Development of Measuring Tools Related to the Technique of Jet Grouting: How Are Electronic Devices Increasing Productivity and Accuracy Predictions in Jet Grouting?

This paper reviews the latest techniques applied to the jet grouting practice in order to define the correct 3D position of the column and its diameter at the project depth. These aims have been already pursued by several companies in different ways. However, the increasing depth of application keeps on moving the goalposts. When contractors ask specialized companies for an effective jet grouting grid, it is imperative to know the position of the hole within the tolerance required to obtain the design columns' overlapping. To do that, new tools have been improved with higher accuracy and real time data delivery. Wired drilling rods and mag./incl. tools allow the driller to receive a continuous flow of data to the surface, thus avoiding loss of time and long stops at the bottom of the hole where risk of getting stuck is high. They further eliminate opening the drill string, which may allow ingress of particles into the air line. In a different way, the slim gyro tools may be inserted through the swivel (again, without opening the string) and quickly lowered into the grout line until reaching the bottom of the string. In both cases, data is transmitted in real time making possible trajectory corrections or making quick decisions in case of excessive deviation. In addition, for the formation required to be treated, it is not always possible to carry on a shallow trial test field (where the columns may be excavated and directly observed), where the nature of such deep formations differs from the formations located at a shallower depth. The existing methods to detect the column diameter at the project depth are often very expensive, not real time, and they also lose accuracy with depth. For such a reason, a mechanical system has been coupled with advanced electronics to reach the border of the column while simultaneously surveying the path of the pipe used to "travel" inside the grouted soil.