Seismic performance of a whole Geosynthetic Reinforced Soil – Integrated Bridge System (GRS-IBS) in shaking table test

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Seismic performance of a whole Geosynthetic Reinforced Soil – Integrated Bridge System (GRS-IBS) in shaking table test Chao Xua,b, Minmin Luob, Panpan Shenb,∗, Jie Hanc, Feifan Renb a

Key Laboratory of Geotechnical and Underground Engineering of Ministry of Education, Tongji University, Shanghai, 200092, China Department of Geotechnical Engineering, College of Civil Engineering, Tongji University, Shanghai, 200092, China c Department of Civil, Environmental, and Architectural Engineering, University of Kansas, Lawrence, KS, 66045, USA b

ARTICLE INFO

ABSTRACT

Keywords: Geosynthetics Abutment Bridge Earthquake Geosynthetic reinforced soil Seismic Shaking table

A scaled plane-strain shaking table test was conducted in this study to investigate the seismic performance of a Geosynthetic Reinforced Soil-Integrated Bridge System (GRS-IBS) with a full-length bridge beam resting on two GRS abutments at opposite ends subjected to earthquake motions in the longitudinal direction. This study examined the effects of different combinations of reinforcement stiffness J and spacing Sv on the seismic performance of the GRS-IBS. Test results show that reducing the reinforcement spacing was more beneficial to minimize the seismic effect on the GRS abutment as compared to increasing the reinforcement stiffness. The seismic inertial forces acted on the top of two side GRS abutments interacted with each other through the bridge beam, which led to close peak acceleration amplitudes at the locations near the bridge beam. Overall, the GRSIBS did not experience obvious structure failure and significant displacements during and after shaking. Shaking in the longitudinal direction of the bridge beam increased the vertical stress in the reinforced soil zone. The maximum tensile forces in the upper and lower geogrid layers due to shaking happened under the center of the beam seat and at the abutment facing respectively.

1. Introduction Over the past few decades, reinforced soil structures have been increasingly used in forms of retaining walls, slopes, embankments, and bridge abutments in seismic areas. Researchers have investigated seismic responses of reinforced soil structures using 1 g shaking table tests (Ling et al., 2005, 2012; Helwany et al., 2012; Guler and Selek, 2014; Zheng et al., 2017, 2018c, 2019 a,b; Xu et al., 2020) and found out that these types of structures had good performance during seismic loading due to their ductile and flexible behavior. Past post-earthquake investigations revealed that most reinforced soil structures had better performance than conventional earth structures (e.g., gravity retaining walls) under actual earthquake events, such as the Northridge earthquake (Sandri, 1997), the Hyogo-ken Nanbu earthquake (Tatsuoka et al., 1996), the Chi-Chi earthquake (Huang, 2000; Ling et al., 2001; Huang et al., 2003), the Niigata earthquake (Mizuhashi et al., 2008), and the Maule earthquake (Yen et al., 2011). However, Yazdandoust (2017) pointed out that, despite the good performance of most reinforced soil structures, several reinforced soil walls failed during the Chi-Chi, the El Salvador, and the Nisqually USA earthquakes due to different reasons, such as insufficient reinforcement length, large

∗

reinforcement spacing, insufficient facing connection, and insufficient compaction of the backfill soil. Therefore, seismic performance of reinforced soil structures still needs further investigation. The US Federal Highway Administration (FHWA) recently developed a Geosynthetic Reinforced Soil – Integrated Bridge System (GRSIBS) (Adams and Nicks, 2018). The term GRS refers to a composite soil mass comprising alternating layers of highly compacted granular fill and closely-spaced geosynthetic layers (i.e., reinforcement vertical spacing no larger than 0.3 m) (Adams and Nicks, 2018). Due to the use of closely-spaced reinforcement layers and highly-compacted backfill, the GRS mass is believed to behave like a composite material through the interaction between soil and geosynthetic reinforcement and have a high bearing capacity (Wu et al., 2006; Nicks et al., 2013; Wu et al., 2013). In recent years, this GRS-IBS technology has been increasingly used to support small to mid-span bridges due to its advantages of reduced construction cost, faster construction time, and effectiveness in eliminating bumps at the end of bridges (Adams and Nicks, 2018). A number of experimental and numerical studies have been carried out to investigate the performance of the GRS abutments under static loading (Adams et al., 2011; Wu et al., 2013; Nicks et al., 2013; Nicks et al., 2016; Saghebfar et al., 2017; Zheng and Fox, 2017; Zheng et al.,

Corresponding author. E-mail address: [email protected] (P. Shen).

https://doi.org/10.1016/j.geotexmem.2019.12.004

0266-1144/ © 2019 Elsevier Ltd. All rights reserved.

