Jet grouting with a newly developed technology: The Twin-Jet method

The Twin-Jet method, a newly developed jet grouting technology for the instant solidification of soft ground, is presented. The basic principles of the Twin-Jet method are introduced and sodium silicate (water-glass) is selected as the binder to accelerate the hardening process of an admixture of grout and soil. Two case histories of the Twin-Jet Method, conducted in both a vertical (constructed in sandy soils) and a horizontal (constructed in clay soils) direction, are presented to show their effectiveness. Field construction shows that the admixture of grout and soil can be gelled within 5 to 10 seconds. For the case history constructed in sandy soils, coring samples indicate that the jet grout columns are properly formed with a total core recovery of 80–100%, a rock quality designation (RQD) of 81–95% and a column diameter reaching 1.1 m, while unconfined compressive strength (UCS) tests suggests that the 28-day UCS is within the range of 5.0–6.0 MPa. For the case history constructed in clay soils, field cone penetration tests (CPT) suggest that the column diameter can reach 1.2 m, and the UCS test results show that the 14-day UCS can reach 0.5 MPa. All of these test results demonstrate the applicability of this newly developed technology in both sandy and clay soils.