In　order　to　study　the　fracture-plane　controlled　blasting　process　in　rock　containing　plane　of　weakness,　transmission-type　experiments　in　dynamic　caustics　were　carried　out　in　PMMA.　The　crack　propagation　mechanism　and　influence　of　closed　joint　and　closed　bedding　on　crack　propagation　of　cutting　seam　cartridge　fracture　controlled　blasting　were　studied.　The　experimental　results　show　that　the　crack　does　not　traverse　the　joint　but　two　wing　cracks　appear　at　both　tips　of　the　closed　joint.　The　mixed-mode　stress　intensity　factors　at　the　tips　of　wing　cracks　take　on　an　oscillating　character.　The　wing　cracks　generally　spread　along　the　initial　crack　direction　and　the　longest　wing　crack　is　5.6　cm.　When　the　crack　runs　into　the　closed　bedding　plane,　it　deviates　a　short　distance　along　the　bedding　and　continues　to　propagate　along　its　initial　direction.　The　longest　secondary　crack　is　1.8　cm.　The　dynamic　stress　intensity　factor　at　the　tips　of　the　secondary　cracks　also　oscillates.　Furthermore,　the　value　of　dynamic　stress　intensity　factor　K　I　d　I　is　smaller　than　that　of　dynamic　stress　intensity　factor　K　I　d.　©　2010　Taylor　&　Francis　Group.