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  1. Erdbau

    Levee Stability - Riverside or Landside Excavation

    An excavation on the landside is risky. During a flood, the clay acts as a confining layer, because it has lower permeability than the sand. The water wants to punch through the clay, i.e. there is an uplift gradient on the base of the clay layer. The resistance of the clay layer to this...
  2. Erdbau

    Triaxial CU test why we apply horizontal and not vertical

    You are mistaken. The water pressure in the chamber acts equally in all directions (radially and vertically). It acts on the top and bottom caps just the same as it does on the sides of the sample. Consolidation is not just a "vertical thing"; it's horizontal as well. When you consolidate...
  3. Erdbau

    Water Flow through a Vertical Column

    So total head at the top of the cylinder is 30cm. No headloss from top of water to top of soil, so total head at top of soil = 30 cm. Elevation head = 20 cm, pressure head = 10 cm. Total head drops from 30 cm to 0 cm over 20 cm of soil, so the gradient = i = delta H / L = 30 cm /20 cm = 1.5...
  4. Erdbau

    Water Flow through a Vertical Column

    Is water flowing through the column? If water is NOT flowing through the column, then YES, the total head is the same at all elevations. Total head = Elevation head + Pressure head. At El. 0m, Pressure head = 30m, Total head = 0 + 30 = 30m. At El. 15m, Pressure head = 15m, Total head = 15 +...
  5. Erdbau

    Odometer on a soil sample (clay)

    1. Typically you will load in increments that double the previous load, and unload in increments of 4, so a typical load sequence would be 10, 20, 40, 80, 160, 320, 640, 1280, 320, 80, 20, 10 kPa. At a minimum you would want to get at least 2 loads past the preconsolidation pressure so you...
  6. Erdbau

    Odometer on a soil sample (clay)

    1. Hard to say without looking at the curve and the beginning and ending loads. If you are unsure, you have the budget, and it's critical enough, then yes, you may want to consider a retest. What I mean by envelope is to bound your stresses. If you are loading to X kPa, you want to load it...
  7. Erdbau

    Odometer on a soil sample (clay)

    Holtz and Kovacs has a great discussion on consolidation. There are other great texts as well. As for your questions: 1. If you reach virgin compression (past the preconsolidation pressure) in the test, you would probably be OK from a magnitude of settlement perspective, maybe less so on the...
  8. Erdbau

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

    Soils from the same geologic origin and mineralogy will generally plot in a straight line on a plasticity chart (LL vs PI). Often the line is roughly parallel to the A-Line (dividing line between silt and clay). You can probably make your own correlation for your local soils, but using data...
  9. Erdbau

    Need Clarification

    8H seems in the right ballpark of an inverted triangular pressure distribution (8H psf at the top, 0 at the bottom) that is added to the EFP, coming from a Mononobe-Okabe solution for earthquake pressure. You are right, the pressure should be greater for a non-yielding wall. I believe AASHTO...
  10. Erdbau

    Information on Thrustblocks required

    Search for raker heel blocks or raker footings instead.
  11. Erdbau

    piezometer installation

    I would add that this is very normal to do.
  12. Erdbau

    Particle size distribution

    Can you use less soil in the cylinder and still be within the weight ranges prescribed in the method? That's the first place to start.
  13. Erdbau

    The Future of CADD Drafters

    Two stories similar to jgailla: 1. I was in a rush and in on markup drew a bunch of freehand lines seemed to me to be pretty straight, and in context of the drawing were obviously (even to a drafter) supposed to be straight. I got the drawing back with wavy lines. I went back to the drafter...
  14. Erdbau

    Getting Beat by Low Proposals

    I suggest some introspection, and thinking about what kind of clients and jobs you are pursuing, and what value you add over the "other guy". If the work you are pursuing is amendable to the cookie-cutter methods the other guy is using, then are the projects technically challenging enough to...
  15. Erdbau

    Initial conditions for triaxial test

    Correction to last sentence of first paragraph: If the piston IS attached to the top platen, then you are actually putting the sample into tension.
  16. Erdbau

    Initial conditions for triaxial test

    If the piston is physically attached (screwed in) to the top platen, you need to apply a vertical compensation load equal to the cell pressure times the area of the piston. You need to do this because the cell pressure pushes up on the piston, trying to blow it out of its bearing. If it is not...
  17. Erdbau

    LIFT OFF TESTS

    Load the anchor past liftoff, slip a short piece of wire between the nut and the bearing plate, lower the pressure back to alignment load, and then pump up again. Read the pressure gage value at the instant the piece of wire falls out (the nut lifts off the bearing plate, causing the wire to...
  18. Erdbau

    Volume of uncompacted soil material

    I don't know. This all depends on how you said you were going to pay him. If the contract says that you were going to pay him for excavation by BANK CUBIC METER (the volume of soil in the ground before it was excavated), then you should only pay him for 78,000 m^3. If the contract says you...
  19. Erdbau

    Volume of uncompacted soil material

    Exactly, Civilman. Swell factor a.k.a bulking factor.
  20. Erdbau

    Volume of uncompacted soil material

    I think you are looking for the bulking factor. Quick google search turned this up: http://www.engineeringtoolbox.com/soil-rock-bulking-factor-d_1557.html

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