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Recent content by Geo69

  1. Geo69

    Determination of Preconsolidation Pressure

    Good evening all, I have a question regarding preconsolidation pressure. I was taught, like many of you, the Casagrande method of determining preconsolidation pressure which includes drawing a straight line along the virgin compression curve and determining where it intersects the angle...
  2. Geo69

    Effect of Acid on Soil

    Thanks to all for your suggestions. I'd considered a lot of what has been said, but its good to know I'm not out in left field.
  3. Geo69

    Effect of Acid on Soil

    The pH is low from the surface to a depth of about 30 feet where a clay layer is encountered, then rises to about 7 to 9 down to the bottom of the borings at about 80 feet. The gravel layers are very dense. The clay is medium stiff to stiff. The fill is predominantly gravel which is loose to...
  4. Geo69

    Effect of Acid on Soil

    Ron, I'm more worried about the surficial soil and its support capability than the bedrock. We performed more than 30 pH tests in the field during drilling and found the shallow soil had pH values in the 1.6 range. The pH values at depth were in the range of 7 to 9. Deterioration of the...
  5. Geo69

    Effect of Acid on Soil

    f-d, Thanks for the response. It is a unique project. The subsurface conditions consist of about 10 feet of fill overlying clay and gravel layers. We may have encountered bedrock at 80 feet. Some of the bedrock in the area is mapped as limstone and would definitely react with the acid. I'm...
  6. Geo69

    Effect of Acid on Soil

    I am working on a project where a structure has settled, likely as a result of concentrated sulfuric acid in the soil. pH values are as low as 1.6. Some of the bedrock in the area is limestone and has likely been affected by the acid. Does anyone know of any publications that discuss the...
  7. Geo69

    MSE/soil nail hybrid walls

    MSE Man, Do you know when the FHWA design manual will be published? I am looking for information about these type of retaining walls. Thanks, Geo69
  8. Geo69

    Coefficient of friction between granular soil and wood

    Ron has a good point. We have done testing in our lab in the past using a sample of the soil and the dissimilar material. Our testing used clay and geosynthetics for slope stability in a landfill design but any material could be used.
  9. Geo69

    Coefficient of friction between granular soil and wood

    Geoduck, Try looking in the NAVFAC DM 7.02. There is a table on page 7.2-63 that lists friction factors between dissimilar materials including a masonry on wood (26 degrees).
  10. Geo69

    Settlement behind retaining wall

    eric, you may consider remolding samples of the sand to say 85%, 90% and 95% compaction into a consolidation ring and measuring their compressibility. You could use this to estimate the amount of settlement that has and/or could occur.
  11. Geo69

    Earth Pressure with Narrow Backfill Zone

    Thanks BigH. Based on calculations, I've previously estimated wall pressures for this case by indicating that the soil pressure will increase down to a depth of two times the distance between the foundation wall and retaining wall. The pressure will stay constant below that depth. I've done...
  12. Geo69

    Settlement behind retaining wall

    eric, We had a project several years ago where a house settled. Approximately 17 feet of free-draining gravel was placed below the house and supposedly compacted. During our investigation, several inches of settlement were observed between the bottom of the floor slab and the top of the fill...
  13. Geo69

    Earth Pressure with Narrow Backfill Zone

    jdonville, Yes, I should have used the earth retention forum. I looked in DM 7.02 and am not sure which figure you are referring to; I may have an older version. Anyway, the foundation wall has been designed using at-rest pressures. The soil nail wall will also be designed as a permanent...
  14. Geo69

    Earth Pressure with Narrow Backfill Zone

    Neither structure has been constructed. The retaining wall is planned to consist of a permanent soil nail wall approximately 14 to 26 feet in height. The soil nail wall is planned to be constructed at a horizontal distance of 4 to 10 feet away from the foundation wall of the proposed building...
  15. Geo69

    Boulder Retaining Wall

    jdmm, The concern that we have with analyzing boulder walls as a gravity wall is that you when you analyze overturning you cannot sum moments at the base of the wall. There is no rigid connection that will transfer forces from the top to the bottom of the wall. There is frictional resistance...
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