Study on the influence of joint spacing on rock fragmentation under TBM cutter by linear cutting test |
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| Affiliation: | 1. Ecole Polytechnique Fédérale de Lausanne (EPFL), Laboratory for Rock Mechanics (LMR), 1015 Lausanne, Switzerland;2. Key Laboratory of Urban Security and Disaster Engineering of Ministry of Education, Beijing University of Technology, Beijing 100124, China;3. CNNC Beijing Research Institute of Uranium Geology, Beijing 100029, China;4. School of Earth Sciences and Engineering, Nanjing University, Nanjing 210008, China;1. School of Civil Engineering, Chongqing University, Chongqing 400045, China;2. School of Geoscience, Hefei university of Technology, Hefei 230009, China;1. Key Laboratory of Urban Security and Disaster Engineering of Ministry of Education, Beijing University of Technology, Beijing 100124, China;2. Xinou Machinery CO. LTD, Guangzhou, China;1. School of Civil Engineering, Chongqing University, Chongqing 400045, China;2. National Joint Engineering Research Center of Geohazards Prevention in the Reservoir Areas, Chongqing 400045, China;3. Key Laboratory of Transportation Tunnel Engineering, Ministry of Education, Chengdu 610031, China;1. College of Mechanical and Electrical Engineering, Central South University, Changsha 410083, China;2. State Key Laboratory of High Performance Complex Manufacturing, Central South University, Changsha 410083, China |
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| Abstract: | Joint spacing is one of the most important geological factors influencing rock fragmentation by TBM cutters and TBM performance. In order to study the influence of joint spacing, full-scale linear cutting tests have been conducted for the Beishan granite samples with different joint spacing (i.e. one intact sample, two jointed samples with joint spacing of 100 mm and 400 mm). For different joint spacing, the influence of penetration depth on rock fragmentation was also explored by varying the penetration depth with an interval of 0.5 mm. During the test process, the three directional forces acting on the TBM cutter were recorded, and the rock chips formed by each cutting pass were weighed, respectively. By analysing the cutting force, crack initiation/propagation and rock chips, the influences of joint spacing on rock fragmentation process by TBM cutter were investigated. The test results showed that the increase of penetration depth cannot improve the TBM breakage efficiency after reaching a certain value for the intact rock sample, and the normal force for intruding the intact rock is larger than that for intruding the rock jointed samples. It is also found that the sample part below the joint plane is intact, thus joint can restrain the crack propagating cross the joint plane and facilitates the chips formation on the cutting surface. For the rock sample with joint spacing of 100 mm, two rock fragmentation modes were found during the cutting process. One mode is that the cracks initiate from the crushed zone under TBM cutter, and the cracks propagate to the joint plane, consequently form large rock chips. The other one is that the cracks initiate from the joint plane and then propagate to the rock cutting surface, and the cracks initiate before the formation of the crushed zone under the cutter. For the rock sample with joint spacing of 400 mm, there are two rock fragmentation stages, i.e., the normal rock fragmentation stage and the joint-controlled rock fragmentation stage. There is a transitional process between these two stages, and also the median crack can be promoted to propagate vertically to joint plane due to the joint existence. This study can provide useful guidance for operation optimization and performance prediction for TBM operating in jointed rock masses. |
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| Keywords: | Joint spacing Linear cutting test Penetration depth Rock fragmentation process |
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