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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.

The paper describes instrumentation, testing, and detailed results of three 1-m high reinforced embankment models that were built in the laboratory at three different gravitational water contents (GWC). Each embankment model was subjected to a strip load near its crest until failure. The embankment models were constructed using lean clay at the GWC values ranging between OMC22% and OMCz2% (OMC: optimum moisture content). Each embankment model included a single reinforcement layer which was placed 180 mm below the embankment surface. The location of the reinforcement layer was selected based on preliminary embankment tests and numerical simulations to ensure that it would intercept the failure surface that developed underneath the strip footing near the embankment slope. The embankments were instrumented with a total of 67 sensors to measure the soil GWC, matric suction and excess pore pressure, reinforcement strains, earth pressure and deformations of the embankment models, and the test box during the tests. The test setup and data described in this paper are part of a long-term study to validate a set of moisture reduction factors (MRF) introduced by the authors in their recent studies which involved pullout and interface shear tests on the same soil and reinforcement materials. Specifically, the data and discussions in this paper provide a basis for further in-depth analysis to verify or modify the authors' proposed MRF values for actual embankment configurations. Furthermore, the test descriptions and results in this study will be used to validate numerical models to examine the influence of the soil matric suction and moisture content on the soil-geotextile reinforcement interface strength and internal stability of reinforced soil structures. The ultimate goal of the study is to develop a better understanding of the influence of matric suction on the performance of reinforced earthen structures constructed with marginal soils, and improved methodologies for their design.