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The Impact of Engineering-geologic Conditions on the Development of Railway Subgrade Design Solutions
Available online at www.sciencedirect.com
ScienceDirect Procedia Engineering 189 (2017) 752 – 758
Transportation Geotechnics and Geoecology, TGG 2017, 17-19 May 2017, Saint Petersburg, Russia
The impact of engineering-geologic conditions on the development of railway subgrade design solutions Alpysova V.A.a, Bushuev N.S.a, Shkurnikov S.V.a, Shulman D.O.a* a
Emperor Alexander I St. Petersburg State Transport University. 9, Moskovsky av., St. Petersburg, 190031, Russia
Abstract An analysis of hydro-meteorological and engineering-geological conditions of the Russia’s Eastern Siberia and the Far East is provided in the article. To assess the disruptive effect of earthquakes on the railway track elements a unified parameter is selected – the magnitude of admissible stress σr. A multi-factor research is conducted for the fixed seismicity value of 8 points. The analysis of stability is based on the formula by G.M. Shakhunyants accounting for seismicity. Basing on the analysis performed the optimal design solutions for embankments with account of soil conditions and earthquake effects are proposed. Recommendations for the embankment structure’s optimization are given. ©2017 2017Published The Authors. Published by Elsevier © by Elsevier Ltd. This is an openLtd. access article under the CC BY-NC-ND license Peer-review under responsibility of the scientific committee of the International conference on Transportation Geotechnics and (http://creativecommons.org/licenses/by-nc-nd/4.0/). Geoecology. Peer-review under responsibility of the scientific committee of the International conference on Transportation Geotechnics and Geoecology Keywords: Subgrade, permafrost soil, seismicity, seismic resistance, damping layer, multiple classification analysis
1. Main text: The country’s economic and social development is based on the creation of an integrated system of transport routes engaged in passenger and freight transportation by different kinds of vehicles. Currently, the center of economic activity in Russia is shifting towards Eastern Siberia and the Far East. This is due to two main reasons:
* Corresponding author. Tel.: +7 (812) 570-76-88. E-mail address: [email protected], [email protected], [email protected], [email protected].
1877-7058 © 2017 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.2017.05.118
V.A. Alpysova et al. / Procedia Engineering 189 (2017) 752 – 758
first, a considerable part of raw material resources is located in this area, and second, their geographic location stimulates the expansion of trade between Russia and countries if the Asia-Pacific (AP) region. The railway transport provides more than 80% of freight turnover and about 40% of passenger traffic in the transport system of Eastern Siberia. Development of new fossil deposits, increase in trade turnover between Russia and AP region as well as growth of transit transportation volumes encourage an improvement of the complex transport system including railway transport. In order to implement the given task of the transportation increase the Russian Government has elaborated and approved the Strategy for Railway Transport Development towards 2030, which involves both construction of new lines and reconstruction of the Baikal-Amur Mainline and Trans-Siberian Railway. It should also be noted that the Eastern Siberia and the Far East regions are characterized by complex hydrometeorological and engineering-geological conditions, which have a considerable effect on the composition and volume of survey works, development of design solutions, construction and maintenance of the whole railway infrastructure. The Eastern Siberia climate is continental and severe. One can observe significant seasonal fluctuations in cloud coverage, temperature, and precipitation level. Winter temperatures can reach the value of -40-60°С. In summer the southern area of the region appears to be relatively hot. It is especially typical of Tyva, Khakassia, and Trans-Baikal. Here the temperature in July is up to +25 degrees. The Far East climate modifies from harsh continental (Yakutia, Kolyma areas of the Magadan region) to monsoon climate (South-East). This is due to the extremely vast territory measured from North to South (almost 