Emergency Repair of a Failing MSE Wall Utilizing Hollow Bar Soil Nails and Compaction Grouting

This paper summarizes the emergency stabilization repair of a newly constructed roadway section originally designed and constructed using a Mechanically Stabilized Earth (MSE) wall to create 40-ft of additional roadway width, including a bike lane and pedestrian walkway. The new roadway section, located on 38 Road, near Palisade, Colorado, began to show signs of movement just days before the ribbon cutting ceremony was marked on the calendar. The movement accelerated rapidly over the next few days and became an emergency situation as the tension cracks in the roadway created hazards to motorists and cyclists. The MSE wall consisted of a wire-faced basket type and appeared to be internally stable. The movement observed in the MSE wall suggested a problem in the foundation soils that the MSE was placed on. In addition to this poor foundation, an approximately 12-ft wide “buttress” of soil was placed at the toe of the finished MSE Wall. This buttress was placed too high on the slope and was over-steepened. This was thought to be another contributing factor in overloading the foundation soils. The approach to mitigate the movement of the existing retaining wall consisted of designing and installing a pattern of hollow bar soil nails, up to 50-ft in length, through the existing wall face and reinforced fill into the shale bedrock. Additionally, the design included reshaping the fill previously placed in front of the newly constructed wall. Reshaping consisted of regrading the mass of the previous over-steepened “soil buttress” downhill, to a more suitable configuration making the mass more useful to resist the movement. During the drilling process, the wall continued to move until enough of the installed soil nails began to take load and “catch” the wall’s movement. Once the combined resistive forces in the soil nails as well as the fill below the wall were at or above equilibrium with the driving forces of the failure, the wall movement quickly reduced to almost zero. Since the wall experienced significant movement for approximately one (1) week, as well as being purportedly founded on less than suitable foundation material, it was then decided to implement a more comprehensive solution and improve the foundation materials as well as increase the density of the sub-grade materials using compaction grouting methods. Compaction grouting was used in the subgrade soils below the roadway to re-densify the soil behind the MSE fill to help mitigate any settlement or reflection cracking that could occur in the roadway after repaving.

Language

  • English

Media Info

  • Media Type: Digital/other
  • Features: Figures; Photos;
  • Pagination: pp 42-53
  • Monograph Title: Proceedings of the 67th Highway Geology Symposium (HGS 2016)

Subject/Index Terms

Filing Info

  • Accession Number: 01627838
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Feb 23 2017 7:39PM