Geogrid is not suitable. rather geotextiles are good.
US corps of Engineers has a well documented tech. manual named"Engineering use of geotextiles" .Army TM 5-818-8
That's air force afjman32-1030. You will find more about other uses of geotextiles too.
dear friends,
I guess you can classify "rigid" foundations as " thick" and " flexible" as " thin". And for sure you know what is a rigid foundaion.
regards