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Abstract The joint orientation is a crucial factor which influences the penetration rate of TBM tunneling. Based on laboratory test，the effect of joint orientation on the penetration under TBM disc cutter is studied. In the test，two kinds of concrete with different strengths are adopted to simulate rock sample. The angle ? between joint plane and tunneling axis varies from 0°，30°，and 60° to 90°. The main conclusions can be drawn as follows：(1) chipping angle ? increases with the increment of angle ? from 0° to 60°，and is about 33°－50° when ? = 90°which agrees with the Hertzian cone crack. The angle Δ? between side crack and joint plane is about 40°－70° whereas ? changes from 0° to 90°. The angle Δ? between median crack and joint plane is about 0°－10° as ?≤30°，and arises sharply when ?≥60° which makes median crack joints with joint plane to cause chipping. (2) The test results show three possible chipping modes of rock fragmentation：first，the side crack initiates beneath the crushed zone and propagates to free surface or joint plane to produce chipping. Second，the median crack propagates downwards to the joint plane to produce chipping as ?≥60°. Third，the crack initiates from the joint plane due to joint deformation and propagates to the free surface when ?≥30°. (3) The penetration rate achieves the highest value at ? = 60° and joint gives more notable effect on fragmentation of the rock with higher strength.
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Received: 19 July 2010
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2011, Vol. 30 
