Fixed-Wall Versus Flexible-Wall Permeameters

Abstract

Permeameters are of two general types: fixed-wall and flexible-wall cells. A controversy has developed over which type of cell is best suited for measuring the hydraulic conductivity of relatively impermeable, fine-grained soils. The various types of permeameters are discussed and their relative advantages and disadvantages are listed. Differences in applied stress, boundary leakages, and degree of saturation are the major differences between cells. It is concluded that no one type of cell is best suited to all applications. Data show that the type of permeameter used has little effect for laboratory-compacted clay permeated with water but can have a major effect for clays permeated with concentrated organic chemicals. Fixed-wall cells are perhaps best suited to testing laboratory-compacted clays that will be subjected to little or no effective overburden pressure in the field. Flexible-wall cells are better suited to testing undisturbed samples of soil (to minimize boundary leakages) and testing soils that will be subjected to significant effective stress.

Towards a more rational approach to chemical compatibility testing of clay

“…Daniel et al (1985) indicated that increasing effective stresses could affect the hydraulic conductivity results, particularly for specimens with pre-existing cracks. On the other hand, Fernandez and Quigley (1985) conducted RWP tests that featured very high effective stresses and hydraulic gradients (hydraulic gradients as high as 1000) and yet, they observed substantial changes in hydraulic conductivity due to chemical changes.…”

“…These structural changes in the soil could result in large increases in hydraulic conductivity. In FWPs, however, the soil specimen can freely consolidate under similar chemical stresses, which may hinder the fabric changes and possible fracturing of soils (Daniel et al 1985). This behaviour is evident in the measurements of volume changes of the soil specimen during the tests (Rahman 2000).…”

“…In certain instances, sensible measurements of hydraulic conductivity were found to be almost impossible (Yang and Barbour 1992;Rahman 2000). The double ring permeameters have been developed to monitor the sidewall leakage during permeation, but this development does not provide a solution to the underlying problem (e.g., Daniel et al 1985;Bowders et al 1986). Mitchell (1994) and Theriault and Mitchell (1997) presented a centrifuge technique for hydraulic conductivity and compatibility testing.…”

Removal rate of compacted clay soil in the batch and continuous reactors and its permeability

“…The soil was constrained against swelling. The clay soil has been saturated under a 0.3-bar pressure [14,15]. Experimental setup is given in Figure 1.…”

Estimation of hydraulic conductivity of unsaturated soils using a geotechnical centrifuge

“…Various researchers have tried to evaluate hydraulic conductivity of soils by conducting either laboratory experiments (Bjerrum and Huder 1957;Daniel et al 1985;Chapuis 1990;Fleureau and Taibi 1995;Huang et al 1995;Uno et al 1995) or in situ studies (Bouma et al 1971;Daniel and Trautwein 1986;Little et al 1995;Ankey et al 1991). These methods have been classified as direct methods and indirect methods.…”