CQA test frequency for geomembranes and geocomposites

October 7, 2009  |  Q&A: GMA Techline

From the GMA Techline Subject: CQA test frequency for geomembranes and geocomposites I have comments from a state agency concerning CQA test frequencies and field tests conducted on geocomposites. The questions I have are: What are the typical frequencies used for CQA testing of geomembranes and geo…
HDPE welding

October 7, 2009  |  Q&A: GMA Techline

From the GMA Techline Subject: HDPE welding [We are] seeking information that would assist on welding 60-mil white HDPE above 104°F. We have successfully demonstrated in the past with destructive and nondestructive testing welds that would exceed project specifications. We are currently on a lar…
Installing prefabricated vertical drains

October 7, 2009  |  Q&A: GMA Techline

From the GMA Techline Subject: Geocomposite question We are looking into installing prefabricated vertical drains to relieve excess pore water pressure for a surcharge fill. Following the information listed in Designing with Geosynthetics, 5th Edition, the statement 1-2 meters is the typical spacing…
GSI/GRI-GG5 and ASTM D6706

October 7, 2009  |  News, Q&A: GMA Techline

GMA techline answers from Bob Koerner Subject: GG5 I referenced GSI/GRI–GG5 on a segmented retaining wall system spec and need to know if this is correct. Supposedly on your website this standard was crossed out and noted to refer to ASTM D6706. Should I replace GG5 with the ASTM standard? Ple…
The difference between strength parameters

June 1, 2009  |  News, Q&A: GMA Techline

By Timothy D. Stark Q: What is the difference between the strength parameters c and ø, and a and δ? A: Good question because these parameters are frequently used interchangeably. c and ø, and a and δ are shear strength parameters used to represent the strength/failure envel…
Maximum slope angle for geosynthetic-lined slopes

June 1, 2009  |  Q&A: GMA Techline

By Timothy D. Stark Q: Is there a maximum slope angle for geosynthetic-lined slopes? A: Yes there is, and the slope angle should not exceed the lowest geosynthetic interface friction angle, δ, of the system. The slope angle should not exceed δ because this condition can/will lead to tens…
Geomembranes and reservoirs

June 1, 2009  |  Q&A: GMA Techline

By Timothy D. Stark Q: Is it possible to cover an entire reservoir with a geomembrane? In addition, is it possible to line an entire reservoir or lake with a geomembrane? A: The answer is yes to both questions. Geomembranes are frequently used to cover reservoirs, especially in California (USA) for …
Testing seams

April 1, 2009  |  Q&A: GMA Techline

From the GMA Techline Subject: Testing — What methods are available to test seams on HDPE and EPDM to ensure quality of joins in the field that should be part of the installation quality assurance? (Masson, New Zealand) Reply: You ask an interesting question in that HDPE is a thermoplastic pol…
Comparing warp and fill

April 1, 2009  |  Q&A: GMA Techline

From the GMA Techline Subject: Warp and fill — What do the terms warp and fill mean with regard to tear strength of a polypropylene liner? (Michael, Alaska) Reply: You ask a fair question that has a simple and difficult answer to it. The simple one is that the polypropylene membrane you are us…
Comparing specs

April 1, 2009  |  News, Q&A: GMA Techline

GMA techline answers from Bob Koerner Subject: Comparing specs — I want to know how can I compare specification values of ASTM with ISO?? I sell products tested with ASTM methods, but some clients give me an ISO specification. I want to know which product fits their requirements. (Claudia, Mex…