High Density Polyethylene Shear Strength

[jimbo2]

I am working on the design of a telescoping manhole comprised of alternating 42" and 48" HDPE pipe. This manhole is to be placed to a depth of over 150 feet in a solid waste landfill. Due to settlement of the waste and the resulting down drag on the pipe system, I will have to allow for the individual pipe sections to telescope longitudinally along the vertical axis. Initially the pipe will be held in place using support rings and (I think 3/4&quotshear pins comprised of HDPE rod. To design the shear pins and support rings I need to know the shear strength of the HDPE rod material. All I have found on the rod I am thinking of specifying (from McMaster-Carr)is tensile strength at 2600 psi and impact strength of 0.4 ft-lbs/in. McMaster Carr has not returned my e-mail request for data; however, I did find a data sheet that gives me the shear strength of PE lumber at 1950 psi. Does anyone know where I can find data on the shear strength of HDPE rod?

 

[Peru]

Jimbo 2

You're not going to get much info out of McMaster Carr. They are sales people so even if they had the info in front of them they wouldn't know what they were looking at.

Try this website for the info...

http://www.matweb.com

Good luck!

 

[boscolee]

jimbo2

I am designing something very similar using 36 inch nomial ID HDPE pipe as a riser for the manhole buried at the base of the landfill 60 feet below grade. I am not sure about the function of your shear ring construction. However, we are using a different type of design to support the pipes using steel bolts which is much stronger.

 

[jimbo2]

I'm not clear on the function of your steel bolts. The telescoping design is meant to relieve the significant axial stress that would develop in the pipe wall due to downdrag, by allowing the alternating sized pipe system to shorten along it's length as the waste settles and degrades. We use thick wall alternating 42" and 48" ID controlled HDPE pipe, and in the final design we went with nylon shear pins to get around the variability of HDPE properties in service. The shear pins are used to fasten support/wipe rings on the outside wall near either end of the 42" ID HDPE pipe, which in turn support that 42" pipe above a lower 48", and support the overlying 48" pipe. The shear pins are designed to break at a combined axial load of about 2 to 3 tons to make sure the telescoping action begins relatively quickly. We have since installed this design in the landfill as a retrofit to a failed (due to poor installation/operational practices) telescoping system, and it is working well.