Evaluation of structure borne noise in jet grouted elements-Paper

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The paper presents vibration monitoring as a construction-stage quality-control method for jet-grouted structures, particularly watertight excavation-pit bottom seals. Conventional practice mainly checks jetting parameters on test columns and assumes comparable ground conditions elsewhere. The proposed approach instead measures structure-borne vibrations in hardened primary columns while adjacent secondary columns are being jetted.<br /><br />Acceleration sensors record vibrations transmitted through the primary columns. Because the jet’s high-frequency energy travels through hardened grout more effectively than through surrounding soil, filtered signals and their moving RMS values can identify when the jet contacts a column. Contact duration can also help estimate column geometry.<br /><br />Signal patterns indicate whether a secondary column makes the intended connection with the primary columns. Normal contact, incomplete erosion at the junction (“gusset” defects), one-sided contact, and no overlap produce distinguishable RMS responses. Field tests found that useful signals could be measured at distances of up to about 7.5 m from the jetting location. The type of construction joint and normal variations in curing time had little effect on monitoring. Sensors installed at regular intervals—potentially in every sixth primary column—may therefore provide practical coverage without instrumenting every column.<br /><br />The method can also flag possible obstructions, such as old wells or boulders, when expected signals are repeatedly absent, allowing corrective columns to be added while equipment remains on site. Overall, vibration monitoring offers immediate verification of column connections and may reduce reliance on time-consuming post-construction leakage investigations and temperature-monitoring tubes. Further field testing is recommended to determine whether the effective sensor range can be increased.

Keywords

vibration monitoring

jet grouting

quality control

watertight excavation

jet-grouted structures

acceleration sensors

RMS signal analysis

column connection

construction-stage monitoring

leakage investigation