Please cite this article as: Chao Xu, et al., Geotextiles and Geomembranes, https://doi.org/10.1016/j.geotexmem.2019.12.004

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2018a,b; Shen et al., 2019; Xu et al., 2019). Regarding the influence of dynamic loading, most of the research reported in the literature focused on the seismic response of geosynthetic-reinforced soil retaining walls (Ling et al., 2005, 2012; Sabermahani et al., 2009; Guler and Selek, 2014; Yazdandoust, 2017). Limited studies (Helwany et al., 2012; Zheng et al., 2017, 2018c, 2019 a,b) were conducted to investigate the seismic performance of the GRS abutments. The major difference between the GRS abutments and the retaining walls is that the GRS abutments are typically subjected to much higher loads on top of the abutments and the loads are close to the facing (Helwany et al., 2007). Helwany et al. (2012) carried out a “field-scale” shaking table test of a GRS abutment under a three-dimensional (3D) condition subjected to a longitudinal sinusoidal wave motion. Test results indicated that the GRS abutment showed satisfactory seismic performance and did not experience significant movement or structural failure. Some local cracks at bottom corners of the abutment were observed when the acceleration amplitude was larger than 0.67 g. Zheng et al. (2017 and 2018c) performed shaking table tests on a 2.7 m high half-scale GRS abutment subjected to shaking in the longitudinal and transverse directions respectively. Their study paid special attention to the similitude relationship between the model and the prototype GRS abutments. Test results showed that the GRS bridge abutments had overall good seismic performance in terms of lateral facing displacements and bridge seat movements. From the preceding literature review, it can be concluded that fewer studies have been conducted to investigate the seismic response of GRS abutments under dynamic loading. All the shaking table tests of the GRS abutments reported in the literature investigated the seismic performance of a single abutment with a segment of the bridge beam resting on its top. The other end of the bridge beam segment was rested on a rigid support wall with rollers or a sliding platform (Helwany et al., 2012; Zheng et al., 2017 and 2018c). It should be noted that the use of the support wall may not reflect the true condition of the GRS abutments constructed in the field since the vertical fixity on top of the support wall did not allow the bridge beam to deform vertically. The vertical deflection of the bridge beam is important when evaluating differential settlement between the bridge beam and the approach roadway and may affect the overall performance of the whole GRS-IBS. Therefore, further studies are necessary to investigate this important factor. In this study, a scaled shaking table test was conducted on a whole GRS-IBS with a full-length bridge beam resting on two GRS abutments at opposite ends under a plane strain condition. A series of input earthquake motions with different peak ground accelerations (PGA) were applied to the model system in the longitudinal direction of the bridge beam. This study aims to investigate the seismic responses of the whole GRS-IBS under serviceability limit conditions. Current design methods assumed that the increase in the reinforcement strength Tf has the same effect as a proportional decrease in the reinforcement spacing Sv (Wu et al., 2013). In addition, the reinforcement strength Tf is approximately proportional to the reinforcement stiffness J under the serviceability limit conditions investigated in this study. To verify whether this assumption is valid for GRS abutments under seismic loading, the current study examined the effects of different combinations of reinforcement stiffness and spacing on the seismic performance of the whole GRS-IBS at the same J/Sv ratio.

Table 1 Similitude relationships for 1 g shaking table testing. Variable

Theoretical scaling factor (Iai, 1989)

Scaling factor used in this study (λ = 4)

Length Density Stress Strain Modulus Stiffness Time Frequency Acceleration

λ 1 λ 1 λ λ2 λ1/2 λ−1/2 1

4 1 4 1 4 16 2 0.5 1

Table 1. This similitude relationship was widely used for 1 g shaking table tests (e.g., El-Emam and Bathurst, 2007; Guler and Selek, 2014; Zheng et al., 2017 and 2018c). Considering the geometry and the payload of the shaking table, a length scaling factor λ of 4 was adopted in this study. 2.2. Test configuration The geometry of a bridge footing on top of an abutment is typically considered as a plane strain condition since the ratio of the footing length to its width is commonly between 7 and 14 (Nicks et al., 2013). Therefore, the shaking table test conducted in this study simulated a scaled model of the whole GRS-IBS under a plane strain condition. Fig. 1 presents the shaking table test configuration of the model GRSIBS. The model GRS-IBS consisted of a full-length bridge beam resting on two GRS abutments of different reinforcement spacing at opposite ends. The model GRS-IBS was constructed inside a rigid test box made of stiffened steel. The rigid test box provided horizontal restraints to the model GRS-IBS in three sides. The abutment facing of both GRS abutments at opposite ends were able to deform laterally since no fixities were applied to them. Expanded Polystyrene (EPS) panels of 0.05 m thick were placed inside the test box as shown in Fig. 1 to prevent wave reflection from the rigid walls during shaking. The front side of the test box was made of a transparent Plexiglas panel to allow visual observation of deformations of the whole system during shaking. The net width of the test box was 0.7 m. The total length of the model GRS-IBS was 4 m. The length of each GRS abutment was 1.3 m including the abutment facing blocks, the reinforced soil zone, and the retained soil zone. The net span of the bridge beam between the two abutments was 1.4 m. The model GRS-IBS had a total height of 1.5 m, consisting of a 0.15 m thick reinforced soil foundation (RSF), a 1.2 m high abutment, and a 0.15 m thick approach roadway. The abutment facing consisted of 24 modular blocks, each having a thickness of 0.05 m. The bridge beam with dimensions of 2.10 m × 0.68 m × 0.15 m (length × width × thickness) was placed directly on top of the two GRS abutments at opposite ends. Wrapped-around reinforcement layers at the top of both abutments served as beam seats for the bridge beam. The beam seat for the bridge beam was 0.25 m wide at both ends and the setback distance between the back of the abutment facing and the beam seat was zero. The gap between the top of the abutment facing and the bottom of the bridge beam was 0.05 m. Two different reinforcement spacing values were used in the two GRS abutments at opposite ends, i.e., 0.10 and 0.05 m in the left and right GRS abutments respectively. The length of the geosynthetic reinforcement Lr was kept the same in both abutments, which was 0.7 times the abutment height Ha (i.e., Lr = 0.7Ha = 0.84 m). Both the RSF and the approach roadway consisted of wrapped-around reinforcement layers placed at the reinforcement spacing of 0.05 m.

