nonlinear earthquake behaviour of highway tunnels · 2020. 7. 15. · 2756 b. sevim: nonlinear...

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Nat. Hazards Earth Syst. Sci., 11, 2755–2763, 2011 www.nat-hazards-earth-syst-sci.net/11/2755/2011/ doi:10.5194/nhess-11-2755-2011 © Author(s) 2011. CC Attribution 3.0 License. Natural Hazards and Earth System Sciences Nonlinear earthquake behaviour of highway tunnels B. Sevim um¨ us ¸hane University, Department of Civil Engineering, 29000, G¨ um¨ us ¸hane, Turkey Received: 14 August 2011 – Revised: 12 September 201 – Accepted: 15 September 2011 – Published: 13 October 2011 Abstract. This paper describes the Arhavi Highway Tun- nel which has two tubes, its geometrical properties, finite element model, and the nonlinear earthquake behaviour un- der a huge ground motion considering soil-structure interac- tion. The Arhavi Highway Tunnel is one of the tallest tun- nels constructed in the Black Sea region of Turkey as part of the Coast Road Project. The tunnel has two tubes and each of them is about 1000 m tall. In the study, the modal anal- yses of the tunnel considering soil-structure interaction are performed and natural frequencies and mode shapes are ob- tained. Then, nonlinear transient analysis of the tunnel using Drucker-Prager criteria is performed applying acceleration components of 1992 Erzincan, Turkey earthquake’s ground motion. In the time history analyses, Rayleigh damping coef- ficients are calculated using main natural frequency obtained from modal analysis. Element matrices are computed using the Gauss numerical integration technique. The Newmark method is used in the solution of the equation of motion. Be- cause too much memory for the analyses is required, the first 7.5 s of the ground motions, which is the most effective dura- tion, is taken into account in calculations. The displacement and stress results are observed to be the allowable level of the concrete material. 1 Introduction Highway tunnels as underground facilities are an integral part of the infrastructure of modern society. They are built in ar- eas subject to earthquake activity and must withstand both seismic and static loading. The highway tunnels have fea- tures that make their seismic behaviour distinct from most surface structures. Hovewer, some highway tunnels have Correspondence to: B. Sevim ([email protected]) experienced significant damage in recent large earthquakes, including the 1995 Kobe, Japan earthquake, the 1999 Chi- Chi, Taiwan earthquake and the 1999 Kocaeli, Turkey earth- quake (Hashash et al., 2001). Therfore, the determination of seismic behaviour of these underground structures may have importance for researchers (Asakura et al., 2000; Amberg and Russo, 2001; Lanzano et al., 2001). Earthquake effects on underground structures can be grouped into two categories: ground shaking, ground failure such as liquefaction, fault displacement, and slope instabil- ity. Ground shaking refers to the deformation of the ground produced by seismic waves propagating through the Earth’s crust. The major factors influencing shaking damage include: the shape, dimensions and depth of the structure; the proper- ties of the, 1987; Hashash et al., 2001). The earthquakes can endanger tunnels and other structures if they are buried in loose, water-saturated soil that can be liquefied by dy- namic excitation. Liquefaction implies a drastic loss of shear strength, the consequence of which can be large displace- ments of structures. Countermeasures are stone columns or soil improvement by densification or grouting (Kolymbas, 2005). In the early days of FEM applications in tunnelling, com- puters had a very limited memory. Thus, the management of data was the most important issue, whilst the choice of the appropriate constitutive equation was considered of mi- nor importance. This attitude has survived until our days and one can observe cases of numerical simulation where the used constitutive equation is not even mentioned. This is by no means justified. The use of the proper constitutive equation is of decisive importance. True, the behaviour of soil and rock is extremely complex and, therefore, realistic constitutive equations can be complex to such an extension that they can not be used (Kolymbas, 2005; Cheng et al., 2007; Mroueh and Shahrour, 2008). Nowadays, computer skills have been increaed. This gives a chance to obtain real- istic models. A nonlinear procedure is required to assess the Published by Copernicus Publications on behalf of the European Geosciences Union.

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Page 1: Nonlinear earthquake behaviour of highway tunnels · 2020. 7. 15. · 2756 B. Sevim: Nonlinear earthquake behaviour of highway tunnels 6/ 21 Figure 1. A photograph of the Arhavi Highway

Nat. Hazards Earth Syst. Sci., 11, 2755–2763, 2011www.nat-hazards-earth-syst-sci.net/11/2755/2011/doi:10.5194/nhess-11-2755-2011© Author(s) 2011. CC Attribution 3.0 License.

