Bentonite Production with CETCO

Available now and standard on all Bentomat products, the “Winning Edge™” is a new overlapped seam enhancement system that brings higher levels of performance and convenience to the world’s best-selling GCL. The patented SuperGroove™ eliminates the need for accessory bentonite in the overlapped seam. Available only on Bentomat products, the SuperGroove will increase performance and decrease GCL installation headaches.

All Bentomat products have at least one non-woven needle-punched geotextile. In comparison to woven geotextiles, needle-punched non-wovens are thicker and can transmit flow in the plane of the geotextile. Planar flow can cause excessive leakage in the overlapped seam of a GCL. The addition of granular bentonite within the overlap area can eliminate this preferential flow by sealing the non-woven geotextile, which has been the standard of practice for many years.

The SuperGroove is a precision cut in the non-woven geotextile of Bentomat that allows bentonite to more freely extrude into the overlap zone (Figure 1). Upon hydration, a seal is formed, eliminating the possibility of preferential seam flow (Figure 2). Supplemental bentonite is not required.

The SuperGroove ensures that the hydraulic performance of the entire seamed GCL system is equal to that of unseamed portions. Added benefits include:

The SuperGroove is located approximately 3 inches (75 mm) inside the outermost limit of the bentonite clay component of the GCL, about 4 inches (100 mm) outside the first lap line (Figure 3). The SuperGroove is placed on both longitudinal edges of the Bentomat product

Performance of the SuperGroove seam was evaluated in comparison to a traditional bentonite-enhanced seam. Third-party laboratory tests were performed under a variety of head pressures and confining pressures. A test at low confining pressure is a “worst-case” scenario because the volume of void spaces in the overlap is larger than when a higher confining pressure is applied. Even in low-stress conditions, test data shows that the SuperGroove still allowed extrusion to completely seal the overlap (Table 1).;

Table 1. Comparative performance of Bentomat ST with traditional bentonite-enhanced seam and with new SuperGroove™.

Hydraulic Pressure (psi)	Unseamed Flux (mł/m˛/s)	Seamed Flux (mł/m˛/s)	Flux difference (mł/m˛/s)	Seam correction factor*	Seam flux (mł/m˛/s)**	Seam flux (% of total flux of seamed sample
2	4.4 x 10^-10	5.28x10^-10	8.8 x 10^-11	13.7	6.42 x 10^-12	1.2%
5	1.37 x 10^-⁹	1.63x10^-9	2.6 x 10^-10	13.7	1.9 x 10^-11	1.2%
10	3.41 x 10^-9	3.85x10^-9	4.4 x 10^-10	13.7	3.21 x 10^-10	0.8%

*Laboratory tests are performed with 13.7 times more seam length (per unit area of GCL) than in field seams.
**Flux difference divided by seam correction factor results in estimated preferential flow per unit area through field seam.

The test data shows that in all test conditions, there is a very small component of the total flux that is attributable to the overlapped seams. Expressed as a percentage of total seam area (3.9% on full-size GCL rolls laid in a large area) it can be seen that the percentage of total seam flux is proportionally less than the percentage of seamed area. Thus, it can be concluded that SuperGroove seams function effectively.

It should be noted that the SuperGroove does not appear on end-of-roll overlaps. CETCO recommends the continued use of supplemental bentonite for all end-of-roll overlaps of Bentomat.

Bentomat—the GCL with the Winning Edge™

The Winning Edge, featuring the SuperGroove, comes on all orders of Bentomat ST, Bentomat DN, Bentomat SDN and Bentomat YSDN. For more information about the Winning Edge, contact your local CETCO representative.

References

SGI Project No. SGI1029, Document No. SGI 01071, “Final Report, Large-Scale Flow Rate Testing, Seamed and Unseamed Bentomat GCL,” 3 August 2001.

SGI Project No. SGI1029, Document No. SGI 01071, SGI02037, “Final Report, Large-Scale Flow Rate Testing, Seamed and Unseamed Bentomat GCL,” 4 February 2002.