Geosynthetic Interface Friction at Low Normal Stress: Two Approaches with Increasing Shear Loading

Paolo Pavanello,Paolo Carrubba,Nicola Moraci

doi:10.3390/app12031065

Paolo Pavanello, Paolo Carrubba + Show 1 more

Open Access

https://doi.org/10.3390/app12031065

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Abstract

The evaluation of geosynthetic interface friction is a key parameter for the stability of coupled geosynthetics, as in landfill capping liner. At the present time, few types of tests are suitable for measuring the interface friction at low normal stress: one of these is the inclined plane, usually carried out under a vertical stress of 5 kPa. This type of test is not without critical aspects, mainly due to the nonuniform normal stress state induced by the inclination of the plane, but, on the other hand, the most widespread direct shear test generally cannot be performed at such low values of normal stress. After a short discussion on the pros and cons of these two types of test, the paper presents a comparison of the interface friction angles obtained, for three interfaces, by means of an inclined plane and an unconventional direct shear apparatus, under the same low normal stress. The peculiarity of this latter device is of ensuring a gradual increase of the mobilized strength, in a way similar to what occurs during the inclined plane test. The good correspondence of the results of the two types of tests confirmed the validity of both the test approaches.

Highlights

Starting from the evidence of the undoubted advantages that the use of geosynthetics entails in geotechnical works, a continuous improvement of the knowledge on the short and long-term behavior of these polymeric materials could be desirable, in order to use these products knowledgably
Idnisapnlaalcoegmyewnitt.h In analogy with what is usually done in the case of the inclined plane test, in this case the interpretation of the results was made assuming a static equilibrium of the block (Equation (2)), even if the block speed and acceleration were not negligible
In this paper, a comparison between the results of inclined plane tests and those obtained by means of a different experimental apparatus, have been presented

Summary

Introduction

Starting from the evidence of the undoubted advantages that the use of geosynthetics entails in geotechnical works, a continuous improvement of the knowledge on the short and long-term behavior of these polymeric materials could be desirable, in order to use these products knowledgably In this context, an adequate expertise of the friction that these materials can mobilize when placed in contact with each other is necessary, since it is a common practice to combine layers of geosynthetics, having different functions, forming multilayer packages. Each contact surface between two geosynthetics, as well as those between geosynthetic and soil, represent a potential critical element for the stability, given the modest friction values that these surfaces generally can mobilize This aspect assumes considerable relevance in the design phase and can be a source of serious errors if not properly addressed, even because a correct characterization of the interface friction is not so simple, having to take into account the peculiarities of the behavior of the polymeric materials. This latter device allows performing horizontal shear test at the same vertical stress of the inclined plane and it is characterized by a sliding force gradually increasing over time

The Direct Shear and the Inclined Plane Tests

Studied Interfaces

Test Results

Conclusions