Natural Hazardsand Earth

System Sciences

Nonlinear earthquake behaviour of highway tunnels

B. Sevim

Gumushane University, Department of Civil Engineering, 29000, Gumushane, Turkey

Received: 14 August 2011 – Revised: 12 September 201 – Accepted: 15 September 2011 – Published: 13 October 2011

Abstract. This paper describes the Arhavi Highway Tun-nel which has two tubes, its geometrical properties, finiteelement model, and the nonlinear earthquake behaviour un-der a huge ground motion considering soil-structure interac-tion. The Arhavi Highway Tunnel is one of the tallest tun-nels constructed in the Black Sea region of Turkey as part ofthe Coast Road Project. The tunnel has two tubes and eachof them is about 1000 m tall. In the study, the modal anal-yses of the tunnel considering soil-structure interaction areperformed and natural frequencies and mode shapes are ob-tained. Then, nonlinear transient analysis of the tunnel usingDrucker-Prager criteria is performed applying accelerationcomponents of 1992 Erzincan, Turkey earthquake’s groundmotion. In the time history analyses, Rayleigh damping coef-ficients are calculated using main natural frequency obtainedfrom modal analysis. Element matrices are computed usingthe Gauss numerical integration technique. The Newmarkmethod is used in the solution of the equation of motion. Be-cause too much memory for the analyses is required, the first7.5 s of the ground motions, which is the most effective dura-tion, is taken into account in calculations. The displacementand stress results are observed to be the allowable level of theconcrete material.

1 Introduction

Highway tunnels as underground facilities are an integral partof the infrastructure of modern society. They are built in ar-eas subject to earthquake activity and must withstand bothseismic and static loading. The highway tunnels have fea-tures that make their seismic behaviour distinct from mostsurface structures. Hovewer, some highway tunnels have

Correspondence to:B. Sevim([email protected])

experienced significant damage in recent large earthquakes,including the 1995 Kobe, Japan earthquake, the 1999 Chi-Chi, Taiwan earthquake and the 1999 Kocaeli, Turkey earth-quake (Hashash et al., 2001). Therfore, the determination ofseismic behaviour of these underground structures may haveimportance for researchers (Asakura et al., 2000; Ambergand Russo, 2001; Lanzano et al., 2001).

Earthquake effects on underground structures can begrouped into two categories: ground shaking, ground failuresuch as liquefaction, fault displacement, and slope instabil-ity. Ground shaking refers to the deformation of the groundproduced by seismic waves propagating through the Earth’scrust. The major factors influencing shaking damage include:the shape, dimensions and depth of the structure; the proper-ties of the, 1987; Hashash et al., 2001). The earthquakescan endanger tunnels and other structures if they are buriedin loose, water-saturated soil that can be liquefied by dy-namic excitation. Liquefaction implies a drastic loss of shearstrength, the consequence of which can be large displace-ments of structures. Countermeasures are stone columns orsoil improvement by densification or grouting (Kolymbas,2005).

In the early days of FEM applications in tunnelling, com-puters had a very limited memory. Thus, the managementof data was the most important issue, whilst the choice ofthe appropriate constitutive equation was considered of mi-nor importance. This attitude has survived until our daysand one can observe cases of numerical simulation wherethe used constitutive equation is not even mentioned. Thisis by no means justified. The use of the proper constitutiveequation is of decisive importance. True, the behaviour ofsoil and rock is extremely complex and, therefore, realisticconstitutive equations can be complex to such an extensionthat they can not be used (Kolymbas, 2005; Cheng et al.,2007; Mroueh and Shahrour, 2008). Nowadays, computerskills have been increaed. This gives a chance to obtain real-istic models. A nonlinear procedure is required to assess the

Published by Copernicus Publications on behalf of the European Geosciences Union.

Page 2: Nonlinear earthquake behaviour of highway tunnels · 2020. 7. 15. · 2756 B. Sevim: Nonlinear earthquake behaviour of highway tunnels 6/ 21 Figure 1. A photograph of the Arhavi Highway

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Figure 1. A photograph of the Arhavi Highway Tunnel

The Arhavi Highway Tunnel was constructed using New Austrian Tunnelling Method. The

rock quality classification was listed based on geological data. The studies show that the

rocks had been constituted 70-110 million years before in Mesozoic time (Satır, 2007).

3. Nonlinear Earthquake Behaviour of the Arhavi Highway Tunnel

The studies of the Arhavi Highway Tunnel involve its finite element modal analysis and

finite element earthquake analyses. The geometrical properties of the Arhavi Highway

Tunnel appear in Figure 2. The tunnel has two tubes and each tube includes reinforced

concrete and shotcrete concrete. The radius of each tunnel is 5.3 m. The constant thickness

of the shotcrete concrete is 0.15 m. However, the thickness of the concrete is changeable. It

has 0.4 m thickness at the top of the tunnel, but the thickness increase through the base and

it has 0.7 m thickness at the road level.

Fig. 1. A photograph of the Arhavi Highway Tunnel.

Table 1. Material properties of the Arhavi Highway Tunnel.