3,900 km) and from West to East (2,500–3,000 km). In the South-West part of the region the climate is moderate with the winter temperature ranging from -32 to -48°С. Winters are usually dry and last for 9 months. Summer temperatures are quite high: from +12 to +20°С. The annual precipitation is 300–500 mm. In the Southern part of the region the monsoon climate has a relatively cold and dry winter (from -12 to -20°С) and a wet and cool summer (+16°С). Analysis of hydro-meteorological conditions allows for the conclusion that almost all territory of the considered region is characterized by a lengthy period of negative temperatures of more than -25°С, which lasts up to 9 months per year, and a short period of positive temperatures (up to +25°С). In the last decades one can observe a change in the region’s climate with sharper temperature fluctuations, stronger winds as well as change in the quantity and type of precipitation. Nowadays, trends in hydro-meteorological shifts are not identified. It is due to a relatively short period of climatic parameters change, their unstable nature, and lack of data needed to obtain verifiable regularities in hydrometeorological modification. When conducting hydro-meteorological survey one should account for the climatic change data as well as analyze the reasons for climatic conditions modification and provide their systematization. What is especially peculiar about the regions of Eastern Siberia and the Far East is the following fact: they are located within the zone of permafrost soil (Fig. 1) and high seismicity (Fig. 2). Basing on the comparison of seismicity and permafrost soil maps one can conclude that a share of Eastern Siberia and practically the whole of the Far East are affected by both factors. Thus, it is strongly recommended to take them into account when performing design works. If we consider the seasonal thawing of ground as the main negative factor, we should design the railway subgrade as an embankment formed by sandy filtering soils in order to preserve the ground in the frozen condition (Design Principle I).
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V.A. Alpysova et al. / Procedia Engineering 189 (2017) 752 – 758
Fig. 1. Map of Permafrost Soils Distribution.
Fig. 2. Seismicity Map of Siberia and the Far East.
755
V.A. Alpysova et al. / Procedia Engineering 189 (2017) 752 – 758
The maximum embankment height can therefore be established on the basis of the seasonal thawing depth. The seasonal thawing depth is identifies in accordance with Construction Code 25.13330.2012 Annex 4 [1]. The standard seasonal thawing depth is determined by the formula: మ
ሺ்ǡష ்್ ሻ௧ǡ
ᇱ ݀௧ǡ ൌ ݀௧ ට
ሺ் ି்್ ሻ௧
,
(1)
where: ᇱ୲୦ stands for the biggest seasonal thawing depth in a year period, m (established on the basis of field observations); ୠ stands for the starting temperature of soil freezing, °С; ୲୦ǡ୫ ǡ ୲୦୫ǡ stand respectively for the average air temperature in the positive period, °С, and for the duration of this period, h, adopted in accordance with Construction Code 131.13330 [2]; ୲୦ , ୲୦ stand respectively for the average air temperature in the negative period, °С, and for the duration of this period, h, in the year of observation adopted in accordance with meteorological data. At a first approximation, due to the necessity of preserving the ground in the frozen condition the embankment height is recommended to be within the limits of 3–6 m, depending on the seasonal thawing depth of the permafrost soils. If the negative impact of seismic waves [9, 10] is taken as a primary factor, the embankment height should be determined by two parameters: the maximum application of damping properties of the embankment and the provision of its general stability. Seismic impacts are wave oscillating movements arising in response to the underground strike of the released energy. It results in the three types of waves: longitudinal waves along the seismic raypath, transversal waves perpendicular to the seismic raypath acting within the rock mass, and transversal surface waves arising at the surface of the ‘ground-air’ environment division [11, 12, 13, 14, 15]. The most destructive are transversal waves. An example of destructive impact of transversal surface waves is showed in Fig. 3.
Fig. 3. Destruction of Track Superstructure as a Result of Seismic Transversal Surface Waves Impact [6].
