Influence of Mass Per Unit Area on the Hydraulic Conductivity of Geosynthetic Clay Liners (GCLs)

Abstract

In the content of this study, barrier performance of geosynthetic clay liners (GCLs) in terms of mass per unit area of bentonite (MPUA) was investigated. For this purpose, a Na-GCL with MPUAs of 3.0 and 5.0 kg/m2 were tested. Hydraulic conductivity tests were conducted with deionized water (DIW) and calcium chloride solutions prepared with various concentrations (i.e., 15 mM and 30 mM CaCl2). The free swell characteristic of bentonite in GCL was also determined. The swell index results showed that increase in the CaCl2 concentration results to a decrease in the swell index values. That is, swell indices were 23, 13, and 10 mL/2g with DIW, 15 mM, and 30 mM CaCl2, respectively. The influence of MPUA on the hydraulic performance of Na-GCL was not observed with DIW. The hydraulic conductivity of GCL with MPUA of 3.0 and 5.0 kg/m2 was 4.6×10-11 and 2.1×10-11 m/s, respectively. However, MPUA had a significant effect on the hydraulic conductivity when CaCl2 solutions were used as the permeant. Increase in MPUA caused to a decrease in the hydraulic conductivity with CaCl2 solutions. It was found with 30 mM CaCl2 solution that the hydraulic conductivity of GCL with MPUA of 5.0 kg/m2 was almost 16 times lower than that of GCL with MPUA of 3.0 kg/m2 (8.3×10-9 vs 1.3×10-7 m/s).

Keywords

• geosynthetic clay liners
• mass per unit area
• swell index
• calcium chloride
• Hydraulic conductivity

Birim Alan Başına Bentonit Kütlesinin Geosentetik Kil Örtülerin (GKÖ’ler) Hidrolik İletkenliği Üzerine Etkisi

Öz

Bu çalışma kapsamında, geosentetik kil örtülerin (GKÖ’ler) bariyer performansı birim alan başına bentonite kütlesi (BABBK) açısından araştırılmıştır. Bu amaç doğrultusunda BABBK’si 3.0 ve 5.0 kg/m2 olan Na-GKÖ’ler test edilmiştir. Hidrolik iletkenlik testlerinde deiyonize su (DS) ve farklı konsantrasyonlarda kalsiyum klörür (15 mM ve 30 mM CaCl2) çözeltileri kullanılmıştır. Ayrıca GKÖ içerisindeki bentonitin serbest şişme karakteristiktikleri de belirlenmiştir. Şişme indeks deney sonuçları, CaCl2 konsantrasyonundaki artışın şişme indeks değerlerinde azalmaya sebep olduğunu göstermiştir. Yani şişme indeksleri DS, 15 mM ve 30 mM CaCl2 ile sırasıyla 23, 13 ve 10 mL/2g olarak elde edilmiştir. BABBK'nin Na-GKÖ'nün hidrolik performansı üzerindeki etkisi DS ile gözlenememiştir. GKÖ’nün 3.0 ve 5.0 kg/m2 BABBK olan GKÖ’lerin DS ile hidrolik iletkenlikleri sırasıyla 4.6×10-11 ve 2.1×10-11 m/s olarak elde edilmiştir. Ancak süzdürme sıvısı olarak CaCl2 çözeltileri kullanılması hidrolik iletkenlik üzerinde önemli bir etki yaratmıştır. CaCl2 çözeltileri ile yapılan deneylerde BABBK’deki artış hidrolik iletkenlikte azalmalara neden olmuştur. 30 mM CaCl2 çözeltisinde 5.0 kg/m2 BABBK’ye sahip GKÖ’nün hidrolik iletkenliği 3.0 kg/m2 BABBK’ye sahip GKÖ’nün hidrolik iletkenliğinden 16 kat daha düşük olduğu bulunmuştur (8.3×10-9 vs 1.3×10-7 m/s).

Anahtar Kelimeler

• geosentetik kil örtüler
• birim alan başına bentonite kütlesi
• şişme indisi
• kalsiyum klorür.
• Hidrolik iletkenlik

Kaynakça

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