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  1. rochplayer

    Determination of the strength gain of soft soils due to consolidation.

    Make sure you do not apply the strength increase due to increased overburden (Su/P ratio) incorrectly. The stress increase varies across the embankment, from the greatest under the center of the embankment to effectively zero at the toe. One big lesson learned from the levee embankment...
  2. rochplayer

    Piles not imposing stress/load on surrounding soil

    It sounds more like isolation casings to me. Basically a double casing - an interior casing filled with concrete and rebar that takes the load from the structure and an exterior casing that is larger providing 3 or so inches clear space to allow pile lateral movement, or less if only axial...
  3. rochplayer

    pseudo-static coefficient

    wshi, The 1.18 is the soil amplification factor. It is used to take the peak bedrock acceleration (PBA) to peak ground acceleration (PGA) and is used to account for site soil amplification. The PBA in Everett is 0.3. The PGA is 0.354. PS. I am part of the I-5 Everett HOV project D/B team.
  4. rochplayer

    When to use T-99 or T-180 Comp Spec?

    The difference between T99 and T180 is compactive energy applied to the soil, applies to both fine and coarse grained soils. T99 was developed when equipment was smaller and lighter. T180 was developed to better model the energy input by more modern compactive equipment. Specifying T180...
  5. rochplayer

    effect of fill on existing pile capacity

    Where are the clay layers? How thick are they? How compressible are they? How much settlement relative to the piles do you expect? 1/4 inch or more of soil settlement relative to pile is thought to be enough to mobilize negative skin friction on a pile. Your net ultimate pile capacity can be...
  6. rochplayer

    Residential Foundation Problems

    RobPE, Map the cracks both inside the house and look for cracks in the street pavement between the house the water well. If they run perpendicular to the radial distance from the municipal well, your client may have a claim against the city that may provide funds for foundation repair, BUT...
  7. rochplayer

    Residential Foundation Problems

    What has the weather been like in the past two years? Do their gutters still work? Has the landscaping changed? Did they plant new flowers/shrubs/roses/etc. near the house and have they been watering them more regularly? Was grading or other construction been done upgradient of the home...
  8. rochplayer

    Bearing Pressure for MSE walls?

    What we prefer to give is a table of allowable capacity (or factored resistance) versus Bmod (Bmod = B - 2e). Since bearing and settlement is foundation width dependent, the MSE wall load is eccentric, and the wall vendor will calculate the eccentricity, it has worked well to provide them Bmod...
  9. rochplayer

    Footings for small cabin re:frost heave

    jike, I agree - bring in the fill, rather than dig down the entire 4-ft. Sorry I was not clearer about building the pad.
  10. rochplayer

    Footings for small cabin re:frost heave

    4-ft is not all that much, relatively speaking. BTW, the frost depth is deeper on streets, not due to traffic, but due to them being kept clear of snow, which is an insulating layer. For the insulating board, the heated/unheated application depends on where you place it. If frost depth is...
  11. rochplayer

    Footings for small cabin re:frost heave

    For frost heave to occur, three things are needed - 1. Freezing temperatures, 2. Water source, 3. Frost susceptible soil. Take away any one of the three, no frost heave occurs. I assume all three are present at your building site. Frost heave is going to be a problem. What is the frost depth...
  12. rochplayer

    10 m High Embankment on Soft Clay+Stone Columns

    Another option is to use geogrid as base reinforcement to tie the roadway fill together and prevent slope failure as the fill is brought up. Tensar geogrids have been used very successfuly to build high embankments over thick peat deposits.
  13. rochplayer

    10 m High Embankment on Soft Clay+Stone Columns

    We performed a similar embankment construction program as outlined by BigH. Our site had 8 m of N5-10 ML-CL with fibrous peat layers up to 1.5 m thick, underlain by 8 m of N = 25 to 50 ML-CL, underlain by 30+ m of N = 0 to 2 ML/ML-CL. Very interesting geology. Embankment widths were 100 m...
  14. rochplayer

    Geofoam at SRW reinforced zone

    It looks like our posts crossed - what is the driving force in the seismic case? There will be virtually no intertial force in the geofoam mass. The 2:1 backfill is like a 2:1 batter so Ka will be very low and delta Kae non-existant. It sounds to me like by going with geofoam the seismic...
  15. rochplayer

    Geofoam at SRW reinforced zone

    MSEdesigns: In my experience, Geofoam is an extremely expensive (>$125 per cubic yard) option which could be eliminated by use of ground improvment methods. Some questions to ask your geotechnical engineer - 1. What is their allowable design based on? Settlement or ultimate capacity/SF? 2...
  16. rochplayer

    Geofoam at SRW reinforced zone

    We evaluated a wall using Geofoam to reduce the stress over a culvert for a highway widening. Basically, the geofoam became part of the facing and the reinforcing wasn't counted until it was within the soil. It made for very long reinforcing. Geogrid gets only a small part of its strength...
  17. rochplayer

    Structure over MSE Wall

    I have used MSE walls to support shallow foundations for bridges in high seismic areas (Alaska and Oregon). Bearing pressure was limited to 4000 psf and "inextensible" MSE wall reinforcing was used (e.g. steel). I have also designed MSE walls with inclusions (e.g. piling), but usually these...
  18. rochplayer

    LRFD Design for Geotechnical Projects

    I think one of the issues I have with LRFD/ASD and geotechnics in general is the issue of conservatism heaped upon conservatism. Do not misunderstand - conservatism is wonderful, but a problem with moving to LRFD from ASD can be best illustrated as follows: Suppose I am designing a bridge. I...
  19. rochplayer

    Bored-In-Pile In Artesian Condition

    BigHarvey We have had the same issue with polymer slurries (excessive loss into the formation), so generally it drives us to temporary casing the if the loss becomes unacceptable. Mineral slurries are falling out of favor here both due to performance concerns (caking, which I agree can be...
  20. rochplayer

    Bored-In-Pile In Artesian Condition

    It sounds like you are using standard construction practice. Concrete and soil bond should be good.

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