Stabilization with Geosynthetics

Stabilization of Foundation Soils in Roadway Systems with Geosynthetics

The mechanisms that lead to roadway improvement using geosynthetic materials are complex. For example, if a geotextile is used as a filter, the design is based on multiple parameters including properties such as permittivity, pore-size distribution, and apparent opening size, as well as the properties of the soil/aggregate that is below and above the geotextile. Most of these parameters may be obtained as part of a laboratory material characterization or relatively simple hydraulic compatibility experiments. In the case of using geogrid in roadway applications, the parameters needed for sound evaluation and design becomes much more complex. Some parameters which may be affecting the behavior extracted from the literature can be summarized as follows: geometry of the geogrid, stiffness of each tensile element, junction rigidity of the geogrid, interaction with soil/aggregate particles (e.g., both as it relates to the geogrid openings and the particle size of the soil/aggregate below and above the geogrid), location of the geogrid in relation to the pavement profile, modulus and the deformations obtained from geogrid/soil/aggregate systems. The effect of most of these parameters (unlike in the filter geotextile example) cannot be obtained from simple laboratory bench-scale tests.

In this research, we will try to quantify the stabilization effect to the foundation of the roadway system, which is defined by ISO 10318-1 as “improvement of the mechanical behavior of an unbound granular material by including one or more geosynthetic layers such that deformation under applied loads is reduced by minimizing movements of the unbound granular material”. We believe that in the case of geogrids, the tensile strength of the geogrid will play a role to achieve stabilization. However, to this date, there is no previous research that shows the extent of the contribution of the tensile strength to achieve this purpose. We believe one of the reasons for this lack of quantification is because there is no laboratory or field test available that can reflect the degree of stabilization in a reliable way. As a result, in our opinion, there is a need to create a new index such that it should be determined based on several parameters and thereby capture the enhancement caused by the geogrid. On the other hand, we think that this research should be relatively easy to obtain so that it can be used practically in engineering projects.