Foundation Performance During Bridge Construction: A Comparison of Ground Improvement Techniques

摘要

Both deep-mixing methods and traditional "remove and replace" methods were used to improve foundation soils below a portion of the spread footing foundations at the newly constructed Glen Road Interchange on US 10/US 61 in Newport, MN. An overview of the site conditions, foundation selection, design, construction, and quality control aspects of the work is presented. A large portion of the original ground improvement work was changed to a more traditional "remove and replace" technique through a contractor value-engineering (VE) arrangement to reduce the project cost and advance the construction timeline. An excavation removal, replacement, and recompaction technique with extensive quality control (QC) monitoring was adopted in site areas where relatively shallow soil improvement had been planned. The QC program incorporated a variety of technologies including the pressuremeter, cone penetration test, and soil stiffness GeoGauge. A post-installation monitoring program was developed to study the performance of each ground improvement system. Earth pressure cells, strainmeters, and exten-someters were installed in the deep mixed columns and the adjacent unimproved soil to assess stress distribution and deflection behavior; similar instrumentation was installed to assess the performance of the VE improvement method under the east bridge abutment. Instrumentation and lab data from both the deep mixing and VE construction efforts are compared; data interpretation and irregularities are discussed.