Downdrag contribution by reinforced strap zone of MSE wall

[Geola]

We calculated downdrag for abutment drilled shafts based on contribution of the reinforced strap zone of MSE wall and the underneath compressible soils. But the structure engineer said they typically do not consider downdrag in these locations. Is it reasonable?
Thanks a lot.

 

[geoman110]

Without knowing all the details and circumstances, it is hard to comment. Generally, if a surcharge (e.g., MSE wall) is added over compressible soil, it should cause downdrag forces. If the drilled shafts are end bearing on the bedrock, the downdrag forces does not come to effect in geotechnical bearing capacity. However, they should be considered in structural design.

 

[jrm73]

More information would be helpful. The downdrag becomes an additional load to be resisted by the foundation soils. The geotech has to predict the load and the structural should make sure the foundation pile/pier can structurally withstand the additional load. If this is a fiction pile, the pile will settle. If it is an end bearing pile, the soil below the pile tip could be overstressed if the load was not considered.