Geotextile selection

[peterb1441]

I need some ideas on the selection of a geotextile for specific purposes. We have oil and gas pipelines crossing active faults, and the pipelines will be buried, contrary to advice to put them above ground, but that's another topic. The trench bottom will be lined with a granular layer, then a geotextile. The trench backfill will be expanded clay/shale, which will allow the pipes to flex during a seismic event. It is important to prevent any contamination getting into the lightweight fill, and so the geotextile should only allow water through. Many of the fault crossings are areas of high groundwater.

 

[GeoPaveTraffic]

I don't understand what you are trying to accomplish with the geotextile. Are you trying to let water through but stop oil and gas in the event of a leak? or are you trying to allow water to pass but not allow any of the expanded clay/shale to pass?

 

[LHA]

You probably want more detail on permeability, etc., but here's a good general guide to Class for a start. If table is mis-aligned, copy and paste into .doc or .txt, and it should line back up

AASHTO Specs - Table 1

Table 1 lists the M288-96 default geotextile class and design class for the subsurface drainage, permanent erosion control, separation and stabilization applications.

TABLE 1. DEFAULT GEOTEXTILE CLASSES FOR M288-96

Application Class Default Class Design
Subsurface Drainage Class 2 Class 3
Permanent Erosion Control Class 2 for woven monofilaments Class 2
Class 1 for all others
Separation Class 2 Class 3
Stabilization Class 1 Class 2 or 3


Engineering is the practice of the art of science - Steve

 

[Tippys]

Sounds to me like you need a filter fabric - try a needle punched fabric. The pore size is dependent on the gradation of the surrounding soil.

 

[civilperson]

Use a filter fabric with exterior layers of fine sand/small gravel acting as a filter blanket to prevent premature clogging of the fabric with fines.