Designing the foundation for a Hybrid Systems Retaining Wall involves integrating various retaining wall technologies. The checklist below outlines the key considerations with explanations and examples for the design of such a 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 hybrid systems 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 180 kN/m and the soil bearing capacity is 250 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. Foundation Geometry:
- Explanation: Determine the appropriate dimensions and shape of the foundation.
- Example: Design a foundation that integrates elements of different retaining wall systems, such as combining reinforced soil slopes with anchored walls.
6. Reinforcement:
- Explanation: Specify reinforcement in the foundation, walls, and other components if required.
- Example: Include geogrid reinforcement in the reinforced soil slopes and use tiebacks for additional reinforcement in the anchored walls.
7. 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, considering the requirements of each retaining wall system.
8. Drainage:
- Explanation: Implement drainage measures to reduce hydrostatic pressure.
- Example: Install drainage pipes, geocomposite drains, or other drainage systems as needed behind the retaining wall components to ensure proper water management.
9. Backfill Specifications:
- Explanation: Specify backfill material properties and compaction requirements for each retaining wall system.
- Example: Utilize granular backfill with proper gradation and compaction for reinforced soil slopes, and choose suitable backfill for anchored walls based on soil conditions.
10. Facing Connection:
- Explanation: Detail the connection between different facing elements and the foundation.
- Example: Ensure secure connections between reinforced soil slope facings and anchored wall facings to create a cohesive and stable hybrid system.
11. Construction Sequence:
- Explanation: Develop a construction sequence that ensures stability during and after construction.
- Example: Coordinate the construction of different retaining wall components, ensuring proper sequencing to maintain stability and avoid disruptions.
12. Quality Control:
- Explanation: Implement quality control measures during construction.
- Example: Monitor the compaction of backfill, check reinforcement placement, verify the dimensions of the foundation, and ensure proper installation of facing elements.
13. 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 for each retaining wall system.
14. Professional Engineer Involvement:
- Explanation: Engage a qualified geotechnical and structural engineer to oversee the design.
- Example: Have licensed engineers review and approve the hybrid systems retaining wall foundation design to ensure it meets safety and code requirements.
15. Record Keeping:
- Explanation: Maintain detailed records of the hybrid systems 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 foundation for a Hybrid Systems Retaining Wall that effectively integrates various retaining wall technologies, resists lateral loads, provides stability, and minimizes potential failure modes.
