Multichannel optical sensor to quantify particle stability under seepage flow

• Published in: Canadian geotechnical journal Vol. 48; no. 12; pp. 1772 - 1787
• Main Authors: MAROT, Didier, BENDAHMANE, Fateh, KONRAD, Jean-Marie
• Format: Journal Article
• Language: English
• Published: Ottawa, ON NRC Research Press 01-12-2011; National Research Council of Canada; Canadian Science Publishing NRC Research Press
• Subjects: Clay; Clay (material); concentration en particules solides; Conductivity; Design and construction; Devices; Earth sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; Engineering design; Engineering geology; Engineering Sciences; essais en laboratoire; Exact sciences and technology; Filtration; Flow rates; Fluid dynamics; Fluid flow; Fluids; Hydraulic gradient; Hydraulics; laboratory testing; Light emitting diodes; Materials; Mechanics; Methods; Optical detectors; Optical sensors; pore velocity; Sand; Seepage; Soil erosion; Soil types; Soils; solid particle concentration; suffusion; transparence; transparency; vitesse dans les pores; écoulement; Canada; experimental studies; particulate matters; effluents; concentration; seepage; transport; velocity; grains; sand; hydraulic conductivity; filtration; granulometry; hydraulics; coarse-grained materials; erosion; particles; soils; loam; flow; stability; laboratory studies; solid particle concentration; pore velocity; essais en laboratoire; transparency; transparence; laboratory testing; vitesse dans les pores; suffusion; écoulement; concentration en particules solides
• ISSN: 0008-3674; 1208-6010
• DOI: 10.1139/t11-074

An optical sensor was designed to measure the fine solid particles concentration contained in a fluid flow. This sensor is composed of four light-emitting diodes and four associated light-dependent resistors, allowing the measurement of fluid transparency. Given the small device dimensions, it can be placed close to the particles exit from the specimen. The optical sensor is able to instantaneously measure a large range of clay or silt concentrations in the effluent, without a significant influence of flow rate. The presence of sand grains in fluid flow can be detected. The use of this sensor with a specific triaxial device allows precise characterization of the initiation and development of the suffusion process on clayey sand specimens. It is shown that suffusion of clay particles induces a decrease of hydraulic conductivity, which is due to a diffuse process of eroded particles filtration. Clay suffusion and filtration processes are influenced by grain-size distribution and also by grain shape of the coarse fraction. Under a high hydraulic gradient, clay suffusion can be accompanied by sand erosion. The critical value of mean pore velocity to initiate clay suffusion was determined for the types of soils.