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  1. LRJ

    Drillability assessment questions

    I've been looking at several drilling rate of penetration (ROP) models and noticed that many of them have empirical factors which are undefined in the original publications. This includes Maurer (1962), Galle and Woods (1963), D-exponent (Bingham; Jorden and Shirley; Rehm and McClendon)...
  2. LRJ

    Non-destructive confirmation of bored pile capacity

    I'm involved in a project where the client plans on installing bored piles. These have been designed according to the relevant standards for the area they will be installed in, but there is some suggestion that these capacities should be confirmed post-construction. Some static pile load...
  3. LRJ

    Moisture content of coal

    I understand that the moisture content of coal is normalised by the wet weight of the material as opposed to the dry weight (dry weight is used to normalise for soils). What is the basis for this? I understand it has something to do with volume change.
  4. LRJ

    Suction from lifting drilling tools

    I understand that lifting tools from an open drillhole on the seafloor can be critical for hole stability due to the suction that results from lifting these tools. My question is: what methods exist for predicting the magnitude of this suction?
  5. LRJ

    Offshore grouting

    Something I've always wondered is how the water content of offshore cement grouting is specified. Surely the grout is surrounded by water, so there is relatively little control regarding the mix? Are there any references for this? I'm guessing the cement can only take so much water in the...
  6. LRJ

    Typical offshore drilling rates

    I'm wondering if anyone has information on typical offshore drilling times considering different soil/rock conditions and well diameters? In addition, I wondered what the typical timescale for grouting of conductor wells was? If anyone has personal experience they can share or publications they...
  7. LRJ

    Borehole stability/hydrofracture in rock

    I was wondering if anyone knew of a calculation procedure to predict the pressure at which borehole stability can be ensured and/or hydraulic fracture would be initiated in a borehole in rock? The aim would be to determine the allowable pressure range during the drilling construction stage of a...
  8. LRJ

    Wellhead growth

    Does anyone know of any methods for calculating the axial displacement at a conductor (pile) head due to thermal expansion? This is also known as wellhead growth. The thermal expansion results from operating conditions where there is a large temperature range which causes expansion of the...
  9. LRJ

    Calculate lateral deformation beneath embankment

    Does anyone know of a simple (e.g. elastic) method to calculate the lateral deformation beneath an embankment which is caused by the (vertical) embankment load? A really simple approach might just be to relate vertical settlement to radial movement using Poisson's ratio, but this seems far too...
  10. LRJ

    Communicate with .exe via VBA

    I've seen very mixed comments elsewhere regarding the ability to communicate with a .exe file via VBA. It seems that one can use sendkeys (unreliably) to communicate with other Microsoft software (e.g. word), though communicating to engineering software .exe files does not seem possible. Has...
  11. LRJ

    Consolidation settlement of piles/caissons

    I was wondering whether anyone knew of a good method to calculate the settlement of piles and/or caissons, specifically the long-term primary and secondary consolidation. I've created something in spreadsheet format using basic consolidation theory as a start and essentially reducing the load...
  12. LRJ

    Pile tip torsional capacity

    I was reading a paper which stated the pile tip torsional capacity was as follows: Tt = π.(D/2)2.L.γ.(D/3).tan(δ) Where: Tt = Pile tip torsional capacity π = pi (3.14...) D = Pile diameter L = Pile length γ = Material unit weight (concrete in the example) δ = Interface friction angle at pile...
  13. LRJ

    Script to perform Gaussian elimination with back substitution for 6DOF model

    I was wondering whether anyone had an existing VBA subroutine/function which can perform Gaussian elimination with back-substitution for a 6DOF model (i.e. contains a 6 x 6 stiffness matrix)?
  14. LRJ

    Stress ratio of normally consolidated clay

    Hi all, Typically the stress ratio (su/σ'v0) for normally consolidated clay is taken in the range of 0.25 to 0.35ish. For several sites where there is no geological explanation for underconsolidation, I have seen ratios as low as 0.20 or even 0.15. The value of stress ratio is dependent on the...
  15. LRJ

    Eigenvalue/frequency benchmarking

    Hi, I'm looking to implement eigenvalue and eigenfrequency analyses to my own FE code (1D analysis of laterally loaded pile), and was wondering if anyone knew of: 1) Some good references which can aid in implementing the above analyses in my code (I have a few references, but maybe there are...
  16. LRJ

    Incorporating moment-rotation springs to 1D FEA

    Does anyone know how to include moment-rotation springs into a 1D FEA model, or know of a reference which explains this? I've got my own program to model a laterally loaded pile with p-y springs, but now I want to incorporate M-θ springs and was wondering how to implement them. Specifically, the...
  17. LRJ

    Viscous damping

    I'm trying to teach myself a bit more about viscous damping and I had some questions. I've found a number of references stating that the damping matrix, |C|, is: |C| = a0 |M| + a1 |K| Where: a0 = 4πζ/(T1 + T2) a1 = T1*T2*ζ/π*(T1 + T2) And where: T1 = Period of oscillation of a target mode...
  18. LRJ

    Finite difference and finite element analysis of beam-columns

    I appreciate that the finite element method (FEM) has considerable advantages over the finite difference method (FDM) when analysing 2D and 3D problems. However, for 1D beam-column problems I am not aware of any publications considering or comparing the differences between the methods. What are...
  19. LRJ

    Moment distribution

    A few times I have encountered the problem of a structure, rectangular in plan view, which is supported at its four corners by piles (I guess from a conceptual level they could be columns instead). If V-Hx-Hy-Mx-My-T loading is given at the centre of the rectangular structure, how would you go...
  20. LRJ

    1D FEA of laterally loaded pile: inclusion of moving soil

    Hi, I've got a 1D finite element beam-column model working which I use to analyse laterally loaded piles. The only thing left that I want to implement is a way to model moving soil, e.g. from landslides. The usual way to do this is by including so-called 'y-shifts' in the model. My...

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