the treatment layers. Based on the presented improvement results, correlations are established of both the pre-treatment N-value and fines content with the increase in K0 with respect to the injected grout volume.

INTRODUCTION

At the intersection area of A- and B-runways of Tokyo International Airport, compaction grouting was performed to minimize the liquefaction potential of the foundation soils during earthquakes. Compaction grouting was qualified as the appropriate ground improvement alternative, because of the possibility of performing the grouting works without much disruption to the normal operations of the airport. Unlike the commonly injected compaction grout piles that are continuous throughout the soil profile, intermittent compaction grout piles were injected to treat only the liquefiable soil layers. The compaction grouting works were performed in five working stages. This paper describes the grouting works of the fifth stage and discusses the obtained improvement in terms of the increase in N-value of the SPT test and the increase in the coefficient of earth pressure at rest (K0) as evaluated by the self-boring pressuremeter (SBP) test.

DESCRIPTION OF GROUTING WORKS

A liquefaction potential assessment of the foundation soils of B-runway of Tokyo International Airport revealed that some of the soil layers arepotentially liquefiable during earthquakes.

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