# Experimental Determination of Mechanical Properties of Waste Tyre Bales Used for Geotechnical Applications

^{*}

## Abstract

**:**

^{3}, the Young’s modulus—826 kPa, the Poison’s ratio—0.11, the dry tyre–tyre interface: cohesion of 0.03 kPa and friction angle of 46.0°, the wet tyre–soil interface: cohesion 0.77 kPa and a friction angle of 29.6°, creep deformation of 6.1% of the average height of the bale, and no stiffness degradation of tyre bales under cyclic load. These results could be directly applied for the designing and construction of the tyre-baled structures.

## 1. Introduction

^{3}[7]. Waste tyre bales have considerable potential for use in geotechnical applications, particularly where their low density, permeability, and ease of handling give them an advantage. The use of lightweight bales in the construction of a lightweight embankment or road foundation over soft ground, the backfilling of retaining structures, the slope stabilization or landslide repairs has the potential to satisfy the demand for low-cost materials exhibiting such a beneficial property.

## 2. Materials

#### 2.1. Manufacturing of Tyre Bales

^{3}bale having a roughly estimated size of 2.0 ± 0.05 m × 1.3 ± 0.05 mm × 0.7 ± 0.05 m and weigh approximately 1030 ± 20 kg. Tyre baling results in a 4:1 volume reduction of loose tyres. The consistency of tyre bales production was ensured and indirectly controlled by the measurement of steel tie wires’ tension. Six 4 mm galvanized steel wires were spaced at 300 ± 20 mm along the length of the bale. Figure 1 shows a typical tyre bale used in the current research.

#### 2.2. Tyre Bales Characteristics

_{avg}of the tyre bale is defined as the average volume measured. Table 1 provides the average dimensions, volume, weights, and unit weight measured and calculated for each tyre bale used in the current research.

#### 2.3. Filling Material

- Granulation (particle size): 0.25–1.00 mm;
- Coefficient of uniformity: 1.3;
- Coefficient of curvature: about 1.1;
- Void ratio: 0.59–0.83;
- Moisture: 12.6–12.8%;
- Specific gravity: 2.66 g/cm
^{3}; - Friction angle: 35.2°;
- Bulk weight (density): 19.0 ± 0.5 kN/m
^{3}.

## 3. Methods

#### 3.1. Compressibility Test

#### 3.2. Full-Scale Direct Shear Tests

#### 3.2.1. Tyre–Tyre Interface Test

- (a)
- Stage I–the dead weight of the sliding bale (V
_{I}= 10.0 kN); - (b)
- Stage II–the additional weight of steel plate placed on the sliding bale (V
_{II}= 13.4 kN); - (c)
- Stage III–the additional weight of a tyre bale placed on the sliding bale (steel plate was removed) (V
_{III}= 20.0 kN); - (d)
- Stage IV–the additional weight of concrete road slab placed on the additional tyre bale (V
_{IV}= 26.2 kN).

#### 3.2.2. Tyre–Soil Interface Test

- (a)
- Stage I–the dead weight of the sliding bale and the steel plate (V
_{I}= 22.2 kN); - (b)
- Stage II–the additional weight of a concrete road slab placed on a steel plate (V
_{II}= 28.4 kN); - (c)
- Stage III–the additional weight of a concrete road slab and a tyre bale placed on a steel plate (V
_{III}= 38.4 kN); - (d)
- Stage IV–the additional weight of two concrete road slabs placed on the steel plate (V
_{IV}= 44.0 kN).

#### 3.3. Creep Test

#### 3.4. Cyclic Load Test

## 4. Results and Discussion

#### 4.1. Compressibility Test

_{max}. After reaching P

_{max}the tyre bale was unloaded. Although no bale’s steel tie wires broke at failure load, the decrease of wire tension was observed (loose wires) after unloading (Figure 13b).

- ${\sigma}_{v}$—maximum stress in the range considered;
- $\Delta {\epsilon}_{v}$—vertical strain increase in the range considered.

_{v}value 826 kPa is close to the values reported in [19,21,22] for a similar test setup (i.e., 914 kPa, 831 kPa, and 766 kPa, respectively). Moreover, including a predicted value of the tyre bale stiffness with sand infill, the determined modulus could be increased by 30% according to [21]. To show Young’s modulus variability under increasing load a series of secant moduli with applied load was determined and graphically presented for P-5 bale in Figure 15.

