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  1. dirtman

    Liquid Limit

    You could simply assume a value of 16 percent, as that is considered the value below which realistic values cannot be obtained for the test equipment.
  2. dirtman

    Compression Index Values

    The compression index is estimated by several standard equations. The first is from Terzaghi 0.009(LL-10). The NRCS laboratories developed a good estimate from this equation: Cc = sqrt[0.0032 x LL x (e0-0.4)]. For instance, given a soil with a LL value of 42 and an intial void ratio of 0.76...
  3. dirtman

    Consolidation Quiz

    We have measured post construction settlement of many earth dams and have actually found very little post construction settlement.
  4. dirtman

    hand vane tester

    the absolutely best pocket vane shear tester is made by geotest. It costs twice as much but is more than twice as good. It comes with 3 different size vanes depending on the strength of the soil you need to sample.
  5. dirtman

    Energy in compaction tests

    The Standard Proctor D698 Energy is 12,375 foot pounds of energy per cubic foot. It is simply the multiplication of 5.5 pound hammer times 1 foot drop times 75 drops divided by the volume of the mold which is 1/30 cubic foot. This equates to 12,375. The modified effort D1557 test is 10 lbs...
  6. dirtman

    Shear rate of CD Direct shear

    Part of performing a CD direct shear test is to consolidate the specimen prior to shearing it. You should monitor the consolidation with a dial gage and construct a consolidation versus log of time curve and determine t50 for the soil. The time to failure for the direct shear test then should...
  7. dirtman

    Consolidation Quiz

    Actually, you can expect very little post-construction of compacted embankments that use relatively thin lifts as ordinarily would be the case for engineered fills. We have monitored a number of compacted embankments for years and have found almost no post-construction settlement regardless of...
  8. dirtman

    Engineered fill specifications

    For filter sands we have found a good correlation exists between a one point D698A test performed on a sample of oven dry sand to the value about equal to 70 percent relative denstiy. It is much easier to perform the one point dry Proctor test than the vibrating table test. I wrote an...
  9. dirtman

    Maximum density obtained with different tests

    The only soils on which you should perform relative density vibrating table tests are those with less than 12 percent fines. The NRCS performed testing on C-33 filter sands several years ago and found a good correlation between 70 percent relative density and 100 percent of the D698A one point...
  10. dirtman

    ASTM D698 vs D1557

    The Old Navy Design Manual on Soil mechanics had correlation equations for estimating standard and modified proctor maximum dry density values. The equation for estimating standard proctor maximum dry density in English units is: gammad max = 130.8-0.82*LL + 0.21*PI Based on data given in the...
  11. dirtman

    UC testing on Split Spoon Samples

    Performing unconfined compression tests on remolded samples ignores an important point for some soils - the sensitivity issue. The definition of sensitivity is the ratio of the undisturbed qc strength to the disturbed qc strength. Sensitive clays lose a great deal of their strength when...
  12. dirtman

    pentrometer/shear vane

    The vane shear tester is far superior to the pocket penetrometer. Both are only applicable for saturated, at least moderately plastic clays. It is inappropriate to run the tests on unsaturated clays or soils with plasticity indices less than about 10. The best vane shear tester in my opinion...
  13. dirtman

    Excavating near the toe of a dyke

    There is a technique for putting in a drain in saturated sands. Go to a search engine such as Google.com and input for the search string, "bio-polymer slurry trench". Also, go to inquip.com and geocon.net for more information.
  14. dirtman

    Contractor Doesn't Want to use Water

    Both density and compaction water content affect the engineering properties of the soil being compacted. If the soil in this project were being compacted for a clay liner, even though it met density, it would not meet permeability because of the poor structure that results from compaction at...
  15. dirtman

    Spillway filter design

    I am in complete agreement with the Ohio agency. There is absolutely no justification to allow the use of geotextiles in a critical application where there is limited access to the installation for potential repair work. Granular filters in this situation would only be marginally more...
  16. dirtman

    Hand vane shear strength vs hand penetrometer

    A hand penetrometer is an extremely poor piece of equipment. I personally would never use one, but would instead use a pocket torvane apparaatus for measuring the undrained saturated strength of a clay soil.
  17. dirtman

    Spillway filter design

    The NRCS criteria for filter design together with step by step examples is given at the following URL: http://www.ftw.nrcs.usda.gov/neh26.html
  18. dirtman

    Effective strees analyses in slope stability applications

    The problem with analyzing slopes with zero cohesion in an effective stress analysis is that the critical failure will always be an arc with a very shallow, high radius shape. This is in effect the safety factor you will get from an infinite slope analyses simply using equations for that...
  19. dirtman

    Accurate SPT counts with upward seepage gradients

    In my experience, it is best to have drilling mud in the hole when performing SPT testing. Danny McCook
  20. dirtman

    TEST TO DETERMINATE COLLAPSE POTENTIAL

    There is an ASTM Standard Test method for this evaluation. Refer to Volume 4.08 or 4.09. Also, see the Bureau of Reclamation book Design of Small Dams. It has a chart relating the ratio of insitu dry density to the Standard Proctor dry density and the difference between optimum water content...

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