Papers by Keyword: Rock Fragmentation

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Authors: Woo-jin Jung, Shiro Kubota, Yuji Wada, Yuji Ogata, Hideki Shimada, Kikuo Matsui
367
Authors: Kai Hui Li, Ping Cao, Jie Liu
Abstract: To study the effect of rock joint parameters, the joint orientation, the filling situation of joint and the distance between the center of joint and the position of penetration on rock fragmentation mechanism by tunnel boring machines (TBM) cutters, a series of penetration tests were conducted on rock-like specimens using the modified triaxial testing machine. Data of indentation load and penetration depth during the loading process were recorded and analyzed. Results show that the filling situation of joint can significantly influence the resistance of rock to penetration. The joint interface closer to the position of penetration plays a more positive role in rock fragmentation than that farther to the position of penetration. The joint orientation can greatly affect the peak indentation load, the anti-invasive factor, the crushing work as well as modes of rock fragmentation. With the increase of joint orientation, the peak indentation load, anti-invasive factor and crushing work decrease firstly, and then increase. When joint orientation equals to 60° and 90°, they reach the minimum and maximum values, respectively.
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Authors: Wei Dong Lei, Kai Li, Xue Ping Wang
Abstract: Reasonable distribution of the rock fragmentation can reduce the overall cost in a mining industry. Digital image processing technique can be used to determine the rock fragmentation distribution function. This paper proposes an improved watershed segmentation method in digital image processing technique. The seven key steps in the new method are presented. Meanwhile, the detailed rock fragmentation analysis is performed on an example digital photo of fragmented rock pile taken from a practical underground mine, to further explain the mechanism of the new method. It is found that the new method can overcome the phenomenon of over-segmentation and over-lapping in digital photos, and exactly detect boundaries for every individual target in the photo.
1734
Authors: Yi Lan Kang, Pei Qi Chen, Gan Yun Huang
Abstract: Numerical simulations of pressure loading effects on occurrence of rock lateral cracks under confining pressure were performed by using the numerical analysis software. The results indicate that the rock tends to have median cracks with the increasing of penetration under no confining pressure, while the rock tends to have lateral cracks with the increasing of penetration under confining pressure. The relative position of lateral crack initiation is dependent on the confining pressure when loading, which is independent of the penetration. The greater the confining pressure, the closer the lateral crack location to the rock surface. With the increasing of penetration and confining pressure while loading, the lateral crack direction is towards to the direction parallel to the rock surface.
433
Authors: Gang Li, Li Da Zhu, Jian Yu Yang, Wan Shan Wang
Abstract: The rock breakage process is the interaction process between TBM and rock mass, which is affected by TBM specifications, such as thrust force, cutter tip width and profile, cutter spacing, RPM, and torque, and rock mass properties mainly including rock material strength, rock brittleness, joint spacing and orientation. In this study, based on the systematic study of the existed rock constitutive model achievements and introduction of rock breaking mechanism, main failure mode of rock in the breaking process of disc cutter is added and revised in order to meet the actual situation. The method of establishing finite element model of disc cutter breaking process using ANSYS AUTODYN-3D software is introduced. After the dynamic simulation, we can obtain that geotechnical interface disturbance insulted by disc cutter. Based on plenty of experiments, it confirms reliability of numerical methods and provides a method to study cutting performance for different geological conditions.
2033
Authors: Gang Li, Bo Wang, Ya Dong Chen, Wan Shan Wang
Abstract: The rock fragmentation process is the interaction process between TBM and rock mass, which is affected by TBM specifications, such as thrust force, cutter tip width and profile, cutter spacing, RPM, and torque, and rock mass properties mainly including rock material strength, rock brittleness, joint spacing and orientation. In this study, based on the systematic study of the existed rock constitutive model achievements and introduction of rock breaking mechanism, main failure mode of rock in the breaking process of disc cutter is added and revised in order to meet the actual situation. The method of establishing numerical model of disc cutter breaking process is introduced. After the dynamic simulation, we can obtain that geotechnical interface disturbance insulted by disc cutter. Based on plenty of experiments, it confirms reliability of numerical methods and provides a method to study cutting performance for different geological conditions.
1069
Authors: Pei Qi Chen, Jin Tao Cui, Xiao Jie Zhou
Abstract: This paper performed numerical simulations of effects of unloading on occurrence of rock lateral cracks by using the numerical analysis software. The results indicate that the probability of median cracks and Hertz cracks occurrence was decreased due to the residual stress caused by stress mismatch during unloading, while the probability of lateral cracks occurrence was increased. The lateral cracks were tended to occur with the increasing of the amount of unloading and confining pressure. And the initiation direction of lateral cracks is more parallel to the rock surface, although the initiation direction became the same at the end. The relative positions of lateral cracks occurred were more concentrated during unloading process under the same confining pressure.
635
Authors: Pei Qi Chen, Jin Tao Cui, Xiao Jie Zhou
Abstract: Numerical simulations of effects of confining pressure on occurrence of rock lateral cracks were performed by using the numerical analysis software. The results indicate that the rock tends to have median cracks with the increasing of penetration under no confining pressure, while the rock tends to have lateral cracks with the increasing of penetration under confining pressure. The relative position of lateral crack initiation is dependent on the confining pressure when loading, which is independent of the penetration. The greater the confining pressure, the closer the lateral crack location to the rock surface. With the increasing of penetration and confining pressure, the lateral crack direction is towards to the direction parallel to the rock surface.
850
Authors: F. Lu, C. Zhang, J. Sun, J.X. Tian, M. Liu, Y.H. Wu
Abstract: In order to improve working efficiency of the tunneling process and extend working life of disc cutter, explore the impact of cutter spacing and loading for the cutter rock-breaking effect. With the theory of rock crushing, Based on the finite element analysis software ABAQUS, the process of disc cutter breaking rock is simulated, considering the adjacent cutters sequential constraints, then, to make sure two cutter space with the method of SE in experiment.The simulation results showed that the optimal cutter spacings were both about 80mm in the same loading and the sequentially loading, but the rock-breaking effect of sequentially loading is better than the same loading. The experimental data showed that the minimum specific energy of rock breaking is appeared cutter spacing between 80mm and 90mm. Thus, the correctness and rationality of the simulation was verified. The study is good for understanding the rock-breaking mechanism of double disc cutter and has a certain promoting value to optimize TBM cutter system.Keywords:TBM, rock fragmentation, ABAQUS, cutter spacing, sequentially cutting
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