Field Test Verification of Ground Bearing Pressure Under Rig Tracks and Implications for Working Platform Design-Paper

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The study evaluates ground-bearing pressures (GBPs) beneath tracked geotechnical rigs and their implications for working-platform design. A full-scale field test used a Liebherr LRB 125XL soil-mixing rig. Its loads and centre-of-gravity position were recorded using Liebherr’s Ground Pressure Visualisation (GPV) system, while pressure cells buried beneath one track measured stresses at five leader positions. The measurements were compared with analytical calculations and a calibrated finite-element model.<br /><br />Results show that the conventional “equal eccentricity” method—which assumes both tracks’ loads act at the same longitudinal eccentricity as the rig’s total load—can either overestimate or underestimate track pressures, depending on rig orientation. Underestimation can be unsafe. A proposed “divergent eccentricity” method, which accounts for different load positions on the two tracks, agreed more closely with the measurements and finite-element results within its stated range of applicability. Using GPV is recommended where available.<br /><br />The study also found that the effective track-ground contact length depends on platform susceptibility and settlement. The step-based track-length rule in EN 16228-1 may therefore be oversimplified. For the tested rig, a shorter, mean effective contact length better matched measured pressures than the standard-based length.<br /><br />Applying the revised pressure distributions and contact length reduced calculated platform ultimate bearing capacity by approximately 7–14% compared with conventional calculations. Thus, conventional design methods may overstate a working platform’s safety. Further research is needed to establish reliable contact-length guidance and improve models that account for track flexibility and soil interaction.

Keywords

ground-bearing pressure

tracked geotechnical rigs

working platform design

soil-mixing rig

Liebherr LRB 125XL

ground pressure visualisation

track pressure measurement

finite-element model

eccentricity method

bearing capacity reduction