1. 1
Thin Spray Liners with Fibre Reinforcements
Journal Research Article
Conducted By: Raees Bagdadi
Introduction
Thin spray liners (TSLs) are typically used in underground mines and tunnels which provide
rock support to surfaces with rough and ragged edges. It is used as a sealant and can prevent
weathering from occurring within a rock mass surface. The main advantage of applying a
TSL to a surface would be the ability for it to offer a remote rapid easy spraying technique to
use, since only a small amount of cover of approximately 5 mm needs to be sprayed onto the
surface. The surface will exhibit properties such as increased toughness, durability, resilience
and resistance to impact. TSLs will provide stronger permanent bonds to the substrate as well
as reduced dusting. A much greater tolerance to ground movement and resistance will be
obtained with the use of TSLs. The equipment used for the application tends to be small and
versatile which is beneficial for the use in enclosed environments. Areal coverage of TSLs
can be applied to the surface to prevent early reactions against ground movements and
fractures of essential core blocks. In this manner the rock strength and the excavation
potential of the surface may be enhanced.
Aim & Objectives
The aim of this dissertation is to determine whether the mechanical properties of TSLs with
fibre reinforcements will supersede that of the standardly used shotcrete in the industry, by
assessing properties such as the tensile strength, tensile bond strength, shear strength and
shear bond strength of a standard Oxyliner with the addition of glass and polypropylene
fibres whereby it will be compared to the shotcrete strength results for each category.

2. 2
Experimental Procedure
Three batches of Oxyliner with fibre reinforcements were assessed for the four strength
categories. The first batch includes an Oxyliner with the addition of 0.2% of polypropylene
fibres. The second batch consists of an Oxyliner with the addition of a 0.4% of glass fibres.
The third batch entails an Oxyliner with the addition of 0.3% glass fibres and a 0.15%
polypropylene fibre content. Five specimens were made for the tensile strength test at each of
the curing periods which were 1, 7, 14, 28 days. Three specimens were made for the tensile
bond strength, shear strength and shear bond strength at each of the four curing periods.
For the determination of the tensile strength, OL with fibre reinforcements were cast into a
dog bone shape silicon mould (figure 1a) which were in compliance with the ASTM D638
standard for testing TSLs and were tested at the various curing periods in order to ascertain
the strength gain properties over time. The Instron machine was utilized for the test. A tensile
force was applied to the specimen at a rate of 0.5 mm / min whereby the load at failure is
acquired (figure 1b).the failure mode of the specimen is shown in figure 1c. The tensile
strength can be obtained by taking the load at failure and dividing it by the cross sectional
area of the narrow section of the specimen.
Figure 1: (a) Test Specimens, (b) Test Procedure, (c) Failure Mode

3. 3
In order to attain the shear strength of the OL with fibre reinforcements, the Instron testing
machine was utilized whereby a compressive force is applied at a rate of 3 mm / min to the
steel punch in order to shear the TSL (figure 2a). The shear stress is obtained by taking the
load at failure and dividing it by the perimeter of the steel punch multiplied by the thickness
of the TSL. The failure mode of a shear strength test is shown in figure 2b.
The shear bond strength between the rock interface and OL with fibre reinforcements is
acquired by the Instron machine whereby a compressive force is applied to the rock core at a
rate of 1 mm / min (Figure 3a). The shear bond strength is acquired by taking the load at
failure and dividing it by the perimeter of the rock multiplied by the thickness of the TSL. A
typical shear bond failure mode is observed in figure 3b.
Figure 2: (a) TSL Shear Procedure, (b) Shear Strength Failure Mode
Figure 3: (a) Shear Bond Test Procedure, (b) Shear Bond Failure Mode

4. 4
In order to ascertain the tensile bond strength of the TSL to the rock interface, the specimens
are prepared and cured (Figure 4a). Before the test procedure commences a quick setting
epoxy is applied to the steel dolly which is bonded to the TSL interface and is left for an hour
to gain strength in order to gain a correct failure mode as shown in figure 4c. The rock cores
should be clamped in position and the Instron machine is utilized to apply a tensile force to
the steel dolly at a rate of 0.5 mm / min (Figure 4b). The tensile bond strength is determined
by taking the load at failure where the TSL de-bonds from the rock interface and dividing it
by the area of contact of the TSL and rock interface.
Results
The summarized strength results for the four tests are obtained, categorized and comparisons
are drawn. The average results have been plotted at each of the curing periods for the
different batches. The Oxyliner with a combination of glass and polypropylene fibres are
found to be the strongest TSL at a 28 day curing period for all categories. Shotcrete strength
results have been obtained from H.Yilmaz dissertation on TSLs which are found to possess
the weakest strength at all curing intervals. For a comprehensive analysis of the test results
pertaining to Oxyliner with fibre reinforcements refer to the appendix section of the final
thesis whereby a statistical analysis has been performed.
Figure 4: (a) Tensile Bond Specimens, (b) Tensile Bond Test Procedure, (c) Tensile Bond Failure Mode

