Abstract:
This paper reviews the design of jet grouting at re-entrant corners of excavations where the diaphragm
wall and secant pile wall installation were interrupted by existing utilities in the streel sidewalk. Jet
grout blocks were formed to seal the gaps in the walls for excavation support, consisting of four to six
columns in clusters. Jet grouting was performed around an electrical duct bank which had to be
maintained. Jet grouting was executed through stratified soils using various combinations of jetting
parameters for different soil strata. The installation sequence and age of the neighboring columns within
a cluster will affect the jet’s ability to form subsequent columns. When jet cutting is limited next to
hardened grout columns or embedded obstructions (such as diaphragm walls or secant pile walls in this
case), the specific gravity of spoils would be reduced and tend toward the value of the injected grout
SG. The magnitude of spoil SG is also influenced by the variability of the grout mix supplied. Specific
Gravity Ratio (SGR) defined as the ratio of spoil SG to the actual grout SG at the time of jetting can be
used as an indicator of successful treatment, with SGR > 1.0 indicating effective soil erosion.