756
V.A. Alpysova et al. / Procedia Engineering 189 (2017) 752 – 758
To estimate the destructive impact of earthquakes on the railway track elements (subgrade, ballast, sleepers, rails) a unified parameter has been adopted – magnitude of admissible stress ɐሺሻǡ ˃. Research was conducted by means of multiple classification analysis. As impact factors the thicknesses of subgrade (hsg = 3–21 m), bedrock (hbr = 5– 95 m) and Earth crust (distance to hypocenter r = 10 and 20 km) were selected. Basing on the fact that according to the Construction Code 14.13330.2011 [4] the calculations for structures are performed when seismicity is estimated ≥ 7 points (MSK scale), research was conducted for the site with seismicity of 8 points [7, 8]. Calculations for stress are done using the formulae by V.N. Tyupin and E.V. Nepomnyashchikh [3]. The calculations performed have resulted in the regression equation of the following kind: ݕൌ ʹʹ͵ǡͲ െ Ͳͻǡͷ ή ˘ଵ െ ͺͶʹͷͶǡ ή ˘ଶ െ ͻͺͶ͵ǡͷ ή ˘ଷ ͷͻͶǡ ή ˘ଶ ή ˘ଷ Ǥ
(2)
where: ݕstands for the optimization parameter – stress σr, Pa; ˘ଵ stands for the influence factor (subgrade thickness); ˘ଶ stands for the influence factor (bedrock soil thickness); ˘ଷ stands for the influence factor (distance to the hypocenter). All coefficients of the regression equation are significant. So, the greater is the thickness of the soil layers, the lower is the magnitude of stress acting on the subgrade and track superstructure. In this case the embankment should be seen as a damping structure located between the bedrock soil and track superstructure. Moreover, the higher is the embankment, the lower negative impact of longitudinal waves is conveyed to the track superstructure. Nevertheless, with the embankment height getting larger its general stability decreases. To analyze the embankment stability calculations accounting for the seismic impacts and not accounting for them were performed using the formula of G.M. Shakhunyants [5]:
ܭௗ௬ ൌ
σ సభሺே ή ା ή ା்ೞ ሻ σ సభ ்ೞ ήೞ
ǡ
(3)
where: ܭௗ௬ stands for the dynamic stability factor; ܰ stands for the coercive force in the i section; ݂ௗ௬ stands for the dynamic friction factor in the i section; ܥௗ௬ stands for the specific cohesion in the i section; ݈ stands for the i section foundation length; ܶௗ௬ stands for the coercive dynamic force in the i section; ܶௗ௦ stands for the displacement force in the i section; ܭ௦ stands for the seismicity factor. For embankments of 3–21 m height the general trends of the stability factor change have been established depending on the embankment height, as showed in Fig. 4.
V.A. Alpysova et al. / Procedia Engineering 189 (2017) 752 – 758
Fig. 4. The general trends of the stability factor change depending on the embankment height. The analysis of the embankment stability factor change depending on its height allows to conclude that within the height ranging from 3 to 9 m the largest percentage of stability factor decrease is observed (~20%); within the height ranging from 9 to 21 m this value does not exceed 10%. It should also be noted that at the embankment height of more than 12 m (according to acting standards) it is required to arrange berms which significantly increases the consumption of soil materials, width of the land strip needed to construct an embankment as well as the volume of construction work. Thus, the most rational solution for the embankment height is the range from 3 to 12 m. 2. Conclusions: 1. In Eastern Siberia and the Far East it is recommended to design railway subgrade predominantly on embankments of 3–12 m height, which allows, first, to keep the soil frozen and second, to decrease the negative impact of earthquakes on the track superstructure. 2. The optimal embankment structure shall be identified by means of calculation which will account for hydro-meteorological conditions, trends of their change, conditions of permafrost soil deposits and their thickness as well as the seismic impacts. 3. If the embankment height is insufficient, one shall arrange additional damping layers within the embankments in order to decrease negative earthquake impacts. References [1] SP 25.13330.2012. Aktualizirovannaya redaktsiya “SNiP 2.02.04-88. Osnovaniya i fundamenty na vechnomerzlykh gruntakh” [Construction Code 25.13330.2012. Actualized version of “Construction Norms and Regulations 2.02.04-88. Bedrocks and Foundations on Permafrost Soils”]. Introduced on January 1st, 2013. [2] SP 131.13330. Stroitelnaya klimatologiya. Aktualizirovannaya redaktsiya “SNiP 23-01-99* (c izmeneniyami) [Construction Code 131.13330. Construction Climatology. Actualized version of “Construction Norms and Regulations 23-01-99* (modified)”]. Introduced on January 1st, 2013.
