Dear Michael,

I think you should consider figure 2.11 of Koerner's book as an illustration of
a tendancy, much more then a designing support. As you mention yourself, there
are various machinery for sewing or seaming, and various operators, too.

For landfill applications, it is usually recommended to have an independant
laboratory verifying the seams every 100 to 150 meters (i.e. up to 100 or more
verifications per job), which illustrates more practically the variability of
the seaming techniques, with the same operator and machinery.

Other point : if your design period is 75-100 years, what will be the resistance
of the seam at this time ? If you choose to sew your geotextiles, take care of
the nature of the fibers you will use. Some are more resistant than others,
particulary on a long term basis.

In fact, I think you should not assume that it might be possible to reach a 90 %
efficiency as the design value. However, if you find somehow a mean to reach
this value, or if your contractor is 'sure' he can make it, please don't forget
this step in your quality control program !

If I had this job to do, I think I would consider the possibility of laying
something stronger. There are various kind of geotextiles (or geogrids) on the
market with strength (and price, unfortunately) a little higher than what you
need.

Last point : If the stability of your structure is dependant of this seam, maybe
this materials modulus might be of concern, much more than its strength ! Some
non-woven geotextiles can reach very high elongations before starting to
mobilize any strength.

Do not hesitate to contact us if you need any kind of support (we are located
next to Montreal, Qué - see adress below).

--
________________________
Eric Blond
Project Leader / Chargé de projet
________________________________________________
SAGEOS
Geosynthetics Technology Center
Centre des Technologies Géosynthétiques
3000 Rue Boullé
St-Hyacinthe, Québec
J2S 1H9 CANADA
Tel: (450) 771-4608
Fax: (450) 778-3901
E-mail: [log in to unmask]
________________________________________________


"Bleakney, Michael (DOT/STR)" wrote:

> Do any list members have an opinion on whether a 90% seam strength
> efficiency (wide width tensile strength) is an unreasonably high expectation
> for a geotextile with a basic wide width tensile strength of 105 kN/m (600
> lb./in)?  Either sewn or bonded seams would be permitted.
>
> This is for a permanent (75 to 100 years) support for a structure.
>
> I am aware that sewn seam strength efficiency drops off with increasing
> geotextile strength, based on Koerner's Designing With Geosynthetics, 3rd
> edition (1994), Article 2.3.3.4.  It appears from his Figure 2.11 that the
> efficiency decrease becomes quite significant above 1000 lb./in, which is
> above my range.
>
> I do not know whether this is equally true for bonded seams, or if sewing
> techniques have improved lately.
>
> Any thoughts or comments would be appreciated.
>
> Thanks.
>
> Michael R. Bleakney, P. Eng.
> Geotechnical Engineer
> New Brunswick Department of Transportation
> Structures and Materials Branch
> PO Box 6000
> Fredericton, New Brunswick
> CANADA
> E3B 5H1
>
> Tel: (506) 453-2674
> Fax: (506) 457-6714
> Email: [log in to unmask] <mailto:[log in to unmask]>



%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%