- ${\epsilon}_{h}$—maximum horizontal strain in the range of 0–250 kN;
- ${\epsilon}_{v}$—vertical strain in the range of 0–250 kN.

_{h}was calculated on the assumption of bales symmetry as the double horizontal deformation 2h

_{avg}obtained at P

_{max}(Table 3), divided by the average bale length L (Table 1):

#### 4.2. Full-Scale Direct Shear Tests

#### 4.2.1. Tyre–Tyre Interface Test

_{I}= 10 kN) are shown in the following figures.

- τ—shear strength;
- σ—normal stress;
- ϕ—friction angle of the material (in this case: friction at the tyre–tyre interface);
- c—cohesion of the material (typically, sandy soils are considered cohesion-less).

^{2}equals 0.944. The approximate shear stresses listed in Table 5 were obtained using this function. Error estimation, calculated as a deviation of the actual test result from the envelope function, is within the range of 0.11% to 21.53% (Table 5). The variability of these test results was not more than 25%, but only five results had a deviation of more than 10%. Thus the variability in the data set was moderate, indicating an acceptable variability of shear strength from bale to bale. It may be concluded that the interface shear strength of tyre bales is comparatively high. However, the effect of moisture at the interface and the effect of the directionality of tyre bale placement were not evaluated as part of this study.

#### 4.2.2. Tyre–Soil Interface Test

_{IV}= 44.0 kN) are shown in Figure 20. The load—time behavior of the soil interface is similar to that of the tyre bale only interface, however, no local load drops are observed in the H–Δ curve. In these tests, the irregularity of the stationary tyre bale’s surface was levelled by the soil cover.

^{2}equals 0.962. Error estimation is within the range of 0.18% to 11.8% (Table 6). The variability of these test results was not more than 12%, but only three results had deviation of more than 5%. Thus the variability in the data set was very small. Similarly to the tyre bale only interface, the shear strength of tyre–soil interface is quite high. This time the effect of moisture at the interface was included in the evaluation.

#### 4.3. Creep Test

^{2}) estimated for all particular periods of creep loading. The following symbols were used in Table 7: h

_{0}—initial bale depth, t—load time in h, Δh

_{exp}—the experimental measurement of creep deformation (an average of four records), R

^{2}—coefficients of determination, Δh

_{365}—estimated 1-year creep deformation, c

_{α,365}—estimated 1-year creep coefficient. The Δh

_{365}values were estimated using the fitted regression lines given in Table 7. The regression lines are very well fitted to testing results with the coefficients of determination R

^{2}> 0.94, except one case for specimen P-3 (load slab no.1), when test experienced accelerated movement on one corner after loading. Progressive deformation in different regions of the P-3 specimen resulted in variation in both deformation and load and made the determination of creep strain rate difficult.

_{α,}

_{365}were estimated as 0.0048, 0.0042, and 0.0035 for P-1 to P-3 specimens, respectively, and the average c

_{α,}

_{365}value for the creep test as 0.0039 was obtained. This value is similar to those obtained by La Rocque [19] and Zornberg et al. [21]; the difference is less than 5%. The test indicates relatively little creep response at long-term stress levels. The post-3-day movement would roughly be the anticipated post-construction movement and could be reduced by preloading.

