1. The strength properties of non steel dowels for strata reinforcement in coal mines
Naj Aziz
David Gilbert, Ali Mirza, Xuwei Li, Haleh Resekh, Naj Aziz and Jan Nemcik
Rock Bolting Research, School of Civil, Mining and environmental Engineering, University of Wollongong
Coal 2015

2. Team Bolting
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3. Outline Introduction Polymeric dowels Strength Properties Conclusions
Tensile Strength Test
Single Shear Test
Double Shear Test
In Steel
Concrete
Punch Shear Test
Conclusions
Coal 2015

4. Fibre - Reinforced Polymer (FRP) Dowels : “Plastic Dowels”
Polymer Dowels
Glass-Reinforced Polymer (GRF) Bolts/Dowels
“ Fibre Glass (FG) Dowels”
Dowel colour is indication of length
Fibre - Reinforced Polymer (FRP) Dowels : “Plastic Dowels”
1.8 m
1.5 m
1.2m
Coal 2015

5. FG dowels are made of glass strands mechanically pulled through a saturated thermo set resin and heated. Afterwards the strands are guided through a heated forming and curing die. It leaves the die in a solidified state and tensioned through a pulling system creating a matrix with large resistance to tension.
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6. FG Dowel Specification – typical product
~ 270 to 300 kN
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7. Tensile strength Ave: 303 kN 150 mm 200mm 150 mm 350 mm
G1:312 kN
G2:307 kN
G3:301 kN
G4:307 kN
LS: 314 kN
R2:292 kN
R3: 293 kN
R4:298 kN
101.6 mm
150 mm mm mm
350 mm
110 mm extensometer
Used to monitor mid
Section of the dowel
Coal 2015

8. Average 273.36 Sample Peak Load (kN) 1 264.83 2 273.79 3 275.34 6
279.48
Average
273.36
Tensile strength = 719 MPa
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9. Single Shear test-
Guillotine method
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10. Single Shear Testing Results
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11. Shear Strength: Single – Guillotine test
Coloured FG Dowels Black FG Dowels
Sample
Displacement (mm)
Peak Load (kN)
Shear Stress (MPa) 1
7.25
49.48
130.16 2
8.55
46.59
122.57 3
7.13
48.26
126.96 4
7.35
51.35
135.09 5
7.94
52.74
138.73 6
8.40
49.83
131.08 7
8.26
52.67
138.56 8
8.28
53.26
140.11 9
7.76
50.32
132.39 10
7.64
52.99
139.41
Ave
50.75
133.51
Sample
Peak Load (kN)
Shear Stress (MPa) 1
56.33
148.19 2
47.01
123.67 3
52.79
138.86 4
53.98
141.99 5
60.63
159.49 6
62.35
164.01 7
56.75
149.29 8
58.04
152.68 9
58.43
153.71 10
55.43
145.80
Ave
57.19
150.45
Black Dowel 13% stronger
Coal 2015

12. Shear Strength: Double shear test in steel frame
Coloured FG Dowels Black FG Dowels
Sample
Peak shear Load (kN)
Single face Peak Load (kN)
Shear Stress ( single face) (MPa) 1
103.77
51.88
136.49 2
98.03
49.01
128.94 3
111.04
55.52
146.06 4
90.99
45.50
119.69
Ave
50.48
132.79
Sample
Single face Peak Load (kN)
Single face Shear Stress (MPa) 1
56.90
149.69 2
58.21
153.13 3
60.78
159.90 4
63.78
167.62
Ave
59.91
157.61
Black Dowel 19% stronger
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13. Double Shear tests in Concrete
Coal 2015

14. Double Shear Strength Test
Test strength of fiber glass dowels in two shear planes
Simulate shearing conditions experienced in situ
Observe effects of variations
1- Concrete strength
2- Axial load pre-tension
3- Type of grout and resin
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15. Coal 2015

16. Bolt axial load
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17. Single /double shear test results
Encapsulation Grout: BU100
* Sample 6 - twisted dowel
Encapsulation Grout: TD80
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18. Double shear Strength results in 60 MPa Concrete
262.5
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19. Double Shear in 60 MPa Concrete
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20. Double shear Strength results in 40 MPa Concrete
263.1
224
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21. Initial axial load (kN) Initial Axial Load (kN)
Double shear Strength in 40 and 60 MPa Concrete
Tested Dowel
Initial axial load (kN)
Max axial load (kN)
Peak Shear load ( kN)
Total Displacement at peak shear Load
(mm) 1 5
58.6
263.1
32.18 2 10
39.9
255.0
19.48 3 20
42.0
224.0
23.20
Sample
Initial Axial Load (kN)
Max Axial
Load 1
/Load 2
Peak Shear Load)
(kN)
Total Displacement at peak shear Load
(mm) 1B
2.5
15.91/ 13.64
220.74
19.0 2B 5
25.73/22.39
213.03
22.00 3B 10
22.60/27.79
242.70
25.5 4B 15
29.83/44.14
262.48
32.0
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22. Coal 2015

23. Punch Shear Test
35 mm
Perp Parallel
f =12.5 mm
Samples cut parallel to dowel axis
Samples cut perpendicular to dowel axis
Sample
Punch load (MN) T
(m) D t
(MPa) A
0.012
0.0128
102.22 B
0.0127
102.30 C
0.013
0.0129
107.50
Ave
104.01
Sample MN
T (m)
D (m) t
(MPa) A
0.0021
0.0127
21.12 B
0.0022
0.0128
21.70 C
0.0023
0.0126
20.64 D
0.0028
20.98 E
0.0040
27.97 F
0.0011
15.38 G
0.0039
28.67
Average
22.35
R: 4.65/1
Coal 2015

24. Perpendicular Punch Test Results –Black Dowel
Parallel Punch Test
Results
Punch
Shear Test
Sample MN
T (m)
D (m)
t (MPa) A
0.0129
163.12 B
0.0128
164.98 C
171.50 D
182.01
Ave
170.0
R: 170/51= 3.34
Coal 2015

25. Conclusions
guillotine method of testing dowels in shear yields lower shear strength values than testing dowels using double shear testing in concrete.
Double shear testing in concrete represent a realistic way of simulating the strength property of the composite material in rock and in situ.
Shear values of the FG dowels generally increases with increasing pretension loads.
Shear load values of dowels “appears” to be affected by the grout type
Dowels are weaker in shear, tested parallel to dowel axis / FG Strands than perpendicular to strands
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26. ?
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27. Double embodiment
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28. http:// www.coalconference.com.au
Now Online: All papers of past Coal Operators’ Conference
[All papers since 1998]
UOW Coal Mining Websites: Mining Science and technology
Next Coal Operators’ Conference is February 11/13, 2015:
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29. Sample
Initial axial load
(kN)
10 MPa
Conc.
40 MPa
60 MPa 1 5
194.67
263.1
213.03 2 10
275.86
255.0
242.70
Axial Strength: 270 to 300 kN
Coal 2015