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  1. GTeng

    Coulomb Theory & Cantilevered Retaining Walls

    I suggest you download the Corps of Engineers Engineer Manual for Retaining and Flood Walls. It is available for free download. They have a discussion of the wedge of soil on the heel. They do not discuss the problem of friction you mention though. It seems like it is relatively conservative...
  2. GTeng

    Slide groundwater analysis for circular/axisymmetric problem?

    Have any of you used Slide (by Rocscience) or similar programs that have seepage analysis capabilities to evaluate circular or axisymmetric problems? The Slide tutorial includes an example problem for a cofferdam but never states the configuration. It is assumed that this is a long linear...
  3. GTeng

    Pseudostatic Analyses

    The R envelope is not the same as the total stress envelope that you probably learned in soil mechanics classes. It is actually intended to represent the variation in total stress shear strength that occurs with effective stresses (that's my understanding of it). Technically, it is not exactly...
  4. GTeng

    Forensic Evaluation of Engineered Fills

    I read the posts pretty quickly, so maybe I'm missing the technical details, but here is a slightly different take. In this case it seems like a good lawyer is exactly what is needed. A contractor signs a contract to place and compact fill to the requirements of the contract, which include...
  5. GTeng

    Use of conical points for pipe piles in sandy material

    I am looking for technical information regarding the use of conical points for pipe piles as opposed to using a steel closure plate. I have always assumed they increase the ability of the pile to penetrate the soil (or decrease the toe capacity) so that the pile can be driven to a target depth...
  6. GTeng

    drained vs/ undrained strength

    According to Wroth and Houlsby, Soil Mechanics-Property Characterization and Analysis Procedures, Proceedings 11th ICSMFE, 1985: Undrained strength ratio in triaxial compression, su/sigmav0', can be calculated as follows: su/sigmav0'=(M/2)*(R/r)^Lambda M=6sin(phi)/(3-sin(phi))...
  7. GTeng

    drained vs/ undrained strength

    Following on to BigH's response, you could theoretically ( based on critical state soil mechanics principles) estimate the undrained strength if in addition to the effective stress phi you know the OCR of the soil. But, if you knew that you could do your calculations much more easily based the...
  8. GTeng

    Determination of the strength gain of soft soils due to consolidation.

    I agree that the drained case could not possibly be the critical case (because the material sounds to be normally consolidated), but I still think it is a good check. It gives you and idea of the limiting conditions you could reach, if you could imagine the construction being drained. In other...
  9. GTeng

    Determination of the strength gain of soft soils due to consolidation.

    A comment/clarification: I doubt you could build the embankment to a height of 40 ft in a single stage of undrained loading.
  10. GTeng

    Determination of the strength gain of soft soils due to consolidation.

    My experience has been with MSE Walls, so I may be offbase, but the heights you mention appear very high compared to the strengths you measured. I doubt that you build a slope to 40 ft on that material, depending on the depth/thickness of the soft clay. Here are some references. I didn't add...
  11. GTeng

    Lateral pressure from narrow granular zone between two walls

    You could do a calculation to estimate the earth forces, either by trial wedge, or using "silo" type calculations (I think Bowles covers this). However, it may boil down to things that you can't calculate like: 1) field compaction - if the material is compacted or overcompacted then significant...
  12. GTeng

    Trench foundation on Geopiers

    Off the cuff, a couple of things come to mind reading your email. You said that "contractors" commented on the design and found them unacceptable. They mention "rollover" and tremendous "weight" on "small" footings. Apparently they don't understand the technical terms "bearing capacity" or...
  13. GTeng

    Effective strength parameters for clay

    Can't be done from the parameters you supplied. You can look at correlations with plasticity parameters (Holz and Kovacs, NAVFAC) but the only way to actually measure is by a triaxial compression test, either drained or undrained with pore pressure.
  14. GTeng

    Need suggestions for possible friction piles

    Several things come to mind as I read the original post and replies. The site includes loose sandy and silty soil, yet several of the methods suggested may cause vibrations that could result in settlement damage to nearby utilities or structures. Steel H-piles don't seem to be a good idea...
  15. GTeng

    Mohr envelope for overconsolidated soil :common Yet puzzling

    Can you check with the lab to find if they checked B values after consol and prior to shearing? That should answer the questions about saturation. It sounds like the effective stress phi from your p-q diagram should be reliable. However, it sounds like you are worried about the undrained case...
  16. GTeng

    Mohr envelope for overconsolidated soil :common Yet puzzling

    Haven't charted the data, but it appears to me that the results are should be as expected considering the apparently widely varying OCRs. The sample tested at 100 kPa appears to be lightly overconsolidated, based on the A value. Therefore, the sample at 20 kPa may have an OCR greater than 5...
  17. GTeng

    Lateral pressure due to strip load surcharge

    Thanks for your reply. I look forward to another refernce on the issue. Could you describe the geometry of the wall in more detail? I don't understand what you mean by two "stems". If I understand the geometry correctly, in my opinion, the design of the upper 4 ft portion of the wall is the...
  18. GTeng

    Lateral pressure due to strip load surcharge

    The NAVFAC Design Manual and Elastic Solutions for Soil and Rock Mechanics by Poulos and Davis give similar forms for calculating horizontal stress, i.e., Sigma-x = (q/pi)[alpha - sin(alpha)Cos(alpha +2delta)] where alpha is the angle encompassed between the left and right edge of the strip...
  19. GTeng

    Negative Skin Friction for Abutment Pile

    I suggest you consider the "Unified Method" as proposed by Bengt Fellenius. The Unisoft website (unisoftltd.com) includes several technical papers that can be downloaded and which explain a proposed relationship between drag loads and settlement. These can help you get a better...

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