Minnesota DOT Twin Ports Interchange - Use of Drill Rig Real-time Monitoring and Data Acquisition to Verify In-Situ Soil Conditions as a Measure of Quality Assurance in Highly Variable Soils-PPT Presentation

PPT Presentation

Pdf Summary

The presentation describes how drill-rig data acquisition systems support quality assurance for rigid inclusions (RIs) and can help interpret subsurface conditions during construction.<br /><br />RIs are typically unreinforced grout or concrete columns used beneath embankments to reduce settlement and improve bearing capacity in weak, compressible soils. Data systems record installation indicators such as drilling and withdrawal rates, rotary pressure (a proxy for torque), crowd force, penetration resistance, depth, grout pressure, and grout volume.<br /><br />Installation data can help distinguish loose or soft soils from dense or hard layers. Dense sand is generally associated with slower penetration and higher crowd force and penetration resistance; loose silt tends to show the opposite. However, readings depend on the rig, tooling, diameter, and operator methods, so comparisons are most reliable within a single project. Thin layers under five feet and intermediate soil conditions can be difficult to identify.<br /><br />The case study is MnDOT’s Twin Ports Interchange in Duluth, Minnesota, where ground improvement was carried out in 2022–2023. The project included 6,600 concrete columns, each 16 inches in diameter, totaling approximately 330,000 linear feet and extending 30–104 feet deep. The project team used design-phase borings and CPT soundings to establish initial depths, then used installation data to verify and refine termination criteria. Compression load tests and post-construction monitoring—including strain gauges, shape arrays, settlement plates, and piezometers—provided additional verification.<br /><br />The central lesson is that drill-rig monitoring can complement geotechnical explorations: teams can interpolate between borings to set initial installation depths, then assess conditions and adjust decisions using field data. Calibration against site-specific investigations and recognition of the method’s limitations are essential.

Keywords

drill-rig data acquisition

quality assurance

rigid inclusions

subsurface conditions

installation data

geotechnical monitoring

penetration resistance

grout pressure

ground improvement

Twin Ports Interchange