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Investigation on the hydraulic behaviour of nanoparticles based LBF exposed to salt solutions

University of British Columbia

In this study, the effect of pore fluid chemistry on the hydraulic behaviour of the light backfill (LBF i.e. 50-50 bentonite-sand compacted at a dry density of 1.24 Mg/m³) was investigated. The experimental results showed that pore fluid reduce the swelling pressure and increase the hydraulic conductivity of LBF. The change in the pore structure such as pore size, pore distribution and pore connectivity due to the presence of pore fluid was also investigated using Xradia Micro XCT-400. The X-ray source, detector, and a small portion of LBF specimen (5.5 mm in diameter) were placed closely to acquire a good quality image with a voxel size of 1.15 x 1.15 x 1.15 μm. The scanned images were de-noised and segmented to study the pore space. An algorithm was developed to compute the volume porosity and pore-size distribution of the scanned samples. Additionally, the interconnected pore components and absolute permeability of the LBF samples were analyzed using Avizo software. The results of microstructure analysis demonstrate that the porosity, pore size, volume of interconnected pores and hydraulic conductivity of the LBF increased due to pore fluids. The effectiveness of using nanoparticles of bentonite to minimize the impact of saline solutions on hydraulic responses of LBF, were studied. Both the mechanical attrition (planetary ball mill) and the synthesis process (ultra-sonication, centrifuging and filtering techniques) were integrated to prepare the nanoparticles. The particle size analysis of nanoparticles through Scanning Electron Microscopy (SEM) showed particles range between 30 to 140 nm. Additionally, the chemical and mineralogical composition of nanoparticles analyzed by Energy Dispersive Spectroscopy (EDS) and X-Ray Diffraction (XRD) exhibited similar behaviour of the parent bentonite. Subsequently, two different percentage of nanoparticles (1 % and 2 % of dry bentonite) were carefully mixed with the bentonite-sand mixture to prepare nanoparticles based LBF. Nanoparticle based LBF showed excellent performance in reduction of hydraulic conductivity, when LBF is exposed to both fresh water and saline solutions.

Text

2015-05-05

Attribution-NonCommercial-NoDerivs 2.5 Canada

http://hdl.handle.net/2429/53041

Civil Engineering

University of British Columbia

UBCO

http://creativecommons.org/licenses/by-nc-nd/2.5/ca/