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Design Concepts for 6m high walls

These Design Concepts are based on the Bosun Robust Block.

NOTE: These design concepts are merely just GUIDELINES ONLY. An engineers consultation is needed before building Retaining Walls.

For walls higher than 1.4m an engineer design and certificate is required.

A registered geotechnical engineer is required to design and certify a retaining wall higher than 6m.
Click on a heading below for more information.

Normal conditions

Normal conditions can be defined as:

  • The area must have good compactable soil (No sand or clay).
  • If the area does not have good compactable soil, fill material should be imported (G5 or G6 is acceptable).
  • No structural or vehicular loading.
  • No severe surface or ground water in the area.

Foundation:

  • Excavate to a depth of ±500mm.
  • Compact the soil 150mm below the intended concrete foundation to 93% MOD ASSHTO.
  • Construct a 500mm x 350mm, 20 Mpa concrete foundation – A concrete foundation will enable easier levelling.
  • Y10 reinforcing should be used.
  • The first two blocks should preferably be placed below the ground level.

Construction:

  • It is recommended that the wall  be constructed at a 75° angle.
  • After each block layer the soil should be compacted to 93% MOD ASSHTO. Do not compact layers more than 150mm thick.
  • Use a vibrating roller or jumping jack tamper for compaction. Any mechanical compaction must not be closer than 300mm behind the block. 300mm and closer must be hand compacted in order to prevent blocks from tilting.
  • Install 40/40 composite reinforcing geogrid between every second row of blocks.  The geogrid should be ±800mm from the front edge of the blocks (It is recommended to use RockGrid® by Kaytech).
  • After the first five layers of geotextile, the width can be reduced to 3000mm.
  • The geotextile should be laid flat without creases.

Bosun Versoblock installations, use a geotextile after every third block.

  • The most important aspect of Retaining Block Walls is the compaction behind the blocks. The Blocks act merely as the system’s skin.

2 x Subsoil drains:

  • The lowest subsoil drain should preferably be installed ±1500mm behind the blocks and the highest subsoil drain should be installed ±2500mm behind the blocks in order for water to flow into the drain opposed to the compacted area.
  • Use a 110mm perforated pipe, enclosed in 19mm or 6mm stone and wrapped in 200mm x 200mm A2 nonwoven filament geotextile (It is recommended to use A2 Bidim® by Kaytech).
  • Fines will clog the system if a geotextile is not used.
  • Construct outlets every 6 meters dispose of water at the lowest end of the subsoil drain.

Click on image to enlarge

6 meter Retaining Wall Design

6 meter Retaining Wall earth works

Retaining Wall Perforated pipe

For areas with moderate surface or sub-surface water including a wick drain

Normal condition definition must be considered.

Foundation:

  • Excavate to a depth of ±500mm.
  • Compact the soil 150mm below the intended concrete foundation to 93% MOD ASSHTO.
  • Construct a 500mm x 350mm, 20 Mpa concrete foundation – A concrete foundation will enable easier levelling.
  • Y10 reinforcing should be used.
  • The first two blocks should preferably be placed below the ground level.

Construction: 

  • It is recommended that the wall  be constructed at a 75° angle.
  • After each block layer the soil should be compacted to 93% MOD ASSHTO. Do not compact layers more than 150mm thick.
  • After the first five layers of geotextile, the width can be reduced to 3000mm.
  • The geotextile should be laid evenly without creases.

Bosun Versoblock installations, use a geotextile between every third block.

  • The most important aspect of Retaining Block Walls is the compaction behind the blocks. The Blocks act merely as the system’s skin.

Lowest subsoil drain:

  • The lowest subsoil drain should preferably be installed ±1500mm behind the blocks.
  • Use a 110mm perforated pipe, enclosed in 19mm or 6mm stone and wrapped in 200mm x 200mm A2 nonwoven filament geotextile (Bosun recommends A2 Bidim® by Kaytech).
  • Fines will clog the system if a geotextile is not used.
  • Construct outlets every 6 meters dispose of water at the lowest end of the subsoil drain.

