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I I I I I I I I I I I I I I I I I I I Simons, Li and Associates, Inc, Job Number 6l43J002 Project Portland Flume Reconstruction vided during excavation and during the placement and compaction of all backfill. Lateral Earth Pressures: Recommended lateral earth pressure values are presented in the following tabulation: Equivalent active pressure: Undisturbed subsoil ------------------- Compacted backfill (on-site or imported soils)------------ 35 psf/ft 30 psf/ft 250 psf/ft 325 psf/ft 450 psf/ft 0.30* Equivalent passive soil pressure: Shallow wall/wall footings ------------ Shallow column/column footings -------- Drilled Caissons----------------------- Equivalent friction coefficient---------- *The coefficient of base friction should be reduced to 0.20 when used in conjunction with passive pressure, At rest soil pressures should be used for structures with rigid, restrained, relatively unyielding walls, such as the box culverts, Fill against footings, box culverts, basement walls, and flume walls should be placed to densities specified in 'Site Prepara- tion' to minimize total active pressures and to develop passive resistances at relatively low strains, It is recommended that free-draining, granular soils containing less than five percent fines (by weight) passing a No, 200 sieve be placed adjacent to the walls. Compaction of each lift adjacent to unbraced walls should be accomplished with hand-operated tampers or other lightweight compactors, Over-compaction may cause excessive lateral earth pressures which could result in pro- gressive wall movements. -6- @