Influence of matric suction on geotextile reinforcement-marginal soil interface strength

This paper presents descriptions and results of multi-scale pullout and interface shear tests on a woven polypropylene (PP) geotextile reinforcement material in a marginal quality soil. A main objective of these tests was to develop a moisture reduction factor (MRF) for the pullout resistance equation in the currently available design guidelines. The tests were carried out at different overburden pressure and gravimetric water content (GWC) values. The differences in the soil-geotextile interface strength among the cases with different GWC values were used to determine the corresponding MRF values. Results of the study indicate that the reinforcement interface strength and pullout resistance could decrease significantly as a result of the loss in the matric suction (e.g. by 42% between the cases of 2% dry and 2% wet of the soil optimum moisture content). It is concluded that wetting of the soil-geotextile interface during construction or service life of a reinforced soil structure can measurably reduce the interface strength and pullout resistance of the geotextile reinforcement which needs to be accounted for in design. Results of the study will be also useful to estimate the difference in the pullout capacity of geotextile reinforcement in a marginal soil when placed at different GWC values during construction. The methodology described in the paper could be used to expand the database of MRF results to include a wider range of soil types and geotextile reinforcement for practical applications.