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Experimental Study of Stoneblowing Track Surfacing Technique
Available online at www.sciencedirect.com
ScienceDirect Procedia Engineering 189 (2017) 75 – 79
Transportation Geotechnics and Geoecology, TGG 2017, 17-19 May 2017, Saint Petersburg, Russia
Experimental study of stoneblowing track surfacing technique Alexander Abrashitov*, Artem Semak Moscow State University of Railway Engineering of Emperor Nicholas II, Moscow Russia
Abstract Ballast is known to be one of the most widely used materials for railtrack construction. Although ballast is comprised of crushed hard stones, it undergoes gradual and continual degradation under cyclic rail loading and requires constant maintenance. Due to the limitations of the commonly used ballast tamping technique for recovering railway track geometry, other technical solutions are currently being considered. Stoneblowing is an alternative technique of track level adjustment, that is defined as injection of the premeasured amount of small fresh stones with pressurized air under the sleepers, lifted to a desired level. This technique has been reported to lack most of the known disadvantages of tamping. However, postmaintenance behavior of ballast was found to be sensitive to the procedure aspects, thus further investigations in controlled laboratory conditions are required. This paper is focused on measurement and analysis of ballast settlement under cyclic loads after reinstating of a railway track with stoneblowing. Experimental results show that usage of stoneblowing leads to a predictable level of settlement, which remains constant even after a large number of loading cycles. Moreover, we propose a two-step stoneblowing technique and provide experimental evidence that this approach is more effective for reinstating the railway track than a conventional single step approach. © 2017 Published by Elsevier Ltd. Ltd. This is an open access article under the CC BY-NC-ND license 2017The TheAuthors. Authors. Published by Elsevier (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the scientific committee of the International conference on Transportation Geotechnics and Peer-review under responsibility of the scientific committee of the International conference on Transportation Geotechnics and Geoecology Geoecology. Keywords:stoneblowing; dynamic load; laboratory tests; settlement
Tamping can be described as lifting of sleepers to the required level and packing of ballast around the sleepers into the gaps beneath them. Due to a number of drawbacks, such as ballast damage [1], loosening of ballast bed and
* Corresponding author. E-mail address: [email protected].
1877-7058 © 2017 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license
(http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the scientific committee of the International conference on Transportation Geotechnics and Geoecology
doi:10.1016/j.proeng.2017.05.013
76
Alexander Abrashitov and Artem Semak / Procedia Engineering 189 (2017) 75 – 79
subsequent quick revert to a pre-maintenance geometry [2], usage of this method leads to high costs of track maintenance. Stoneblowing is another technique of track level adjustment, originated in the UK [3]. It is reported to cause less disturbance to the existing compacted ballast than tamping and to result in improved track quality [4,5]. Unfortunately, this technology has not got enough attention and has not found wide application, despite the potential benefits. In order to understand all the possible effects on the mechanical properties of railway track after the maintenance with new method, more in-depth studies should be carried out. In this paper we discuss laboratory experiments of the ballast settlement under dynamic loads after adjustment of track level by stoneblowing. The obtained experimental results are used to examine the potential of stoneblowing for track maintenance. 2. Materials and methods Preliminary tests were conducted to choose a ballast sample which shows minimal settlement and thus is expected to cause negligible impact on the experimental results. The chosen ballast sample was collected at railway turnout № 47 of Likhobory station on 50th kilometer of Little Ring of Moscow Railways. Table 1 presents size distribution of stones in the ballast sample, which was determined by means of sieve analysis. For pneumatic ballast injection commercially available small-sized (5 – 10 mm) sidewalk gravel was used. According to conducted tests this gravel corresponds to the Russian technical standards (GOST 8269.0-97) in terms of abrasion and impact values. Table 1. Ballast sample size distribution.
Stone size, mm
60-70
40-60
25-40
10-25
2-10
0.1-2
< 0.1
Mass fraction, %
3
33
24
30
5.7
3.0
1.3
The experimental setup [Fig. 1a] included a universal testing machine EUS-40, produced by Werkstoffpruefmachinen, Leipzig (frequency 5 – 25 Hz, maximum load 400 kN), box (300 mm by 600 mm by 400 mm deep) and two hard flat wooden stamps 290 × 590 mm2 and 240 × 250 mm2 for static and dynamic load procedures respectively. Stage 1, “Compression”. In the first step the box was filled with ballast sample (base ballast) and a static load was applied through a stamp over the whole horizontal surface. After 5 minutes the load was removed and the stamp settlement was measured. This procedure was repeated iteratively until the change in settlement between two subsequent iterations was less than 1.0 mm. Stage 2, “Stoneblowing”. In the next step the stamp was lifted above the surface of compressed ballast and fixed at a height of 30 mm [Fig. 1b]. Stones of base ballast were placed around the stamp to prevent the small gravel particles to be thrown out of the sample. One side of the stamp was left free to make it accessible for the stoneblowing apparatus. Then the stoneblowing procedure was performed. After that the last side was covered with base ballast stones as well.
a
b
Fig. 1. (a) View on experimental setup. One can see the sample on the measurement stage with a hard wooden stamp on top of it and coloured base ballast stones; (b) Sample on the stage of stoneblowing procedure.
