Compressibility behaviour of clays at large pressures

In this study, a method is proposed on the basis of the diffuse double layer theory to determine the compressibility of clays for one-dimensional conditions for vertical pressures far greater than the testing range of conventional oeodometer tests. Experimental e–p curves of several reported bentonitic clays were considered to verify the proposed method. It is shown that the parameters required to use the diffuse double layer theory can be obtained from the experimental e–p data for a low range of pressure and those can in turn be used to compute void ratios at higher vertical pressures. The stepwise procedure to calculate the e–p relationships at high pressure is given. The results showed that the agreement between the calculated and experimental compression characteristics at large vertical pressures is very good for the clays considered in this study.Key words: clays, compressibility, consolidation, expansive soils.

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Swelling pressures of compacted bentonites from diffuse double layer theory

Canadian Geotechnical Journal ◽

10.1139/t03-096 ◽

2004 ◽

Vol 41 (3) ◽

pp. 437-450 ◽

Cited By ~ 99

Author(s):

Snehasis Tripathy ◽

Asuri Sridharan ◽

Tom Schanz

Keyword(s):

Radioactive Waste ◽

Double Layer ◽

Expansive Soils ◽

Chemical Properties ◽

Weighted Average ◽

Swelling Pressure ◽

Radioactive Waste Disposal ◽

Diffuse Double Layer ◽

Barrier Materials ◽

Double Layer Theory

The swelling pressures of several compacted bentonites (MX80, Febex, and Montigel) proposed for use as barrier materials in storing high-level radioactive waste in many countries were determined from the GouyChapman diffuse double layer theory. The swelling pressures thus determined were compared with the reported experimental swelling pressures. The study revealed that, in general, at low compaction dry densities of the bentonites, the experimental swelling pressures are less than their theoretical counterparts, with the reverse trend at high compaction dry densities. Based on the reported experimental results for the three bentonites, relationships between the nondimensional midplane potential function, u, and the nondimensional distance function, Kd, were established. New equations for the swelling pressure were proposed on the basis of the diffuse double layer theory and the reported experimental data to compute swelling pressures of compacted bentonites. The suitability of the new equations was also verified with additionally reported experimental swelling pressures from three other bentonites (Kunigel V1, Kunigel, and bentonite S-2) that have been also proposed for use as barrier materials. Very good agreement was found in all the cases between the experimental swelling pressures and the swelling pressures obtained using the proposed equations. The use of the proposed equations is based on the weighted average valency of the cations present in bentonites, since the valency of the cations present has a significant influence on the swelling pressure.Key words: clays, compressibility, swelling pressure, expansive soils, chemical properties, radioactive waste disposal.

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