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  1. shorebob

    Tension in a cable

    Can anyone provide the formula for the tension generated in a taut horizontal cable under the influence of a vertical load applied at mid-span. I know 'taut' is actually a function of initial installation tension with some resulting sag in the cable based on span and cable weight. I can...
  2. shorebob

    Capacity of doubled wood lagging

    Thanks for the confirmation. The issue here is an extreme soldier beam spacing in 2 bays to clear an U/G 108" existing sewer. The client wants as much clearance as possible so the driller doesn't nick it. Regarding arching, we typically use the 400 psf max. soil load per CalTrans, then add...
  3. shorebob

    Capacity of doubled wood lagging

    Does anyone know of a simple way to calc. the capacity of a double layer of 4x12 lagging in a soldier beam installation? This is a cost issue. Researching 'beam on elastic foundation' leads only to finite element, differential eqn. solutions. There must be a simpler way. Thanks.
  4. shorebob

    Jacking Pit Thrust Block Design

    Sorry. The term 'arching' has skewed the discussion. 'Arching' is actually an active pressure phenom., allowing reduced soil load on, say, lagging between the fixed points of adjacent soldier beams. Here I'm searching opinions as to whether the 'effective width increase' allowed at the toe of...
  5. shorebob

    Jacking Pit Thrust Block Design

    Perhaps my terminology is imprecise. 'Arching' suggests soils' self-supporting tendency between 2 or more fixed points. However, CalTrans' Trenching & Shoring Manual describes a permissable increase in the Effective Width of a soldier beam's toe due to a "..wedge-shaped resisting soil...
  6. shorebob

    Jacking Pit Thrust Block Design

    I read a very informative thread re: thrust blocks in jacking pits, but it has been closed. I'm designing a thrust block in a slide-rail-shored pit in which the lower panels will be raised, and the thrust block will bear horizontally on the soil, developing passive pressure. The transition has...
  7. shorebob

    compaction loading

    For designing soldier beam walls to retain backfill, I usually include an add-on pressure for compactive effort. Is this pressure residual, or, like traffic surchage, is it only present during actual backfill operations? I'm currently using a methodology from the Canadian Foundation Manual...
  8. shorebob

    Open Web Joist alternate support point

    I must provide temporary underpinning support for a group of in-place "K" type OWJ's so their support beam can be replaced. The mfgr. and "model" No. are unknown. Is there a generic alternative support point on these OWJ's that I can use?
  9. shorebob

    soil nail wall

    Are soil nails AS EFFECTIVE when drilled into old concrete slurry fill as when drilled into the weathered bedrock we thought was there ? This is under a structure which must be supported by the soil nail wall. If the concrete/slurry is NOT competent as a foundation mat'l., it'll have a failure...
  10. shorebob

    Active pressure in bedrock + thanks

    First, my deep thanks to all respondants who helped with experiential insight re: wood lagging left in place. The compilation of replies helped turn the tide and, on this job, it will now be permitted. Now, does anyone have a reference for development of active pressure values for bedrock...
  11. shorebob

    wood lagging

    To PEinc. Thanks very much for your comprehensive reply. This mirrors my experience that lagging need not be removed in light of no records of deleterious effects. I'd be curious in what region of the country you've seen untreated lagging used. Here in SoCal it's the standard. To answer...
  12. shorebob

    wood lagging

    As a shoring designer, I'm running into some clients and consultants who won't allow pressure treated (.4 pcf per AWPA guidelines) 3x12 DFir wood lagging to remain in the ground, citing potential voids and resulting soil subsidence. This is particularly problematic when the lagging is used as a...
  13. shorebob

    Sheet Piling (single line) to retain water only

    I cannot find a combined active and passive pressure diagram for a single line of sheet piling driven into a river mudline to retain one-side hydrostatic load, only, above that mudline. They all show retained earth (shoreline bulkhead), even USS Manual and NAVDOCKS. Thanks for any direction...

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