1. The safety factor criteria used in the design of reinforced soil retaining walls

2. The criteria related to the approval of material suppliers

The part related to material supplier approval is related to “Safety factor for materials,” and the test certificate for reinforcement materials should include the ultimate tensile strength, elongation for breakage, and tensile strength at 5% elongation. There are two aspects to verify regarding the materials.

• The ultimate tensile strength and design tensile strength of the materials specified in the structural calculation document.
• The ultimate tensile strength and tensile strength at 5% elongation specified in the test report.

3. Considerations in the design and structural calculation of reinforced soil retaining walls

• Ultimate tensile strength : Tult = (Product’s strength property : 60, 80, 100, 150, 200…)
• Reduction factors : RF = RFcr X RFd X RFid

  RFcr : Reduction factors for creep rupture, Typical values are as follows.

  

  RFd : Reduction factors for biochemical durability ( ≥1.1 )

  RFid : Reduction factors for construction damage ( ≥1.1 )

• Safety factor : FS = 1.5

• Tensile strength of design : Ta

  

  Reinforcement materials that undergo significant tensile deformation at lower tensile strengths may induce excessive horizontal displacement of the wall structure. Therefore, reinforcement materials with tensile strength at 5% elongation, as determined by applying a strength reduction factor, lower than the long-term design tensile strength, are discouraged from use.

4. Final review criteria for the suitability of Geogrids

• · Ultimate tensile strength from the structural calculation document < Ultimate tensile strength from the test report

• · Long-term design tensile strength from the structural calculation document < Tensile strength at 5% elongation from the test report