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Internal erosion involves the transport of soil particles from within or beneath a geotechnical structure due to seepage flow, influencing the subsequent mechanical and hydraulic behaviour of the soil. However, predicting changes in small-strain modulus ( G max ) with eroded fines and varying principal stress directions can be challenging due to various factors related to soil fabric. The present study investigates the impact of seepage flow on G max , as well as the effect of principal stress rotation (PSR), of gap-graded soil with a fines content of 20%, using a novel erosion hollow cylindrical torsion shear apparatus. The erosion test results indicate that, regardless of density, the G max generally increases with seepage time. The trend of G max measured in the vertical and torsional directions varies significantly, as seepage is applied always downward, resulting in a different impact on the vertical and horizontal bedding planes. After a cycle of PSR, the induced torsional shear strain is found larger for the eroded specimens, while vertical strain decreases due to fine removal accompanied by seepage flow. In the PSR tests, the specimens subjected to erosion exhibit a greater reduction in G max compared to non- eroded specimens, with increasing the angles of principal stress direction. This reduction may be due to the inefficacy of the reinforced soil skeleton established by erosion against shearing. The distribution of fine particles and anisotropy induced by seepage flow contribute to non-trivial mechanical behaviour during principal stress rotation, particularly regarding small-strain shear modulus. (c) 2024 Production and hosting by Elsevier B.V. on behalf of The Japanese Geotechnical Society. This is an open access article under the CC BY- NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

期刊论文 2024-12-01 DOI: 10.1016/j.sandf.2024.101518 ISSN: 0038-0806

Geosynthetic-reinforced soil (GRS) walls built on hillslopes are more increasingly incorporated with geocomposite side drain in order to prevent the side-seepage entering the fill. This study evaluates the long-term moisture, pore-water pressure, and shear modulus, of a 6.5 m-high geogrid-reinforced soil wall in western Thailand. Through extensive field monitoring and in-situ spectral analysis of surface wave (SASW) tests, conducted during the Years 2018-2019, as well as laboratory tests, several key findings emerge. Free-free resonant frequency (FFR) testing of non-reinforced samples reveals the role of soil wetting and drying history and hysteresis in the stiffness-moisture relationship. In-situ pore-water pressure was found to be highest below the road surface near the wall face, decreasing with depth due to underdrainage, with values ranging from -27 to 5 kPa. The inter of the side drainage board with the underdrain bottom layer shows the highest water content. In-situ and laboratory-derived soil-water retention curve (SWRC) were found to differ at greater depths. In unsaturated conditions, the in-situ small strain modulus of GRS appeared insensitive to suction stress below 10 kPa but was slightly affected under positive pore-water pressure, with multiple linear regression modeling indicating a dependency of stiffness on depth and pore-water pressure.

期刊论文 2024-10-01 DOI: 10.1016/j.geotexmem.2024.05.005 ISSN: 0266-1144
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