#### 4.4. Cyclic Load Test

## 5. Summary

- The cuboid tyre bales comprising approximately 135 car tyres are used in the research. The baling machine produced tyre bales of approximate dimensions 2.05 m × 1.30 m × 0.75 m, a mass of around 1030 kg, the average volume of around 2.0 m
^{3}, and the unit weight defined using the average volume of approximately 0.515 Mg/m^{3}. This unit weight was found to be slightly lower than the respective values reported in the literature. - The approximate Young’s modulus for the tyre bales determined on the basis of the compression testing is 826 kPa and is close to the values reported in the literature. The horizontal deformation measurements indicate a relatively low Poison’s ratio on the order of 0.11, while these values reported in literature ranged from 0.08 to 0.24.
- The results from the dry tyre–tyre interface testing can be combined and modelled with a linear failure envelope with the cohesion of 0.03 kPa and friction angle of 46.0°, showing moderate variability between different bales within the range of 0.11% to 21.53%. The corresponding results from the wet tyre-soil interface testing indicate that for medium sand a linear failure envelope can be estimated with a small cohesion 0.77 kPa and a friction angle of 29.6° with the small variability of test results not more than 12%. Both results match well with the values provided in the literature.
- The tyre–soil interface strength determined in the test is about 15% weaker than the medium sand strength, while up to 20% reduction was revealed in the literature.
- Creep deformation due to sustained normal compressive load for up to five days of loading constitutes 6.1% of the average height of the bale. A significant portion of the creep deformation (approximately 95%) occurred in the first day and the maximum deformation appeared within three days. The 1-year creep coefficient was estimated as 0.0039 and this value is very similar to those obtained in the literature.
- The cyclic load test results obtained as a resilient value (the difference between maximum and minimum deformations) within about 400 min of loading revealed no stiffness degradation of tyre bales.

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Conflicts of Interest

## References

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**Figure 3.**The sieve analysis result for medium sand according to [24].

**Figure 11.**The behavior of P-4 bale under load p = 250 kN: (

**a**) vertical displacements; (

**b**) horizontal displacements.

**Figure 12.**Average displacement plots for all bales under load p = 250 kN: (

**a**) vertical displacements; (

**b**) horizontal displacements.

**Figure 13.**The typical failure mode of tyre bales under compression: (

**a**) excessive platen rotation at failure load; (

**b**) loose side wires after unloading.

**Figure 17.**Typical curves for P-4 specimen in stage I: (

**a**) load–time curve; (

**b**) load–displacement curve for average front displacement.

**Figure 20.**Typical curves for P-2 specimen in stage IV: (

**a**) load–time curve; (

**b**) load-displacement curve for average front displacement.

**Figure 21.**Shear stress–displacement curves for average front displacements in subsequent load stages for P-2 specimen.

Bale No. | Number of Tyres | Length L | Width B | Hight H | Area A | Volume V | Weight G | Unit Weight γ_{avg} |
---|---|---|---|---|---|---|---|---|

[m] | [m^{2}] | [m^{3}] | [kN] | [kN/m^{3}] | ||||

P-1 | 135 | 2.070 | 1.310 | 0.747 | 2.712 | 2.026 | 10.18 | 5.03 |

P-2 | 135 | 2.040 | 1.317 | 0.757 | 2.689 | 2.034 | 10.02 | 4.93 |

P-3 | 135 | 2.050 | 1.310 | 0.740 | 2.686 | 1.987 | 9.92 | 4.99 |

P-4 | 135 | 2.040 | 1.323 | 0.737 | 2.699 | 1.989 | 10.14 | 5.10 |

P-5 | 135 | 2.070 | 1.317 | 0.750 | 2.726 | 2.045 | 10.29 | 5.03 |

P-6 | 135 | 2.060 | 1.295 | 0.750 | 2.668 | 2.001 | 10.12 | 5.06 |

Avg. | 135 | 2.055 | 1.312 | 0.747 | 2.697 | 2.014 | 10.11 | 5.02 |

Bale No. | Cyclic Load [kN] | Amplitude [kN] | Frequency [Hz] | Stress Transferred Pointwise to the Specimen [kPa] | Number of Cyclic Loads [No.] | ||
---|---|---|---|---|---|---|---|

Max. | Min. | Max. | Min. | ||||

P-1 | 20 | 3 | 17 | 0.4 | 283 | 42.5 | 10,000 |

P-2 | 20 | 3 | 17 | 0.4 | 283 | 42.5 | 10,000 |

P-3 | 20 | 15 | 5 | 0.8 | 268.9 | 212.3 | 16,000 |

Bale No. | v_{avg} (P_{250kN}) | h_{avg} (P_{250kN}) | P_{max} | v_{avg} (P_{max}) |
---|---|---|---|---|

[mm] | [mm] | [kN] | [mm] | |

P-1 | 102 | 25 | 436 | 156 |

P-2 | 90 | 9 | 355 | 116 |

P-3 | 69 | 10 | 396 | 120 |

P-4 | 79 | 12 | 367 | 126 |

P-5 | 65 | 11 | 366 | 113 |

P-6 | 70 | 16 | 370 | 116 |

Avg | 79 | 14 | 382 | 125 |

Load Range (Cycle) | P-1 Bale | P-2 Bale | P-3 Bale | P-4 Bale | P-5 Bale | P-6 Bale | ||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|

