Mandatory Checklist for Gravity Retaining Wall Foundation Design.

Designing the foundation for a gravity retaining wall involves considerations for stability, bearing capacity, and soil-structure interaction. Below is a detailed checklist with explanations and examples for the design of a gravity retaining wall foundation:

1. Site Investigation:

• Explanation: Conduct a thorough site investigation to understand soil conditions.
• Example: Perform soil tests (SPT, CPT) to determine soil properties, bearing capacity, and potential sliding or settlement.

2. Load Analysis:

• Explanation: Analyze and calculate loads acting on the retaining wall.
• Example: Consider the weight of the wall, backfill soil pressure, surcharge loads, water pressure, and seismic loads to determine the total lateral load.

3. Bearing Capacity:

• Explanation: Ensure that the soil bearing capacity is sufficient for the applied loads.
• Example: If the total lateral load is 100 kN/m and the soil bearing capacity is 150 kN/m², the foundation is considered suitable.

4. Sliding Stability:

• Explanation: Check and ensure the foundation resists sliding.
• Example: Calculate the sliding force and compare it to the resisting force provided by the foundation. Use appropriate safety factors.

5. Overturning Stability:

• Explanation: Verify the foundation’s resistance to overturning.
• Example: Assess the moments and forces acting on the wall and ensure they are counteracted by the resisting moments and forces provided by the foundation.

6. Foundation Geometry:

• Explanation: Determine the appropriate dimensions and shape of the foundation.
• Example: Design a trapezoidal or rectangular foundation with dimensions that distribute the loads evenly.

7. Reinforcement:

• Explanation: Specify reinforcement in the foundation, if required.
• Example: Include reinforcing bars in the foundation to enhance its tensile strength and improve overall stability.

8. Foundation Depth:

• Explanation: Determine the optimal foundation depth for stability.
• Example: Increase the foundation depth if weak or compressible soil layers are present near the surface.

9. Toe and Heel Details:

• Explanation: Address toe and heel details to enhance stability.
• Example: Extend the foundation in the direction of potential sliding (toe) and provide a keying-in detail to resist sliding.

10. Drainage:

• Explanation: Implement drainage measures to reduce hydrostatic pressure.
• Example: Install drainage pipes behind the wall to relieve water pressure and prevent water accumulation.

11. Backfill Compaction:

• Explanation: Specify compaction requirements for the backfill soil.
• Example: Compaction should be done in lifts with specified moisture content to achieve adequate density.

12. Surcharge Loads:

• Explanation: Consider and account for any additional surcharge loads on the wall.
• Example: If there are adjacent structures or loads, factor them into the design to ensure stability.

13. Construction Sequence:

• Explanation: Develop a construction sequence that ensures stability during and after construction.
• Example: Excavate, place and compact the foundation material, and construct the wall in a manner that minimizes disturbances to the foundation.

14. Quality Control:

• Explanation: Implement quality control measures during construction.
• Example: Monitor the compaction of backfill, check reinforcement placement, and verify the dimensions of the foundation.

15. Code Compliance:

• Explanation: Ensure compliance with local building codes and standards.
• Example: Adhere to relevant codes such as AASHTO LRFD Bridge Design Specifications or local geotechnical standards.

16. Professional Engineer Involvement:

• Explanation: Engage a qualified geotechnical and structural engineer to oversee the design.
• Example: Have licensed engineers review and approve the gravity retaining wall foundation design to ensure it meets safety and code requirements.

17. Record Keeping:

• Explanation: Maintain detailed records of the retaining wall foundation design process.
• Example: Document all design calculations, soil test results, construction activities, and as-built drawings for future reference and audits.

By following this checklist, engineers can ensure a well-designed gravity retaining wall foundation that effectively resists lateral loads, provides stability, and minimizes potential failure modes.