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  1. AussieGeoEng

    time rate of clay swelling settlements

    By rebound, I am assuming you are referring to unloading? For a saturated soil this is analogous to consolidation, however mv will be different and affect the calculated cv.
  2. AussieGeoEng

    Triaxial test

    I find it strange that the onus is on the tester to prevent the sample from cracking. You should be able to complete this test in a standard triaxial (noting a confining pressure of 100 kPa). Just check the capacity of the load cell. A 5kN load cell is good for up to 2500kPa axial stress.
  3. AussieGeoEng

    Consolidated Undrained Triaxial Test Back Pressure Problem

    I assumed you figured this out - but it sounds like you have a leak.
  4. AussieGeoEng

    Validity of Atterberg Limit charts that has been used in Geotechnical Engineering

    Check out the paper below, where a method is proposed for determining wP based on the fall cone. Feng, T. W. (2000). Fall-cone penetration and water content relationship of clays. Geotechnique, 50, 181-187. I don't think this has really been picked up in practice, but in a discussion by Prof...
  5. AussieGeoEng

    Field Density Test after 6 Months

    I disagree with dBasement... if the soil swells or shrinks then your dry density will change. For example, if you have an expansive clay and it was placed dry of optimum and there was a wet period, then chances are that you dry density will have reduced (swelling), on the other hand if you have...
  6. AussieGeoEng

    Settlement with a Soil Vapor Extraction System

    If you are changing the relative humidity of the pore space, then using Kelvin's law (see Fredlund & Rahardjo,1993) you are altering the suction. So if the relative humidity is decreasing, then suction is increasing resulting in the compression you are observing.
  7. AussieGeoEng

    testing for saturated moisture content

    You can calculate it from the phase relationship w(Gs)=e(Sr)... If you know density/void ratio (e) and specific gravity (Gs), adopt Sr=1.0 and calculate w.
  8. AussieGeoEng

    Criteria for punching failure footing on compact sand over soft clay

    You first need to check that the failure envelope will extend into the clay. Bowles (1995) has some guidance on this. Bearing capacity is sum of the bearing capacity of the clay plus a contribution due to shearing of the sand - roughly worked out based on the perimeter of the foundation...
  9. AussieGeoEng

    What is passive wedge?

    When referring to a passive wedge it is typically the wedge of soil in front of a retaining wall.
  10. AussieGeoEng

    Compaction Specification - 5% air voids

    f-d & BigH, Thanks for the last two posts. f-d do you have any references to the work you talked about? I will have some more reading to do.
  11. AussieGeoEng

    Compaction Specification - 5% air voids

    f-d, I realise that the optimum varies for each compaction level. I like to think of the SP OMC as a good reference. I have heard of other moistures - even machine optimum. Which would be the optimum moisture for achieving compaction with a certain type of machine and compaction procedure...
  12. AussieGeoEng

    How to obtain Surface movement and depth of suction change values

    If they don't provide money for testing you may as well pluck numbers from thin air. Give them plenty of scatter so no one can make sense of them. :-)
  13. AussieGeoEng

    Subgrade Optimum Moisture Content

    I would tend to disagree - moisture content is important. If the test was completed on different samples, then that is another story. A relative compaction of 99% can be achieved dry of optimum - it would however require significantly more effort. I.e similar to the shift in the compaction...
  14. AussieGeoEng

    Normally Consolidated clays specimens

    Is the compaction static or dynamic (e.g. Proctor)? If it is static then you can measure the load. With dynamic it depends on the amount of energy exerted - I would usually esitmate around 200kPa. Therefore no, I would not call the sample dynamically compacted NC. With the oedometer you can...
  15. AussieGeoEng

    Normally Consolidated clays specimens

    There are two procedures to produce specimens in the laboratory. Compaction or reconstition. You mention both so a little confusing? Reconstitution is preparing a sample at a moisture (well) content inexcess of the liquid limit. Then consolidating (note the difference between compaction -...
  16. AussieGeoEng

    Preconsolidation pressure against moisture content / dry density?

    Are you trying to determine yield pressure for saturated or partially saturated? Can you post the results?
  17. AussieGeoEng

    Preconsolidation pressure against moisture content / dry density?

    Determination of preconsolidation pressure on a natural specimen specimen is difficult at the best of times. Preconsolidation pressure seems a little misleading for a compacted specimen - I would prefer to use yield pressure - i.e. change from elastic to elasto-plastic behaviour. Compaction in...
  18. AussieGeoEng

    Depth Correction for Clays

    I was wondering what sort of reliance do you put on UU testing? i.e. what would be your ratio of UU to CU testing? Obviously somebody does, from the response to the discussion: "Since Hurricane Katrina, about 3,500 consolidation tests, 6,000 CPTs, and 22,000 UU triaxial (Q) tests have been...
  19. AussieGeoEng

    Depth Correction for Clays

    f-d, Just out of interest, do you still do a lot of UU tests? Came across this discussion by Ladd last week and found it very interesting. LADD, C. C. 2009. Discussion of "Stability of I-Walls in New Orleans during Hurricane Katrina" by J. M. Duncan, T. L. Brandon, S. G. Wright, and N...
  20. AussieGeoEng

    UU Triaxial Test Results

    moe333 is correct. With a partially saturated soil you will experince some consolidation when the cell pressure is applied (even though all the drainage valves are closed).

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