Four Tier segmental Retaining Wall w/o Geo-Grid
Four Tier segmental Retaining Wall w/o Geo-Grid
(OP)
I originally posted this in the geotech forum but there very little traffic there!
I was looking for some suggestions to repair this segmental retaining wall that was not constructed correctly in the first place. After a section of the wall collapsed, I was called to inspect it and found out that there was no geo-grid installed and now, after over ten years, there are signs of movements but mostly at the top of the walls. Plan and photo are attached.
The blocks are not the interlocking type and can even slide on each other. There is a filter fabric directly behind the wall with about a couple of inches of crushed stone.
I was thinking of using soil anchors like Manta-Ray and build a CMU wall section by section as we remove and replace the existing blocks. This way, the CMU wall and the anchor will hold back the soil and the blocks could be used as decorative facing. I also thought about gravity walls but they are big and take too much space and not practical here.
The only info I have on soil is that this was cut into a hill and it’s about 500’ from ocean. There is no way I can get boring done at the top.
Any suggestion is appreciated.
I was looking for some suggestions to repair this segmental retaining wall that was not constructed correctly in the first place. After a section of the wall collapsed, I was called to inspect it and found out that there was no geo-grid installed and now, after over ten years, there are signs of movements but mostly at the top of the walls. Plan and photo are attached.
The blocks are not the interlocking type and can even slide on each other. There is a filter fabric directly behind the wall with about a couple of inches of crushed stone.
I was thinking of using soil anchors like Manta-Ray and build a CMU wall section by section as we remove and replace the existing blocks. This way, the CMU wall and the anchor will hold back the soil and the blocks could be used as decorative facing. I also thought about gravity walls but they are big and take too much space and not practical here.
The only info I have on soil is that this was cut into a hill and it’s about 500’ from ocean. There is no way I can get boring done at the top.
Any suggestion is appreciated.






RE: Four Tier segmental Retaining Wall w/o Geo-Grid
Here is the Plan & Section view.
RE: Four Tier segmental Retaining Wall w/o Geo-Grid
RE: Four Tier segmental Retaining Wall w/o Geo-Grid
RE: Four Tier segmental Retaining Wall w/o Geo-Grid
I couldn't view your attachments, but I don't know if it's from your end, my end or Eng-Tips end.
RE: Four Tier segmental Retaining Wall w/o Geo-Grid
RE: Four Tier segmental Retaining Wall w/o Geo-Grid
It was probably designed by a landscaper not familiar with what is needed.
Even though the heights of the individual walls are not great, a flat surface has no way to be stacked with a consistent batter that is needed, especially when water and fine soil provide lubrication for sliding.
What is needed in the end is is a real SRW (possibly a smaller size) that provides positive shear resistance (lugs or pins) and a controlled batter. There are such units that are "tumbled/antiqued" that can also have geo-grid (if needed) attached while maintaining a similar appearance. The major 4 retaining walls systems (Allan Block, Anchor Wall Systems, Keystone and Versalok) all have some units that could be used. All have run real life tests to determine the connection of the SRW to the geo-grid under wet conditions.
What has happened in one area can be expected to occur to the rest of the walls sometime in the future.
Many Geo engineers are familiar with the problems and products and even some structural engineers get involved.
Dick
Engineer and international traveler interested in construction techniques, problems and proper design.
RE: Four Tier segmental Retaining Wall w/o Geo-Grid
I thought about soil anchors and reinforced CMU walls starting at the bottom tier. The cost will probably be significantly less than replacing the pavers with SRW blocks and the installation of geogrid.
RE: Four Tier segmental Retaining Wall w/o Geo-Grid
The arbitrary 4' (or 5' in some areas) is a simple administrative number to go by. I does not take into account the surcharge or the soil level rising above the top of the wall that usually has an effect with the magnitude depending on the soil properties.
Just replacing the units with real SRWs with shear lugs and a uniform batter may be a place to start and eliminate the excessive excavation for the geo-grid.
Dick
Engineer and international traveler interested in construction techniques, problems and proper design.
RE: Four Tier segmental Retaining Wall w/o Geo-Grid
EIT
www.HowToEngineer.com
RE: Four Tier segmental Retaining Wall w/o Geo-Grid
Unfortunately, the "design"/engineering was made to easily fit the contours and provide access. With a guess at the actual slope, a SRW design and installation with 2 or 3 walls with geogrid (if necessary). Unfortunately this is not a "pick and shovel" project for an individual and equipment is required. The SRW systems that allow plantings are not adequate fot the walls heights
I have over 20 similar installations within 2 miles of me of similar heights (5 to 10'), but most of them use geo-grid for an economic solution, considering the wall curvature and varying height.
The reinforce CMU or concrete walls are not practical considering the varying heights and curvature of the walls necessary. This is exemplified by the use of high, curved walls up to 35' high of varying heights.
Dick
Engineer and international traveler interested in construction techniques, problems and proper design.