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  1. LRJ

    Pore pressure response during CIU test

    It's to do with excess pore-water pressure. Think of it in terms of the stress path: during an ideal saturation stage, the effective stress would remain constant (i.e. cell pressure minus pore-water pressure is constant), and usually the deviatoric stress would be zero. In contrast, during the...
  2. LRJ

    What is a Monotonic Triaxial?

    Monotonic triaxial tests are loaded in one direction only until they reach failure, however that is defined. Cyclic triaxial tests undergo cyclic loading, whereby the direction of loading is reversed, typically multiple times until a defined failure limit is reached. So yes, a monotonic...
  3. LRJ

    Strategies for dealing with the 'uh uh uh' people

    The examples cited in the OP didn't seem to me to be 'reinventing the wheel' sort of stuff. Rather, they seemed to be legitimate disagreement within a highly subjective profession. Ultimately the statements indicate differences in judgement and/or preferences, and they at least seem to be...
  4. LRJ

    Strategies for dealing with the 'uh uh uh' people

    To be honest, the examples cited in the OP are all fair challenges - and persistently matters of debate amongst geotechnical engineers. This is somewhat inevitable in an imprecise field with still a lot of subjectivity: it is the old adage of asking 3 geotechnical engineers a question and...
  5. LRJ

    Vertical and Lateral Soil Springs

    If this is a shallow foundation with vertical and lateral loads being applied simultaneously, then don't forget that the response will be 'coupled', i.e. you can't separate the vertical and lateral responses. If this is the case, then a stiffness matrix approach is likely to be more appropriate.
  6. LRJ

    Confidence intervals from shear strength test (e.g. triaxial test)

    Thanks for sharing. The video was a good summary of the paper and seems logical. I guess one comment to make: conventionally the internal friction angle is calculated from a 'set of three' drained tests (unless you have a stress path device) and the results from multiple 'sets of three' tests...
  7. LRJ

    Settlement - Conventional/Log (Cr, Cc, eo) vs. Linear (mv) Pressure Scales

    The point is that the Cc/Cr approach is a simpler approximation. Too often I have seen engineers use a single value of mv.
  8. LRJ

    Settlement - Conventional/Log (Cr, Cc, eo) vs. Linear (mv) Pressure Scales

    I don't know why anyone would use the mv approach - you need numerous different values depending on the stress/strain level. With the Cc/Cr approach you just need those two values. Both approaches should give the same answer, so the decision should be about using the simplest of the methods -...
  9. LRJ

    an alternative to GINT

    Fugro have a piece of software called GeODin which is good. There is also a program called Holebase which seems okay too. As ever with these things, you obviously need to spend a bit of time creating the logs in the format you want first, but once created, it's obviously much more efficient to...
  10. LRJ

    Soil in drained vs undrained condition

    The shear stress is equal to normal stress multiplied by the tangent friction angle. If you have lower pore pressure (due to positive excess pore pressure during shearing, i.e. contraction), then this will lower the normal stress, and lower the shear stress. The reverse is true for dilation...
  11. LRJ

    Correction Factors when using split spoon samples for direct shear testing?

    The direct shear test is used to obtain friction angle data - either internal friction angle or interface friction angle. Given these are cohesive samples, I'd expect you'd be more interested in the interface friction angles. Contrary to the widespread outrage here, there is nothing inherently...
  12. LRJ

    Overestimation of soil´s hydraulic conductivity using the Kozeni-Carman permeability model

    Hydraulic conductivity (often erroneously referred to as 'permeability' by geotechnical engineers) is notoriously difficult to measure, despite its fundamental importance for many geotechnical analyses. Generally the Kozeny-Carman equation works well, but I seem to recall it falls apart a little...
  13. LRJ

    Determining Total Stress Parameters from CU Triaxial Results

    Whoever wrote that quote in the OP has, at best, not explained themselves clearly or, at worst, doesn't know what they are talking about . The consolidation stress applied to a CU triaxial is supposed to represent the in situ condition! CU triaxials are much more reliable than UU triaxials...
  14. LRJ

    Drillability assessment questions

    I've been looking at several drilling rate of penetration (ROP) models and noticed that many of them have empirical factors which are undefined in the original publications. This includes Maurer (1962), Galle and Woods (1963), D-exponent (Bingham; Jorden and Shirley; Rehm and McClendon)...
  15. LRJ

    Triaxial shear speed determination

    If you've undertaken a consolidation stage (i.e. drained; volumetric change), then why do you have excess pore-water pressure (i.e. undrained)? This is a little worrying. With regard to consolidation time, t50 (and similar) is supposed to represent the time to dissipate 50% (or whatever the...
  16. LRJ

    Non-destructive confirmation of bored pile capacity

    Do you mean undertaking a suite of static pile load tests (i.e. a destructive test) to confirm the capacity? What exact ASTM standard? As per my previous post, this if this is what was meant, then it is not feasible to undertake due to cost and time constraints, hence asking about...
  17. LRJ

    Non-destructive confirmation of bored pile capacity

    I'm involved in a project where the client plans on installing bored piles. These have been designed according to the relevant standards for the area they will be installed in, but there is some suggestion that these capacities should be confirmed post-construction. Some static pile load...
  18. LRJ

    Chloride content of soil

    Dutch is, well... Dutch! to me, so I don't know what those documents say. However, in the first link I can't see how the formation factor comes up in the equation on page 5. In any case, it looks like you've got some correlations there. I would just suggest that you undertake some tests so you...
  19. LRJ

    Static Cone Penetrometer Correlations to N-Values

    Do you mean a pocket penetrometer (PP) test? Or a fall cone? I don't recognise your terminology.
  20. LRJ

    Foundation engineering

    As an aside, if you are looking at a type of foundation where the vertical, horizontal, moment and torsion responses are 'coupled' (e.g. a shallow foundation), then creating a stiffness matrix would be required. Generally for deep foundations such as piles the responses are sufficiently...

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