Properties

Material Element ElasticityModulus(N m−2)

PoissonRatio(–)

MassDensity(kg m−3)

Reinforced Concrete PLANE42 3.00E10 0.2 2500Shotcrete Concrete PLANE42 2.75E10 0.2 2400Rock PLANE42 3.00E10 0.2 –

dynamic behavior of the engineering structures realistically.Many damage criteria are available for the determination ofthe yield surface or the yield function of materials for non-linear finite element analysis. The Drucker-Prager criterionis widely used for frictional materials such as rock, concreteand masonry. Drucker and Prager (1952) also obtained a con-venient yield function to determine elasto-plastic behaviourof concrete, known as the smoothing Mohr-Coulomb crite-rion (Drucker and Prager, 1952). This criterion is definedas:

f = αI1+

√J2−k (1)

In Eq. (1), I1 is the first invariant of stress tensor, andJ2 isthe second invariant of deviatoric stress tensor.α andk areconstants which depend on cohesion (c) and angle of inter-nal friction (φ) of the material given in Eq. (2) (Drucker andPrager, 1952; Chen and Mizuno, 1990).

α =2Sinφ

√3(3−Sinφ)

k =6cCosφ

√3(3−Sinφ)

(2)

This paper investigates nonlinear earthquake behaviour of aparticular highway tunnel, Arhavi, which has two tubes. In

the paper, the Arhavi Highway Tunnel and its geometry arefirst described. After that, the finite element model of thetunnel is modelled using ANSYS software considering soil-structure interaction. Lastly, the nonlinear earthquake be-haviour of the tunnel considering Drucker-Prager criteria isinvestigated applying the 1992 Erzincan, Turkey earhquake’sground motion records.

2 Description of the Arhavi Highway Tunnel

The Arhavi Highway Tunnel is one of the tallest tunnelsconstructed in the Black Sea region of Turkey, as part ofthe Coast Road Project. The tunnel is located in Arhavi inArtvin, Turkey. It has two tubes and each of them is about1000 m tall. One of the photographs of the tunnel appears inFig. 1. The tunnel has been used for the traffic since 2006.

The Arhavi Highway Tunnel was constructed using NewAustrian Tunnelling Method. The rock quality classificationwas listed based on geological data. The studies show thatthe rocks had been constituted 70–110 million yr before inMesozoic time (Satır, 2007).

Nat. Hazards Earth Syst. Sci., 11, 2755–2763, 2011 www.nat-hazards-earth-syst-sci.net/11/2755/2011/

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Figure 2. Geometrical properties of the Arhavi Highway Tunnel (Cengiz Project, 2006)

Finite Element Model (FEM) of the tunnel is constituted using ANSYS (2010) software.

2497 PLANE42 elements are used in the FEM of the tunnel. The element can be used

either as a plane element (plane stress or plane strain) or as an axisymmetric element. The

element is defined by four nodes having two degrees of freedom at each node: translations

in the nodal x and y directions. The element has plasticity, creep, swelling, stress stiffening,

large deflection, and large strain capabilities. The FEM of the tunnel appears in Figure 3.

Figure 3. TheFEM of the Arhavi Highway Tunnel

Three main materials as reinforced concrete, shotcrete concrete and rock are considered in

Fig. 2. Geometrical properties of the Arhavi Highway Tunnel (Cengiz Project, 2006).

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Figure 2. Geometrical properties of the Arhavi Highway Tunnel (Cengiz Project, 2006)

Finite Element Model (FEM) of the tunnel is constituted using ANSYS (2010) software.

2497 PLANE42 elements are used in the FEM of the tunnel. The element can be used

either as a plane element (plane stress or plane strain) or as an axisymmetric element. The

element is defined by four nodes having two degrees of freedom at each node: translations

in the nodal x and y directions. The element has plasticity, creep, swelling, stress stiffening,

large deflection, and large strain capabilities. The FEM of the tunnel appears in Figure 3.

Figure 3. TheFEM of the Arhavi Highway Tunnel

Three main materials as reinforced concrete, shotcrete concrete and rock are considered in

Fig. 3. TheFEM of the Arhavi Highway Tunnel.

3 Nonlinear earthquake behaviour of the ArhaviHighway Tunnel

The studies of the Arhavi Highway Tunnel involve its finiteelement modal analysis and finite element earthquake analy-ses. The geometrical properties of the Arhavi Highway Tun-nel appear in Fig. 2. The tunnel has two tubes and each tubeincludes reinforced concrete and shotcrete concrete. The ra-dius of each tunnel is 5.3 m. The constant thickness of theshotcrete concrete is 0.15 m. However, the thickness of theconcrete is changeable. It has a thickness of 0.4 m at the topof the tunnel, but the thickness increases through the baseand it has 0.7 m thickness at the road level.

A Finite Element Model (FEM) of the tunnel is constitutedusing ANSYS (2010) software. 2497 PLANE42 elementsare used in the FEM of the tunnel. The element can be usedeither as a plane element (plane stress or plane strain) or as anaxisymmetric element. The element is defined by four nodes

having two degrees of freedom at each node: translationsin the nodal x and y directions. The element has plasticity,creep, swelling, stress stiffening, large deflection, and largestrain capabilities. The FEM of the tunnel appears in Fig. 3.

