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Recent content by dgillette

  1. dgillette

    Critical state soil mechanics

    I've seen very little about CSSM in typical practice, although about a year ago, I heard Ken Been talk about stability of a massive tailings project in Africa, where they made good use of it. That was an ideal use for it, where they had very large volumes of relatively uniform material...
  2. dgillette

    soil classification

    Gsp-graded soils (lacking grains of certain sizes, therefore having flat portions in their gradation curves) do indeed exist. They can be a real headache for dam foundations and cores.
  3. dgillette

    Liquefaction Assessment | SPT

    One caution on the "threshold": If you are getting the threshold N values from the 1997 NCEER report (also published as Youd et al in the 2001 ASCE Journal of Geotech Engrg.) or most other sources, the cyclic resistance on the curve represents about 15% probability of liquefaction, not ~zero...
  4. dgillette

    Wall friction angle - Seismic case

    Interesting question. I suppose at one extreme you would have Mononobe-Okabe (basically Coulomb active pressure with horizontal acc. in addition to gravity). Is that what WALLAP uses? I have never seen MO done with water pressures, and I believe the original derivation was for a nonsaturated...
  5. dgillette

    Direct Shear - Pore Water Pressure - Undrained and Drained

    Just curious - are we talking about direct shear, or direct simple shear? The latter is generally undrained or a pseudo-undrained constant-volume test. I've never heard of a drained DSS test anyway - why would you bother with DS or drained TX being quick and easy, and readily available?
  6. dgillette

    Pore water pressure

    I suppose it could contribute to increased pore pressure initially (like a clay consolidation problem), but within a few seconds to a few months, the pore pressure would match the surrounding area, due to seepage. Did I understand the question correctly?
  7. dgillette

    Rankine Earth Pressures

    MacGruber - Does that last quote refer to the friction angle between fill and wall, rather than internal friction within the soil? The original Rankine model assumed (in effect) that there is no friction on the wall, so the major and minor effective stresses are vertical and horizontal. That's...
  8. dgillette

    Subsurface Exploration

    It depends on what you are trying to find. In granular soils, we usually adjust blow count for overburden stress if we are trying to predict relative density or some related property like cyclic resistance ratio because, for a given relative density, the blow count increases with confining...
  9. dgillette

    Finally, Dam is Finished (except for the Make-Up)

    Dang, I'm a little jealous. I need to go build something again instead of just analyzing, analyzing, analyzing.
  10. dgillette

    Quick Undrained Shearbox Test

    Sounds like something to avoid unless the client can tell you which ASTM standard to follow (and I don't think there is one). In a typical shear box, I don't think you can shear it fast enough to actually be fully undrained, and how would you know if you had? Maybe if you had a hydraulic...
  11. dgillette

    Site response handbook

    If you do get it translated into English, make sure that YOU approve the final. I have a book on dam engineering from Spain, with a few glitches in the translation, fortunately minor ones that just sound silly.
  12. dgillette

    Problem with effective stress path in CU test.

    In that case, I've run out of ideas.
  13. dgillette

    Problem with effective stress path in CU test.

    For whatever reason, my employer's server forbids me to link to your data, so I can't look at it. My point was that a strongly dilative material like a dense sand or a clay with OCR>5 causes negative excess pore-water pressure, so the stress path curves off to the right, instead of curving left...
  14. dgillette

    Site response handbook

    If only I could read Italian... Best regards, DRG
  15. dgillette

    Problem with effective stress path in CU test.

    Sounds like either it's strongly dilative, or the sign of the output from the u transducer has gotten flipped. What's the material, and what is its OCR, or relative density, percent compaction, or whatever other parameter might be applicable?
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