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[3] V.N. Tyupin, E.V. Nepomnyashchikh, Vozdeistviye zemletryaseniya na zheleznodorozhnyi put’ [Earthquake Impact on Railway Track] // Put’ i putevoye khozyaistvo [Railway Track and Track Maintenance]. 2008. #9. P. 24–26. [4] SP 14.13330.2011. Stroitelstvo v seismicheskikh rayonakh. Aktualizirovannaya redaktsiya SNiP II – 7-81* [Construction Code 14.13330.2011. Construction in Seismic Regions. Actualized version of Construction Norms and Regulations II – 7-81*]. [5] G.M. Shakhunyants, Zheleznodorozhnyi put’ [Railway Track]. – Мoscow, 1987. [6] http://blogs.agu.org/landslideblog/files/2010/11/10_10-Canterbury-22.jpg [7] Y.S.Merkuryev, V.A. Alpysova, Vliyaniye dempfiruyuschego sloya na seismoustoichivost’ puti [The damping layer influence on the track’s seismic resistance] // Put’ i putevoye khozyaistvo [Railway Track and Track Maintenance]. 2015. #5. P. 19–20. [8] V.A.Alpysova, Y.S. Merkuryev, Vliyaniye parametrov zemletryaseniy na konstruktsiyu zemlyanogo polotna [Influence of earthquake parameters on the subgrade structure] // Sovremennye metody proektirovaniya transportnykh magistraley kak elementov pripodno-tekhnicheskoy sistemy [Modern design techniques for transport routes as elements of natural and technical systems]: Proceedings of the conference dedicated to the 100th anniversary of Prof. A.K. Dyunin. – 2015, P. 63-72. [9] V.A.Alpysova, A.S. Tenau, Osobennosti konstruktsii zemlyanogo polotna dlya usloviy Efiopii. Problemy razrabotki natsional'nykh standartov respubliki Efiopiya. // Sbornik materialov mezhdunarodnoy nauchnoprakticheskoy konferentsii: St. Petersburg State Transport University. – 2014, P. 95-99. [10] V.A.Alpysova, T.D. Mengesha, Uchet seysmicheskikh vozdeystviy pri proyektirovanii zemlyanogo polotna v usloviyakh FDRE. Osobennosti konstruktsii zemlyanogo polotna dlya usloviy Efiopii. // Sbornik materialov mezhdunarodnoy nauchno-prakticheskoy konferentsii: St. Petersburg State Transport University. – 2014, P. 100108. [11] Scherbaum F. et. al., Determination of shallow shear waves velocity profiles in theCologne, Germany area using ambient vibrations. Geophys. J. Int. (2003) 152, 597–612. [12] Sorensen C. and Asten M. (2005) Comparison of shear wave velocity profiles of Quaternary sediments in the Newcastle area estimated from SCPT, microtremor spectral ratios and array studies, and drilling. Earthquake Engineering in Australia, Proceedings of a conference of the Australian Earthquake Engineering Soc., Albury Vic., Paper 9. [13] Stephenson W.R., Factors bounding prograde Rayleigh-wave particle motion in a soft- soil layer. Pacific Conference on Earthquake Engineering. 2003. [14] Nakamura, Y. 1989. A method for dynamic characteristics estimation of subsurface using microtremor on the ground surface. Quaterly Report Railway Tech. Res. Inst., 30(1): 25‒33. [15] Roberts J.C and M.W. Asten, Resolving a velocity inversion at the geotechnical scale using the microtremor (passive seismic) survey method. Exploration Geophysics (2004) 35, 14–18.