Three main materials, reinforced concrete, shotcrete con-crete, and rock are considered in the analyses. The materialproperties used in the analyses are summarized in Table 1(Cengiz Project, 2006; G.D.H., 2006; Satır, 2007). The tun-nel foundation is assumed as massless. Because of the mass-less foundation, the analyses considered only the effects ofthe foundation flexibility. So, the foundation model extendedto a distance beyond which its effects on deflections and nat-ural frequencies of the tunnel become negligible (USACE,2003). As boundary conditions, all of the degrees of free-doms on the four sides of the foundation are fixed.

www.nat-hazards-earth-syst-sci.net/11/2755/2011/ Nat. Hazards Earth Syst. Sci., 11, 2755–2763, 2011

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Figure 4. The mode shapes of the Arhavi Highway Tunnel

3. 2. Nonlinear Earthquake Behaviour of the Arhavi Highway Tunnel

The nonlinear transient analyses of the tunnel are performed considering ERZIKAN/ERZ-

NS and ERZIKAN/ERZ-UP components of 1992 Erzincan ground motion as the excitation

sources. This earthquake event occurred in the North Anatolian Fault, which is the nearest

fault to the tunnel. The components of the earthquakes appear in Figure 5 (PEER, 2010).

The reason of using these two components is to simulate the realistic behaviour of the

earthquake.

Fig. 4. The mode shapes of the Arhavi Highway Tunnel.

3.1 Modal Characteristics of the ArhaviHighway Tunnel

Figure 4 shows the natural frequencies and the mode shapesof the Arhavi Highway Tunnel. As it is seen in Fig. 4, themode shapes are related to the main concrete of the tunnel.It is not to be wrong to class them as bending modes fromFig. 4.

3.2 Nonlinear Earthquake Behaviour of theArhavi Highway Tunnel

The nonlinear transient analyses of the tunnel are performedconsidering ERZIKAN/ERZ-NS and ERZIKAN/ERZ-UPcomponents of the 1992 Erzincan ground motion as the exci-tation sources. This earthquake event occurred in the NorthAnatolian Fault, which is the nearest fault to the tunnel.The components of the earthquakes appear in Fig. 5 (PEER,2010). The reason for using these two components is to sim-ulate the realistic behaviour of the earthquake.

The Drucker-Prager damage criterion is preferable for in-troducing the nonlinear behavior of concrete to the finite el-ement model as its smooth failure surface provides very def-inite analytical and computational advantages (Barla et al.,2008). The two nonlinear Cohesion (c) and Friction angle(8) material parameters were selected from the literature.c = 0.61 MPa,8 = 28◦ are assumed (Barla et al., 2008) forthe concrete material.

The element matrices are computed using the Gauss nu-merical integration technique (Bathe, 1996) in the analyses.The Newmark method is used in the solution of the equa-tion of motion. Because of the computational demand ofthis method, only the first 7.5 s of the ground motions, whichis the most effective duration, are considered during calcu-lations (Fig. 5). Because the damping ratios are unknown,the author estimates the Rayleigh damping coefficients foran assumed 5 % damping ratio, and Rayleigh damping coef-ficients are calculated using the first eight natural frequencyvalues obtained from modal analysis.

Nat. Hazards Earth Syst. Sci., 11, 2755–2763, 2011 www.nat-hazards-earth-syst-sci.net/11/2755/2011/

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The Drucker-Prager damage criterion is preferable for introducing the nonlinear behavior

of concrete to the finite element model as its smooth failure surface provides very definite

analytical and computational advantages (Barla et al., 2008). The two nonlinear Cohesion

(c) and Friction angle (Φ) material parameters were selected from the literature. c= 0.61

MPa, Φ=28o are assumed (Barla et al., 2008) for the concrete material.

The element matrices are computed using the Gauss numerical integration technique

(Bathe, 1996) in the analyses. The Newmark method is used in the solution of the equation

of motion. Because of the computational demand of this method, only the first 7.5 seconds

of the ground motions are considered during calculations. As the first few seconds of the

Erzincan Earthquake are of greater magnitude (Figure 5). Because the damping ratios are

unknown the author estimate the Rayleigh damping coefficients for an assumed 5%

damping ratio, and Rayleigh damping coefficients are calculated using first eight natural

frequency values obtained from modal analysis.

(a) ERZIKAN/ERZ-NS component

b) ERZIKAN/ERZ-UP component

Figure 5. The time histories of ground motion accelerations of 1992 Erzincan earthquake.

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The Drucker-Prager damage criterion is preferable for introducing the nonlinear behavior

of concrete to the finite element model as its smooth failure surface provides very definite

analytical and computational advantages (Barla et al., 2008). The two nonlinear Cohesion

(c) and Friction angle (Φ) material parameters were selected from the literature. c= 0.61

MPa, Φ=28o are assumed (Barla et al., 2008) for the concrete material.