2. Shake table test 2.1. Similitude relationship The prototype case simulated in this study was the Guthrie Run Bridge in Delaware, USA, which is a typical GRS-IBS structure with a height of 6.0 m (Talebi, 2016). The similarity of the conditions between the model (reduced scale) and the prototype (full scale) was guaranteed by the similitude relationship proposed by Iai (1989) as shown in 2

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Fig. 1. Test configuration of the model GRS-IBS: (a) top view and (b) cross-sectional view in the longitudinal direction of the bridge beam (not to scale).

2.3. Material

of the geogrid were 3.5 and 1.0 mm respectively. Since the reinforcement spacing used in the right GRS abutment was half of that used in the left GRS abutment, special treatment was made to the geogrid used in the right GRS abutment to maintain the same ratio of the reinforcement tensile strength (or stiffness) to the reinforcement spacing (i.e., Tf/Sv or J/Sv) between the left and right GRS abutments. Every other rib in the MD of the geogrid was cut off in the right GRS abutment as shown in Fig. 3(b) to reduce the reinforcement tensile strength and stiffness. Wide-width tensile tests were conducted to determine the tensile strength of the geogrids in the MD with and without the removed ribs. Fig. 3(c) and Table 2 show that the removal of ribs in the MD of the geogrid reduced both the tensile strength and the stiffness of the reinforcement by approximately 50%. The tensile strengths Tf of the geogrids used in the left and right GRS abutments were 10 and 5 kN/m respectively. The tensile stiffness values at 2% tensile strain J@2% of the geogrids used in the left and right GRS abutments were 170 and 80 kN/ m respectively. Therefore, the ratios of Tf/Sv and J@2%/Sv were kept

The backfill soil used in this study was a poorly-graded quartz sand with a coefficient of uniformity Cu = 2 and a coefficient of curvature Cc = 0.95. Fig. 2(a) presents the particle size gradation curve of the backfill soil. The maximum and the minimum dry unit weights were 17.1 and 13.0 kN/m3 respectively. During construction, the backfill soil was compacted to the dry unit weight of 16.1 kN/m3, which corresponded to a relative density of approximately 80%. Triaxial test results shown in Fig. 2(b) and (c) indicate that the backfill soil had a peak friction angle of 49° and zero cohesion at the relative density of 80%. The reinforcement used in this study was a biaxial geogrid made of polypropylene, which was carefully selected to meet the scaling requirements in Table 1. Table 2 provides the detailed properties of the geogrid. The geogrid was placed in a way that its machine direction (MD) was perpendicular to the abutment facing. The aperture dimensions of the geogrid were 33 mm × 33 mm. The rib width and thickness 3

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Fig. 2. Physical and mechanical properties of the backfill soil: (a) particle size gradation curve; (b) triaxial test results.

approximately the same for the left and right GRS abutments. The bridge beam was simulated using an aluminum plate weighed 650 kg with dimensions of 2.10 m long × 0.68 m wide × 0.15 m thick. Considering the beam seat width of 0.25 m, the weight of the aluminum plate resulted in a uniform pressure of 18.3 kPa applied to each GRS abutment. This applied pressure on the GRS abutment satisfied the stress scaling requirement as shown in Table 1 without considering live loads caused by vehicles. The abutment facing was simulated using modular blocks with dimensions of 0.23 m long × 0.10 m wide × 0.05 m thick.