ScienceDirect Procedia Engineering 189 (2017) 752 – 758
Transportation Geotechnics and Geoecology, TGG 2017, 17-19 May 2017, Saint Petersburg, Russia
The impact of engineering-geologic conditions on the development of railway subgrade design solutions Alpysova V.A.a, Bushuev N.S.a, Shkurnikov S.V.a, Shulman D.O.a* a
Emperor Alexander I St. Petersburg State Transport University. 9, Moskovsky av., St. Petersburg, 190031, Russia
Abstract An analysis of hydro-meteorological and engineering-geological conditions of the Russia’s Eastern Siberia and the Far East is provided in the article. To assess the disruptive effect of earthquakes on the railway track elements a unified parameter is selected – the magnitude of admissible stress σr. A multi-factor research is conducted for the fixed seismicity value of 8 points. The analysis of stability is based on the formula by G.M. Shakhunyants accounting for seismicity. Basing on the analysis performed the optimal design solutions for embankments with account of soil conditions and earthquake effects are proposed. Recommendations for the embankment structure’s optimization are given. ©2017 2017Published The Authors. Published by Elsevier © by Elsevier Ltd. This is an openLtd. access article under the CC BY-NC-ND license Peer-review under responsibility of the scientific committee of the International conference on Transportation Geotechnics and (http://creativecommons.org/licenses/by-nc-nd/4.0/). Geoecology. Peer-review under responsibility of the scientific committee of the International conference on Transportation Geotechnics and Geoecology Keywords: Subgrade, permafrost soil, seismicity, seismic resistance, damping layer, multiple classification analysis
1. Main text: The country’s economic and social development is based on the creation of an integrated system of transport routes engaged in passenger and freight transportation by different kinds of vehicles. Currently, the center of economic activity in Russia is shifting towards Eastern Siberia and the Far East. This is due to two main reasons:
* Corresponding author. Tel.: +7 (812) 570-76-88. E-mail address: [email protected], [email protected], [email protected], [email protected].
1877-7058 © 2017 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.2017.05.118
V.A. Alpysova et al. / Procedia Engineering 189 (2017) 752 – 758
first, a considerable part of raw material resources is located in this area, and second, their geographic location stimulates the expansion of trade between Russia and countries if the Asia-Pacific (AP) region. The railway transport provides more than 80% of freight turnover and about 40% of passenger traffic in the transport system of Eastern Siberia. Development of new fossil deposits, increase in trade turnover between Russia and AP region as well as growth of transit transportation volumes encourage an improvement of the complex transport system including railway transport. In order to implement the given task of the transportation increase the Russian Government has elaborated and approved the Strategy for Railway Transport Development towards 2030, which involves both construction of new lines and reconstruction of the Baikal-Amur Mainline and Trans-Siberian Railway. It should also be noted that the Eastern Siberia and the Far East regions are characterized by complex hydrometeorological and engineering-geological conditions, which have a considerable effect on the composition and volume of survey works, development of design solutions, construction and maintenance of the whole railway infrastructure. The Eastern Siberia climate is continental and severe. One can observe significant seasonal fluctuations in cloud coverage, temperature, and precipitation level. Winter temperatures can reach the value of -40-60°С. In summer the southern area of the region appears to be relatively hot. It is especially typical of Tyva, Khakassia, and Trans-Baikal. Here the temperature in July is up to +25 degrees. The Far East climate modifies from harsh continental (Yakutia, Kolyma areas of the Magadan region) to monsoon climate (South-East). This is due to the extremely vast territory measured from North to South (almost 3,900 km) and from West to East (2,500–3,000 km). In the South-West part of the region the climate