Use of indentation tests to study the influence of confining stress on rock fragmentation by a TBM cutter

In this paper, General Particle Dynamics (GPD3D) is developed to simulate rock fragmentation by TBM disc cutters under different confining stress. The processes of rock fragmentation without confining pressure by one disc cutter and two disc cutters are investigated using GPD3D. The crushed zone, initiation and propagation of cracks, and the chipping of rocks obtained from the proposed method are in good agreement with those obtained from the previous experimental and numerical results. The effects of different confining pressure on rock fragmentation are investigated using GPD3D. It is found that the crack initiation forces significantly increase as the confining stress increases, while the maximum angle of cracks decreases as the confining stress increases. The numerical results obtained from the proposed method agree well with those in previous indentation tests. Moreover, the effects of equivalent confining stress on rock fragmentation are studied using GPD3D, and it is found that rock fragmentation becomes easier when the equivalent confining stress is equal to 15MPa.

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The Influence of Confining Stresses on Rock Fragmentation, Thrust Force, and Penetration Energy in Sandstone Indentation Tests Using Disc Cutters

Advances in Civil Engineering ◽

10.1155/2021/5541538 ◽

2021 ◽

Vol 2021 ◽

pp. 1-13

Author(s):

Gaofeng Wang ◽

Ting Ren ◽

Gaolei Zhu

Keyword(s):

Thrust Force ◽

Coal Mines ◽

Rock Fragmentation ◽

Disc Cutter ◽

Confining Stress ◽

Disc Cutters ◽

Underground Coal Mines ◽

Indentation Tests ◽

Boring Machines ◽

Maximum Thrust

Hard rock Tunnel Boring Machines (TBMs) engaging disc cutters as cutting tools have been employed in considerable underground coal mines to accommodate the requirement of more stone drivage as operations are going deeper. This study conducted a set of disc cutter indentation tests to explore the influence of confining stresses on rock fragmentation, thrust force, and penetration energy on sandstone, which is commonly encountered in underground coal mines. The test results show that there exists a critical confining stress, under which the maximum thrust force and penetration energy keep increasing with confining stress mounting while the maximum thrust force and penetration energy will decrease or flatten if it is surpassed. By combining with previous studies and comparing the critical confining stress values to the rock mechanical properties’ values, the critical value is most likely to be of cohesion. For subsurface rock fragmentation, the Constant Cross Section (CCS) disc cutter indentation has denser cracks and their orientations are more lateral than those under the V shape one; the V shape disc cutter indentation is less sensitive to confining stresses, with no notable increase of crack number and crack reorientation with increasing confinement. Thus, the CCS disc cutter is more favorable than the V shape one from the perspective of rock fragmentation under confining stresses.

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Numerical study of the effect of confining stress on rock fragmentation by TBM cutters

International Journal of Rock Mechanics and Mining Sciences ◽

10.1016/j.ijrmms.2011.05.002 ◽

2011 ◽

Vol 48 (6) ◽

pp. 1021-1033 ◽

Cited By ~ 66

Author(s):

Hongsu Ma ◽

Lijun Yin ◽

Hongguang Ji

Keyword(s):

Numerical Study ◽

Rock Fragmentation ◽

Confining Stress

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Study on the influence of joint spacing on rock fragmentation under TBM cutter by linear cutting test

Tunnelling and Underground Space Technology ◽

10.1016/j.tust.2016.02.018 ◽

2016 ◽

Vol 57 ◽

pp. 137-144 ◽

Cited By ~ 24

Author(s):

Lijun Yin ◽

Chongtong Miao ◽

Guanwen He ◽

Fuchu Dai ◽

Qiuming Gong

Keyword(s):

Rock Fragmentation ◽

Joint Spacing ◽

Cutting Test ◽

Tbm Cutter

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Mechanical and Acoustic Emission Responses of Rock Fragmentation under Disc Cutter Penetration

Advances in Civil Engineering ◽

10.1155/2021/8829046 ◽

2021 ◽

Vol 2021 ◽

pp. 1-17

Author(s):

Qi Liu ◽

Yucong Pan ◽

Penghai Deng

Keyword(s):

Acoustic Emission ◽

Damage Zone ◽

Three Dimensional ◽

Rock Fragmentation ◽

Disc Cutter ◽

Rock Damage ◽

Rock Types ◽

Penetration Ability ◽

Indentation Tests ◽

Spatio Temporal

To better understand the rock fragmentation mechanism and optimize cutter design and selection for rock excavation by TBM, a set of three-dimensional indentation tests was conducted with different rock and cutter types. Acoustic emission (AE) monitoring technique was employed to capture the information of the rock damage evolution real-timely. It is found that the penetration by using the constant cross section (CCS) cutter tends to induce inconspicuous rock chips formation before the sudden occurrence of the macrocrack, but that by using the V-type cutter tends to induce gradual rock fragmentation accompanied by the multiple local rock chips formation and the sawtooth force-penetration curve. Meanwhile, rock fragmentation models for CCS and V-type cutters were compared, and the spatio-temporal evolution of AE events was quantitatively analyzed to reflect the rock damage zone development process. Results indicate that the V-type cutter has greater penetration ability and the CCS cutter can cause larger unit damage zone radius. Microscopic observation by using the scanning electron microscope (SEM) reveals that the fracture mechanism for the crushed zone of rock is mainly shear type and that for the major crack is tensile type. It does not matter with rock types or cutter types.

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