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Recent content by SixDegrees

  1. SixDegrees

    Plaxis large stiffness difference between layers

    Afro, You could try inserting an interface between the material which have large contrasts in stiffness. This will allow some relative displacement between the materials and confine the local shear failure to the interface rather than distributing it through the elements. Martin
  2. SixDegrees

    geogrid in soil using Abaqus 6.13

    Hi, I'm not sure of the details of interface elements in Abaqus, but I have modeled the pullout of geogrids using Plaxis. In plaxis the geogrid is modeled as a continuous element (i.e. doesn't model the gaps between the grids), so there is an geogrid/soil interface above and below the...
  3. SixDegrees

    flac2d

    Hi geoBrendan, There's a couple of ways that you can manipulate the FLAC grid to get the mesh geometry. 1. Try generating the mesh using the x,y coordinates if the bottom, left, top and right of the layers you need. FLAC actually has a virtual builder to help with this 2. You can also change...
  4. SixDegrees

    Limiting Value of Peak Particle Velocity for Buried Pipes

    I searched the threads for information on limiting values of PPV for buried pipes and only found references to criteria for buildings, plaster, concrete foundations etc... I need references for construction vibration effects on buried pipelines. I know for buried structures like tunnels we...
  5. SixDegrees

    UU triaxial test interpretation - sample not failed

    Could this be from capillary pressure? The water pressure at 130 m is 1274 KPa, which is on the same order of magnitude was what your measuring from strengths. Perhaps the pore pressure in your test starts out as -1274 KPa (or less depending on how much time has passed to allow drainage). Just a...
  6. SixDegrees

    Undrained or drained condition

    Both is always a good idea, but generally for a loading condition the undrained strength will govern, because clays generally gains strength with consolidation. The live loading will be undrained.
  7. SixDegrees

    Removal of Silty Soil

    You also need to consider the depth of the the foundation walls, drainage, and frost penetration, and as Ron pointed out settlements if this layer is compressible and loaded. A Glacial Till can have 20% fines and is a perfectly suitable bearing layer for a three story house.
  8. SixDegrees

    Timber Retaining Wall with Deadman

    The sketch looks fine. My only comment is that the deadman approach does not seem to be compatible with a wall face that has no bending stiffness. There needs to be horizontal equilibrium of forces and moment equilibrium. And the wall face needs to be able to transmit shear and bending these...
  9. SixDegrees

    Modelling of a sheet pile wall in Plaxis

    It all depends on what you're using Plaxis )or any finite element program for). If all you're interested in is stability you can get a lot more information out of a finite element analysis using the mohr-Coloumb criteria than you can get from a slope stability, toppling or basal heave analysis...
  10. SixDegrees

    Minimum factor of safety

    I agree with you that the contours should not indicate a minimum factor of safety has been found. For a simple slope, with constant radius surfaces the statement may make sense. But how do you plot contours for differing radius from the same center, or for that matter contours for block...
  11. SixDegrees

    Modelling of a sheet pile wall in Plaxis

    I always use Plaxis Ko computation for initial stresses. You're correct if the problem is not fully horizontal then the resulting stresses will not be in equilibrium. For this condition I always follow up the initial stresses computation with a "Null" step (finite element computation for...
  12. SixDegrees

    Walkout Basement Question

    I'm sure you can do that. My house is built into a hillside like that. You still need to take the downhill side down below frost line and as deep as the local building codes specify. and be sure to build a really good drainage system on the uphill side. If you're worried about out of balance...
  13. SixDegrees

    Modeling of Reinforced Concrete / Concrete in Stability Analysis

    In slope stability I'd model the concrete using self weight and shear strength of the concrete. The shear strength of un-reinforced concrete is about Sqrt(Compressive Strength). I'd run the analysis with and without the shear strength of the concrete (but use the weight).
  14. SixDegrees

    Proctor test on coarse aggregates

    The relevant parameter to compute maximum density is void ratio, which is a measure of the amount of voids in the soil. The specific gravity is a constant and does not change with compaction. Dry Density = (GammaWater * Specific Gravity)/(1+Void Ratio). Therefore your X=GammaWater (62.4 pcf)...
  15. SixDegrees

    Piles under horizontal load into bedrock

    I agree with dcarr, will be way too conservative to ignore the contribution of 6 m. of soil. Consider using a program like LPILE which will take into account the bedrock,overburden and caisson stiffness. The analysis will give you the deflection and bending moment in the caissons. You could also...
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