Compaction was applied to the RSF using a hand-held plate vibrator. The compacted lift thickness was approximately 0.05 m and each lift had a mass of 80.4 kg, thus resulting in an average unit weight of 16.1 kN/m3 and a relative density of 80%. The GRS abutment was then constructed in 24 lifts using the mass-volume control method. In each lift, a layer of modular blocks were placed, followed by a layer of backfill soil. Compaction was also applied to the backfill soil of the GRS abutment using the hand-held plate vibrator. The thickness and mass of each lift were 0.05 m and 70.0 kg respectively, thus resulting in the same average unit weight of 16.1 kN/m3 and the relative density of 80% as the RSF. According to the test plan, geogrid layers were placed at different reinforcement spacing in the left and right GRS abutments. Mechanical connections were used between the geogrids and the abutment facing blocks by inserting steel wires through the front apertures of the geogrids and connecting the wires together throughout the whole height of the abutment. The bridge beam was then carefully placed on top of the two GRS abutments to ensure the same beam seat width of 0.25 m at both ends. Finally, the approach roadways behind the bridge beam were constructed in two lifts using the mass-volume control method. The same average unit weight and relative density for the approach roadways as those for the RSF and the GRS abutments were achieved through compaction.

2.4. Construction Before the construction of the model GRS-IBS, measures were taken to reduce the friction of the inner sides of the test box to ensure the plane strain condition. A layer of silicone oil was applied to the inner surface of the Plexiglas panel. A lubrication layer consisted of a 0.4mm-thick polytetrafluoroethylene membrane and an approximately 1.0-mm-thick Vaseline was applied to the remaining inner surfaces of the test box. The 0.15-m-thick RSF was first constructed at the bottom of the test box to provide a firm base for the GRS abutment. The RSF was constructed in three lifts using a mass-volume control method.

Table 2 Wide width tensile test results of the geogrid in the MD with and without removal of ribs. Type Geogrid without removal of ribs used in the left GRS abutment Geogrid with removal of ribs used in the right GRS abutment

Ultimate tensile strength (kN/m)

Tensile strength at 2% tensile strain (kN/m)

Tensile stiffness at 2% tensile strain (kN/m)

10.0

3.4

170

5.0

1.6

80

4

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Fig. 3. Wide-width tensile tests of geogrids in the MD: (a) without removal of ribs used in the left GRS abutment; (b) with removal of ribs used in the right GRS abutment; and (c) tensile test results of geogrids with and without removal of ribs.

2.5. Instrumentation

zone (A5 to A8) were close to the junction between the bridge beam and the approach roadway in the horizontal direction. In addition, two accelerometers were placed inside the approach roadway, which were horizontally in align with the accelerometers placed inside the reinforced soil zone and the retained soil zone. Two additional accelerometers were attached to the top of the bridge beam (A15) and the bottom of the test box (A16) respectively. Four LVDTs (L1 to L4) were attached to the abutment facing at different heights to monitor the distribution of the lateral displacements of the abutment facing. Two LVDTs were used to monitor the vertical displacements of the bridge beam (L5) and the approach roadway (L6) respectively. Four earth pressure cells (E1 to E4) were embedded inside the reinforced soil zone under the center of the beam seat to monitor the vertical stresses of the

Fig. 4 shows the instrumentation layout in the longitudinal centerline section of the model GRS-IBS. The responses of the model GRS-IBS were measured using four different types of sensors including accelerometers for accelerations, linear variable differential transducers (LVDT) for lateral and vertical displacements, earth pressure cells for horizontal and vertical soil stresses, and strain gauges for reinforcement strains. Fig. 4 shows that the accelerometers were attached to the abutment facing and placed inside the reinforced soil zone and the retained soil zone at different heights to measure horizontal accelerations in the longitudinal direction. Accelerometers placed inside the reinforced soil

Fig. 4. Instrumentation in the longitudinal centerline section of the model GRS-IBS. 5

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Fig. 5. Calibration relationship for strain gauge measurements.

backfill soil. Besides, four earth pressure cells (E5 to E8) were placed behind the abutment facing at different heights to monitor the lateral earth pressures. One additional earth pressure cell (E9) was placed at the end of the bridge beam to monitor the contact pressure between the bridge beam and the approach roadway. Reinforcement strains were monitored using strain gauges mounted onto the upper surfaces of the geogrids at four different heights. Considering the effects of strain gauge attachment technique, the measured local strains of a geogrid by strain gauges might be different from the global strains of the geogrid over single or multiple apertures (Perkins et al., 1997; Bathurst et al., 2002; Jiang et al., 2016; Shen et al., 2018). The tensile tests of the model geogrid mentioned above were also used to establish the relationship between the local and global strains by fixing the strain gauge at the center of the model geogrid sample. Fig. 5 indicates that the calibration factor (CF), defined as the ratio of the global strain to the local strain at the same tensile force, was 2.05 for the geogrids used in this study. All measured geogrid strains presented in this study were converted into global strains using this CF value.

