Model tests on 3D soil arching in pile-supported embankments with and without geotextile

Compared to traditional soil improvement methods such as preloading, vertical drains, or grouting injection, et al., pile-supported reinforced embankments are increasing widely employed in the construction of highways on soft soils. A series of three-dimensional model tests on pile-reinforced embankments, utilizing a square arrangement for pile caps, were conducted to investigate the effects of pile-subsoil relative displacement, embankment height, tensile strength of geotextiles, and clear spacing of pile caps on the stress concentration ratio and the height of the equal settlement plane. The results indicate a close relationship between the soil arching effect and pile-subsoil relative displacement. The stress concentration ratio, from the results of this study, reaches its maximum value when the pile-subsoil relative displacement is approximately 6 to 8 mm. A larger embankment height to pile-cap clear spacing ratio, h/s, as well as the of pile-cap width to its clear spacing ratio, b/s, will result in a larger stress concentration ratio and a smaller differential settlement on the embankment surface. The inclusion of geotextiles can effectively enhance the soil arching effect, i.e., increasing the stress concentration ratio and lessening the fill differential settlement, especially for those low embankments. The model test results also shown that the height of the equal settlement plane in 3D soil arch is approximately 3.5 times the pile-cap clear spacing regardless of the inclusion of the geotextiles or not. In addition, by comparing the measured stress concentration ratio with the calculated values from various design methods, valuable conclusions have been derived.