The National Academies

NCHRP IDEA 20-30/IDEA 186 [Completed (IDEA)]

Development of an Electrical Probe for Rapid Assessment of Ground Improvement
[ NCHRP 20-30 (NCHRP-IDEA) ]

  Project Data
Funds: $126,958.00
Staff Responsibility: Inam Jawed
Research Agency: Colorado School of Mines
Principal Investigator: Mike Mooney
Effective Date: 9/1/2015
Completion Date: 10/12/2018
Fiscal Year: 2015

Soil improvement via jet grouting and deep soil mixing has numerous applications in transportation construction. The performance of jet grout material depends on the realized diameter, however, the realized diameter is influenced by the varying ground and machine operation parameters. Inspection of jet grout column diameter is critical but techniques to perform rapid non-destructive assessment are lacking. Through a combination of finite element modeling, prototype development and field testing, this research developed an electrical probe to assess the diameter of freshly mixed jet grout columns. This report summarizes the study. Research included computational modeling, prototype development, field deployment and field data analysis. A plan was developed for commercial implementation of the push probe into practice.  The developed probe is inserted into a freshly jet grouted column immediately after removing the jet grout monitor. The test requires 20-30 minutes to collect sufficient data to estimate column diameter. The probe has been implemented on multiple jet grout construction project sites, primarily granular soil sites (sands, silty sands). In all cases, the estimated diameter was found to be within 5% of the actual constructed diameter. Commercial implementation should follow the approach used by the Osterberg load cell that was licensed to a specific company (companies). The push probe deployment should involved highly trained field personnel to carry out each test. This will build confidence in the test and build a record of test results that can be used to further interpretation and confidence in the results. 
The final report is available.

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