EXPERIMENTAL AND NUMERICAL STUDY ON GEOMATERIAL BEHAVIOR OF UPLIFTING BELLED PILE UNDER LOW CONFINING PRESSURE

Zonal disintegration, a phenomenon of fractured zones and intact zones distributed alternately in deep rock mass, is different from the excavation-damaged zone of shallow rock mass. In this study, bonded block model of 3DEC was employed to study the fracture mode and origination condition of zonal disintegration. Initiation, propagation, and coalescence progress of fracture around the roadway boundary under different triaxial stress conditions are elaborated. Numerical simulation demonstrated that zonal disintegration may occur when the direction of maximum principal stress is parallel to the roadway axis. It is interesting to find that the fracture around the roadway boundary traced the line of a spiral line, while slip-line fractures distributed apart from the roadway boundary. The extent of the alternate fracture zone decreased as the confining pressure increased, and alternate fracture zone was no longer in existence when the confining pressure reaches a certain value. Effects of roadway shape on zonal disintegration were also studied, and the results indicated that the curvature of the fracture track line tends to be equal to the roadway boundary in shallow surrounding rock of the roadway, while the fractures in deep surrounding rock seems unaffected by the roadway shape. Those findings are of great significance to support design of deep underground openings.

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Experimental and Numerical Study on Mechanical Properties and Deformation Behavior of Beishan Granite considering Heterogeneity

Advances in Civil Engineering ◽

10.1155/2021/6622958 ◽

2021 ◽

Vol 2021 ◽

pp. 1-13

Author(s):

Z. H. Wang ◽

Y. L. Tan ◽

S. M. Li ◽

T. Z. Wang ◽

X. C. Wu

Keyword(s):

Numerical Simulation ◽

Mechanical Response ◽

Numerical Study ◽

Failure Process ◽

Confining Pressure ◽

Sample Volume ◽

Mechanical Tests ◽

Peak Strength ◽

Research Subjects ◽

Beishan Granite

Disposal of high-level radioactive waste (HLW) deep underground is one of the most challenging research subjects in rock engineering. In China, Beishan granite is usually chosen as host rock for the construction of the HLW repository. In this study, mechanical tests are conducted on Beishan granite and the stress-strain state during the complete failure process is analyzed by numerical simulation. The results show that the tensile strength and uniaxial compressive strength of Beishan granite are 8.66 and 162.9 MPa, respectively. Dilatancy appears when the stress reaches about 81% of the peak strength. Heterogeneity is introduced by Weibull distribution in numerical simulation. With the increase of homogenization degree, the degraded elements are more easily to concentrate locally. Based on experimental and numerical simulation results, it is noticeable that the sample volume is basically in the state of compaction before reaching the peak strength. The elements are more likely to show expansion, and the splitting failure dominates the destroy mode when the confining pressure is relatively low. With increasing confining pressure, more and more degraded elements are concentrated in the shear band, which develops from the surface to the interior of the sample during loading. Therefore, the granite shows ductile mechanical response characteristics when the confining pressure is relatively high. The results are instructive for the construction of the repository.

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NUMERICAL STUDY ON CONFINING PRESSURE EFFECT IN THE PROCESS OF ROCK FAILURE

Computational Methods ◽

10.1007/978-1-4020-3953-9_119 ◽

2007 ◽

pp. 1817-1822

Author(s):

D.P. Qiao ◽

Y.N. Sun ◽

S. H. Wang ◽

C.A. Tang

Keyword(s):

Pressure Effect ◽

Numerical Study ◽

Confining Pressure ◽

Rock Failure ◽

Confining Pressure Effect

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Failure Mechanism of Rock Specimens with a Notched Hole under Compression—A Numerical Study

Applied Sciences ◽

10.3390/app11177797 ◽

2021 ◽

Vol 11 (17) ◽

pp. 7797

Author(s):

Amin Manouchehrian ◽

Pinnaduwa H. S. W. Kulatilake ◽

Rui Wu

Keyword(s):

Numerical Study ◽

Confining Pressure ◽

Compressive Test ◽

Separate Model ◽

Failure Evolution ◽

Uniaxial Compressive Test ◽

Notch Length ◽

The Stability ◽

Fracturing Mechanism ◽

Rock Specimens

Discontinuities are natural structures that exist in rocks and can affect the stability of rock structures. In this article, the influence of notch presence on the strength and failure evolution around a hole in compressed rock specimens is investigated numerically. Firstly, the uniaxial compressive test on a rock specimen with a circular hole is modeled, and the failure evolution in the specimen is simulated. In a separate model, notches are created at the surface of the hole. Results show that, when the notches are created in the model, a failure zone around the hole is transferred to a distance away from the surface of the hole. In addition, a parametric study is carried out to investigate the influence of the notch length and the confining pressure on the fracturing behavior of the specimen. Numerical results presented in this article indicate that the presence of notches at the surface of the hole and their dimensions can affect the fracturing mechanism of the specimen. In some cases, the failure at the boundary of the hole is prevented when the notches of certain dimensions are added to the hole. The insights gained from this numerical study may be helpful to control the failure around underground excavations.