Fig. 6. Time histories of earthquake motions: (a) the original records for the N–S component of the Kobe earthquake versus the scaled input motion used in shaking event No. 16 and (b) scaled input motions used in shaking events No. 8, 12, and 20.

the acceleration amplitudes of the original motion were kept unchanged while the frequencies were divided by a factor of 0.5 according to the similitude relationship shown in Table 1. This scaled Kobe earthquake input motion was referred to as “motion of similitude” and was used in shaking event No. 16. In order to investigate the effects of the magnitudes of PGA on the performances of the whole system, the acceleration amplitudes of the “motion of similitude” were further scaled to reach different input target PGAs in different shaking events as shown in Table 3 while the frequencies were kept unchanged. In other words, the input motions used in different shaking events had the same frequencies but different acceleration amplitudes. Fig. 6(b) shows the examples of acceleration-time histories of the scaled input motions. It should be noted that only the “motion of similitude” (i.e., the input motion used in the shaking event No. 16) satisfied the similitude relationship shown in Table 1. The positive direction of the Kobe earthquake motion corresponded to the west direction in this study shown in Fig. 1. In other words, the positive direction of the input motion acted towards the left GRS abutment.

2.6. Input motions A series of input motions, including white noises and scaled earthquake motions, were applied to the model GRS-IBS in the longitudinal direction of the bridge beam with a short pause of 5 min between each motion. Table 3 summarizes all the 21 input motions. The shaking table was operated in an acceleration-control mode. The nominal white noise motion had a peak acceleration of 0.05 g and frequencies ranging from 0.1 to 50 Hz. This study used the North-South (N–S) component of the earthquake motion recorded by the Japan Meteorological Agency during the Kobe earthquake. Fig. 6 shows the time histories of the original Kobe earthquake motion, which had a PGA of 0.8 g. To obtain the input acceleration-time histories for the shaking test,

3. Test results Before the analysis of the test results, the sign convention of the measured acceleration and seismic inertial force should be specified

Table 3 Input motions for the shaking test. Shaking event No.

Motion

Input target PGA (g)

Duration (s)

Shaking event No.

Motion

Input target PGA (g)

Duration (s)

1 2 3 4 5 6 7 8 9 10 11

White noise Scaled Kobe White noise Scaled Kobe White noise Scaled Kobe White noise Scaled Kobe White noise Scaled Kobe White noise

0.05 0.1 0.05 0.2 0.05 0.3 0.05 0.4 0.05 0.5 0.05

100 15 100 15 100 15 100 15 100 15 100

12 13 14 15 16 17 18 19 20 21

Scaled Kobe White noise Scaled Kobe White noise Scaled Kobe (“Motion of Similitude”) White noise Scaled Kobe White noise Scaled Kobe White noise

0.6 0.05 0.7 0.05 0.8 0.05 0.9 0.05 1.0 0.05

15 100 15 100 15 100 15 100 15 100

6

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phase with the shaking table. In other words, the shaking table accurately reproduced the target input motion. 3.2. Acceleration response As mentioned previously, the geometries of the left and right GRS abutments were symmetrical along the center of the bridge span. The waveform of the input motion was scaled from the original Kobe earthquake motion; however, it had different acceleration amplitudes and frequencies in the two opposite outward directions at the facing of the left and right GRS abutments. In other words, the waveform of the input motion was asymmetrical. Therefore, the left and right GRS abutments were subjected to different positive PGAs. Table 4 shows the actual positive PGAs of both abutments versus the input target PGA of each shaking event. The actual positive PGAs of both abutments were essentially the measured peak acceleration amplitudes of the shaking table in opposite directions. As stated previously, the positive direction of the input motion acted toward the left GRS abutment and the positive direction of the measured acceleration of a single GRS abutment acted outward from its facing. Therefore, the measured peak acceleration amplitudes of the shaking table in the positive direction of the input motion corresponded to the actual positive PGAs of the right GRS abutment while the measured peak acceleration amplitudes in the negative direction of the input motion corresponded to the actual positive PGAs of the left GRS abutment. Table 4 indicates that the measured positive PGAs of the left GRS abutment were larger than those of the right abutment due to the asymmetrical waveform of the input earthquake motion. Taking the shaking event No. 16 with an input target PGA = 0.8 g as an example, Fig. 8 shows the measured acceleration-time histories of different zones of the GRS abutments (i.e., the abutment facing, the reinforced soil zone, and the retained soil zone) at four selected elevations. Similar results were found for other shaking events and are not presented in this paper due to the page limit. Fig. 8 shows that the measured positive acceleration amplitudes in different zones of the left GRS abutment were generally larger than those in the right GRS abutment. In fact, due to the opposite outward directions of the left and right GRS abutment facing, the earthquake motions applied to the left and right GRS abutments were essentially opposite. Fig. 8 also shows that different zones of each GRS abutment had similar acceleration-time histories with small differences in the peak acceleration amplitudes. Fig. 9 shows the distributions of the peak acceleration amplification coefficients along the abutment height at the abutment facing and the reinforced soil zone. The peak acceleration amplification coefficient was defined as the ratio of the measured peak acceleration amplitude at a specific height to the measured PGA. Fig. 9 shows that with the increase of the input target PGA, the left and right GRS abutments had different distributions of the peak acceleration amplification coefficients. For the left GRS abutment, the peak acceleration amplification coefficients decreased with the increase of the input target PGA from 0.4 g to 1.0 g. For the right GRS abutment, however, the peak acceleration amplification coefficients did not have any significant change with the increase of the input target PGA. A similar trend was found for the peak acceleration amplification coefficients in the reinforced soil zone to those at the abutment facing. Since the reinforcement spacing in the right GRS abutment was half of that in the left GRS abutment and

