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Testing the rocks loosening process by undercutting anchors Cover

Testing the rocks loosening process by undercutting anchors

Studia Geotechnica et Mechanica
Volume 42 (2020): Issue 3 (September 2020)
By: Michał Siegmund,  Marek Kalita,  Domink Bałaga,  Krzysztof Kaczmarczyk and  Jonak Józef  
Open Access
|Jul 2020
Figures & tables

Figures & Tables

Figure 1

The concept of cutting the solid rock through destruction of its integrity: 1. solid rock, 2. loosened rock, 3. pulling rod, 4. expansion sleeve [4, 16, 20].

Figure 2

Different failure mechanisms of cast-in and post-installed mechanical anchors [2].

Figure 3

Base material failure models according to: a) ACI 349-85 (conical failure) and b) CCD (four-sided pyramid failure) [2, 9, 22, 23] CCD, concrete capacity design.

Figure 4

Real extent of the loosening process based on literature data: a, b) concrete cone [12, 23]; c) radius R observed by test and effective radius R’ used in model [3]; d) comparison between LEFM predictions (dashed lines) and experimental crack propagation patterns [19]. LEFM, linear elastic fracture mechanics.

Figure 5

An example of the undercutting anchor [13].

Figure 6

Loosening process with use of an undercutting anchor: a) line of crack propagation, b) fixation method.

Figure 7

Computer simulations [14]: a) scheme of the task, b) the average value of the angle of the concrete cone failure (section plane ABCD in Figure 7c), c) maximal principal stress distribution and crack propagation path in the FEM model (a quarter of the model). FEM, finite element method.

Figure 8

The RODEST test stand equipment As a standard, the testing device is equipped with the following components (Figure 8): cylinder support,hydraulic cylinder with a cylindrical through hole,supply unit (hand pump + hoses, pressure gauge, connectors),undercut anchor with fastening equipment, andsupply pressure recorder.

Figure 9

Place of tests: a) ZALAS, b) BRACISZÓW, c) GUIDO, d) BRENNA.

Figure 10

Scheme of processing the scans of rocks surfaces after their loosening.

Figure 11

Examples of a cross-sections through a loosened rock, specifying the effective anchoring depth Hef, maximum Zmax, and minimum Zmin loosening range (on the example of BRENNA mine). CCD, concrete capacity design.

Figure 12

Determination of maximum force Fmax, recorded during the loosening test.

Figure 13

Curves of maximum loosening force Fmax in relation to the effective anchoring depth Hef for different rock types.

Figure 14

Curves drawn using the maximum loosening forces Fmax determined experimentally (Figure 13) with the anchoring load capacity Nu,m calculated from equation (2).

Figure 15

Curves of mean range values Zav. in relation to the effective anchoring depth Hef for different rock types.

Figure 16

Changes in the coefficient R in relation to the effective anchoring depth Hef for different types of rocks.

Figure 17

Schematic presentation of the procedure for determination of loosened rocks’ surface area and volume.

Figure 18

Curves of mean volumes Vav. versus the effective anchoring depth Hef for different rock types with the volume function based on CCD method. CCD, concrete capacity design.

Average values of R coefficient_

ZALASBRACISZÓWGUIDOBRENNA
R=Zav./Hef3.94.13.94.2

Results of laboratory tests of the material samples [24]_

Mean values of laboratory test resultsUniaxial compression strength, Rc,Tensile strength, Rrb,Cohesion, cAngle of internal friction, φ
Material/mine(MPa)(MPa)(MPa)(°)
Porphyry ZALAS106.55.98.654.0
Sandstone BRACISZÓW155.38.014.549.5
Sandstone GUIDO97.46.211.949.6
Sandstone BRENNA58.83.96.053.0

Number of successful rock loosening attempts_

Material/mineNumber of successful loosening attempts
Porphyry ZALAS30
Sandstone BRACISZÓW27
Sandstone GUIDO36
Sandstone BRENNA22
Σ115
DOI: https://doi.org/10.2478/sgem-2019-0052 | Journal eISSN: 2083-831X | Journal ISSN: 0137-6365
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Language: English
Page range: 276 - 290
Submitted on: Nov 18, 2019
Accepted on: May 5, 2020
Published on: Jul 9, 2020
Published by: Wroclaw University of Science and Technology
In partnership with: Paradigm Publishing Services
Publication frequency: 4 issues per year
Keywords:
destroying the integrity of rocks,
tearing out rock fragments,
mine rescue operations,
unconventional rock cutting,
rock strength tests
Related subjects:
Geosciences,
Geosciences, other,
Materials sciences,
Composites,
Porous materials,
Physics,
Mechanics and fluid dynamics

© 2020 Michał Siegmund, Marek Kalita, Domink Bałaga, Krzysztof Kaczmarczyk, Jonak Józef, published by Wroclaw University of Science and Technology
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License.

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