DEVELOPMENT OF MEASURING TOOLS RELATED TO THE TECHNIQUE OF JET GROUTING.-Paper

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The paper reviews electronic tools designed to improve the accuracy and productivity of jet grouting, particularly at depths where column position and diameter are difficult to verify. Reliable three-dimensional positioning is essential to ensure adjacent columns overlap as designed.<br /><br />For borehole deviation control, the paper describes two real-time approaches. Wired drilling rods transmit data from a magnetic/inclinometer tool near the drill bit to the surface, allowing deviations to be detected and corrected without opening the drill string. Where magnetic interference or inclined drilling makes compass-based measurements unreliable, a slim gyroscope can be lowered through a swivel to survey the borehole. These systems have been tested for deep drilling, including applications reaching approximately 85 metres.<br /><br />Measuring column diameter at project depth remains challenging. Shallow trial columns may not represent deeper ground conditions, while existing direct and indirect methods—such as callipers, painted rods, coring, temperature monitoring, geophones, sonic waves and electrical resistivity—have limitations involving cost, time, accuracy, calibration or sensor positioning.<br /><br />The paper presents Check Grout, a direct measurement system for freshly grouted columns. A flexible pipe is guided outward from a drill string by a deviator until it reaches the boundary between treated and untreated soil. An inclinometer chain inside the pipe records its three-dimensional path in real time, enabling the distance from the column centre to its edge to be assessed. Measurements can be taken at different elevations and orientations, and temperature data can also help describe the column. The system can additionally survey part of the drill string to check verticality and compensate for pendulum effects.<br /><br />Check Grout has not yet been validated in gravelly soils, so its use there is discouraged pending further testing. A planned version will integrate the measurement tool with the drilling system to enable measurements without retrieving and reconfiguring the string.

Keywords

jet grouting

borehole deviation

three-dimensional positioning

column diameter

real-time surveying

inclinometer

gyroscope

Check Grout

drilling depth

soil treatment