The element matrices are computed using the Gauss numerical integration technique

(Bathe, 1996) in the analyses. The Newmark method is used in the solution of the equation

of motion. Because of the computational demand of this method, only the first 7.5 seconds

of the ground motions are considered during calculations. As the first few seconds of the

Erzincan Earthquake are of greater magnitude (Figure 5). Because the damping ratios are

unknown the author estimate the Rayleigh damping coefficients for an assumed 5%

damping ratio, and Rayleigh damping coefficients are calculated using first eight natural

frequency values obtained from modal analysis.

a) ERZIKAN/ERZ-NS component

(b) ERZIKAN/ERZ-UP component

Figure 5. The time histories of ground motion accelerations of 1992 Erzincan earthquake. Fig. 5. The time histories of ground motion accelerations of 1992 Erzincan earthquake.

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The time histories of displacements and principal stresses on nodes such as A, B, C, D, E,

and F (Figure 6) are the results of the nonlinear transient analyses of the Arhavi Highway

Tunnel, additionally the variations in the lateral displacements along to I-I and II-II

sections (Figure 6), the displacements and the stresses contour diagrams are obtained.

Figure 6. Location of presented nodes, I-I and II-II sections on the Arhavi Highway Tunnel

3.2.1. Displacements

The maximum horizontal and vertical displacement contours of the tunnel are presented in

Figure 7(a-b), respectively. These contours represent the distribution of the peak values

reached by the maximum displacement at each point within the section. It can be seen from

Figure 8a that the maximum horizntal displacements occur at the bases of the tunnel. The

maximum vertical displacements occur at the nearly half height of the tunnel as seen in

Figure 8b. In addition, the vertical displacements have a symmetric distribution on both

models. Hovewer, the both of horizontal and vertical displacements are too small to make

damage in the tunnel.

Fig. 6. Location of presented nodes, I–I and II–II sections on the Arhavi Highway Tunnel.

The time histories of displacements and principal stresseson nodes such as A, B, C, D, E, and F (Fig. 6) are the resultsof the nonlinear transient analyses of the Arhavi HighwayTunnel; additionally, the variations in the lateral displace-ments along to I–I and II–II sections (Fig. 6), the displace-ments and the stresses contour diagrams are obtained.

3.2.1 Displacements

The maximum horizontal and vertical displacement con-tours of the tunnel are presented in Fig. 7a, b, respectively.These contours represent the distribution of the peak val-ues reached by the maximum displacement at each point

within the section. It can be seen from Fig. 8a that the max-imum horizntal displacements occur at the bases of the tun-nel. The maximum vertical displacements occur at nearlythe half height of the tunnel as seen in Fig. 8b. In addition,the vertical displacements have a symmetric distribution onboth models. However, the both of horizontal and verticaldisplacements are too small to make damage in the tunnel.

Figure 8a, b shows the variation of maximum horizontaldisplacements (x direction – Fig. 6) on I–I section (Tube 1)and II–II section (Tube 2) of the Arhavi Highway Tunnel,respectively. As it can be seen from Fig. 8, there is not aregular distribution along the I–I and II–II sections, however,the graphs (a) and (b) are almost closed to eachother. This

www.nat-hazards-earth-syst-sci.net/11/2755/2011/ Nat. Hazards Earth Syst. Sci., 11, 2755–2763, 2011

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(a) Horizontal displacement contour (b) Vertical displacement contour

Figure 7. The maximum a) horizontal and b) vertical displacement contours of the Arhavi

Highway Tunnel

Figure 8(a-b) show the variation of maximum horizontal displacements (x direction-Figure

6) on I-I section (Tube 1) and II-II section (Tube 2) of the Arhavi Highway Tunnel,

respectively. As it can be seen from Figure 8, there is not a regular distribution along I-I

and II-II sections, however, the graph a) and b) are almost closed to eachother. This shows

that both of the tubes behave similarly, because of same geometry and material.

a) The displacements on I-I section b) The displacements on II-II section

Figure 8. The variation of maximum horizontal displacements on a) I-I section b) II-II section of the Arhavi Highway Tunnel

Figure 9(a-b) show the variation of maximum vertical displacements (z direction-Figure 6)

Fig. 7. The maximum(a) horizontal and(b) vertical displacement contours of the Arhavi Highway Tunnel.

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a) Horizontal displacement contour b) Vertical displacement contour

Figure 7. The maximum a) horizontal and b) vertical displacement contours of the Arhavi

Highway Tunnel

Figure 8(a-b) show the variation of maximum horizontal displacements (x direction-Figure

6) on I-I section (Tube 1) and II-II section (Tube 2) of the Arhavi Highway Tunnel,

respectively. As it can be seen from Figure 8, there is not a regular distribution along I-I

and II-II sections, however, the graph a) and b) are almost closed to eachother. This shows

that both of the tubes behave similarly, because of same geometry and material.