Fig. 7. Acceleration-time histories of shaking event No. 16: (a) target input versus shaking table and (b) shaking table versus test box.

first. In this study, the positive sign represents a measured acceleration or a seismic inertial force acting outward from the GRS abutment facing. Since the geometry of the left and right GRS abutments were symmetrical along the center of the bridge span, the outward directions of the two GRS abutments’ facing were opposite, thus resulting in a 180° difference in the positive direction of the measured accelerations in the left and right GRS abutments. It should also be mentioned that the test results presented in this paper were the responses caused by seismic loading only since this paper focused on the seismic responses of the system. In other words, the readings of all the sensors shown in Fig. 4 were zeroed out after the completion of the construction of the whole GRS-IBS and prior to shaking. The results induced by static loading, such as the construction of the two abutments and the placement of the bridge beam, were excluded. 3.1. System identification Fig. 7 shows the acceleration-time histories of the shaking table and the test box at the shaking event No. 16. The acceleration-time histories in other shaking events were similar and therefore are not presented in the paper. Fig. 7(a) shows that the acceleration-time histories of the shaking table were essentially the same as those of the input motions, indicating that the shaking table performed well in the accelerationcontrol mode. Fig. 7(b) shows that the acceleration-time histories of the test box matched well with those of the shaking table, indicating that the test box was sufficiently stiff and moved essentially in the same Table 4 Input target PGAs versus actual positive PGAs of both GRS abutments. Shanking event No. Input target PGA Actual positive PGA

Left abutment (Sv = 0.1 m, J@2% = 170 kN/m) Right abutment (Sv = 0.05 m, J@2% = 80 kN/m)

2 0.1 g 0.11 g

4 0.2 g 0.21 g

6 0.3 g 0.31 g

8 0.4 g 0.40 g

10 0.5 g 0.48 g

12 0.6 g 0.57 g

14 0.7 g 0.70 g

16 0.8 g 0.83 g

18 0.9 g 0.93 g

20 1.0 g 1.04 g

0.09 g

0.15 g

0.22 g

0.29 g

0.35 g

0.43 g

0.51 g

0.57 g

0.66 g

0.73 g

7

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Fig. 8. Measured acceleration-time histories for shaking event No. 16 with an input target PGA = 0.8 g at: (a) abutment facing; (b) reinforced soil zone; and (c) retained soil zone.

8

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Fig. 9. Distributions of peak acceleration amplification coefficients along the height of the GRS abutment at: (a) abutment facing and (b) reinforced soil zone.

the ratio of J@2%/Sv was approximately the same for both abutments, Fig. 9 indicates that reducing the reinforcement spacing was beneficial to minimize the seismic effect on the abutment and could prevent structural damage from happening under strong earthquake motions. Sabermahani et al. (2009) found similar results. In other words, as compared to increasing the tensile stiffness of the reinforcement, reducing the reinforcement spacing was more beneficial to improve the seismic performance of the GRS structure in terms of the acceleration responses. Fig. 10 shows the distributions of the peak acceleration amplitudes along the height of the abutments at different monitoring zones. Fig. 10 shows that the left and right GRS abutments had different peak acceleration amplitudes at the bottom of the abutment despite the change of the monitoring zones. In other words, at the bottom of the abutment facing, the reinforced soil zone, and the retained soil zone, the left and right GRS abutments showed different acceleration responses. However, for the abutment facing and the reinforced soil zone, the peak acceleration amplitudes in the left and right GRS abutments became closer with the increase of the elevation as shown in Fig. 10(a) and (b). On the other hand, for the peak acceleration amplitudes in the retained soil zone as shown in Fig. 10(c), the differences existed between the left and right GRS abutments regardless of the elevation change. The existence of the bridge beam might have affected the distribution of the peak acceleration amplitudes near the top of both GRS abutments. The seismic inertial forces acted on the top of the left and right GRS abutments interacted with each other through the bridge beam. This interaction led to close peak acceleration amplitudes between the two abutments happening at the locations near the bridge beam, such as the abutment facing and the reinforced soil zone. However, the influence of the bridge beam on the retained soil zone was not significant since the retained soil zone was relatively far away from the bridge beam, thus resulting in different peak acceleration amplitudes in the retained soil zone between the left and right GRS abutments. This study investigated the important effects of the bridge beam on the distribution of the peak acceleration amplitudes that could not have been observed if a single

