Soil - Virtual Anchor Length

Hi

I am modelling a DN900 undergriund HDPE pipeline.

When calculating Virtual Anchor Lengths I am getting La value less than 3xLb. Is it possible?

I am guessing it's because the E is low for HDPE compared to Steel.

If that's the case how should I assign the spacings in Zone 2?


Some numbers:

Pipe: DN900 HDPE 81.4mm thick
Pressure = 800 kPa

Temperature= 5 to 25 deg C

Soil - Stiff Sandy Clay
Ultimate longitudinal soil resistance, P1= 105,000 N/m
Transversr stiffness, K = 184 

Lb = 1300 mm
La = 3000 mm 



  • Greetings, 

    As mentioned in AutoPIPE help:

    Thus, three basic zones of pipe-soil interaction can be identified.

    Zone 1, nearest the bend, is the area of high bending effects which produce the major lateral displacement of the pipe.

    Zone 2 is a transition region where bending effects have reduced to small levels, and as the distance from the bend increases they go to zero, leaving only axial effects.

    Zone 3 is the region where the pipe and soil displace identically (the pipe is effectively, or virtually anchored in the soil).

    As you can see a rough estimate on calculating La and Lb are based on pipe diameters.  On average, LA should be about 120x longer than Lb. 

    Please provide screen shot of your Virtual Anchor Length dialog and also screen shot of related pipe identifier. for review. 

    Did you change pipe sizes between Zones 1 to Zone 3?

     Regards,
    Mike Dattilio
    Design Analysis Engineering Group
    Senior Analyst Bentley Systems Inc
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