Experimental Study of Dynamic Responses of Special Tunnel Sections under Near-Fault Ground Motion

Round 1

Reviewer 1 Report

1. A few sentences can be added in Abstract.

 

2. Introduction, more descriptions should be added to highlight the novelty of the paper.

 

3. More sentences should be added to introduce the experiment.

 

4. Figure 8, the color of the background should be deleted, and different line types are suggested to be used, the same as figure 14.

 

5. Why are so many time histories figures necessary?

 

6. Conclusions can be improved.

 

7. There are too few references, more related studies should be included. For example, how to control the dynamic response? We can use some newly developed controllers such as adaptive-passive eddy current pendulum tuned mass damper, adaptive-passive variable stiffness tuned mass damper, etc.

Author Response

1. A few sentences can be added in Abstract.

Reply: Thank you.

The related content has been added in the revised manuscript as follows:

Abstract: Data survey shows that the near fault ground motion has a great damage to the tunnel structure, especially the portal section and fault zone. In this paper, a series of shaking table model tests of near fault tunnel were conducted and the surrounding rock-fault zone-lining model of the near fault tunnel was established. Accelerometers and strain gauges were arranged at specific locations, the experimental process of earthquake occurrence was simulated by inputting seismic waves of different working conditions, which obtained the characteristics of stress, damage and deformation of the tunnel model. The tested results showed that the acceleration response of tunnel portal section was close to the wave shape of input seismic wave, and the acceleration response of arch shoulder, arch waist and arch foot was more prominent. The internal force of lining at the arch shoulder and arch foot was greater than that at the arch crown, and the peak internal force appeared at the arch foot. The internal force and the maximum or minimum principal stress of the lining under impulse ground motion were larger than those under non impulse ground motion. Additionally, the surrounding rock had a filtering effect on the high frequency band of seismic wave. Meanwhile, when the geological characteristics of fault zone were poor, and the tensile damage first appeared at the arch foot, and the compressive damage appeared at the junction of surrounding rock and fault zone. The study will offer a practical guidance for tunnel engineering earthquake damage.

Please see the lines 12 to 28 in the revised manuscript.

 

2. Introduction, more descriptions should be added to highlight the novelty of the paper.

Reply: Thank you.

The related content has been added in the revised manuscript as follows:

The data surveys show that the earthquake disaster has a huge destructive effect on the tunnel structure. The damage to the near-fault is more serious, especially the special tunnel section, such as the portal section and fault zone. The portal section belonging to the exposed part of the tunnel is easier to be damaged than the main body of the tunnel under seismic action [8-10]. The basic reason is that the buried depth of the portal section is shallow, and the geological conditions are poor (mostly strongly weathered broken rock mass or loose accumulation). Once the tunnel is subjected to a strong earthquake, the side and front slopes of the portal section are prone to collapse, cracking and other seismic disasters, which will block the portal, interrupt traffic, and directly cause different degrees of seismic damage to the tunnel opening and lining structure, affecting the stability and availability of the tunnel structure. Therefore, the study of near fault ground motion to tunnel damage is essential, and it is also urgent to establish a systematic theoretical system. Due to the own particularity, the research methods of seismic response of underground structures are quite different from those of ground structures. These research methods can be mainly divided into prototype observation, model test and theoretical analysis. The related content will be introduced [11, 12]. Han et al. [13] considered the influence of near-fault ground motions with different characteristics on the dynamic response of isolated structures, and three types of forward directional effect velocity pulse, slip impact effect velocity pulse and no velocity pulse were inputted in the shaking table tests. Experimental results showed that the dynamic response of near fault ground motions with pulses was significantly greater than that without pulses, and the response with pulses was related to the structural period. Wang et al. [14] studied the seismic response of the tunnel by a series of shaking table tests. Tao et al. [15] conducted shaking table tests to verify the analytical solution of the single free surface slope model, which can provide a reference for the seismic design of the tunnel portal section in mountainous areas, and had a positive impact on the reasonable interpretation of the seismic response characteristics of this section. Moreover, there is no systematic research on the acceleration response and stress-strain relationship of tunnel structures caused by near fault ground motions [16, 17]. Hacıefendioğlu [18] investigated the deconvolution effect of the random near-fault earthquake ground motions on the stochastic dynamic response of tunnel-soil deposit interaction systems. The analyses showed that the standard rigid-base input model is inadequate to evaluate the stochastic dynamic response of tunnel-soil deposit interaction systems subjected to the random near-fault earthquake ground motions. El-Nabulsi et al. [19] constructed the seismic wave equation in fractal dimensions based on the concept of product-like fractal measure introduced recently by Li and Ostoja-Starzewski in their formulation of anisotropic media. Liu et al. [20] presented numerical studies on seismic waves, considering propagation effect, and aims to illustrate the response principle and structural failure mechanism of tunnel structures under long-period ground motion. Zhou et al. [21] studied the dynamic response of the lining structure in a long tunnel passing through an adverse geological structure zone subjected to a non-uniform seismic load. Meanwhile, some scholars have also studied the damping control of tunnel dynamic response. Yan et al. [22] proposed a compartment-type particle damper and its design method suitable for immersed tube tunnel, and a shaking table test on the model tunnel before and after setting the particle damper was performed. Jin et al. [23] investigated a passive Tuned Mass Damper (TMD) to dampen resonant motions of a Submerged Floating Tunnel (SFT) in waves and earthquakes. The results showed that TMD played a crucial role in controlling SFT vibrations when environmental loads were close to the system's fundamental lateral natural frequency under both wave and seismic excitations, and also enhanced the comfort of passengers and reduced static and dynamic mooring tensions. We can know that scholars also have continuously studied the relationship between these characteristics and earthquake damage distribution, providing reliable basic data for a deeper understanding of the earthquake generating process. However, there is no systematic research on the acceleration response and stress-strain relationship of tunnel structures caused by near-fault ground motions. Therefore, it is of great scientific significance and engineering application value to carry out systematic research on the analysis of seismic response characteristics of near fault tunnels and improve the design of tunnel construction system.