E_{v} | ν | E_{v} | ν | E_{v} | ν | E_{v} | ν | E_{v} | ν | E_{v} | ν | |

kPa | [-] | kPa | [-] | kPa | [-] | kPa | [-] | kPa | [-] | kPa | [-] | |

0–50 kN (I) | 960 | 0.09 | 620 | 0.06 | 715 | 0.05 | 690 | 0.06 | 725 | 0.05 | 720 | 0.10 |

0–50 kN (II) | 1040 | 0.11 | 770 | 0.07 | 930 | 0.08 | 830 | 0.08 | 900 | 0.06 | 940 | 0.14 |

0–100 kN (I) | 905 | 0.12 | 760 | 0.11 | 915 | 0.09 | 805 | 0.09 | 960 | 0.08 | 900 | 0.14 |

0–100 kN (II) | 870 | 0.16 | 780 | 0.13 | 980 | 0.11 | 865 | 0.11 | 1020 | 0.10 | 965 | 0.15 |

0–250 kN (I) | 590 | 0.19 | 680 | 0.14 | 860 | 0.11 | 765 | 0.13 | 890 | 0.13 | 835 | 0.18 |

0–250 kN (II) | 570 | 0.22 | 670 | error | 730 | 0.11 | 790 | 0.11 | 930 | 0.16 | 865 | 0.21 |

Avg | 822.5 | 0.15 | 713.5 | 0.10 | 855.0 | 0.09 | 791.0 | 0.10 | 904.0 | 0.10 | 871.0 | 0.15 |

Bale No. | Area A | Normal Load V | Failure Shearload H_{f} | Normal Stress σ | Shear Stress τ | Approx. Shear Stress τ_{app} | Error Estimation |
---|---|---|---|---|---|---|---|

[m^{2}] | [kN] | [kN] | [kPa] | [kPa] | [kPa] | [%] | |

P-1 | 2.712 | 10.00 | 10.53 | 3.69 | 3.88 | 3.85 | 0.84 |

13.40 | 14.61 | 4.94 | 5.39 | 5.15 | 4.61 | ||

20.00 | 21.00 | 7.37 | 7.74 | 7.67 | 0.94 | ||

26.20 | 27.66 | 9.66 | 10.20 | 10.04 | 1.58 | ||

P-2 | 2.689 | 10.00 | 12.69 | 3.72 | 4.72 | 3.88 | 21.53 |

13.40 | 15.29 | 4.98 | 5.69 | 5.19 | 9.49 | ||

20.00 | 21.47 | 7.44 | 7.98 | 7.74 | 3.20 | ||

26.20 | 30.33 | 9.74 | 11.28 | 10.13 | 11.39 | ||

P-3 | 2.686 | 10.00 | 8.33 | 3.72 | 3.10 | 3.89 | 20.22 |

13.40 | 13.95 | 4.99 | 5.19 | 5.20 | 0.11 | ||

20.00 | 18.70 | 7.45 | 6.96 | 7.75 | 10.11 | ||

26.20 | 28.08 | 9.75 | 10.45 | 10.14 | 3.13 | ||

P-4 | 2.699 | 10.00 | 9.87 | 3.71 | 3.66 | 3.87 | 5.48 |

13.40 | 13.78 | 4.96 | 5.11 | 5.17 | 1.33 | ||

20.00 | 19.35 | 7.41 | 7.17 | 7.71 | 6.99 | ||

26.20 | 24.12 | 9.71 | 8.94 | 10.09 | 11.42 |

Bale No. | Area A | Normal Load V | Failure Shear Load H_{f} | Normal Stress σ | Shear Stress τ | Approx. Shear Stress τ_{app} | Error Estimation |
---|---|---|---|---|---|---|---|

