Protecting the MSE retaining walls from Ultraviolet light
Protecting the MSE retaining walls from Ultraviolet light
(OP)
I am designing the wing walls of a 2.5m*2.5m square culvert below a road in the northwest of the UK. The road side slopes are 2:1. The wing walls has a height that start at 4m and goes down to 0.0m at the end of the embankment slope. The wing wall inclination to the horizontal is 70 degrees, and the client want it to be made from MSE with a rape araound facing. That means I will use geogrid layers. The culvert life period is 120 years. So, the wing wall life period should be the same, but may be reduced to 60 years because with slopes not steeper than 70 degrees, it is still considered a reinforced earth by the British Highway Agency (HA).
I am worried about the effect of the ultraviolet light on the raparaound part of the geogrid. The makers of the geogrid (e.g. Tensar and Huesker) say that the geogrid layers include black carbon which protect the layers from degradation together with the vegetation. Prof. Das book "Principles of foundation engineering" says that the exposed wall face MUST be covered to protect the layers, and the wall face should be sprayed by bitumin emulsion or gunite, with a wire mesh anchored to the geotextile to keep the coating on. My questions are:
1- Do you have an advice about how to protect the reinforcement in the long term (60-120 years)?
2- Do you think that vegetation can grow on a 70 degree slope and protect it (together with the black carbon in the reinforcement layers)from the Ultraviolet rays? and if the answer is yes, what would the situation be during relatively dry seasons
Best regards
Ala'a
I am worried about the effect of the ultraviolet light on the raparaound part of the geogrid. The makers of the geogrid (e.g. Tensar and Huesker) say that the geogrid layers include black carbon which protect the layers from degradation together with the vegetation. Prof. Das book "Principles of foundation engineering" says that the exposed wall face MUST be covered to protect the layers, and the wall face should be sprayed by bitumin emulsion or gunite, with a wire mesh anchored to the geotextile to keep the coating on. My questions are:
1- Do you have an advice about how to protect the reinforcement in the long term (60-120 years)?
2- Do you think that vegetation can grow on a 70 degree slope and protect it (together with the black carbon in the reinforcement layers)from the Ultraviolet rays? and if the answer is yes, what would the situation be during relatively dry seasons
Best regards
Ala'a





RE: Protecting the MSE retaining walls from Ultraviolet light
As a British manufacturer of geogrid, they have substantial experience with the type of structure you are designing.
I hope this helps.
RE: Protecting the MSE retaining walls from Ultraviolet light
1- the culvert will work like an underpass for sheeps below a road. So, the sheeps can eat the vegetation.
2- Due to some reasons, the ground water level is at the foundation level for the culvert at one end and 0.45m above its foundation level on the other end of the inclined culvert. Therefore, unless someone is brave enough to change the height or the foundation level of the culvert, the MSE wall bottom reinforcement layer will be 0.95m below the permanent ground water level in a sand and gravel soil layer.
RE: Protecting the MSE retaining walls from Ultraviolet light
RE: Protecting the MSE retaining walls from Ultraviolet light
Talk with local suppliers to get recommendations on materials that are suited to your project. Just be sure to get complete technical information on the product so you can better understand the properties you are dealing with.
I also recommend you download the following:
Reinforced Soil Structures Mechanically Stabilized Earth Walls and Reinforced Soil Slopes Design and Construction Guidelines 2000 FHWA-NHI-00-043
and
Reinforced Soil Structures Corrosion/Degradation of Soil Reinforcements for Mechanically Stabilized Earth Walls and Reinforced Slopes 2000 FHWA-NHI-00-044
at: htt
RE: Protecting the MSE retaining walls from Ultraviolet light
RE: Protecting the MSE retaining walls from Ultraviolet light
RE: Protecting the MSE retaining walls from Ultraviolet light
You pay a slight premimum for the material, but you get a lifespan easily 75 years+
RE: Protecting the MSE retaining walls from Ultraviolet light
RE: Protecting the MSE retaining walls from Ultraviolet light
These systems are also routinely combined with geogrid for MSE and RSS applications. Whenever the mesh is not strong enough, geogrids make for very cost effective structures.
RE: Protecting the MSE retaining walls from Ultraviolet light
RE: Protecting the MSE retaining walls from Ultraviolet light
it sounds like this is a sheep crossing, not a drainage culvert. Unless I have misinterpreted the posting, no water will flow through this.
RE: Protecting the MSE retaining walls from Ultraviolet light
RE: Protecting the MSE retaining walls from Ultraviolet light
RE: Protecting the MSE retaining walls from Ultraviolet light
I should have referenced my post. I was commenting on GabionGuy's comments on Macceferri's PVC coated products.
"You pay a slight premimum for the material, but you get a lifespan easily 75 years+"
Thanks,
RE: Protecting the MSE retaining walls from Ultraviolet light
Every project should be looked at on it's merits. In some instances, the PVC coating may be insufficient on its own and the Engineer/owner may want to look enhanced polymer coatings or perhaps a PVC + galfan wire material.
The original PVC coated wire structures were built in the early 1950's and are permanently exposed to salt water and wave action. These structure are still intact and performing satisfactorily.
The 75 year life is a general expectation based upon ongoing monitoring of in situ structures, testing of material properties of built structures and accelerated testing in order to determine expected lifespan of a structure.
A typical galvanized wire structure siting in freshwater in Northamerica will be lucky if it survives 15 years. I know structures that are much older in that situation and are in good condition, but I am also aware that in other parts of Northamerica, people are lucy to get 10 years out of the structure.
RE: Protecting the MSE retaining walls from Ultraviolet light
WallGuy770