1. In-Situ Temperature Monitoring of Liner and Cover Geomembranes in Dry and Wet Landfills* - George Koerner is measuring the in-situ temperature behavior of liner and cover geomembranes and has installed multiple thermocouples for long term measurements in both wet and dry municipal solid waste landfills in Pennsylvania. The project has been extended into its 19th-year and has resulted in an extremely authoritative set of real-life data which is being used by many researchers in their geomembrane lifetime predictions.
2. Field Exposed Lifetime of Geogrids Used at the Facing of Landfill Berms - The facing of mechanically stabilized earth landfill berms (and other walls and slopes as well) is often using a wrap-around configuration leaving the geogrid exposed to the atmosphere. A project being conducted by George Koerner is presently investigating the behavior of two different geogrids and two erosion control materials over time. These four materials are also being exposed on the roof of the GSI carport. A 50-year time frame is envisioned! The long-term behavior will eventually be compared to UV laboratory predicted data as noted previously.
3. Laboratory Exposed Lifetime of Geomembranes* - GSI is using three UV-fluorescent devices to estimate the projected exposed lifetime of six different types of geomembranes. They are HDPE, LLDPE, fPP, EPDM, PVC (N.A.) and PVC (Euro.). They are being incubated at 60, 70, and 80°C until halflife of strength and elongation are measured. The goal is lifetime prediction. Incubation times are now over 60,000 light hours (8.2 years) and are not yet complete. Some will take at least 90,000 light hours (~ 12.3 years). GRI Report #44 is available on results to date and a webinar is also available. The information was made available to the public April 6, 2016 at Orlando and was again presented in Peru on March 30. 2017. It has now been republished in the International Geosynthetics Journal. A copy is available. (In this regard, it should be noted that we have withheld the information before publication for well over a year, which has been our custom.)
4. HDPE Geomembrane Lifetime as a Function of Thickness - This often encountered question is being evaluated by exposure at 80°C in a QUV weathering device per ASTM D7238. Formulations are exactly the same and only the sample thicknesses vary. These thicknesses are 2.76, 2.44, 1.58, 1.08, 0.77 and 0.48 mm. Parameters being evaluated in this decade’s long study are change in thickness and presence of crazing or cracking. Time will tell!
5. Exposed Lifetime of Creased Geomembranes - Stemming from a recent webinar on the effect of backfilled GM waves or wrinkles we have seven geomembranes, which are purposely creased in double 180° bends being incubated at 80, 65, 55 and 25°C temperatures as of February 10, 2017. They are HDPE, LLDPE, LLDPE-R, fPP, fPP-R, EPDM and PVC. We are focused on if, and where, cracking might occur. The project promises to take many years but should be interesting.
6. Laboratory Exposed Lifetime of PVC (European) Geomembranes - We have been evaluating five different European formulations for four years using three dedicated UV-fluorescent devices and the results are very impressive. The study is being conducted for CARPI Tech, a GSI member organization. The project also allows us to distinguish between PVC geomembranes manufactured in North America versus Europe. The differences are in the type of plasticizers used in the formulations as well as thicknesses.
7. Laboratory Exposed Lifetime of Geotextiles - A similar UV study as with geomembranes, geogrids and TRM filaments has been conducted on various geotextiles. Woven monofilaments, woven slit films, nonwoven heat bonded and needle punched types are included. In the latter are four different weights of needle punched nonwovens. All data along with laboratory and field lifetime predictions are included in GRI Report #44 and the aforementioned International Geosynthetics Journal paper in Item #3.
8. Cable Tied Geonet Evaluations - A study has been focused on the plastic cable ties used to connect the overlapped ends and edges of geonets and geospacers. The draft of a new GRI Test Standard is available as well as the draft of a technical paper to be published at the IGS Conference in Seoul, Korea.
9. Retaining Wall Failure Evaluations* - We have past GRI Reports 38, 39, and 40 addressing mechanical stabilized earth (MSE) walls using geosynthetic reinforcement which document 82-failures. Our data base has now grown to 141, then 171, then 286 and now 312! Readers, we have a very serious situation in this regard! The failures are either excessive deformation or collapses. We have presented one-day courses on this topic along with inspector training and development insofar as a field inspector’s certification program; see the certification section of this Newsletter/Report. A paper was published by the Journal of Geotextiles and Geomembranes in October, 2013 and the publisher (Elsevier) reports that 1400 requests have been made to date. It was voted as being the best paper of 2013 by the journal. This was the topic of a GSI course and lecture presented at GeoAmericas in April, 2016. An up-to-date GSI webinar is available.