Please see the lines 41 to 90 in the revised manuscript.

 

3. More sentences should be added to introduce the experiment.

Reply: Thank you.

The related content has been added in the revised manuscript as follows:

• Design and fabrication of lining

The safety performance of the tunnel lining structure is mainly controlled by bending stiffness. Therefore, the model similarity should be based on the bending stiffness. Considering its bending capacity and bending strain, the lining shell is regarded as a thin plate structure according to the similarity criteria. The lining model was considered as a plane strain model, with a longitudinal dimension of 70.3 cm, a thickness of 10 mm, a tunnel gap of 20.6 cm, and a tunnel height of 19.35 cm. Fine wire mesh with a diameter of 0.2 mm was used in the lining to simulate reinforcement.

Please see the lines 215 to 221 in the revised manuscript.

 

 

4. Figure 8, the color of the background should be deleted, and different line types are suggested to be used, the same as figure 14.

Reply: Thank you.

The original figures 8 (figure 7) and 14 have been in the revised manuscript.

 

FIGURE 7 Acceleration response spectrum of measuring point with different damping ratio

(0.15 g). (A) A3. (B) A4

 

FIGURE 11 Acceleration response spectrum with different damping ratio. (A) 1244-0.15 g. (B) 960-0.15 g

 

 

 

 

5. Why are so many time histories figures necessary?

Reply: Thank you.

Some unimportant time histories figures (original figures 6 and 12) have been removed in the revised manuscript.

 

6. Conclusions can be improved.

Reply: Thank you.

The related content has been improved in the revised manuscript as follows:

In this paper, the damage evolution and seismic response analysis of the lining and surrounding rock of the special tunnel section under the action of non pulse and forward directional pulse ground motions were studied based on the actual earthquake damage phenomenon of the special tunnel section by the shaking table model test. The following conclusions are drawn:

• High frequency seismic wave will be filtered out by surrounding rock, and the low frequency (<30 Hz) seismic wave had obvious influence on the tunnel structure. The acceleration response of the structure decreased with the increase of damping ratio, and it tended to be stable and consistent when damping ratio exceeded 20%. The acceleration amplification factors were gradually decreasing with a fluctuation range of 0.4-1.1.
• The peak internal force and bending moment of the tunnel portal lining appeared at the arch foot and the arch waist, respectively, which was more prone to plastic damage under the action of near fault ground motion. Additionally, the acceleration response and frequency spectrum of the fault zone were more obvious than that of the other tunnel section, and this trend increased with the elevation. With larger seismic acceleration response of the fault zone, the more obvious of the damage to the structure crossing the fault zone.
• The arch foot, arch waist, arch shoulder and arch crown of tunnel portal and fault zone were vulnerable to damage, and the tensile failure arear first appeared at the arch foot crossing the fault zone. The compression failure first occurred at the junction of surrounding rock, and the compression degree at the arch waist was prominent.

The stochasticity found in the spectrum curves should be explained here, which may be due to the following reasons. Firstly, the noise existing in the surrounding environment, the equipment itself and the acquisition process causes some fluctuations. Secondly, the selection of seismic wave does not match the adaptability of tunnel model. Thirdly, the sampling frequency is too high, resulting in data overlap. Additionally, the safety factor of lining structure is not calculated. Therefore, the following work will solve the two problems, and obtain better spectrum data and solve the reliability and failure probability of the tunnel.

Please see the lines 487 to 508 in the revised manuscript.