(a) The displacements on I-I section (b) The displacements on II-II section

Figure 8. The variation of maximum horizontal displacements on a) I-I section b) II-II section of the Arhavi Highway Tunnel

Figure 9(a-b) show the variation of maximum vertical displacements (z direction-Figure 6)

Fig. 8. The variation of maximum horizontal displacements on(a) I–I section(b) II–II section of the Arhavi Highway Tunnel.

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on I-I section (Tube 1) and II-II section (Tube 2) of the Arhavi Highway Tunnel,

respectively. As it can be seen from Figure 9, the vertical displacements are low at the

bases of the tubes when compared to middle parts of the tubes. In addition, the vertical

displacements obtained for I-I section (Tube 1) and II-II section (Tube 2) have a

symmetrical distribution.

(a) The displacements on I-I section (b) The displacements on II-II section Figure 9. The variation of maximum vertical displacements on a) I-I section b) II-II section

of the Arhavi Highway Tunnel

When compared to horizontal and vertical displacements from Figures 8 and 9 that

maximum horizontal displacements occur on Nodes B, C, E and F. However maximum

vertical displacements occur on the middle height nodes of the tunnel. This shows that the

tunnel has a horizontal motion at the base nodes; however it has a vertical motion near to

middle nodes of the tunnel.

The time histories of horizontal displacements at the nodal points B and C of the tunnel

(Figure 6), where the maximum horizontal displacements occurred, are plotted in Figure

10(a-b), respectively. The time histories of vertical displacements at the nodal point A of

the tunnel are plotted in Figure 11.

Fig. 9. The variation of maximum vertical displacements on(a) I–Isection(b) II–II section of the Arhavi Highway Tunnel.

shows that both of the tubes behave similarly because of thesame geometry and material.

Figure 9a, b shows the variation of maximum verticaldisplacements (z direction-Fig. 6) on I–I section (Tube 1)and II–II section (Tube 2) of the Arhavi Highway Tunnel,respectively. As it can be seen from Fig. 9, the verticaldisplacements are low at the bases of the tubes when com-pared to middle parts of the tubes. In addition, the vertical

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0.0 2.5 5.0 7.5Time (s)

-1.2

-0.6

0.0

0.6

1.2

Disp

lace

men

ts (m

m)

0.0 2.5 5.0 7.5

Time (s)

-1.2

-0.6

0.0

0.6

1.2

Disp

lace

men

ts (m

m)

(a) Displacements of Node B (b) Displacements of Node C

Figure 10. The time histories of horizontal displacements at a) Node B and b) Node C of the Arhavi Highway Tunnel

0.0 2.5 5.0 7.5Time (s)

-1.2

-0.6

0.0

0.6

1.2

Disp

lace

men

ts (m

m)

Figure 11. The time histories of vertical displacements at Node A of the Arhavi Highway

Tunnel

3.2.2. Principal Stresses

The maximum and minimum principal stress contours of the tunnel are presented in Figure

12(a-b), respectively. These represent the distribution of the peak values reached by the

maximum stresses at each point within the section. As it is seen from Figure 12, maximum

and minimumprincipal stresses occur at the bases of the tunnel. In addition the stresses

have a symmetrical distribution along to sections. Also, the maximum stresses are about

3.5-4.0 MPa, the minimum stresses are about 6.0-4.5 Mpa. The maximum and minimum

Fig. 10. The time histories of horizontal displacements at(a) NodeB and(b) Node C of the Arhavi Highway Tunnel.

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0.0 2.5 5.0 7.5Time (s)

-1.2

-0.6

0.0

0.6

1.2

Disp

lace

men

ts (m

m)

0.0 2.5 5.0 7.5

Time (s)

-1.2

-0.6

0.0

0.6

1.2

Disp

lace

men

ts (m

m)

a) Displacements of Node B b) Displacements of Node C

Figure 10. The time histories of horizontal displacements at a) Node B and b) Node C of the Arhavi Highway Tunnel

0.0 2.5 5.0 7.5Time (s)

-1.2

-0.6

0.0

0.6

1.2

Disp

lace

men

ts (m

m)

Figure 11. The time histories of vertical displacements at Node A of the Arhavi Highway

Tunnel

3.2.2. Principal Stresses

The maximum and minimum principal stress contours of the tunnel are presented in Figure

12(a-b), respectively. These represent the distribution of the peak values reached by the

maximum stresses at each point within the section. As it is seen from Figure 12, maximum

and minimumprincipal stresses occur at the bases of the tunnel. In addition the stresses

have a symmetrical distribution along to sections. Also, the maximum stresses are about

3.5-4.0 MPa, the minimum stresses are about 6.0-4.5 Mpa. The maximum and minimum

Fig. 11. The time histories of vertical displacements at Node A ofthe Arhavi Highway Tunnel.

Nat. Hazards Earth Syst. Sci., 11, 2755–2763, 2011 www.nat-hazards-earth-syst-sci.net/11/2755/2011/

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B. Sevim: Nonlinear earthquake behaviour of highway tunnels 2761

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principal stress values in the tunnel can be acceptable level compared to strength of the

concrete during the earthquakes.

