Calculate the Factor of Safety for a geocomposite used behind a concrete retaining wall 10m high if the transmissivity of the geocomposite is 1.8x10-3 m2/min. The permeability of the backfilled soil is 3 x 10-5 m/s. The flow rate coming to the geocomposite (q) = 0.03m2/min. Solution FS = qact /qtheoritical qtheoritical = 5 x 10-5 m2/sec qact = KH (Nf/Nd) = 3 x 10-5 m/s x 10 m = 3 x 10 -4 m2/sec F= 3 x 10 -4 m2/sec/5 x 10-5 m2/sec = 6.