Top subsoil drain with wick drain:

  • The highest subsoil drain should preferably be installed ±2500mm behind the blocks in order for water to flow into the drain opposed to the compacted area.
  • Use a 110mm perforated pipe, enclosed in 19mm or 6mm stone and wrapped in 200mm x 200mm A2 nonwoven filament geotextile (Bosun recommends A2 Bidim® by Kaytech).
  • Fines will clog the system if a geotextile is not used.
  • Construct outlets every 6 meters dispose of water at the lowest end of the subsoil drain.
  • Wick drains (Bosun recommends WickDrain® by Kaytech) are laid at 45° angle with 1.8m spacing, rearward.  Lengths vary according to design, e.g. 1.7m (1.7m x length of the wall / 1.5 = length needed).

V drain or kerb:

  • The purpose of the V drain is to direct water away from the Retaining Block Wall.
  • The V drain or kerb should be ±3.5m behind the top edge of the wall, in order to divert water from the compacted area.

Click on image to enlarge

6 meter Retaining Wall water drainage system

For areas with moderate surface or sub-surface water including flo drain

Normal condition definition must be considered.

Foundation:

  • Excavate to a depth of ±500mm.
  • Compact the soil 150mm below the intended concrete foundation to 93% MOD ASSHTO.
  • Construct a 500mm x 350mm, 20 Mpa concrete foundation – A concrete foundation will enable easier levelling.
  • The first two blocks should preferably be placed below the ground level.

Construction: 

  • Bosun recommends the wall to be constructed at a 75° angle.
  • After each block layer the soil should be compacted to 93% MOD ASSHTO. Do not compact layers more than 150mm thick.
  • Use a vibrating roller or jumping jack tamper for compaction. Any mechanical compaction must not be closer than 300mm behind the block. 300mm and closer must be hand compacted in order to prevent blocks from tilting.
  • Install 40/40 composite reinforcing geogrid between every second row of blocks.  The geogrid should be ±800mm from the front edge of the blocks (It is recommended to use RockGrid® by Kaytech).
  • After the first five layers of geotextile, the width can be reduced to 3000mm.
  • The geotextile should be laid evenly without creases.

Bosun Versoblock installations, use a geotextile between every third block.

  • The most important aspect of Retaining Block Walls is the compaction behind the blocks. The Blocks act merely as the system’s skin.

Lowest subsoil drain:

  • The lowest subsoil drain should preferably be installed ±1500mm behind the blocks.
  • Use a 110mm perforated pipe, enclosed in 19mm or 6mm stone and wrapped in 200mm x 200mm A2 nonwoven filament geotextile (Bosun recommends A2 Bidim® by Kaytech).
  • Fines will clog the system if a geotextile is not used.
  • Construct outlets every 6 meters dispose of water at the lowest end of the subsoil drain.

Top subsoil drain with flo drain:

  • The highest subsoil drain should preferably be installed ±2500mm behind the blocks in order for water to flow into the drain opposed to the compacted area.
  • Use a 110mm perforated pipe, enclosed in 19mm or 6mm stone and wrapped in 200mm x 200mm A2 nonwoven filament geotextile (Bosun recommends A2 Bidim® by Kaytech).
  • Fines will clog the system if a geotextile is not used.
  • Construct outlets every 6 meters dispose of water at the lowest end of the subsoil drain.
  • Flo drains (Bosun recommends Flo-Drain® by Kaytech) are laid 1.5m alongside the wall, 2.3m behind the edge of the front block where the subsoil drain level is situated.  The flo drain should be tilted to a 75° angle to manage the speed of the water flow.

V drain or kerb:

  • The purpose of the V drain is to direct water away from the Retaining Block Wall.
  • The V drain or kerb should be ±3.5m behind the top edge of the wall, in order to divert water from the compacted area.

Click on image to enlarge

6 meter Retaining Wall drainage system

Structural loads / Vehicular loads for areas with sufficient space

Load is at least 6.5m from edge of wall.

Normal conditions definition must be considered.

Foundation:

  • Excavate to a depth of ±500mm.
  • Compact the soil 150mm below the intended concrete foundation to 93% MOD ASSHTO.
  • Construct a 500mm x 350mm, 20 Mpa concrete foundation – A concrete foundation will enable easier levelling.
  • Y10 reinforcing should be used.
  • The first two blocks should preferably be placed below the ground level.

