Neoweb® Slope Protection Engineering Design

Neoweb® Slope Protection Engineering Design Engineering Seminar, PRS July 2010 Neoweb® Slope Protection System • • • • Reinforced cover protection Erosion control for stable slopes Extend local stability life-span Vegetated landscape solution Section I INPUT • • • • • Checklist Project Plans Objectives - Client’s preferences Goal & Cost Slope Definition I - INPUT Checklist • Summary of design properties • Includes most/all design properties • Enables relatively quick design for preliminary evaluation I - INPUT Project Plans • Advantages – Alternative solutions – More details – enables more customized solution for specific site conditions – Confirm design checklist – questions I - INPUT Objectives - Client’s Preferences • Understanding main objectives of client Preferences, e.g.: – Min cover thickness for vegetation – Min cover thickness for geomembrane protection – Type of surface cover protection • Vegetated • Granular • Concrete I - INPUT Goal & Cost • Cost of alternative solutions (if any) per sqm or linear meter of solution • Determine go/no-go I - INPUT Slope Definition (1) Slope Type: I - INPUT Slope Definition (2) Geometry: • • • • Height Inclination Crest Area Toe Area I - INPUT Slope Definition Sub-base / Native Soil: • • • • Description, Internal friction angle φ [°] Cohesion C [kPa] Unit weight γ [kN/m3] Why? • Examining slope global stability • Evaluating stakes resistance III – Neoweb Design Anchorage System ANCHORAGE SYSTEM Impenetrable Slopes Penetrable Slopes (Landfill, Reservoir, Rocky slope) (Native cut/fill slope) Anchorage System: Tendons, clips and crest anchor Anchorage System: Metal pin stakes with Neo-Clip III – Neoweb Design Anchorage System- Penetrable Slopes Default system III – Neoweb Design Anchorage System - Penetrable Slopes Typical properties of a pin stake anchor: Plastic Embedded length (eff.) = 500mm Neo-Clip™ Diameter = 10mm Downslope resistance = 0.5-0.6kN Plastic Neo-Clip™ attached ** Minimum Stakes in either way (for retaining Neoweb shape) is app 0.6-0.7 stakes/sqm III – Neoweb Design Anchorage System- Penetrable Slopes Next Step: Defines stakes density according to cell opening, to provide sufficient Factor of Safety Upper first crest row is defined with stake every cell Rstakes = Total downslope stakes resistance for 1m strip ** Minimum Stakes Density in either way (for retaining Neoweb shape) is app.0.6 stakes/sqm III – Neoweb Design Anchorage System- Penetrable Slopes EXAMPLE LAYOUT: III – Neoweb Design Checking Neoweb Stability Downslope Interface friction resistance, RI + Crest Shoulder Interface friction resistance, RSHL + Embedded Toe resistance, RT + Downslope Stakes Resistance, Rstakes ≥ FSsl (=1.30) OK! III – Neoweb Design Checking Neoweb Stability - EXAMPLE OK! III – Neoweb Design Anchorage System- Impenetrable Slopes Tendons (cables) are expanded in the middle height of Neoweb cell prior section expansion downslope Tendons are tied to clips/clamps holding uphill cell wall III – Neoweb Design Anchorage System- Impenetrable Slopes Tendons are secured to a crest Deadman Anchor III – Neoweb Design Anchorage System- Impenetrable Slopes EXAMPLE LAYOUT: III – Neoweb Design Anchorage System- Impenetrable Slopes Tendons Type: • Polyester or Galvanized Metal- depends on required tensile strength (metal tendon is stronger); default tendon diameter is 6mm Clips/Clamps: • Plastic Neo-Clips™ are used with polyester Tendons; • Galvanized Metal Clamps are used with Galvanized Metal Tendons; ** Minimum range of Clips/Clamps in either way (for retaining Neoweb shape) is app 0.7-1.0 units/sqm III – Neoweb Design Anchorage System- Impenetrable Slopes • Special Neoweb Manufacturing Run: – The tendons are expanded in specific holes in the middle of cell height – These sections are not default Neoweb section – Hence required to be defined for a customized project III – Neoweb Design Anchorage System- Impenetrable Slopes • Stages for Design Tendons: • Define tendon type (polyester/metal), diameter, ultimate tensile strength and reduction factors • Evaluate Allowed Tensile Strength of tendon • Define tendons horizontal spacing (every cell/every cells, etc…) • Calculate un-factored applied force on tendon (depends on the spacing between tendons) • If Allowed Tensile Strength of tendon is greater than applied force OK! III – Neoweb Design Anchorage System- Impenetrable Slopes • Stages for Design Crest Anchor: • Define crest anchor type: • PVC pipe / concrete beam • Most of resistance is achieved by height of deadman and buried thickness below ground level • Define deadman’s dimensions: • Width, height, unit weight, buried thickness • Calculate passive resistance • Calculate friction resistance • If passive + friction resistance are equal or greater than applied OK! factored tensile strength on tendons (for 1m strip) III – Neoweb Design Impenetrable Slopes - EXAMPLE: OK!