Unsaturated soil–woven geotextile interface strength properties from small-scale pullout and interface tests

Abstract

One main concern related to the performance of unsaturated soils during the construction and service life of earthen structures is loss of matric suction due to the seasonal variations of gravimetric water content (GWC), ground water infiltration and possible development of excess pore water pressure. In addition to reducing the soil shear strength, loss of matric suction as a result of wetting could also reduce the soil-reinforcement interface shear strength in comparison with the as-built value at a lower GWC. This paper presents the results of small-scale pullout and interface tests on a woven geotextile reinforcement material in different marginal soils in order to quantify the difference in the soil-geotextile interface shear strength as a function of GWC for practical applications. A moisture reduction factor [MRF ¼ ì(ø)] is used to account for the reduction in the soil-geotextile interface shear strength as a function of matric suction over a range of GWC values that includes the dry and wet sides of the soil optimum gravimetric water content (GWC opt ) or optimum moisture content (OMC). It was observed that the interface shear strength of geotextile reinforcement in marginal soils could be significantly lower (e.g. by as much 50%) at only 2% wet of optimum (i.e. OMC+2%) in comparison with OMCÀ2%, which is assumed to represent the as-built condition.

Measured Performance and Stability Analysis of Large-Scale Reinforced Model Embankments at Different Moisture Contents

“…[5,6,13]). Those results indicated that the small-scale cell that was used in those tests was adequate for the geotextile and the fine-grained soils that were the focus of those studies.…”

“…60 mm square test box; [5,6,13,26]) was carried out on the embankment soil at different GWC (i.e. OMC-2 % and OMC?2 %) and overburden pressure values (i.e.…”

“…As part of a long-term research study, the authors have investigated the influence of suction and moisture content in different marginal soils on the soil-reinforcement interface behavior through a series of multi-scale direct shear and pullout tests in the laboratory [5,6,[8][9][10][11]13]. In those studies, a moisture reduction factor (MRF) was introduced to quantify the anticipated loss in the soil-reinforcement interface shear strength as a result of increased moisture content in the soil due to factors such as precipitation and water infiltration.…”

Performance evaluation of geogrid reinforced soil walls with marginal backfills through centrifuge model tests

“…Chen and Wu (2012) had reported 50% reduction in pullout resistance with increase in degree of saturation of silty sand up to 94%. The loss of matric suction as a result of wetting was found to reduce soil shear strength and soil-reinforcement interface shear strength by Hatami and Esmaili (2014).…”

“…The interface properties are determined either by direct shear tests or pullout tests. The interaction mechanisms between marginal backfill and geogrid have been investigated through pullout tests by Sridharan et al (1991), Bergado et al (1992), Farrag and Griffin (1993), Abdi and Arjomand (2011), Chen and Wu (2012), Esmaili et al (2014) and Hatami and Esmaili (2014). The frictional resistance along the soilegeogrid interface was observed to decrease with increase in moisture content.…”