Radial versus Parallel Tie Arrays in Earth Backfills

Ties or reinforcements are normally connected to the backside of a retaining wall and extend horizontally into the backfill. This horizontal, parallel array was compared with a radial tie array in which ties radiated in clusters from single points. The latter array simulates the roots of woody plants growing in the frontal interstices of retaining walls and also the action of a ``reticulated root pile'' system of criss-crossing ties or inclusions. The study was carried out using a rigid model retaining wall, dry sand backfill, and natural reed fibers as ties. Reduction in lateral forces or overturning moment against the wall was measured as a function of tie length and attachment at the wall. Test results showed that clusters of radiating ties were equally, if not more effective than horizontal, parallel tie arrays in reducing overturning moments.