Lessons learned from the design and construction of walls in soil reinforced with Geogrids
Throughout time, the technical literature reports cases of failures in reinforced soil walls, whose analysis leaves important lessons and a collection of recommendations for an adequate design and construction of this type of structures, as is the case of the following example Failures in reinforced soil retaining walls
"As a result of the heavy rains that fell in the region, a crack appeared for the first time on the road. As it continued to rain, the road from Akçakoca to Düzce collapsed completely at night."
The causes of this event could include a failure of the foundation of the structure due to insufficient bearing capacity and/or an excessive accumulation of interstitial water pressures in the backfill (increased pore pressure), leading to failure of the backfill slope. The latter would involve inadequate drainage of the fill, either due to poor design or construction or poor maintenance.
The following are the most common causes of retaining wall failures:
- Incorrect placement of reinforcement
- Saturated fill
- Design error Failures in reinforced soil retaining walls
- Unforeseen loads
- Errors in the use of the software
- Inadequate specifications and notes
- Poor quality construction
LESSONS LEARNED:
1. Inadequate design
Geotechnics: Failure to perform a detailed soil survey can lead to a design that does not consider the actual soil properties.
Overload: Designing the wall without considering additional loads, such as traffic, seismic activity, nearby structures or significant increases in the level of the roadway grade above the wall, can result in failure.
Changes in land drainage or underdrainage that alter the design assumptions can also lead to wall failure.
2. Construction Problems
Non-compliance with conformation soil specifications
Insufficient compaction: Lack of adequate soil compaction can reduce the bearing capacity of the wall and may result in failure due to pull out or extraction of the reinforcements from within the soil mass.
Incorrect installation of GeogridsIt is recommended to verify that the reference of the Geogrid in each of its layers is as indicated in the calculation reports and drawings of the wall.
Lack of control of surface runoff water into the landfill
3. Environmental Conditions
Erosion: Erosion on the face of the wall can lead to loss of fill material and instability of the wall. On the other hand, erosion of the foundation soil can generate gullies that can trigger landslides. It is recommended to leave a berm in front of the wall and to provide a lined ditch to manage runoff water that flows into a body of water without generating erosion.
Water infiltration: Water can weaken soil and reinforcement materials, especially if adequate drainage and underdrainage systems have not been implemented.
4. Poor maintenance
Lack of monitoring: Failure to perform regular inspections for deformations or deficiencies in drainage and underdrainage systems can allow small problems to develop into major failures.
5. External Factors
Seismic activity: Earthquakes can generate additional forces that should have been considered in the designs.
Changes in land use: Alterations in the environment, such as overloads associated with the construction of new structures nearby or changes in surface drainage can affect the stability of the wall.
These lessons highlight the importance of proper design, meticulous construction and ongoing maintenance to ensure the durability and stability of reinforced soil walls. Would you like to know more about a specific case or how to prevent these failures?