Segmental Retaining Wall Design
Segmental Retaining Wall Design
(OP)
I have a situation whereby i am designing a Segmental Retaining Wall is Ht:- 1.575m it is holding up 2H:1V slope above i have designed tie back of 1.3m (0.83 base to ht ratio). The slope runs about 5.8m and then it tapers to Rail track. I am asked to account for rail load Cooper E90. I drew a 10H : 7V from the rail track. It just touches the back of Geogrid behind the wall. The structural engineer of the client recommends i use 2H : 1V as load influence from the rail track. How should i account for this extra load. I if draw 2H : 1V slope line from rail track the load line is hitting the Facing system at almost mid of wall.
Thanks for all your suggestions.
Thanks for all your suggestions.





RE: Segmental Retaining Wall Design
You should use Boussinesq formula for horizontal pressures from strip loading. Beyond this you need to ensure no slip circle failure.
HTH
VOD
RE: Segmental Retaining Wall Design
thread255-150849: Surcharge Pressure on Retaining Walls.
RE: Segmental Retaining Wall Design
RE: Segmental Retaining Wall Design
Thanks for all your suggestions
Thanks for all your suggestions
RE: Segmental Retaining Wall Design
Internally and structurally, you will need to ensure that the lateral pressure from the Cooper loading does not tend to bulge the facing from the attached reinforcing strips, presuming the strips can take the tensile forces, ie check the facing rebars and facing to strip connections.
Externally, you should apply the increased lateral pressure due to the lengthening of the strips (iterative) for overall sliding and overturning at this stage.
RE: Segmental Retaining Wall Design
Externally, you should apply the increased lateral pressure due to the lengthening of the strips (iterative at this stage) for overall sliding and overturning.
RE: Segmental Retaining Wall Design
In my case its polyester geogrids (Strata grid 200) but i guess the principle remains the same. Apply increased lateral pressure check external, internal stability of wall and also check global stability of entire wall slope geomerty.Based on the guide line i have attached i should apply resultant pressure Ph for base sliding calculation and Ph X hp for overturning calcualtion my other doubt do i have to apply correction in the equation for wall batter since in my case its flexiable system Segmental retaining wall.
RE: Segmental Retaining Wall Design
First, yes, statics should be followed for slip circle, max allowable bearing pressures, overturning and sliding.
Second, wall facing batter has no effect on the applied pressure. The Code you should be using is the AREMA code NOT the CANFEM. Last I checked, CANFEM is not a Code but a manual of Canadian practice. AREMA has the correct formulas for horizontal pressures from strip loading on flexible walls as well, the pdf you refer to shows point load only.
As you probably know, make sure that you are accounting for the upward sloping fill above the top of the wall. Ka values are notably high for this case. You must also account for earthquake as well using AREMA, even though this is in Canada, as CN and CP require this.
RE: Segmental Retaining Wall Design
I also worry that your grid length will be inadequate. Normal practice is 2.4m min although this can be reduced if small comapction plant is used. In AASHTO the minimum Le, (i.e. length in the resistant zone) should be 1m. From my experience, with such a large surcharge slope, relative to the very short wall height, I'd expect to be seeing L to H ratios of more like 1.2 or greater.
You will also want to specify very good fill, consider sub base or AASHTO #57 stone (sub base is probably better since the extra weight will help with global stability.)
Personally, I'm not 100% comfortable with NCMA, I think AASHTO LRFD produces a more reliabe design.