Bentonite:Kaolinite Clay Liner

Abstract

Conventional geosynthetic clay liners (GCLs) contain bentonite. Since high-quality bentonite is not easily available in Southeast Asia in comparison to kaolinite, an alternative cost-effective method is necessary. The concept of creating a GCL with a bentonite and kaolinite mixture on a biodegradable jute base is discussed in the present paper. The hydraulic conductivity and consolidation behaviour of bentonite: kaolinite mixtures was investigated. It was revealed that at least 30% bentonite was required in the mixture to result in the same decreasing coefficient of consolidation trend with pressure as shown using pure bentonite. The 50:50 bentonite:kaolinite (50:50 B:K) ratio yielded approximately the same hydraulic conductivity, k, as pure bentonite; hence, the remainder of the study focused on the 50:50 B:K mixture. For the 50:50 B:K mixture hydraulic conductivity measurements, the following permeants were used: (i) distilled water, (ii) 0.25M calcium chloride, (iii) 0.1M hydrochloric acid, and (iv) 0.1M sodium hydroxide. With the calcium chloride permeant, the hydraulic conductivity of the mixture was found to be in the range of 10−10 m/s, whereas the hydrochloric acid and sodium hydroxide permeants yielded values near 10−11 m/s. It was also found that the liquid limit and swell index tests carried out on bentonite and the B:K mixture were significantly affected by the presence of a large amount of calcium chloride. A jute-based clay liner was then created with the 50:50 B:K mixture. Its effectiveness in the landfill liner system was investigated for equivalency and was found to be satisfactory when using distilled water as the permeant. The biodegradability of jute and the effect of organic chemicals on the clays are beyond the scope of the present paper.

Modified Terzaghi consolidation curves with effective stress-dependent coefficient of consolidation

“…Figure 1(a) shows c v -s' v relationships for the three cases where, according to experimental evidence from the literature (Duncan, 1993;Robinson & Allam, 1998a;Karunaratne et al, 2001), a non-linear relationship is proposed for cases 2 and 3. Assuming that c v changes linearly as s' v increases within the incremental effective stress generating consolidation, a dimensionless parameter, i cv , which describes c v change within the consolidation stress increment can be expressed as…”

“…One of these weak assumptions is that the coefficient of consolidation, c v , is a material property that remains constant during the consolidation process (Thomas, 1987). An examination of available experimental data in the literature shows that c v is a function of effective stress, s' v (Robinson & Allam, 1998a;Karunaratne et al, 2001). The value of c v can either decrease or increase as s' v increases based on whether the soil consolidation process is controlled by a mechanical or a physicochemical mechanism (Olson & Mesri, 1970;Sridharan & Rao, 1973;Robinson & Allam, 1998a;Karunaratne et al, 2001).…”

“…The value of c v can either decrease or increase as s' v increases based on whether the soil consolidation process is controlled by a mechanical or a physicochemical mechanism (Olson & Mesri, 1970;Sridharan & Rao, 1973;Robinson & Allam, 1998a;Karunaratne et al, 2001). In soils whose consolidation behaviour is mainly governed by mechanical factors (such as kaolinite), c v is found to increase as s' v increases; the opposite behaviour can be observed for montmorillonite, as its consolidation behaviour is primarily governed by physicochemical factors (Karunaratne et al, 2001).…”

Design chart for prefabricated vertical drains improved ground

“…4. It should be mentioned that c h can either decrease or increase as s 0 v increases based on whether the soil consolidation process is controlled by a mechanical or a physicochemical mechanism (Olson and Mesri, 1970;Sridharan and Rao, 1976;Robinson and Allam, 1998;Karunaratne et al, 2001). For soils where its consolidation behaviour is mainly governed by mechanical factors (such as kaolinite), c h is found to increase as s 0 v increases whereas an opposite behaviour can be observed for montmorillonite as its consolidation behaviour is primarily governed by physicochemical factors (Karunaratne et al, 2001).…”

Study on Swell Pressure Stress of Bentonite in Geosynthetic Clay Liners

“…The rate of decrease amounts to 1.53~10-~ MPa per hour. From the mineralogical viewpoint, the temporal changes in the style of swell pressure stress variation reflect a different water-sorbing rate and the change of water content of the bentonite (Karunaratne et al, 2001;Koch, 2002). Zn the first segment, because dry bentonites have only a little water in them, the sorbility of the bentonite is very strong.…”