(a) Maximum principal stress contour (b) Minimum principal stress contour

Figure 12. a) Maximum and b) Minimum principsl stress contours of the Arhavi Highway Tunnel

Figure 13(a-b) show the variation of maximum principal stresses on I-I section (Tube 1)

and II-II section (Tube 2) of the Arhavi Highway Tunnel, respectively. As it can be seen

from Figure 13, the maximum stresses are low at the top of the tunnel; however they are

high at the bases. The stresses obtained for I-I section (Tube 1) and II-II section (Tube 2)

have a symmetrical distribution.

a) The maximum stresses on I-I section b) The maximum stresses on II-II section

Figure 13. The variation of maximum principal stresses on a) I-I section b) II-II section of the Arhavi Highway Tunnel

Fig. 12. (a)Maximum and(b) Minimum principal stress contours of the Arhavi Highway Tunnel.

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principal stress values in the tunnel can be acceptable level compared to strength of the

concrete during the earthquakes.

a) Maximum principal stress contour b) Minimum principal stress contour

Figure 12. a) Maximum and b) Minimum principsl stress contours of the Arhavi Highway Tunnel

Figure 13(a-b) show the variation of maximum principal stresses on I-I section (Tube 1)

and II-II section (Tube 2) of the Arhavi Highway Tunnel, respectively. As it can be seen

from Figure 13, the maximum stresses are low at the top of the tunnel; however they are

high at the bases. The stresses obtained for I-I section (Tube 1) and II-II section (Tube 2)

have a symmetrical distribution.

(a) The maximum stresses on I-I section (b) The maximum stresses on II-II section

Figure 13. The variation of maximum principal stresses on a) I-I section b) II-II section of the Arhavi Highway Tunnel Fig. 13. The variation of maximum principal stresses on(a) I–I

section(b) II–II section of the Arhavi Highway Tunnel.

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Figure 14 (a-b) show the variation of minimum principal stresses on I-I section (Tube 1)

and II-II section (Tube 2) of the Arhavi Highway Tunnel, respectively. As it can be seen

from Figure 14, the minimum stresses have a symmetrical distribution like as maximum

principal stresses.

(a) The minimum stresses on I-I section (b) The minimum stresses on II-II section

Figure 14. The variation of minimum principal stresses on a) I-I section b) II-II section of the Arhavi Highway Tunnel

When compared to maximum and minimum principal stresses from Figures 13 and 14 that

both of highest stresses occur on Nodes B, C, E and F. This shows that the tunnel has the

highest forcing at the base nodes of the tunnel.

The time histories of maximum principal stresses at the nodal points B and C of the tunnel

(Figure 6), where the maximum horizontal displacements occurred, are plotted in Figure

15(a-b), respectively. The time histories of minimum principal stresses at the nodal point A

of the tunnel are plotted in Figure 16(a-b). There are little differences on the frequency

content of the both nodes.

Fig. 14. The variation of minimum principal stresses on(a) I–Isection(b) II–II section of the Arhavi Highway Tunnel.

displacements obtained for the I–I section (Tube 1) and II–IIsection (Tube 2) have a symmetrical distribution.

When compared to horizontal and vertical displacementsfrom Figs. 8 and 9 that maximum horizontal displacementsoccur on Nodes B, C, E and F. However maximum verticaldisplacements occur on the middle height nodes of the tun-nel. This shows that the tunnel has a horizontal motion atthe base nodes; however it has a vertical motion near to themiddle nodes.

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0.0 2.5 5.0 7.5Time (s)

0

2

4

6

Max

imum

Prin

cipa

l Stre

ss (M

Pa)

0.0 2.5 5.0 7.5

Time (s)

0

2

4

6

Max

imum

Prin

cipa

l Stre

ss (M

pa)

(a) Maximum stresses of Node B (b) Maximum stresses of Node C

Figure 15. The time histories of maximum principal stresses at a) Node B and b) Node C of the Arhavi Highway Tunnel

0.0 2.5 5.0 7.5Time (s)

-6

-4

-2

0

Min

imu

Prin

cipa

l Stre

ss (M

Pa)

0.0 2.5 5.0 7.5

Time (s)

-6

-4

-2

0

Min

imu

Prin

cipa

l Stre

ss (M

Pa)

a) Minimum stresses of Node B b) Minimum stresses of Node C

Figure 16. The time histories of minimum principal stresses at a) Node B and b) Node C of the Arhavi Highway Tunnel

5. Conclusions

This paper investigates nonlinear earthquake behaviour of the Arhavi Highway Tunnel

considering foundation-structure interaction. Finite element model of the tunnel is

Fig. 15. The time histories of maximum principal stresses at(a) Node B and(b) Node C of the Arhavi Highway Tunnel.

