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Geotechnical Engineering

 

Checklist and Guidelines for Review of Geotechnical
Reports and Preliminary Plans and Specifications

GTR Review Checklist for Embankments Over Soft Ground


C. Embankments Over Soft Ground

Where embankments must be built over soft ground (such as soft clays, organic silts, or peat), stability and settlement of the fill should be carefully evaluated. In addition to the basic information listed in Section A, is the following information provided in the project geotechnical report?

Embankment Stability
 (Pgs. 5-1 to 5-3, 5-20 to 5-22)
  1. *Has the stability of the embankment been evaluated for minimum F.S. = 1.25 for side slope and 1.30 for end slope of bridge approach embankments?

        (Yes   /   No   /   Unknown or N/A)

  2. *Has the shear strength of the foundation soil been determined from lab testing and/or field vane shear or cone penetrometer tests?

        (Yes   /   No   /   Unknown or N/A)

  3. *If the proposed embankment does not provide minimum factors of safety given above, are recommendations given or feasible treatment alternates, which will increase factor of safety to minimum acceptable (such as change alignment, lower grade, use stabilizing counterberms, excavate and replace weak subsoil, lightweight fill, geotextile fabric reinforcement, etc.)?

        (Yes   /   No   /   Unknown or N/A)

  4. *Are cost comparisons of treatment alternates given and a specific alternate recommended?

        (Yes   /   No   /   Unknown or N/A)

Settlement of Subsoil
 (Pgs. 6-7 to 6-20)
  1. Have consolidation properties of fine-grained soils been determined from laboratory consolidation tests?

        (Yes   /   No   /   Unknown or N/A)

  2. *Have settlement amount and time been estimated?

        (Yes   /   No   /   Unknown or N/A)

  3. For bridge approach embankments, are recommendations made to get the settlement out before the bridge abutment is constructed (waiting period, surcharge, or wick drains)?

        (Yes   /   No   /   Unknown or N/A)

  4. If geotechnical instrumentation is proposed to monitor fill stability and settlement, are detailed recommendations provided on the number, type, and specific locations of the proposed instruments?

        (Yes   /   No   /   Unknown or N/A)

Construction Considerations
 (Pgs. 10-8, 10-9)
  1. If excavation and replacement of unsuitable shallow surface deposits (peat, muck, top soil) is recommended, are vertical and lateral limits of recommended excavation provided?

        (Yes   /   No   /   Unknown or N/A)

  2. Where a surcharge treatment is recommended, are plan and cross-section of surcharge treatment provided in geotechnical report for benefit of the roadway designer?

        (Yes   /   No   /   Unknown or N/A)

  3. Are instructions or specifications provided concerning instrumentation, fill placement rates and estimated delay times for the contractor?

        (Yes   /   No   /   Unknown or N/A)

  4. Are recommendations provided for disposal of surcharge material after the settlement period is complete?

        (Yes   /   No   /   Unknown or N/A)

*A response other than (yes) or (N/A) for any of these checklist questions is cause to contact the appropriate geotechnical engineer for a clarification and/or to discuss the project.

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Updated: 04/07/2011
 

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