Alexander Abrashitov and Artem Semak / Procedia Engineering 189 (2017) 75 – 79
Stage 3, “Dynamic load”. The last step included dynamic loads application experiment. The experiments were conducted in two different load (stress) ranges. In the case of “normal load” maximal stress value was ͲǤ͵͵ ܽܲܯor 3.25 ݂݇݃Ȁܿ݉ଶ (axle load value 25 tons). In the case of “high load” maximum was 0.51 ܽܲܯor 5.0 ݂݇݃Ȁܿ݉ଶ (axle load value 38 tons). Minimal value was 90% of maximum in both cases. One million loading cycles at a frequency of 12 Hz were applied to each of the samples, which corresponds to 25 million tons of railway traffic in case of “normal load” and 38 million tons in case of “high load”.
3. Results and discussion In the conducted experiments the following samples were considered: x Sample G: ballast after one pneumatic gravel injection x Sample GG: ballast after two pneumatic gravel injections separated by a dynamic load application step x Sample GG’: the same as GG, but at high dynamic load range x Sample GR: ballast after one pneumatic gravel injection, followed by a dynamic load application step and one pneumatic rubber injection As can be seen from Figure 2, for all the samples examined in this study the settlement level during the dynamic loading reached plateau quickly and remained constant even after a large number of cycles (up to one million). This high stability of track level after stoneblowing maintenance is in agreement with other experimental studies [6]. 3.1. Study of samples under “normal load” At first, we compare the settlement under dynamic load for samples G and GG, i.e. after one and two consequent pneumatic gravel injections. As one can see from Figure 2a, the settlement value on the plateau for sample G is 16 mm. It is more than a half of the height, that the stamp was lifted for the stoneblowing procedure. After the second gravel injection (sample GG) the settlement value on the plateau was reduced to 7 mm.
a
b
Fig. 2. Dependence of settlement on the number of cycles in (a) “normal load” regime, load = 3.25 ݂݇݃Ȁܿ݉ଶ ; (b) “high load” regime with load= 5.0 ݂݇݃Ȁܿ݉ଶ .
To explain this significant difference the distribution of different types of ballast along the sample height was examined. To distinguish between the gravel injected in the first and second stoneblowing steps, the former was coloured green. The sample was filled with gelatin and its cross-section was examined [Figure 3a]. As one can see, the non-coloured and green stones form separate layers that practically do not intermix with each other. The model of the sample GG is presented in Figure 3b: gravel that was injected first fills the voids between the larger stones of
77
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Alexander Abrashitov and Artem Semak / Procedia Engineering 189 (2017) 75 – 79
a
b
Fig. 3. (a) Cross-section of sample GG. The injected gravel is coloured green. (b) Schematic representation of sample GG after the dynamic load procedure.
base ballast and forms a stable stiff ground for the gravel of the second injection. This results in a lower value of settlement that is observed in the experiment. Next we compare the dynamic load settlement results for samples GG and GR, that have different materials injected during the second stoneblowing step: gravel and rubber, respectively. Despite the fact that usage of rubber increases the settlement level to 14 mm compared to 7 mm in case of sample GG, this level still remains constant after a million loading cycles that evidences that rubber material does not degrade significantly that was confirmed after the measurement by visual examination of the material. These observations indicate that rubber is not suitable as the only injection component due to a high settlement level, but could be applicable as an additive. Recent studies [6,7] show that a mixture of gravel and rubber pneumatically injected under the slipper may improve longevity of ballast and the results of settlement tests are still comparable with pure gravel. 3.2. Study of samples under “high load” Even under higher load the samples after one stoneblowing procedure (sample G) and two stoneblowing procedures (sample GG’) demonstrate the stable settlement level, though this level is higher than in the case of “normal load” (15 mm compared to 7 mm for GG sample). 4. Summary and conclusions By means of dynamic load experiments we investigated the ballast settlement after application of stoneblowing track surfacing technique. It was demonstrated, that this technology provides a better controlled results if applied two times, because the first gravel injection forms a stable base and the following injection can be used for the controlled adjustment of the track level. Replacement of stones with rubber particles for the second injection step leads to the increase of settlement level. It was also shown that, even under high loads, the track level adjusted by stoneblowing does not decrease over time after initial settlement. Acknowledgements The authors express their appreciation to the director of the Institute of Road, Construction and Engineering Taisiya Shepitko (MIIT) and to the head of the chair of path and track facilities, Evgenij Ashpiz (MIIT).
