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  1. FixedEarth

    How Do Residential Basement Walls Stand?

    A bit of cohesion in the soil, some wall jogs, and less than 8 ft backfill height works in many cases. But when the temperature drops 30 Deg., or you backfill with soft cohesive soils or you have no wall jogs, then the stem wall will crack. It is a chance many spec. builders take...
  2. FixedEarth

    Embedded Retaining Wall - Method of design

    See attached. http://www.soilstructure.com/http://files.engineering.com/getfile.aspx?folder=05b02a6e-f018-4534-b452-d5e3cca654c8&file=Cantilever_Pile_in_CLAY.jpg
  3. FixedEarth

    Retaining wall and a pool

    In the past, we have recommended crushable material between the retaining wall and the pool. This way, when the wall deflects, it doesn't push on the pool. http://www.soilstructure.com/
  4. FixedEarth

    Limit on Passive Pressure

    If we are using the Net earth pressure method distribution on a cantilever pile, approx. 0.7H distance below base of excavation is the point of zero deflection. At this this point, the Passive resistance zone ends and the triangular net earth pressure jogs back to the Active zone. Therefore, we...
  5. FixedEarth

    Earth Pressure Competition

    The first equation looks good to me. As far as reality, there is a lot of approximations to Ka, Ko and Kp. As you go down the wall height, friction angle can change. Also you go along the wall length, soils parameters can also change. http://www.soilstructure.com/
  6. FixedEarth

    Rectangular Concrete Tank: Stability Forces

    A cross section will help clarify your case. http://www.soilstructure.com/
  7. FixedEarth

    Earth Pressure Competition

    This is friendly competition on how to calculate the at rest earth pressure coefficient for a given wall/soil scenario. Details are shown on the link below. Ends in couple of weeks. https://www.hightail.com/download/bXBaOU1Uayt0QTNSc01UQw http://www.soilstructure.com/
  8. FixedEarth

    Retaining Wall

    Over the design life of the retaining wall, the rock face may topple or move forward increasing the backfill earth pressure. So we can't rely on the active earth pressure just caused by the gravel. Talk with the soils engineer and the geologist. Some of these rock formations have out of plane...
  9. FixedEarth

    Use of active earth pressure for retaining wall design.

    Near the corners it can be argued that the earth pressure is at rest. That is possible, however, cantilever retaining walls designed for active earth pressure with eccentricity in the middle third and where the allowable bearing capacities are not exceeded, can withstand the at rest earth...
  10. FixedEarth

    Is there a way to estimate Coefficient Friction without testing?

    We normally use 0.67*Tan(Phi) for sliding friction coefficient. http://www.soilstructure.com/
  11. FixedEarth

    Partial depth pile reinforcement

    In addition to wannabeSE comments, if the pier length to diameter ratio is 10 or less, we recommend full length reinforcement. For piers with L/D > 10, we suggest you perform lateral foundation analysis and determine point of zero moment and that is a reasonable place to stop the drilled pier...
  12. FixedEarth

    Passive Pressure and Shallow Octagon Foundation

    In addition to soil consistency, we need to know proximity to descending slope, compressibility & allowable bearing capacity for the 10 ft or so beneath the foundation. The wind design & seismic codes have changed drastically since the 60's and this could be the reason why you have...
  13. FixedEarth

    Cant Retaining Wall - neglect bearing pressure at heel

    There seems to be three camps on this issue. Some designers take all the upward heel pressure in to consideration, some use 40% to 70% of that value and some ignore the entire upward heel bearing pressure. Same thing on the RetWall chapters in most RC books. When we make software, we don't know...
  14. FixedEarth

    Lateral Force on Pile

    GeoBo- Not sure if we can close the 200% or so gap that exists between us, but I will give a last try. I did a third check using Teng's method of granular soils and came up with 630 kN-m max. moment (see attached). So it seems that 400 to 600 kN-m is what I have found and you are around 1100...
  15. FixedEarth

    Lateral Force on Pile

    avscorreia- I also did simple analysis to double check my earlier rsults. If you convert the round section to an equivalent square pile and assume uniform lateral spring of SAND and then rotate the pile 90 degrees so that it becomes a beam on elastic foundation problem, we get rough values...
  16. FixedEarth

    Lateral Force on Pile

    GeoBo- You said "More importantly, it depends on the soil stiffness around the pile" - in my experience, you can vary the lateral subgrade modulus by 300% and you will see little effect on induced shear, moment & deflection. You also said "especially the top 10 m thick loose sand layer for...
  17. FixedEarth

    Lateral Force on Pile

    A 1200 to 1400 kN-m maximum moment seems high considering shear force is only 416 kN. Something is off. http://www.soilstructure.com/
  18. FixedEarth

    Reporting lateral capacities of piles

    You will have to get the tea today! For steel piles, filled with concrete or driven hollow with a soil plug, just do lateral load analysis using service level V and service level M. Then take your Mmax and factor that by 1.6 and call it Mu. Similarly take your vmax and factor it by 1.2 or 1.6...
  19. FixedEarth

    Reporting lateral capacities of piles

    My error. In that case, just calculate the moment due to the eccentricity and see your Max. moment induced to the pier, usually at 2B to 3B below the soil surface. The magnitude of Mmax a given pier can handle depends mostly on its pier diameter, f'c, stronger upper soil presence and pier...
  20. FixedEarth

    Reporting lateral capacities of piles

    Ok-The B/8 limit for shear load eccentricity is something I picked up a while ago from a source. If I find that book title, I will gladly post its here. What happens is when you have a shear load that is off center, it creates a torsional moment which is less favorable than a bending moment. The...

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