10. pH Between Masonry Block Wall Units* - George Koerner has been measuring the pH between three types of masonry blocks for over eight years to monitor the values. Concern here is over PET geogrids, which are known to be sensitive to very high alkalinity environments. Indeed, the values started high, but over time they are now down to eight and lower. George has a paper in this regard.
11. Landfill Failure Analysis - Since our originally reported paper on ten landfill failures in a 2000 publication, we have accumulated ten more. All 20-failures have been analyzed using the ReSSA Code and are now available to members and associate members as GRI Report #41. There are two recent failures in this regard, both in Pennsylvania, and one resulted in a worker’s death!
12. Slow Pressurization of HDPE Geomembranes in Axi-Symmetric Testing* - The ASTM D5716 method of testing geomembranes in a 3-D axi-symmetric mode uses a pressure rate of 6.9 kPa/min (1.0 psi/min). While such a rate is appropriate for most geomembrane types, it is very fast for HDPE, which is semi-crystalline and cannot readily stress relax so as to accommodate the applied pressure. To investigate slower rates we have initiated a project with rates as low as 6.9 kPa/month (1.0 psi/month)! The last test, just now begun, is at a rate of 6.9 kPa/six months (1.0 psi/six months) and it will take an estimated five years to conclude. A preliminary paper was presented at Geosynthetics ’15 in Portland.
13. PVD Strengthening of Soft Foundation Soils* - A new project, conducted over the past summer, addresses the use of PVDs for drainage (as customary) plus tensile reinforcement (never recognized to date). The experimental device was developed and used to assess three different PVDs. This data was then used with the ReSSA soil stability code on an old foundation soil failure that did not have PVDs. The FS-values increased 4% and could go higher with closer spacing or stronger PVDs. A journal paper is available.
14. Seams of Reinforced Geomembranes - There are now five scrim reinforced geomembranes available and the properties are listed in our GRI Specifications. To compliment these sheet products a set of shear and peel tests are have been evaluated. A new specification designated GRI-GM19(b) has been developed… GRI-GM19(a) is presently solely for homogeneous geomembranes.
15. Methods of Testing Multi-Component Geomembranes - Co-Extruded geomembranes are becoming commonplace, e.g., white-black-conductive types. As such, testing (e.g., density, OIT, SCR, etc.) is problematic. George Koerner is investigating ways of separation and then individual component testing… more later.
16. Generic Specifications - A major continuing effort is ongoing with respect to the development and updating of GRI’s generic geosynthetic specifications. The current status of these specifications is as follows. Incidentally, all 17 are currently being copyrighted.
Completed and Available on our Website
GM13 – HDPE Geomembranes
GM17 – LLDPE Geomembranes
GM18 – fPP and fPP-R Geomembranes
GM19a – Geomembrane Seams-Homogeneous
GM19b – Geomembrane Seams-Fabric Reinforced
GM21 – EPDM and EPDM-R Geomembranes
GM22 – Scrim Reinforced PE Barriers
GM25 – LLDPE-R Geomembranes
GM28 – CSPE-R Geomembranes
GM30 – Coated Tape PE Barriers
GCL3 – Geosynthetic Clay Liners
GS15 – Geocells using HDPE Strips
GT10 – Geotextile Tubes
GT12 (a and b) – Geotextile Cushions
GT13 (a and b) – Geotextile Separators
GCL3 – Geosynthetic Clay Liners
GC14 – Turf Reinforcement Mats
GC16 – Prefabricated Vertical Drains
Working; Available Upon Request
GGXX – Bidirectional Geogrids (tabled)
GGXX – Unidirectional Geogrids (tabled)
GNXX – Geonet Drainage Composites (tabled)
The complete set of formalized specifications are available to everyone (members and nonmembers) on the open section of our Home Page. Please download and use them accordingly. There is a brief tutorial accompanying each specification. Also note that this is where the latest modification will always be available. They are updated/modified on an as-required basis.
17. Other GRI Standards - There are several GRI Standards in various forms of preparation. These include the following:
· A practice on field seaming inspection emphasizing the electrical leak location system (ELLS).
· Three standards on GCL joining so as to prevent/monitor panel separation.
· A standard on GN joining with plastic cable ties… see Item #8.
· A guide as to recommended testing of drainage geocomposites.
· A practice explaining the use of MARV for geotextiles
· A transverse rib bending test for homogeneous geogrids