is moderate with the winter temperature ranging from -32 to -48°С. Winters are usually dry and last for 9 months. Summer temperatures are quite high: from +12 to +20°С. The annual precipitation is 300–500 mm. In the Southern part of the region the monsoon climate has a relatively cold and dry winter (from -12 to -20°С) and a wet and cool summer (+16°С). Analysis of hydro-meteorological conditions allows for the conclusion that almost all territory of the considered region is characterized by a lengthy period of negative temperatures of more than -25°С, which lasts up to 9 months per year, and a short period of positive temperatures (up to +25°С). In the last decades one can observe a change in the region’s climate with sharper temperature fluctuations, stronger winds as well as change in the quantity and type of precipitation. Nowadays, trends in hydro-meteorological shifts are not identified. It is due to a relatively short period of climatic parameters change, their unstable nature, and lack of data needed to obtain verifiable regularities in hydrometeorological modification. When conducting hydro-meteorological survey one should account for the climatic change data as well as analyze the reasons for climatic conditions modification and provide their systematization. What is especially peculiar about the regions of Eastern Siberia and the Far East is the following fact: they are located within the zone of permafrost soil (Fig. 1) and high seismicity (Fig. 2). Basing on the comparison of seismicity and permafrost soil maps one can conclude that a share of Eastern Siberia and practically the whole of the Far East are affected by both factors. Thus, it is strongly recommended to take them into account when performing design works. If we consider the seasonal thawing of ground as the main negative factor, we should design the railway subgrade as an embankment formed by sandy filtering soils in order to preserve the ground in the frozen condition (Design Principle I).
753
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V.A. Alpysova et al. / Procedia Engineering 189 (2017) 752 – 758
Fig. 1. Map of Permafrost Soils Distribution.
Fig. 2. Seismicity Map of Siberia and the Far East.
755
V.A. Alpysova et al. / Procedia Engineering 189 (2017) 752 – 758
The maximum embankment height can therefore be established on the basis of the seasonal thawing depth. The seasonal thawing depth is identifies in accordance with Construction Code 25.13330.2012 Annex 4 [1]. The standard seasonal thawing depth is determined by the formula: మ
ሺ்ǡష ்್ ሻ௧ǡ
ᇱ ݀௧ǡ ൌ ݀௧ ට
ሺ் ି்್ ሻ௧
,
(1)
where: ᇱ୲୦ stands for the biggest seasonal thawing depth in a year period, m (established on the basis of field observations); ୠ stands for the starting temperature of soil freezing, °С; ୲୦ǡ୫ ǡ ୲୦୫ǡ stand respectively for the average air temperature in the positive period, °С, and for the duration of this period, h, adopted in accordance with Construction Code 131.13330 [2]; ୲୦ , ୲୦ stand respectively for the average air temperature in the negative period, °С, and for the duration of this period, h, in the year of observation adopted in accordance with meteorological data. At a first approximation, due to the necessity of preserving the ground in the frozen condition the embankment height is recommended to be within the limits of 3–6 m, depending on the seasonal thawing depth of the permafrost soils. If the negative impact of seismic waves [9, 10] is taken as a primary factor, the embankment height should be determined by two parameters: the maximum application of damping properties of the embankment and the provision of its general stability. Seismic impacts are wave oscillating movements arising in response to the underground strike of the released energy. It results in the three types of waves: longitudinal waves along the seismic raypath, transversal waves perpendicular to the seismic raypath acting within the rock mass, and transversal surface waves arising at the surface of the ‘ground-air’ environment division [11, 12, 13, 14, 15]. The most destructive are transversal waves. An example of destructive impact of transversal surface waves is showed in Fig. 3.
Fig. 3. Destruction of Track Superstructure as a Result of Seismic Transversal Surface Waves Impact [6].
