INNOVATIONS IN HYDRAULIC-CONDUCTIVITY MEASUREMENTS

Innovations in laboratory methods for hydraulic-conductivity measurements have been developed by using a flow pump to generate a constant rate of flow through a test specimen and monitoring the hydraulic gradient induced thereby with a differential-pressure transducer. In most applications of this constant-flow method to date, hydraulic-conductivity tests have been conducted on stress-controlled specimens following conventional loading increments in one-dimensional consolidometers and also after increments of three-dimensional consolidation in triaxial cells. Similarly, a constant rate of flow through one end of a test specimen has been generated with a flow pump while flow through the opposite end of the specimen is driven to or from a pressure-controlled reservoir. More recent innovations include a new flow-pump actuator that enables identical flow rates to be infused and withdrawn from opposite ends of a test specimen and the use of additional flow pumps to control the effective stress and volume of a specimen. These innovations provide a convenient approach for obtaining hydraulic conductivity versus effective stress data in triaxial cells on a wide variety of materials, including sandstones and shales that cannot be trimmed and mounted in fixed-ring permeameters or one-dimensional consolidometers. These innovations also provide a means to integrate constant-flow hydraulic conductivity measurements with continuous-loading consolidation tests on fully saturated specimens in both back-pressured consolidometers and in triaxial cells.