Soldier Pile Lagging in fill

[PastorQ]

After discussion in-house, I would appreciate outside input. We are designing a temporary 12'-20' high embankment (temporary roadway) with clean stone (#1) that is retained on both sides with soldier piles, timber lagging and tiebacks between the horizontal lines of soldier piles. The question that is being discussed is whether the empirical design tables for timber lagging are applicable in this fill situation or how will soil arching be different in fill versus in-situ soil?
Thanks

 

[aeoliantexan]

Your structure may be similar to a crib wall. They used to be constructed with timbers, later with precast concrete or corrugated steel members. Tschebotarioff dicusses crib walls in his book "Foundations and Earth Structures", 1951 and 1974. He says the members are designed for a lateral force of (d+e)* a * 0.5 * Gamma *b, where d is the effective height of each member (the height plus the spacing), a is the menber length, Gamma is the unit weight of the granular fill, and b is the width of the wall (transverse to the length). However, the members also carry a vertical load due to friction and settlement of the fill. They share some issues with silos.

Contech still sells corrugated steel crib walls. You could talk with their engineers.