756
V.A. Alpysova et al. / Procedia Engineering 189 (2017) 752 – 758
To estimate the destructive impact of earthquakes on the railway track elements (subgrade, ballast, sleepers, rails) a unified parameter has been adopted – magnitude of admissible stress ɐሺሻǡ ˃. Research was conducted by means of multiple classification analysis. As impact factors the thicknesses of subgrade (hsg = 3–21 m), bedrock (hbr = 5– 95 m) and Earth crust (distance to hypocenter r = 10 and 20 km) were selected. Basing on the fact that according to the Construction Code 14.13330.2011 [4] the calculations for structures are performed when seismicity is estimated ≥ 7 points (MSK scale), research was conducted for the site with seismicity of 8 points [7, 8]. Calculations for stress are done using the formulae by V.N. Tyupin and E.V. Nepomnyashchikh [3]. The calculations performed have resulted in the regression equation of the following kind: ݕൌ ʹʹ͵ǡͲ െ Ͳͻǡͷ ή ˘ଵ െ ͺͶʹͷͶǡ ή ˘ଶ െ ͻͺͶ͵ǡͷ ή ˘ଷ ͷͻͶǡ ή ˘ଶ ή ˘ଷ Ǥ
(2)
where: ݕstands for the optimization parameter – stress σr, Pa; ˘ଵ stands for the influence factor (subgrade thickness); ˘ଶ stands for the influence factor (bedrock soil thickness); ˘ଷ stands for the influence factor (distance to the hypocenter). All coefficients of the regression equation are significant. So, the greater is the thickness of the soil layers, the lower is the magnitude of stress acting on the subgrade and track superstructure. In this case the embankment should be seen as a damping structure located between the bedrock soil and track superstructure. Moreover, the higher is the embankment, the lower negative impact of longitudinal waves is conveyed to the track superstructure. Nevertheless, with the embankment height getting larger its general stability decreases. To analyze the embankment stability calculations accounting for the seismic impacts and not accounting for them were performed using the formula of G.M. Shakhunyants [5]:
ܭௗ௬ ൌ
σ సభሺே ή ା ή ା்ೞ ሻ σ సభ ்ೞ ήೞ
ǡ
(3)
where: ܭௗ௬ stands for the dynamic stability factor; ܰ stands for the coercive force in the i section; ݂ௗ௬ stands for the dynamic friction factor in the i section; ܥௗ௬ stands for the specific cohesion in the i section; ݈ stands for the i section foundation length; ܶௗ௬ stands for the coercive dynamic force in the i section; ܶௗ௦ stands for the displacement force in the i section; ܭ௦ stands for the seismicity factor. For embankments of 3–21 m height the general trends of the stability factor change have been established depending on the embankment height, as showed in Fig. 4.
V.A. Alpysova et al. / Procedia Engineering 189 (2017) 752 – 758
Fig. 4. The general trends of the stability factor change depending on the embankment height. The analysis of the embankment stability factor change depending on its height allows to conclude that within the height ranging from 3 to 9 m the largest percentage of stability factor decrease is observed (~20%); within the height ranging from 9 to 21 m this value does not exceed 10%. It should also be noted that at the embankment height of more than 12 m (according to acting standards) it is required to arrange berms which significantly increases the consumption of soil materials, width of the land strip needed to construct an embankment as well as the volume of construction work. Thus, the most rational solution for the embankment height is the range from 3 to 12 m. 2. Conclusions: 1. In Eastern Siberia and the Far East it is recommended to design railway subgrade predominantly on embankments of 3–12 m height, which allows, first, to keep the soil frozen and second, to decrease the negative impact of earthquakes on the track superstructure. 2. The optimal embankment structure shall be identified by means of calculation which will account for hydro-meteorological conditions, trends of their change, conditions of permafrost soil deposits and their thickness as well as the seismic impacts. 3. If the embankment height is insufficient, one shall arrange additional damping layers within the embankments in order to decrease negative earthquake impacts. References [1] SP 25.13330.2012. Aktualizirovannaya redaktsiya “SNiP 2.02.04-88. Osnovaniya i fundamenty na vechnomerzlykh gruntakh” [Construction Code 25.13330.2012. Actualized version of “Construction Norms and Regulations 2.02.04-88. Bedrocks and Foundations on Permafrost Soils”]. Introduced on January 1st, 2013. [2] SP 131.13330. Stroitelnaya klimatologiya. Aktualizirovannaya redaktsiya “SNiP 23-01-99* (c izmeneniyami) [Construction Code 131.13330. Construction Climatology. Actualized version of “Construction Norms and Regulations 23-01-99* (modified)”]. Introduced on January 1st, 2013.