GRS abutment were used as in other studies. 3.3. Lateral facing displacements As mentioned previously, the left and right GRS abutments were subjected to different positive PGAs at each shaking event. Therefore, lateral facing displacements were modified in this section in order to make the monitoring data of the left and right GRS abutments comparable. The following equation shows the calculation of the modified lateral facing displacement δN: N

=

fA

=

Aactual / At arg et

(1)

where δ is the measured lateral facing displacement; fA is the PGA modification factor, which equals to the ratio of the actual positive PGA of the GRS abutment to the input target PGA; Aactual is the actual positive PGA of the GRS abutment; and Atarget is the input target PGA. Fig. 11 shows the distribution of the modified peak and residual lateral facing displacements along the height of the abutment induced by earthquake motions. As expected, both the peak and the residual lateral facing displacements increased with the increase of the input target PGA. The lateral facing displacements were close to zero at the bottom of the abutments and increased with the elevation. The maximum residual lateral facing displacements happened at the top of the abutments, indicating that overturning of the abutment facing could happen when the input target PGA was further increased. Smaller lateral facing displacements happened in the right GRS abutment than those in the left abutment, indicating that the decrease of reinforcement spacing could effectively reduce the lateral facing displacements while the ratio of J@2%/Sv was kept unchanged. Fig. 12 shows two photos of the left and right GRS abutments after the completion of the shaking test. These two photos show that the left GRS abutment had obvious facing inclination as compared to the right GRS abutment, which was consistent with the results of the measured residual lateral facing displacements. In conclusion, as compared to increasing the tensile 9

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Fig. 10. Distributions of measured peak acceleration amplitudes along the height of the GRS abutments at: (a) abutment facing; (b) reinforced soil zone; and (c) retained soil zone.

stiffness of the reinforcement, reducing the reinforcement spacing was more beneficial to improve the seismic performance of the GRS abutment in terms of the lateral facing displacements induced by earthquake motions. Fig. 13 shows the variation of the degree of the recovered lateral facing displacement with the change of the input target PGA. The degree of the recovered lateral facing displacement is defined as the percentage of the average recovered lateral facing displacement along the abutment height to the average peak lateral facing displacement along the abutment height. The recovered lateral facing displacement

was calculated by subtracting the residual lateral facing displacement from the peak lateral facing displacement. Fig. 13 shows that the degree of the recovered lateral facing displacement was greater than 60% for the right GRS abutment when the input target PGA was smaller than 0.5 g, indicating that most of the lateral facing displacements recovered after shaking. Zheng et al. (2017 and 2018c) found similar results that dynamic lateral facing displacements were largely recovered after shaking, especially for the upper section of the abutment. However, Fig. 13 also shows that the degree of the recovered lateral facing displacement decreased significantly with the increase of the input target 10

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Fig. 11. Distribution of modified lateral facing displacements along the height of the GRS abutments induced by earthquake motions: (a) peak lateral facing displacements and (b) residual lateral facing displacements.

PGA. The degrees of the recovered lateral facing displacements in both left and right GRS abutments decreased from approximately 100% to 30% when the input target PGA increased from 0.1 g to 1.0 g, indicating that most of the lateral facing displacements induced by earthquake motions could not completely recover when the input target PGA was relatively larger.

input target PGA. The modified bridge beam vertical displacement is defined as the measured bridge beam vertical displacement by the LVDT L5 divided by the PGA modification factor shown in Eq. (1). The bars in Fig. 14 represent the maximum and minimum modified vertical displacements in each shaking event and the points between 2 bars represent the average values. A positive value corresponded to the settlement (i.e., downward movement) of the bridge beam while a negative value corresponded to the upward movement. Fig. 14 shows that when the input target PGA was smaller than 0.3 g, the modified average vertical displacements were close to zero, indicating that approximately no displacement occurred. When the input target PGA was

3.4. Bridge beam vertical displacement Fig. 14 shows the variation of the modified vertical displacement of the bridge beam induced by earthquake motions with the change of the

Fig. 12. Photos of the left and right GRS abutments after the completion of the shaking test. 11

