Different types of soil nails, retaining wall tie-backs & ground anchors

[designrider]

There are many types of tie-back and bonded strand anchor systems available to designers. Without favoritism to any manufacturer, is there a "rule of thumb" for what type works best in various soils: clay, silt, loose sand, compacted sand, gravel, fractured rock, stable rock, etc?

Pre-drilled: Straight Shaft Gravity-Grouted (cased or uncased), Pressure Grout Injected, Post-grouted, Underreamed or mechanically enlarged belled ends.

Self-Drilling/Installed: Hollow bar grout injected (Williams or DSI Dywidag), Helical tieback (Chance Helical anchors), deformed screw anchors (Hilfiker Spiralnail), tipping plate soil anchors (Mantaray & Stingray anchors), others?

I know every project has specific constraints such as load demands, groundwater level, right-of-way, equipment access, contractor preference, etc. Please ignore those factors (if possible) and suggest where each tieback 'type' is optimally used. Or at the very least which soils are these types of anchors NOT good for?

 

[Geomike]

As you alluded to, there are many types of systems and even more conditions that would warrant the use of one system over another. That being said if I had to dig a deep hole in the middle of nowhere this is how I would propose to shore things.

Sands and other finer grained soils that don't stand well. I would go with sheet piles as they are easily driven into these materials and don't require the vertical to near vertical intermittent faces of soil nails.

Gravel/boulder containing materials very unstable rock. Drilled piles with lagging. Sheet piles will be damaged if not impossible to drive and it will be difficult to drill soil nail anchors through real bony material

Silty sands with gravel. Soil nails hands down, as they have the cohesion or apparent cohesion to stand during the construction phases. Depending on how loose the materials are would dictate hollow bar or solid. Hollow bar are better for loose soils where there is the potential for hole collapse during the drilling of the nails.