Geosynthetic reinforcement layers arranged in a horizontal direction are useful for slope stability preventing the potential for deep seated. This reinforced slope can be in the form of slope improvement and/or to strengthen the sides of an embankment construction. This reinforcement layer allows the slope surface to be built at a more upright angle in the unreinforced slope. In addition, if it is necessary for the stability of the slope surface (especially during backfilling and compaction work), relatively short layers with shorter distances are used as secondary reinforcement by wrapping the reinforcement layer on the facing side.
In many cases the slope surface must be protected against erosion, this requires soil-filled geosynthetic materials or also lightweight materials such as geo-meshes which are often used for temporary retaining of vegetation. The typical image below also shows any collector drainage that may be required to remove additional seepage and hydrostatic forces in the reinforcement zone.
This factor of safety analysis can be calculated using the conventional method of limit equilibrium modification by including the additional stabilized force obtained from the reinforcement.
The position, quantity, length and strength of the primary/reinforcement material are required to provide an adequate factor of safety to prevent failure.
The planner can use the cut approach method or what is known as the slice method by assuming the failure mechanism is a surface line that can be circular, composite, wedge-shaped or in the form of multiple wedges. The layer of reinforcing material is assumed to provide a resisting force at the point where it intersects with the potential failure surface that has been assumed during the analysis. One method to obtain the safety factor of this system is using the Bishop method which can be written with the following formula:
where MR and MD are the resisting and pushing moments for the unreinforced slope, α is the angle of tensile force with respect to the horizontal plane, and Tallow is the allowable tensile strength of the reinforced material. Since geosynthetic reinforcement is usually continuous, the designer can assume that the reinforcing force acts tangentially to the failure surface so that it is found that RT cos α = R.