Alexander Abrashitov and Artem Semak / Procedia Engineering 189 (2017) 75 – 79
References [1] Counter B. et al. Refurbishment of ballasted track systems; the technical challenges of quality and decision support tools //Construction and Building Materials. – 2015. – Т. 92. – С. 51-57. [2] Esveld, C. (1989). Track Geometry and Vehicle Reactions. Rail Engineering International Edition, (4), p13. [3] Anderson, W. F., Wilde, C., & Thompson, J. (2002). Experiences with the stoneblower on the UK East Coast Main Line. In PROCEEDINGS OF THE INTERNATIONAL CONFERENCE RAILWAY ENGINEERING 2002, HELD LONDON, UK, JULY 2002-CD ROM. [4] Claisse, P., Keedwell, M., & Calla, C. (2003, May). Tests on a two-layered ballast system. In Proceedings of the Institution of Civil Engineers-Transport (Vol. 156, No. 2, pp. 93-102). London: Published for the Institution of Civil Engineers by Thomas Telford Services, 1992[5] McMichael, P., & McNaughton, A. (2003). The Stoneblower-Delivering the Promise: Development, Testing and Operation of a New Track Maintenance System. In TRB 2003 Annual Meeting CD-ROM. [6] Sol-Sánchez, M., Moreno-Navarro, F., Martínez-Montes, G., & Rubio-Gámez, M. C. (2017). An alternative sustainable railway maintenance technique based on the use of rubber particles. Journal of Cleaner Production, 142, 3850-3858. [7] Chan, C. M., & Johan, S. F. S. (2016). Performance enhancement of railtrack ballast with rubber inclusions: a laboratory simulation. Japanese Geotechnical Society Special Publication, 2(47), 1640-1643.
79
ScienceDirect Procedia Engineering 189 (2017) 75 – 79
Transportation Geotechnics and Geoecology, TGG 2017, 17-19 May 2017, Saint Petersburg, Russia
Experimental study of stoneblowing track surfacing technique Alexander Abrashitov*, Artem Semak Moscow State University of Railway Engineering of Emperor Nicholas II, Moscow Russia
Abstract Ballast is known to be one of the most widely used materials for railtrack construction. Although ballast is comprised of crushed hard stones, it undergoes gradual and continual degradation under cyclic rail loading and requires constant maintenance. Due to the limitations of the commonly used ballast tamping technique for recovering railway track geometry, other technical solutions are currently being considered. Stoneblowing is an alternative technique of track level adjustment, that is defined as injection of the premeasured amount of small fresh stones with pressurized air under the sleepers, lifted to a desired level. This technique has been reported to lack most of the known disadvantages of tamping. However, postmaintenance behavior of ballast was found to be sensitive to the procedure aspects, thus further investigations in controlled laboratory conditions are required. This paper is focused on measurement and analysis of ballast settlement under cyclic loads after reinstating of a railway track with stoneblowing. Experimental results show that usage of stoneblowing leads to a predictable level of settlement, which remains constant even after a large number of loading cycles. Moreover, we propose a two-step stoneblowing technique and provide experimental evidence that this approach is more effective for reinstating the railway track than a conventional single step approach. © 2017 Published by Elsevier Ltd. Ltd. This is an open access article under the CC BY-NC-ND license 2017The TheAuthors. Authors. Published by Elsevier (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the scientific committee of the International conference on Transportation Geotechnics and Peer-review under responsibility of the scientific committee of the International conference on Transportation Geotechnics and Geoecology Geoecology. Keywords:stoneblowing; dynamic load; laboratory tests; settlement
Tamping can be described as lifting of sleepers to the required level and packing of ballast around the sleepers into the gaps beneath them. Due to a number of drawbacks, such as ballast damage [1], loosening of ballast bed and
* Corresponding author. E-mail address: [email protected].