5. 5
The tensile strength results are shown in Figure 5 a,b and c. The Oxyliner with fibre
reinforcements can be categorized as a medium class TSL with respect to its tensile strength
using figure 5d. The tensile bond strength comparisons at the various curing periods are
shown in figure 6.
Figure 5: (a),(b),(c) = OL with fibres Tensile Strength, (d) Tensile Strength Classification
Figure 6: Tensile Strength Comparisons

6. 6
The shear strength results are shown in Figure 7 a,b and c. The Oxyliner with fibre
reinforcements can be categorized as a strong class TSL with respect to its shear strength
using figure 7d. The tensile bond strength comparisons at the various curing periods are
shown in figure 8.
Figure 7 :( a), (b), (c) = OL with Fibres Shear Strength, (d) = Shear Strength Classification
Figure 8: Shear Strength Comparison

7. 7
The shear bond strength results are shown in Figure 9 a,b and c. The Oxyliner with fibre
reinforcements can be categorized as a strong class TSL with respect to its shear bond
strength using figure 9d. The tensile bond strength comparisons at the various curing periods
are shown in figure 10.
Figure 9: (a),(b),(c) = Shear Bond Strength of OL with Fibres, (d) = Shear Bond Strength Classification
Figure 10: Shear Bond Strength Comparisons

8. 8
The tensile bond strength results are shown in Figure 11 a,b and c. The Oxyliner with fibre
reinforcements can be categorized as a medium class TSL with respect to its tensile bond
strength using figure 11d. The tensile bond strength comparisons at the various curing periods
are shown in figure 12.
Figure 11: (a),(b),(c) = Tensile bond strength of OL with fibres, (d) = Tensile bond strength classification
Figure 12: Tensile Bond Strength Comparison

9. 9
Conclusion
From the results obtained for the Oxyliner with fibre reinforcements a few pertinent
deductions can be made regarding the behaviour of TSLs. The strength properties of a TSL
increases over time until a maximum strength is achieved provided that proper curing of the
TSL is ensured. The fibre reinforcements provide additional strength to the TSL which
enhances the durability of the liners surface.
The mechanical properties of the Oxyliner product can be summarised as follows. The
average tensile strength after a 28 day curing period for the liner with reinforcements is 3.167
MPa. The average shear strength after curing for 28 days is found to be 8.7 MPa. The average
tensile bond strength ascertained for the liner is 0.96 MPa. The average shear bond strength
for the liner after a 28 day curing period is 3.77 MPa. The Oxyliner TSL with the addition of
fibres can be classified as a medium to strong TSL. To enhance the strength characteristics of
the Oxyliner attempts can be made to increase the fibre content of the mix design or to alter
the chemical composition of the cementitious based polymer into polyurethane based TSL.
The Oxyliner strength characteristics for the various tests tend to supersede the shotcrete
characteristics. Therefore I will conclude by recommending that TSLs can indeed become a
viable alternative to shotcrete as it provides various benefits that shotcrete does not offer.
TSLs are easier to apply in terms of the equipment required which makes it more versatile.
The thickness of application required is much less than the shotcrete requirements where a
reduction in cost can be capitalized upon. The strength gain of TSLs exceeds that of the
standardly used shotcrete within the industry.
A point analysis is conducted for the various batches of OL with fibre reinforcements as well
as the standardly used shotcrete within the industry. Points are given ranking the various
categories for the different classes of strength as well as cost where 5 is of excellent quality
and 1 is of the poorest quality. A maximum of 25 points can be obtained. The Oxyliner with a
combination of fibres yields the best strength at 28 days. Shotcrete yields the lowest strengths
compared to the TSL with fibres. The ranking system can be classified as follows
 1 = Poor
 2 = Average
 3 = Good
 4 = Very good

10. 10
 5 = Excellent
Recommendations
For the purpose of future experimentation of TSLs the EFNARC specifications can be
referred to for additional tests such as the Gap shear Load Test as well as the TSL linear
block Support Test. Increasing the fibre content of the mix design would produce an
enhancement of the strength characteristics. Large scale tests can also be undertaken in order
to ascertain the health risks and the strength gain of the TSL to various rock substrates under
different working conditions as all tests were performed in a controlled environment of a
laboratory. The type of rock that is to be stabilized using TSLs may yield different strength
characteristics and should be assessed.
Table 1: Point Analysis of OL with Fibres vs Shotcrete
Category Tensile Strength Tensile Bond Strength ShearStrength ShearBond Strength Cost Total
Oxylinerwith PP Fibres 4 4 4 4 2 18
Oxylinerwith glass Fibres 3 3 3 3 4 16
Oxylinerwith Combo Fibres 5 5 5 5 3 23
Shotcrete 1 1 1 1 1 5