 

7. There are too few references, more related studies should be included. For example, how to control the dynamic response? We can use some newly developed controllers such as adaptive-passive eddy current pendulum tuned mass damper, adaptive-passive variable stiffness tuned mass damper, etc.

Reply: Thank you.

The many related study has been added in the revised manuscript as follows:

Meanwhile, some scholars have also studied the damping control of tunnel dynamic response. Yan et al. [22] proposed a compartment-type particle damper and its design method suitable for immersed tube tunnel, and a shaking table test on the model tunnel before and after setting the particle damper was performed. Jin et al. [23] investigated a passive Tuned Mass Damper (TMD) to dampen resonant motions of a Submerged Floating Tunnel (SFT) in waves and earthquakes. The results showed that TMD played a crucial role in controlling SFT vibrations when environmental loads were close to the system's fundamental lateral natural frequency under both wave and seismic excitations, and also enhanced the comfort of passengers and reduced static and dynamic mooring tensions.

 

[22] Yan, W.M.; Xie, Z.Q.; Zhang, X.D.; et al. Tests for compartmental particle damper's a seismic control in an immersed tunnel. Journal of Vibration and Shock 2016, 35(17), 7-12.

[23] Jin, C.; Kim, S.J.; Kim, M.H. Vibration control of submerged floating tunnel in waves and earthquakes through tuned mass damper. International Journal of Naval Architecture and Ocean Engineering 2022, 14, 100483.

Please see the lines 76 to 84 in the revised manuscript.

Author Response File: Author Response.pdf

Reviewer 2 Report

I have read the present work. It is interesting to some extent. However, some points require revision:

1-Equations must well-written and explained. Besides, equation 3 must be well-addressed and introduced. More explanations are required.

2-Tables are well-done and clear. But any reference?

3-The stochasticity found in all numerical figures must be explained and justified. Its correlations to numerical data must be more clarified. The spectrum is highly fluctuations although equations introduced are free from any type of fluctuation that could be encountered during the experimental process.

4-What about the stability problem.

5-I must also state that the present study may be correlated indirectly to earthquake study.  Please clarify clearly. 

Missing references: Nat. Hazards Earth Syst. Sci., 12, 1151–1157, 2012; Acta Mechanica 233, 2107-2122 (2022); Sustainability 15, (2023) 60; Energies  15, (2022) 4599 

Author Response

Equations must well-written and explained. Besides, equation 3 must be well-addressed and introduced. More explanations are required.

Reply: Thank you for your suggestion.

Equations 1-3 in this paper are mainly for the representation of similarity ratio.

We can clearly know the explanations of Equations 1-2. Combining Equations 1 and 2, Equation 3 can be expressed based on dimensional analysis.

The similarity scale is obtained through dimensional analysis, that is, the similarity scale of density is . The similarity scales of , ,  are ,  and . The units of  and  are the same. Therefore, the similarity relationship can be expressed as follows:

                          (3)

where,  is dynamic shear modulus,  is shear strain and  is similarity scale of dynamic shear modulus, respectively.  and  are model and prototype, respectively. ,  and  are similarities of geometry, density and acceleration, respectively.

In this study ,  and  are 1/50, 1 and 1/50, respectively [24-26]. Other similitude ratios used in the paper are listed in Table 2.

TABLE 2 Model test similarity

Physical quantity	Similarity index	Similarity scales
Stain	Sε	1
Geometric length	Sl	1/50
Density	Sρ	1
Elastic modulus	SGd	1/50
Speed	Sv=SGd1/2·Sρ-1/2	0.141
Poisson's ratio	/	1
Internal friction angle	/	1
Time	St=Sl·SGd-1/2·Sρ1/2	0.141
Frequency	Sω=SGd1/2·Sl-1·Sρ-1/2	7.071
Stress	Sσ=SGd	1/50
Acceleration	Sa=SGd·Sl-1·Sρ-1	1
Cohesion	Sc=SGd	1/50

Please see the lines 141 to 162 in the revised manuscript.

 

2. Tables are well-done and clear. But any reference?

Reply: Thank you.

The related content has been improved in the revised manuscript.

The parameters of Tables 3-5 refer to references [24-26].

The parameter of Table 6 refer to references [27].

 

3. The stochasticity found in all numerical figures must be explained and justified. Its correlations to numerical data must be more clarified. The spectrum is highly fluctuations although equations introduced are free from any type of fluctuation that could be encountered during the experimental process.

Reply: Thank you for your consideration.

The stochasticity found in the spectrum curves should be explained here, which may be due to the following reasons. Firstly, the noise existing in the surrounding environment, the equipment itself and the acquisition process causes some fluctuations. Secondly, the selection of seismic wave does not match the adaptability of tunnel model. Thirdly, the sampling frequency is too high, resulting in data overlap. Additionally, the safety factor of lining structure is not calculated. Therefore, the following work will solve the two problems, and obtain better spectrum data and solve the reliability and failure probability of the tunnel.

