Soil liquefaction mitigation in geotechnical engineering: An overview of recently developed methods

Classification and physical characteristics of bound water in loess and its main clay minerals

Non-darcian flow in loess at low hydraulic gradient

Surfactant-modified clay minerals are known for their good sorption properties of both organic and inorganic compounds from aqueous solutions. However, the current knowledge regarding the effect of both cationic and nonionic surfactants on the properties of bentonite is still insufficient. Bentonite, with montmorillonite as the base clay, was modified with hexadecethyltrimethylammonium bromide (a cationic surfactant) in the amount of 1.0 cation exchange capacity (CEC) of bentonite and varying concentrations of t-octylphenoxypolyethoxyethanol (Triton X-100, a nonionic surfactant). We aimed to improve the understanding of the effect of nonionic and cationic surfactants on clay minerals. The modified bentonites were characterized by X-ray diffraction (XRD), thermogravimetric analysis/differential thermal analysis (TG/DTA), Fourier transform infrared spectrometry (FTIR), field emission scanning electron microscopy (SEM) and specific surface area and pore volume (BET). According to our results, the presence of a cationic surfactant significantly increased the amount of the adsorbed nonionic surfactant. Moreover, an increase in the concentration of nonionic surfactants is also associated with an increase in the effectiveness of the modification process. Our results indicate that the amount of nonionic surfactant used has a significant effect on the properties of the obtained hybrid material. Modification of bentonite with a nonionic surfactant did not cause an expansion of the interlayer space of smectite, regardless of the presence of a cationic surfactant. The modification process was found to significantly decrease the specific surface area of bentonite. Improvement of hydrophobic properties and thermal stability was also observed.

https://www.mdpi.com/1996-1944/12/22/3772/pdf

Modification of Bentonite with Cationic and Nonionic Surfactants: Structural and Textural Features.

Earthquake-induced liquefaction causes soil to exhibit fluidlike behavior due to a sudden increase in pore water pressure and a concurrent decrease in effective stress. The liquefaction ca...

State of the Art Review of Emerging and Biogeotechnical Methods for Liquefaction Mitigation in Sands

Studies on hydraulic conductivity and compressibility of backfills for soil-bentonite cutoff walls.

Temperature effects on non-Darcy flow of compacted clay

Studies on the chemical compatibility of soil-bentonite cut-off walls for landfills.

Effect of the leachate head on the key pollutant indicator in a municipal solid waste landfill barrier system.

Compacted clay liner plays a crucial role in preventing leakage and migration of pollutants. Clay often appears in Non-Darcy phenomenon, one of which is characterized by having the threshold gradient. The threshold gradients exhibited by different clays are usually quite different. The reason for the discrepancy is currently unknown. To solve this problem, the mineral compositions of two clays were selected for test. The tests included threshold gradient, aperture and the pore water content. The test results showed that kaolin-based Clay A had no threshold gradient, whereas illite and Montmorillonite-based Clay B presented the threshold gradient that decreased with the increase of the porosity. For the samples mixed with Clay A and Clay B, the values of the threshold gradient increased with increasing the content of Clay B in the mixed samples. The reason is that the porosity and mineral content can affect the bound water content. If the value of pF is greater than 3.8, the bound water is gelatinous “immobile water”. Based on the water retention curves, the effective porosity can be obtained by subtracting the volume occupied by “immobile water” from the void of the soil particles. Then the modified effective aperture can be obtained by Hangen-Poiseuille law. The modified effective aperture will decrease with the decrease in the porosity and the increase of the content of illite and montmorillonite. This is the key reason why the different clays have different values of the threshold gradients.

Haoqing Xu

Papers

Studies on hydraulic conductivity and compressibility of backfills for soil-bentonite cutoff walls.

Temperature effects on non-Darcy flow of compacted clay

Studies on the chemical compatibility of soil-bentonite cut-off walls for landfills.

Effect of the leachate head on the key pollutant indicator in a municipal solid waste landfill barrier system.

Study of threshold gradient for compacted clays based on effective aperture