1877-7058 © 2017 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license
(http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the scientific committee of the International conference on Transportation Geotechnics and Geoecology
doi:10.1016/j.proeng.2017.05.013
76
Alexander Abrashitov and Artem Semak / Procedia Engineering 189 (2017) 75 – 79
subsequent quick revert to a pre-maintenance geometry [2], usage of this method leads to high costs of track maintenance. Stoneblowing is another technique of track level adjustment, originated in the UK [3]. It is reported to cause less disturbance to the existing compacted ballast than tamping and to result in improved track quality [4,5]. Unfortunately, this technology has not got enough attention and has not found wide application, despite the potential benefits. In order to understand all the possible effects on the mechanical properties of railway track after the maintenance with new method, more in-depth studies should be carried out. In this paper we discuss laboratory experiments of the ballast settlement under dynamic loads after adjustment of track level by stoneblowing. The obtained experimental results are used to examine the potential of stoneblowing for track maintenance. 2. Materials and methods Preliminary tests were conducted to choose a ballast sample which shows minimal settlement and thus is expected to cause negligible impact on the experimental results. The chosen ballast sample was collected at railway turnout № 47 of Likhobory station on 50th kilometer of Little Ring of Moscow Railways. Table 1 presents size distribution of stones in the ballast sample, which was determined by means of sieve analysis. For pneumatic ballast injection commercially available small-sized (5 – 10 mm) sidewalk gravel was used. According to conducted tests this gravel corresponds to the Russian technical standards (GOST 8269.0-97) in terms of abrasion and impact values. Table 1. Ballast sample size distribution.
Stone size, mm
60-70
40-60
25-40
10-25
2-10
0.1-2
< 0.1
Mass fraction, %
3
33
24
30
5.7
3.0
1.3
The experimental setup [Fig. 1a] included a universal testing machine EUS-40, produced by Werkstoffpruefmachinen, Leipzig (frequency 5 – 25 Hz, maximum load 400 kN), box (300 mm by 600 mm by 400 mm deep) and two hard flat wooden stamps 290 × 590 mm2 and 240 × 250 mm2 for static and dynamic load procedures respectively. Stage 1, “Compression”. In the first step the box was filled with ballast sample (base ballast) and a static load was applied through a stamp over the whole horizontal surface. After 5 minutes the load was removed and the stamp settlement was measured. This procedure was repeated iteratively until the change in settlement between two subsequent iterations was less than 1.0 mm. Stage 2, “Stoneblowing”. In the next step the stamp was lifted above the surface of compressed ballast and fixed at a height of 30 mm [Fig. 1b]. Stones of base ballast were placed around the stamp to prevent the small gravel particles to be thrown out of the sample. One side of the stamp was left free to make it accessible for the stoneblowing apparatus. Then the stoneblowing procedure was performed. After that the last side was covered with base ballast stones as well.
a
b
Fig. 1. (a) View on experimental setup. One can see the sample on the measurement stage with a hard wooden stamp on top of it and coloured base ballast stones; (b) Sample on the stage of stoneblowing procedure.
Alexander Abrashitov and Artem Semak / Procedia Engineering 189 (2017) 75 – 79
Stage 3, “Dynamic load”. The last step included dynamic loads application experiment. The experiments were conducted in two different load (stress) ranges. In the case of “normal load” maximal stress value was ͲǤ͵͵ ܽܲܯor 3.25 ݂݇݃Ȁܿ݉ଶ (axle load value 25 tons). In the case of “high load” maximum was 0.51 ܽܲܯor 5.0 ݂݇݃Ȁܿ݉ଶ (axle load value 38 tons). Minimal value was 90% of maximum in both cases. One million loading cycles at a frequency of 12 Hz were applied to each of the samples, which corresponds to 25 million tons of railway traffic in case of “normal load” and 38 million tons in case of “high load”.
3. Results and discussion In the conducted experiments the following samples were considered: x Sample G: ballast after one pneumatic gravel injection x Sample GG: ballast after two pneumatic gravel injections separated by a dynamic load application step x Sample GG’: the same as GG, but at high dynamic load range x Sample GR: ballast after one pneumatic gravel injection, followed by a dynamic load application step and one pneumatic rubber injection As can be seen from Figure 2, for all the samples examined in this study the settlement level during the dynamic loading reached plateau quickly and remained constant even after a large number of cycles (up to one million). This high stability of track level after stoneblowing maintenance is in agreement with other experimental studies [6]. 3.1. Study of samples under “normal load” At first, we compare the settlement under dynamic load for samples G and GG, i.e. after one and two consequent pneumatic gravel injections. As one can see from Figure 2a, the settlement value on the plateau for sample G is 16 mm. It is more than a half of the height, that the stamp was lifted for the stoneblowing procedure. After the second gravel injection (sample GG) the settlement value on the plateau was reduced to 7 mm.
a
b
Fig. 2. Dependence of settlement on the number of cycles in (a) “normal load” regime, load = 3.25 ݂݇݃Ȁܿ݉ଶ ; (b) “high load” regime with load= 5.0 ݂݇݃Ȁܿ݉ଶ .