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[3] V.N. Tyupin, E.V. Nepomnyashchikh, Vozdeistviye zemletryaseniya na zheleznodorozhnyi put’ [Earthquake Impact on Railway Track] // Put’ i putevoye khozyaistvo [Railway Track and Track Maintenance]. 2008. #9. P. 24–26. [4] SP 14.13330.2011. Stroitelstvo v seismicheskikh rayonakh. Aktualizirovannaya redaktsiya SNiP II – 7-81* [Construction Code 14.13330.2011. Construction in Seismic Regions. Actualized version of Construction Norms and Regulations II – 7-81*]. [5] G.M. Shakhunyants, Zheleznodorozhnyi put’ [Railway Track]. – Мoscow, 1987. [6] http://blogs.agu.org/landslideblog/files/2010/11/10_10-Canterbury-22.jpg [7] Y.S.Merkuryev, V.A. Alpysova, Vliyaniye dempfiruyuschego sloya na seismoustoichivost’ puti [The damping layer influence on the track’s seismic resistance] // Put’ i putevoye khozyaistvo [Railway Track and Track Maintenance]. 2015. #5. P. 19–20. [8] V.A.Alpysova, Y.S. Merkuryev, Vliyaniye parametrov zemletryaseniy na konstruktsiyu zemlyanogo polotna [Influence of earthquake parameters on the subgrade structure] // Sovremennye metody proektirovaniya transportnykh magistraley kak elementov pripodno-tekhnicheskoy sistemy [Modern design techniques for transport routes as elements of natural and technical systems]: Proceedings of the conference dedicated to the 100th anniversary of Prof. A.K. Dyunin. – 2015, P. 63-72. [9] V.A.Alpysova, A.S. Tenau, Osobennosti konstruktsii zemlyanogo polotna dlya usloviy Efiopii. Problemy razrabotki natsional'nykh standartov respubliki Efiopiya. // Sbornik materialov mezhdunarodnoy nauchnoprakticheskoy konferentsii: St. Petersburg State Transport University. – 2014, P. 95-99. [10] V.A.Alpysova, T.D. Mengesha, Uchet seysmicheskikh vozdeystviy pri proyektirovanii zemlyanogo polotna v usloviyakh FDRE. Osobennosti konstruktsii zemlyanogo polotna dlya usloviy Efiopii. // Sbornik materialov mezhdunarodnoy nauchno-prakticheskoy konferentsii: St. Petersburg State Transport University. – 2014, P. 100108. [11] Scherbaum F. et. al., Determination of shallow shear waves velocity profiles in theCologne, Germany area using ambient vibrations. Geophys. J. Int. (2003) 152, 597–612. [12] Sorensen C. and Asten M. (2005) Comparison of shear wave velocity profiles of Quaternary sediments in the Newcastle area estimated from SCPT, microtremor spectral ratios and array studies, and drilling. Earthquake Engineering in Australia, Proceedings of a conference of the Australian Earthquake Engineering Soc., Albury Vic., Paper 9. [13] Stephenson W.R., Factors bounding prograde Rayleigh-wave particle motion in a soft- soil layer. Pacific Conference on Earthquake Engineering. 2003. [14] Nakamura, Y. 1989. A method for dynamic characteristics estimation of subsurface using microtremor on the ground surface. Quaterly Report Railway Tech. Res. Inst., 30(1): 25‒33. [15] Roberts J.C and M.W. Asten, Resolving a velocity inversion at the geotechnical scale using the microtremor (passive seismic) survey method. Exploration Geophysics (2004) 35, 14–18.