[m^{2}] | [kN] | [kN] | [kPa] | [kPa] | [kPa] | [%] | |

P-1 | 2.686 | 22.2 | 14.01 | 8.27 | 5.22 | 5.47 | 4.58 |

28.4 | 18.24 | 10.57 | 6.79 | 6.78 | 0.18 | ||

38.4 | 23.00 | 14.30 | 8.56 | 8.90 | 3.74 | ||

44.0 | 25.71 | 16.38 | 9.57 | 10.08 | 5.05 | ||

P-2 | 2.712 | 22.2 | 13.86 | 8.19 | 5.11 | 5.42 | 5.73 |

28.4 | 18.61 | 10.47 | 6.86 | 6.72 | 2.10 | ||

38.4 | 23.00 | 14.16 | 8.48 | 8.82 | 3.82 | ||

44.0 | 28.03 | 16.22 | 10.34 | 9.99 | 3.45 | ||

P-3 | 2.726 | 22.2 | 16.45 | 8.14 | 6.03 | 5.40 | 11.80 |

28.4 | 17.80 | 10.42 | 6.53 | 6.69 | 2.40 | ||

38.4 | 24.70 | 14.09 | 9.06 | 8.78 | 3.25 | ||

44.0 | 28.41 | 16.14 | 10.42 | 9.94 | 4.81 |

Slab No. | h_{0} | t | Δh_{exp} | Fitted Regression Line | R^{2} | Δh_{365} | c_{α,}_{365} |
---|---|---|---|---|---|---|---|

[mm] | [h] | [mm] | [mm] | ||||

Specimen P-1 | |||||||

1 | 640.000 | 20.00 | 19.691 | y = 0.8136 ln x + 16.454 | 0.9795 | ----- | ----- |

2 | 620.309 | 7.16 | 6.139 | y = 0.2976 ln x + 5.551 | 0.8906 | 8.253 | 0.0034 |

3 | 614.170 | 19.89 | 8.521 | y = 0.6348 ln x + 6.5415 | 0.9860 | 12.304 | 0.0051 |

4 | 605.649 | 24.11 | 8.967 | y = 0.8372 ln x + 6.1902 | 0.9682 | 13.790 | 0.0058 |

Total | 71.16 | 43.318 | Average | 0.0048 | |||

Specimen P-2 | |||||||

1 | 665.000 | 20.23 | 21.048 | y = 0.6154 ln x + 19.216 | 0.9569 | ----- | ----- |

2 | 643.952 | 25.07 | 7.774 | y = 0.3026 ln x + 6.8493 | 0.9555 | 9.596 | 0.0038 |

3 | 636.178 | 24.58 | 7.712 | y = 0.6807 ln x + 5.6076 | 0.9542 | 11.787 | 0.0047 |

4 | 628.466 | 24.79 | 7.333 | y = 0.4696 ln x + 5.8459 | 0.9898 | 10.109 | 0.0041 |

Total | 94.67 | 43.867 | Average | 0.0042 | |||

Specimen P-3 | |||||||

1 | 666.000 | 21.34 | 8.534^{(2)} | y = 0.407 ln x + 7.3927 | 0.6542^{2)} | ----- | ----- |

2 | 657.466 | 24.54 | 8.579 | y = 0.6143 ln x + 6.6308 | 0.9406 | 12.207 | 0.0047 |

3 | 648.887 | 24.56 | 6.971 | y = 0.3464 ln x + 5.7583 | 0.9407 | 8.723 | 0.0034 |

4 | 641.916 | 94.95^{(1)} | 8.432 | y = 0.8042 ln x + 4.452 | 0.9489 | 8.813 | 0.0035 |

Total | 165.39 | 32.516 | Average | 0.0039 |

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**MDPI and ACS Style**

Duda, A.; Siwowski, T. Experimental Determination of Mechanical Properties of Waste Tyre Bales Used for Geotechnical Applications. *Materials* **2021**, *14*, 3310.
https://doi.org/10.3390/ma14123310

**AMA Style**

Duda A, Siwowski T. Experimental Determination of Mechanical Properties of Waste Tyre Bales Used for Geotechnical Applications. *Materials*. 2021; 14(12):3310.
https://doi.org/10.3390/ma14123310

**Chicago/Turabian Style**

Duda, Aleksander, and Tomasz Siwowski. 2021. "Experimental Determination of Mechanical Properties of Waste Tyre Bales Used for Geotechnical Applications" *Materials* 14, no. 12: 3310.
https://doi.org/10.3390/ma14123310