To explain this significant difference the distribution of different types of ballast along the sample height was examined. To distinguish between the gravel injected in the first and second stoneblowing steps, the former was coloured green. The sample was filled with gelatin and its cross-section was examined [Figure 3a]. As one can see, the non-coloured and green stones form separate layers that practically do not intermix with each other. The model of the sample GG is presented in Figure 3b: gravel that was injected first fills the voids between the larger stones of
77
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Alexander Abrashitov and Artem Semak / Procedia Engineering 189 (2017) 75 – 79
a
b
Fig. 3. (a) Cross-section of sample GG. The injected gravel is coloured green. (b) Schematic representation of sample GG after the dynamic load procedure.
base ballast and forms a stable stiff ground for the gravel of the second injection. This results in a lower value of settlement that is observed in the experiment. Next we compare the dynamic load settlement results for samples GG and GR, that have different materials injected during the second stoneblowing step: gravel and rubber, respectively. Despite the fact that usage of rubber increases the settlement level to 14 mm compared to 7 mm in case of sample GG, this level still remains constant after a million loading cycles that evidences that rubber material does not degrade significantly that was confirmed after the measurement by visual examination of the material. These observations indicate that rubber is not suitable as the only injection component due to a high settlement level, but could be applicable as an additive. Recent studies [6,7] show that a mixture of gravel and rubber pneumatically injected under the slipper may improve longevity of ballast and the results of settlement tests are still comparable with pure gravel. 3.2. Study of samples under “high load” Even under higher load the samples after one stoneblowing procedure (sample G) and two stoneblowing procedures (sample GG’) demonstrate the stable settlement level, though this level is higher than in the case of “normal load” (15 mm compared to 7 mm for GG sample). 4. Summary and conclusions By means of dynamic load experiments we investigated the ballast settlement after application of stoneblowing track surfacing technique. It was demonstrated, that this technology provides a better controlled results if applied two times, because the first gravel injection forms a stable base and the following injection can be used for the controlled adjustment of the track level. Replacement of stones with rubber particles for the second injection step leads to the increase of settlement level. It was also shown that, even under high loads, the track level adjusted by stoneblowing does not decrease over time after initial settlement. Acknowledgements The authors express their appreciation to the director of the Institute of Road, Construction and Engineering Taisiya Shepitko (MIIT) and to the head of the chair of path and track facilities, Evgenij Ashpiz (MIIT).
Alexander Abrashitov and Artem Semak / Procedia Engineering 189 (2017) 75 – 79
References [1] Counter B. et al. Refurbishment of ballasted track systems; the technical challenges of quality and decision support tools //Construction and Building Materials. – 2015. – Т. 92. – С. 51-57. [2] Esveld, C. (1989). Track Geometry and Vehicle Reactions. Rail Engineering International Edition, (4), p13. [3] Anderson, W. F., Wilde, C., & Thompson, J. (2002). Experiences with the stoneblower on the UK East Coast Main Line. In PROCEEDINGS OF THE INTERNATIONAL CONFERENCE RAILWAY ENGINEERING 2002, HELD LONDON, UK, JULY 2002-CD ROM. [4] Claisse, P., Keedwell, M., & Calla, C. (2003, May). Tests on a two-layered ballast system. In Proceedings of the Institution of Civil Engineers-Transport (Vol. 156, No. 2, pp. 93-102). London: Published for the Institution of Civil Engineers by Thomas Telford Services, 1992[5] McMichael, P., & McNaughton, A. (2003). The Stoneblower-Delivering the Promise: Development, Testing and Operation of a New Track Maintenance System. In TRB 2003 Annual Meeting CD-ROM. [6] Sol-Sánchez, M., Moreno-Navarro, F., Martínez-Montes, G., & Rubio-Gámez, M. C. (2017). An alternative sustainable railway maintenance technique based on the use of rubber particles. Journal of Cleaner Production, 142, 3850-3858. [7] Chan, C. M., & Johan, S. F. S. (2016). Performance enhancement of railtrack ballast with rubber inclusions: a laboratory simulation. Japanese Geotechnical Society Special Publication, 2(47), 1640-1643.
79