Application: Determination of Jet Grout Column Diameter

Jet grout injections consolidate the soil and decrease the risks of subsidence from large surface structures. Jet grout columns vary in diameter, depending upon the injection pressure and the soil conditions. The diameter is an important property that should be quantified, especially when several grout columns are connected to form an underground concrete floor. Until now, no proven or tested techniques existed to calculate the diameter ofinjected columns. Until now, it has been almost impossible to conclude whether thejetgrout foundations provide enough stability, especially in underpinning applications.

Applications of TISA 3D in jet grouting

By integrating the TISA 3D Borehole Radar technology into the injection lance, the diameter of the column can be determined on site. The boundary between grout column and hosting medium is a sharp edge and, therefore, a good reflector for incident radar waves.

There are two ways to apply the TISA 3D in the jet grouting process. In both cases, the diameter can be measured very precisely because of the resolution of the TISA 3D method:

1. Integrating the TISA 3D in the jet grouting system. During construction of the column, the radar is located just below the injection point and the grout column diameter is measured from within the column. The injection pressure can be adjusted while the column is being made.
2. Drilling a borehole near the grout column allows the TISA 3D to measure the distance from this borehole to the edge of the column.