Construction: 

  • It is recommended that the wall  be constructed at a 75° angle.
  • After each block layer the soil should be compacted to 93% MOD ASSHTO. Do not compact layers more than 150mm thick.
  • Use a vibrating roller or jumping jack tamper for compaction. Any mechanical compaction must not be closer than 300mm behind the block. 300mm and closer must be hand compacted in order to prevent blocks from tilting.
  • Install 40/40 composite reinforcing geogrid between every second row of blocks.  The geogrid should be ±800mm from the front edge of the blocks (It is recommended to use RockGrid® by Kaytech).
  • After the first five layers of geotextile, the width can be reduced to 3000mm.
  • The geotextile should be laid evenly without creases.

Bosun Versoblock installations, use a geotextile between every third block.

  • The most important aspect of Retaining Block Walls is the compaction behind the blocks. The Blocks act merely as the system’s skin.

2 x subsoil drains:

  • The lowest subsoil drain should preferably be installed ±1500mm behind the blocks and the highest subsoil drain should be ±2500mm behind the blocks in order for water to flow into the drain opposed to the compacted area.
  • Use a 110mm perforated pipe, enclosed in 19mm or 6mm stone and wrapped in 200mm x 200mm A2 nonwoven filament geotextile (It is recommended to use A2 Bidim® by Kaytech).
  • Fines will clog the system if a geotextile is not used.
  • Construct outlets every 6 meters dispose of water at the lowest end of the subsoil drain.

V drain or kerb:

  • The purpose of the V drain is to direct water away from the Retaining Block Wall.
  • The V drain or kerb should be ±3.5m behind the top edge of the wall, in order to divert water from the compacted area.

Click on image to enlarge

6 meter Retaining Wall weight / load distribution6 meter Retaining Wall weight / load distribution

Structural loads / Vehicular loads for areas with limited space

Loads should not be closer than 3m from the top edge of the Retaining Block Wall (Consult a Civil Engineer if the load is closer than 1m).

Normal conditions definition must be considered.

Foundation:

  • Excavate to a depth of ±500mm.
  • Compact the soil 150mm below the intended concrete foundation to 93% MOD ASSHTO.
  • Construct a 500mm x 350mm, 20 Mpa concrete foundation – A concrete foundation will enable easier levelling.
  • Y10 reinforcing should be used.
  • The first two blocks should preferably be placed below the ground level.

Construction: 

  • It is recommended that the wall  be constructed at a 75° angle.
  • After each block layer the soil should be compacted to 93% MOD ASSHTO. Do not compact layers more than 150mm thick.
  • Use a vibrating roller or jumping jack tamper for compaction. Any mechanical compaction must not be closer than 300mm behind the block. 300mm and closer must be hand compacted in order to prevent blocks from tilting.
  • Install 40/40 composite reinforcing geogrid between every second row of blocks.  The geogrid should be ±800mm from the front edge of the blocks (It is recommended to use RockGrid® by Kaytech).
  • The last two geotextile layers must be laid under the load foundation.
  • The geotextile should be laid evenly without creases.

Bosun Versoblock installations, use a geotextile between every third block.

  • The most important aspect of Retaining Block Walls is the compaction behind the blocks. The Blocks act merely as the system’s skin.

2 x subsoil drains:

  • The lowest subsoil drain should preferably be installed ±1500mm behind the blocks and the highest subsoil drain needs to ±2500mm behind the blocks in order for water to flow into the drain opposed to the compacted area.
  • Use a 110mm perforated pipe, enclosed in 19mm or 6mm stone and wrapped in 200mm x 200mm A2 nonwoven filament geotextile (It is recommended to use A2 Bidim® by Kaytech).
  • Fines will clog the system if a geotextile is not used.
  • Construct outlets every 6 meters dispose of water at the lowest end of the subsoil drain.

V drain or kerb:

  • The purpose of the V drain is to direct water away from the Retaining Block Wall.
  • The V drain or kerb should be ±3.5m behind the top edge of the wall, in order to divert water from the compacted area.

Click on image to enlarge

6m Retaining Wall vehicular load

Contact Us

Head Office
Cnr Cresset and Musket Roads
Midrand Industrial Park
Phone: 011 310 1176
Email: info@bosun.co.za