Please see the lines 502 to 508 in the revised manuscript.

 

4. What about the stability problem.

Reply: Thank you.

Additionally, the safety factor of lining structure is not calculated. Therefore, the following work will solve the two problems, and obtain better spectrum data and solve the reliability and failure probability of the tunnel.

Please see the lines 506 to 508 in the revised manuscript.

 

5. I must also state that the present study may be correlated indirectly to earthquake study.  Please clarify clearly.

Missing references: Nat. Hazards Earth Syst. Sci., 12, 1151–1157, 2012; Acta Mechanica 233, 2107-2122 (2022); Sustainability 15, (2023) 60; Energies, 15, (2022) 4599

Reply: Thank you.

The many related study has been added in the revised manuscript as follows:

Hacıefendioğlu [18] investigated the deconvolution effect of the random near-fault earthquake ground motions on the stochastic dynamic response of tunnel-soil deposit interaction systems. The analyses showed that the standard rigid-base input model is inadequate to evaluate the stochastic dynamic response of tunnel-soil deposit interaction systems subjected to the random near-fault earthquake ground motions. El-Nabulsi et al [19] constructed the seismic wave equation in fractal dimensions based on the concept of product-like fractal measure introduced recently by Li and Ostoja-Starzewski in their formulation of anisotropic media. Liu et al [20] presented numerical studies on seismic waves, considering propagation effect, and aims to illustrate the response principle and structural failure mechanism of tunnel structures under long-period ground motion. Zhou et al [21] studied the dynamic response of the lining structure in a long tunnel passing through an adverse geological structure zone subjected to a non-uniform seismic load.

 

[18] Hacıefendioğlu, K. Deconvolution effect of near-fault earthquake ground motions on stochastic dynamic response of tunnel-soil deposit interaction systems. Natural Hazards and Earth System Sciences 2012, 12, 1151-1157.

[19] El-Nabulsi, R.A.; Anukool, W. Fractal dimension modeling of seismology and earthquakes dynamics. Acta Mechanica 2022, 233(5), 2107-2122.

[20] Liu, S.F.; Yao, L.Y.; Feng, X.J.; et al. Response analysis of curved tunnel under near-field long-period ground motion considering seismic wave propagation effect. Sustainability, 2022, 15(1), 60.

[21] Zhou, Y.Q.; Wang, H.C.; Song, D.F.; et al. Dynamic response of lining structure in a long tunnel with different adverse geological structure zone subjected to non-uniform seismic load. Energies 2022, 15(13), 4599.

Please see the lines 65 to 76 in the revised manuscript.

 

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

There are still too few references. To highlight the novelty of this paper, it should be improved and the Introduction should be extended. For example, the main novelty of this paper is the seismic response, then, important references about that, Soil Dynamics and Earthquake Engineering. 2022, 158: 107298; Engineering Structures, 2022, 271: 114963; Engineering Structures, 2023, 280: 115714; Smart Structures and Systems. 2020, 25(1): 65-80. can be included.

Author Response

There are still too few references. To highlight the novelty of this paper, it should be improved and the Introduction should be extended. For example, the main novelty of this paper is the seismic response, then, important references about that, Soil Dynamics and Earthquake Engineering. 2022, 158: 107298; Engineering Structures, 2022, 271: 114963; Engineering Structures, 2023, 280: 115714; Smart Structures and Systems. 2020, 25(1): 65-80. can be included.

Reply: Thank you.

The many related study has been added in the revised manuscript as follows:

Meanwhile, some scholars have also studied the damping control of tunnel dynamic response [22-25].

[22] Wang, L.K.; Shi, W.X.; Zhou, Y. Adaptive-passive tuned mass damper for structural aseismic protection including soil–structure interaction. Soil Dynamics and Earthquake Engineering, 2022, 158, 107298.

[23] Wang, L.K.; Nagarajaiah, S.; Shi, W.X.; et al. Seismic performance improvement of base-isolated structures using a semi-active tuned mass damper. Engineering Structures, 2022, 271, 114963.

[24] Wang, L.K.; Nagarajaiah, S.; Zhou, Y.; et al. Experimental study on adaptive-passive tuned mass damper with variable stiffness for vertical human-induced vibration control. Engineering Structures, 2023, 280, 115714.

[25] Wang, L.K.; Shi, W.X.; Zhou, Y.; et al. Semi-active eddy current pendulum tuned mass damper with variable frequency and damping. Smart Structures and Systems 2020, 25(1), 65-80.

Author Response File: Author Response.pdf

Round 3

Reviewer 1 Report

accept