A Device for the Simultaneous Determination of the Water Retention Properties and the Hydraulic Conductivity Function of an Unsaturated Coarse Material; Application to a Green-Roof Volcanic Substrate
- 1 May 2020
- journal article
- research article
- Published by ASTM International in Geotechnical Testing Journal
- Vol. 43 (3), 547-564
- https://doi.org/10.1520/gtj20170443
Abstract
The determination of the water retention curve (WRC) and hydraulic conductivity function (HCF) of a specific volcanic coarse granular material used as a substrate for urban green roofs in Europe was carried out on a newly developed specific device in which low suctions, typical of coarse granular materials, were controlled. Smaller suctions (up to 32 kPa) were imposed by using a hanging column system, and larger suctions (between 32 and 50 kPa) were imposed by using the axis translation technique in the same cell. The changes in suction during the tests were monitored by using a high accuracy differential pressure transducer. They were also used to determine the HCF by means of both Kunze and Kirkham’s and Gardner’s methods. The former technique was used at low suctions (<4 kPa) to account for the impedance effects due to the high air entry value ceramic porous disk and the latter was used between 4 and 50 kPa. Good comparability was observed in the data from both methods, demonstrating the good performance of the device. The mathematical expressions of the WRC of van Genuchten and Brooks and Corey were used, and a good fitting with our experimental data was obtained. Conversely, the HCFs derived from these expressions appeared to lead to a significant underestimation, confirming the need of an operational and simple device for the experimental determination of the HCF. Also, this material proved to be an appropriate material for green urban infrastructures, because of its lightweight, satisfactory water retention capability and hydraulic conductivity.This publication has 17 references indexed in Scilit:
- Unsaturated Soil Mechanics in Engineering PracticePublished by Wiley ,2012
- Practice for Classification of Soils for Engineering Purposes (Unified Soil Classification System)Published by ASTM International ,2008
- Laboratory Hydraulic Testing in Unsaturated SoilsGeotechnical and Geological Engineering, 2008
- Vapour Equilibrium and Osmotic Technique for Suction ControlGeotechnical and Geological Engineering, 2008
- An evaluation of the osmotic method of controlling suction∗Geomechanics and Geoengineering, 2008
- THE DETERMINATION OF THE HYDRAULIC CONDUCTIVITY AND DIFFUSIVITY OF UNSATURATED SOILS1Soil Science, 1972
- Simplified Accounting for Membrane Impedance in Capillary Conductivity DeterminationsSoil Science Society of America Journal, 1962
- Dynamic Determination of Capillary Conductivity Extended for Non-Negligible Membrane ImpedanceSoil Science Society of America Journal, 1958
- Measurement of Water and Air Permeability in Unsaturated SoilSoil Science Society of America Journal, 1957
- Calculation of Capillary Conductivity from Pressure Plate Outflow DataSoil Science Society of America Journal, 1956