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0.0 2.5 5.0 7.5Time (s)

0

2

4

6

Max

imum

Prin

cipa

l Stre

ss (M

Pa)

0.0 2.5 5.0 7.5

Time (s)

0

2

4

6

Max

imum

Prin

cipa

l Stre

ss (M

pa)

a) Maximum stresses of Node B b) Maximum stresses of Node C

Figure 15. The time histories of maximum principal stresses at a) Node B and b) Node C of the Arhavi Highway Tunnel

0.0 2.5 5.0 7.5Time (s)

-6

-4

-2

0

Min

imu

Prin

cipa

l Stre

ss (M

Pa)

0.0 2.5 5.0 7.5

Time (s)

-6

-4

-2

0M

inim

u Pr

inci

pal S

tress

(MPa

)

(a) Minimum stresses of Node B (b) Minimum stresses of Node C

Figure 16. The time histories of minimum principal stresses at a) Node B and b) Node C of the Arhavi Highway Tunnel

5. Conclusions

This paper investigates nonlinear earthquake behaviour of the Arhavi Highway Tunnel

considering foundation-structure interaction. Finite element model of the tunnel is

Fig. 16. The time histories of minimum principal stresses at(a) Node B and(b) Node C of the Arhavi Highway Tunnel.

The time histories of horizontal displacements at the nodalpoints B and C of the tunnel (Fig. 6), where the maximumhorizontal displacements occurred, are plotted in Fig. 10a, b,respectively. The time histories of vertical displacements atthe nodal point A of the tunnel are plotted in Fig. 11.

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2762 B. Sevim: Nonlinear earthquake behaviour of highway tunnels

3.2.2 Principal stresses

The maximum and minimum principal stress contours of thetunnel are presented in Fig. 12a, b, respectively. These repre-sent the distribution of the peak values reached by the max-imum stresses at each point within the section. As it is seenfrom Fig. 12, maximum and minimum principal stresses oc-cur at the bases of the tunnel. In addition, the stresses have asymmetrical distribution along the sections. Also, the max-imum stresses are about 3.5–4.0 MPa, the minimum stressesare about 6.0–4.5 Mpa. The maximum and minimum prin-cipal stress values in the tunnel can be an acceptable levelcompared to the strength of the concrete during the earth-quakes.

Figure 13a, b shows the variation of maximum principalstresses on I–I section (Tube 1) and II–II section (Tube 2) ofthe Arhavi Highway Tunnel, respectively. As it can be seenfrom Fig. 13, the maximum stresses are low at the top of thetunnel; however they are high at the bases. The stresses ob-tained for the I–I section (Tube 1) and II–II section (Tube 2)have a symmetrical distribution.

Figure 14 a, b shows the variation of minimum principalstresses on I–I section (Tube 1) and II–II section (Tube 2)of the Arhavi Highway Tunnel, respectively. As it can beseen from Fig. 14, the minimum stresses have a symmetricaldistribution like the maximum principal stresses.

When comparing the maximum and minimum principalstresses from Figs. 13 and 14, we find that both of higheststresses occur on Nodes B, C, E and F. This shows that thetunnel has the highest forcing at the base nodes.

The time histories of maximum principal stresses at thenodal points B and C of the tunnel (Fig. 6), where themaximum horizontal displacements occurred, are plotted inFig, 15a, b, respectively. The time histories of minimumprincipal stresses at the nodal point A of the tunnel are plot-ted in Fig. 16a, b. There are little differences in the frequencycontent of the both nodes.

4 Conclusions

This paper investigates nonlinear earthquake behaviour of theArhavi Highway Tunnel considering foundation-structure in-teraction. A Finite Element Model of the tunnel is modelledusing ANSYS software and the earthquake behaviour of thetunnel is investigated using 1992 Erzincan, Turkey groundmotion records. In this study, the author noted the fallowingobservations:

– The first eight natural frequencies obtained from theFEM of the Arhavi Highway Tunnel occur in the rangeof 224–320 Hz. The observed mode shapes within thisfrequency range can be basically arranged as bendingmodes. Maximum displacements occur as 1.1 mm and0.6 mm, respectively from earthquake analyses of the

FEM of the tunnel. The displacement levels correspondto less than 1 % of the thickness of the tunnel.

– The horizontal displacements are the highest at the basenodes, and the vertical displacements are the middleheight nodes of the tunnel.

– The maximum and minimum principal stresses occuras 3.43 MPa and 4.63 MPa, respectively from nonlin-ear transient analyses of the Arhavi Highway Tunnel.The principal stress values in the tunnel can be the ac-ceptable strength of the concrete during the earthquakes.Both maximum and minimum principal stresses gener-ally occur at regions around the base of the tunnel.

– The Arhavi Tunnel has a nearly symmetrical geometry;hence, the displacements and stresses obtained from oneof the tubes are very near to the other tube’s results.

Acknowledgements.The author extends his thanks toOmerFettahoglu, who is an engineer in the Cengiz Project, for hislogistical assistance.

Edited by: M. E. ContadakisReviewed by: two anonymous referees

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