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Reinforced Steep Slopes

Strata recognizes that maximizing land use is the most critical need and has a major cost impact on any site development. Challenges in resolving grade change on the site are increasingly necessary as land cost increases and the difficulty to develop property becomes commonplace. To address these challenges, we provide the technical basis and economic solution for severe slope challenges, problematic soil conditions and land development needs.

Strata Systems uses primary and secondary Stratagrids, combined with traditional erosion protection products and vegetation to provide sound engineered solutions for reinforced steep slopes. Steep slopes are classified as structures with a face that is less than 70 degrees from the horizontal.

Any structure greater than 70 degrees should consider our retaining walls solutions.

Types of slopes

Flatter Reinforced

1H:1V or Flatter

What is commonly referred to as 1H:1V or flatter slopes, are slopes where proportion of the height of the rise is less than or equal to the length of the slope.

Wrap Faced

1H:1V or Steeper

These slopes are classified as slopes where the proportion of the height of the rise is higher than the length of the slope.

Embankment

Embankments

Embankments represent a special class of slopes or walls where soil reinforcement is used to stabilize and construct a fill structure having a smaller footprint than what could be constructed with the soil alone. Embankment stabilization is common when constructing roadways or other structures over soft, weak foundation materials.

Facing Options

There are several factors that can help determine the best facing option for your project.

Vegetated

In regions where sufficient rainfall or irrigation is possible, vegetation offers the most economical facing choice. Vegetated slopes have many benefits. They provide the opportunity to utilize indigenous species or select species more tolerant to variations in weather, provide a green aesthetic that softens hard architectural features, provide visual relief for structures subject to settlement, and minimize requirements for select aggregate.

Vegetated structures may be constructed on steep slopes near vertical geometry; however, the more vertical the structure, the more critical irrigation and plant selection.

Flatter Vegetated

For conditions where the slope is 1H:1V or flatter, we combine the primary and secondary geogrids with erosion protection products and vegetation to create a reinforced slope.

Vegetated

For slopes that are 1H:1V or steeper, we utilize a welded-wire form as a construction form, a Microgrid wrap and permanent vegetation to create the reinforced slope.

Stone-facing

In arid regions or situations where structure batter is prohibitive to supporting vegetation, a rock or crushed-stone facing is recommended. Galvanized (often hot-dipped) welded-wire forms are used to provide a long-term facing that also functions as the construction form. Rock selection is based on aesthetics and geometric opening size of the wire form. Stone facing is commonly utilized for permanent structures with near vertical geometry or waterway applications where water elevations prevent the establishment of vegetation.

Stone Facing

Temporary Structures

Woven and non-woven geotextiles are often utilized as the face wrap for temporary structures. Conventional black steel, welded-wire forms are utilized simply as construction forms for temporary applications. Temporary applications include roadway re-alignments, surcharge embankments and staged construction.

Temporary Structures

Slope Stability

Slope stability design is commonly evaluated by calculating the driving and resisting forces to determine the factor of safety against rotation or movement.

This is commonly utilized to define three failure regimes:

Internal

Failure surfaces that are contained entirely within the reinforced soil zone.

Compound

Failure surfaces that begin outside or behind the reinforce soil zone but pass through the reinforcement and exit in the foundation or through the structure face.

Global

Overall/deep seated failure surfaces that pass outside the reinforcement and into the underlying foundation soils.

Regardless of the failure regime, the designer must analyze numerous failure surfaces and isolate that surface which generates the least factor of safety for stability.

Slope System

Computer software allows the designer to rapidly analyze thousands of failure surfaces and optimize reinforcement requirements to provide adequate factors of safety at the best economics. For each failure surface passing through a layer of reinforcement, the analysis considers the tensile strength of the reinforcement to investigate tensile rupture or failure, and geogrid pullout resistance.

Strata makes tools available to designers that allow easy selection of primary and secondary reinforcements. StrataSlope Software is a limit-equilibrium design package that automates primary geogrid reinforcement design utilizing circular or log-spiral failure surfaces with the Bishop’s Method of Slices. Additional tools are available that address surficial stability using parallel failure surface of infinite length (i.e. sliding wedge approach).

See case studies showcasing our work with reinforced steep slopes.

Products Used