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Thanks for your help BigH. Page 54 of Poulos gives the formulae as you say: I[σ]z = 1/(2[π])*[arctan(m*n/sqrt(m²+n²+1)) + {m*n/sqrt(m²+n²+1)}*{1/(1+m²) + 1/(1+n²)}] where I[σ]z = influence coefficient m = B/z n = L/z B = half breadth of foundation L = half...

Has anyone got equations that can be used to represent Fadum's chart for influence values to determine settlement? Fadum R E Influence values for vertical stresses in a semi-infinite solid due to surface loads - School of engineering Harvard university (1941).

I must agree with jdmm. Leave it to soils engineers. Soils are not manufactured materials like steel or aluminum. Their properties vary a lot both vertically and horizontally. When you apply oscillating loads to them, such as from wind turbines, their properties change over time. Refer to...

I would say it is a nicety but it has some basis in stress analysis. If you line up with a pair of bolts straddling the CL, then any moment applied due to gravity will be spread between them both. If one bolt is on CL, then it may take all the force by itself and yield. Then loads would be...

You need to use better wave theories than Airy (linear). Try Dean's stream functions or even Cnoidal theory. But nothing models breaking waves very well. The Ursell number helps select the appropriate theory.

I don't think that the internal carcass is anything more than a support for the pressure liner. It is needed for gas lines. The carcass doesn't contribute to hoop strength from internal pressure. Do you really mean the pressure vault which lies between the liner and the armour layers? My...

ASME VIII and PD 5500 use the same basic method to design flanges. However, the former provides the equations whereas BS/PD 5500 gives only the graphs. It is likely that the engineer that wrote your spreadsheet needed to include moments and axial tension effects. You need to select a bolt...

API 605 gives standard sizes from 26in to 60in.

Design and Installations of Marine Pipelines by Blackwell Publishing - M W Braestrup et al. Don't forget to check for external hydropressure causing collapse during installation if you are in deeper water.

To obtain the submerged density it is necessary to use the outside diameter of the concrete and allow for the density of seawater (usually 1.025 t/m³) and also for the weight of the contents. I am a bit puzzled regarding the low weight you achieve with the input parameters. From what you...

Has anyone got an equation to determine the dynamic (or kinematic) viscosity of seawater? I think there may be one in Riley's Chemical Oceanography Vol 4 developed by Millero, but I haven't got this book.

Dear onrush, You are right in that 5D bends will pass pigs. I agree with DrillerNic on the 'natural' radius. The self-weight is usually enough to hold it in place. By far the greater length of pipelines on land and subsea are laid like this. The few exceptions are where field or...

Thanx DrillerNic, I have lots of info on the pipelines themselves - including the AGA/PRCI software package. But what I really want to know is how the mattresses behave. Are they deemed merely to add weight to the lines? I would have thought that the draped shape would modify the...

Does anyone know of any published papers or methods that I could use to design flexible mattresses to be laid over subsea pipelines? They provide increased stablity against currents and waves but seem primarily to be used for impact protection for short lengths of lines near platforms. These...

Sylvaninhoo is right in saying the coating makes a difference to the endcap force. With impervious insulation coating, it is important to consider the endcap acting over the whole outside diameter. However, the force is only resisted by the steel (at the smaller diameter). However, if the...

Thanks Carl for your help, I have found that one - though it does have a few typos, making me unsure. I also found PRCI/AGA paper Pipeline freespan design Volume 1 Design guideline (Project PR-170-9522) of April 1997, which gives axial resistance. I am still looking for the lateral resistance...

Have you considered archemedian screw pumps? These lift very large volumes with a short head. I have used them for emergency storm water systems.

Has anyone got general formulae for axial/uplift movement of pipelines in soil? Preferably referring to a code. For example, what friction is developed between a pipeline with a known depth of cover and a granular or cohesive soil with known values of friction and cohesion?