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Numerical study of the effect of confining pressure on the rock breakage efficiency and fragment size distribution of a TBM cutter using a coupled FEM-DEM method

Tunnelling and Underground Space Technology ◽

10.1016/j.tust.2019.03.012 ◽

2019 ◽

Vol 88 ◽

pp. 260-275 ◽

Cited By ~ 10

Author(s):

Zhijun Wu ◽

Penglin Zhang ◽

Lifeng Fan ◽

Quansheng Liu

Keyword(s):

Size Distribution ◽

Numerical Study ◽

Fragment Size ◽

Confining Pressure ◽

Fragment Size Distribution ◽

Rock Breakage ◽

Tbm Cutter

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Numerical Study of Elastic-Brittle Failure of Notched Openings in Rocks

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.297-300.2605 ◽

2005 ◽

Vol 297-300 ◽

pp. 2605-2611

Author(s):

Shan Yong Wang ◽

S.K. Au ◽

K.C. Lam ◽

Chun An Tang

Keyword(s):

Numerical Study ◽

Progressive Failure ◽

Process Analysis ◽

Failure Process ◽

Confining Pressure ◽

Numerical Code ◽

Tunnel Wall ◽

Model Studies ◽

Borehole Breakout ◽

Rock Failure Process

Borehole breakout is the process by which portions of borehole or tunnel wall fracture or spall when subjected to compressive stresses. The stress-strain characteristics of rock during loading and unloading confining pressure are studied firstly. To overcome the difficulties in analytical model studies, a numerical code, RFPA2D (Rock Failure Process Analysis), developed by CRISR, Northeastern University, China, is used to investigate the progressive failure of breakout around tunnel. The heterogeneity of rock was also taken into account in the software. The numerical simulation reproduces the formation notch in rocks by the growth, interaction and coalescence of randomly distributed macrocracks. It is illustrated from the numerical simulated results that breakout direction of tunnel is parallel with the minor stress tensor in the plane perpendicular to the borehole axis. Specifically due to the inclusion of heterogeneity, some peculiarities are studied both in the evolution of fracture and the influence of borehole on the peak intensity of specimen as well as the AE event patterns.

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Numerical Study on the Fracture Evolution around Cavities in Rock

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.297-300.2598 ◽

2005 ◽

Vol 297-300 ◽

pp. 2598-2604

Author(s):

Shan Yong Wang ◽

S.K. Au ◽

K.C. Lam ◽

Chun An Tang

Keyword(s):

Shear Fracture ◽

Model Simulation ◽

Numerical Study ◽

Process Analysis ◽

Failure Process ◽

Confining Pressure ◽

Numerical Code ◽

Tensile Fracture ◽

Fracture Evolution ◽

Rock Failure Process

By using numerical code RFPA2D (Rock Failure Process Analysis), the evolution of fracture around cavities subjected to uniaxial and polyaxial compression is examined through a series of model simulation. It is shown from the numerical results that the chain of events leading to the collapse of the cavity may involve all or some of the fractures designated as primary tensile, shear and remote fracture. Numerical simulated results reproduce the evolution of three types of fractures. Under the condition of no confining pressure, the tensile mode dominates with collapse coinciding with the sudden and explosive appearance of the secondary tensile fracture; at moderate higher confining pressure, the tensile mode is depressed, comparatively, the shear effect is strengthened. Nevertheless, tensile fractures especially in remote fractures stage still play a role; at higher pressure, the shear fracture dominates the remote fractures. In addition, the evolution and interact of fractures between multiple cavities is investigated, considering the stress redistribution and transference in compressive and tensile stress field.

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Failure Mechanism of Rock Specimens with a Notched Hole Under Compression - A Numerical Study

10.21203/rs.3.rs-515335/v1 ◽

2021 ◽

Author(s):

Amin Manouchehrian ◽

Pinnaduwa H.S.W. Kulatilake ◽

Rui Wu

Keyword(s):

Numerical Study ◽

Confining Pressure ◽

Separate Model ◽

Failure Evolution ◽

Uniaxial Compressive Test ◽

Notch Length ◽

The Stability ◽

Fracturing Mechanism ◽

Model Failure ◽

Rock Specimens

Abstract Discontinuities are natural structures that exist in rocks and can affect the stability of rock structures. In this article, the influence of notch presence on the failure evolution around a hole in compressed rock specimens is investigated numerically. Firstly, the uniaxial compressive test on a rock specimen with a circular hole is modeled and the failure evolution in the specimen is simulated. In a separate model, notches are created at the surface of the hole. Results show that when the notches are created in the model, failure zone around the hole is transferred to a distance away from the surface of the hole. In addition, a parametric study is carried out to investigate the influence of the notch length and the confining pressure on the fracturing behavior of the specimen. Numerical results presented in this article indicate that the presence of notches at the surface of the hole and their dimensions can affect the fracturing mechanism of the specimen. In some cases, the failure at the boundary of the hole is prevented when the notches of certain dimensions are added to the hole. The insights gained from this numerical study may be helpful to control the failure around underground excavations.

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FRACTAL PLASTIC SHEAR BANDS

Fractals ◽

10.1142/s0218348x9400079x ◽

1994 ◽

Vol 02 (04) ◽

pp. 567-581 ◽

Cited By ~ 71

Author(s):

ALEXEI N. B. POLIAKOV ◽

HANS J. HERRMANN ◽

YURI YU. PODLADCHIKOV ◽

STÉPHANE ROUX

Keyword(s):

Spatial Organization ◽

Numerical Study ◽

Shear Bands ◽

Length Distribution ◽

Confining Pressure ◽

Flow Rule ◽

Plastic Shear ◽

Scaling Exponents ◽

High Confining Pressure ◽

Plastic Flow Rule

We present a numerical study model of shear bands in rocks with a non-associated plastic flow rule. The system drives spontaneously into a state in which the length distribution of shear bands follows a power law and where the spatial organization of the shear bands appears to be fractal. The distribution of local gradients in deviatoric strain rate has different scaling exponents for each moment which we calculate and discuss. Samples of granodiorite from the Pyrenees sheared under high confining pressure are analyzed and their properties compared with the numerical results.

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