Volume 23, Issue 4 (December 2000)
A New Device for Measuring Permeability Under High Gradients and Sinusoidal Gradients
This paper presents the design and testing procedures for a new type of permeameter that combines the methods of a constant-head permeameter for large hydraulic gradients (used to simulate hydraulic gradients in centrifuged geotechnical models) and a sinusoidal head permeameter (used to simulate internal flow in soils due to waves). The flow of permeant through a granular soil specimen is forced by a pump with a control servovalve used to regulate the flow rate according to the desired signal. The measurement instruments, which consist of temperature sensors, differential pressure transducers, flowmeters, and an electrical controller, are linked to a microcomputer and a data acquisition and control system that permits full automation of the tests.
Steady flow tests, carried out on fine sands with high hydraulic gradients, show that the flow is governed by Forchheimer's law. The analysis of the transient flow tests, carried out on fine sands, has shown that the classical Darcy's law is not valid when the material is subjected to a flow simulating a wave; a generalization of Darcy's law for this type of flow is proposed here.