The　present　study　extends　the　numerical　manifold　method　to　investigate　the　effective　permeability　coefficient　(k(eff))　of　soil-rock　mixtures.　The　influence　of　rock　content,　rock　size,　rock　shape,　and　rock　blocks＇　major　axis　direction　on　k(eff)　is　studied.　The　results　show　the　following:　(1)　k(eff)　decreases　as　the　rock　content　increases;　(2)　the　influence　of　rock　size　on　k(eff)　can　be　neglected　if　other　parameters　are　fixed;　(3)　the　values　of　k(eff)　are　nearly　the　same　if　rock　blocks　are　in　circular　or　regular　hexagon　shapes;　and　(4)　the　major　axis　direction　of　rock　blocks　has　some　influence　on　k(eff).