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the maximum differential settlement was smaller than 15 mm (i.e., corresponded to a vertical strain of 1.3%). Careful examination of the model GRS-IBS after shaking indicated that the whole system remained intact and functional without obvious structural damage. Overall, the GRS-IBS was able to withstand the seismic load and did not experience obvious structure failure and significant displacements. 3.5. Lateral earth pressure Fig. 15 shows the distribution of the modified peak and residual lateral earth pressures behind the abutment facing along the height of the GRS abutments induced by earthquake motions. The modified lateral earth pressure is defined as the measured lateral earth pressure behind the abutment facing divided by the PGA modification factor shown in Eq. (1). Fig. 15 shows that as compared to the modified peak lateral earth pressure, the modified residual lateral earth pressure was much lower, indicating that most of the lateral earth pressure induced by earthquake motions recovered after shaking. Generally, the modified lateral earth pressures within the upper portion of the abutments were lower than those within the lower portion of the abutment. When the input target PGA was smaller than 0.4 g, the modified peak lateral earth pressure was lower than 5 kPa. When the input target PGA was 1.0 g, the modified peak lateral earth pressure increased significantly to an average value higher than 10 kPa and the maximum value of 15 kPa happened at the bottom of the GRS abutments. As compared to the static active lateral earth pressure induced by the self-weight of the abutment and the bridge beam (i.e., the maximum value of approximately 5 kPa in total), the lateral earth pressure induced by earthquake motion was significantly higher. Therefore, in seismic design, special attention should be paid to the lateral earth pressure induced by earthquake motions with large PGAs.

Fig. 13. Degree of recovered lateral facing displacement versus input target PGA.

larger than 0.5 g, the bridge beam moved upward and slightly larger upward movements happened in the left GRS abutment than those in the right abutment. Regardless of the change of the input target PGA, the amplitudes of the bridge beam displacements (i.e., the difference between the maximum and minimum values) were no larger than 30 mm, which corresponded to a vertical strain of 2.5%. The modified average vertical displacements were no larger than 8 mm, which corresponded to a vertical strain of 0.7%. Helwany et al. (2007) detected similar amount of vertical compression of the GRS abutment (approximately 1%) induced by a sine-sweep motion with an acceleration amplitude of 0.67 g. The upward movements of the bridge beam may be attributed to the soil dilation behavior due to shearing during seismic loading. The backfill soil for the reinforced zone is considered dense since it had a relative density of 80%. The triaxial test results shown in Fig. 2(b) indicate that the backfill soil had obvious dilative behavior under the confining stresses of 10 and 25 kPa. The theoretical static stress induced by the self-weight of the backfill soil and the bridge beam calculated using Boussinesq's solution corresponded to a confining stress ranging from 10 to 25 kPa. During shaking, the volume of the backfill soil in the reinforced zone increased (i.e., dilation), thus resulting in the upward movements of the bridge beam. Please note that the reduced scale model had lower stresses than a field GRS-IBS, which promoted dilation. Dilation may not necessarily happen in a field system and should be further investigated. The residual displacements of the bridge beam and the approach roadway can also be observed from Fig. 12 when the shaking test was finished. The LVDT L6 shown in Fig. 4 malfunctioned during shaking, thus resulting in no monitoring data of the displacements of the approach roadway. However, Fig. 12 shows that differential settlement happened between the bridge beam and the approach roadway. Hand measurements were conducted after the shaking test and showed that

3.6. Vertical stress Fig. 16 shows the distribution of the modified peak and residual vertical stresses in the backfill soil under the center of the beam seat along the height of the GRS abutments induced by earthquake motions. The modified vertical stress of the backfill soil is defined as the measured vertical stress devided by the PGA modification factor shown in Eq. (1). Fig. 16 shows that shaking in the longitudinal direction of the bridge beam also increased the vertical stress in the reinforced soil zone. This increased vertical soil stress could produce additional tension in the geogrid reinforcement and require additional bearing capacities of both the GRS abutment and the RSF. Generally, the vertical soil stress decreased with the increase of the elevation. The modified residual vertical soil stress was close to the modified peak vertical soil stress, indicating that most of the vertical soil stress induced by earthquake motions, especially those at the bottom portion of the abutment, did not recover after shaking. Zheng et al. (2018c and 2019b) found

Fig. 14. Modified vertical displacements of the bridge beam induced by earthquake motions versus input target PGAs. 12

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Fig. 15. Distribution of modified peak and residual lateral earth pressures behind the abutment facing along the height of the GRS abutments induced by earthquake motions: (a) peak lateral earth pressure and (b) residual lateral earth pressure.

Fig. 16. Distribution of modified vertical stresses in the backfill soil under the center of the beam seat along the height of the GRS abutments induced by earthquake motions: (a) peak vertical stress and (b) residual vertical stress. 13

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Fig. 17. Distribution of modified tensile forces in the geogrid layers induced by earthquake motions: (a) peak tensile forces and (b) residual tensile forces.

similar results. Two possible reasons could explain this phenomenon. Runser et al. (2001) pointed out that the increased vertical stress induced by longitudinal shaking might be attributed to the loss of support (i.e., loss of upward friction generated during construction and bridge beam loading) of the backfill soil near the abutment facing. Zheng et al. (2018c) also indicated that the change of soil arching in the backfill soil near the abutment facing could cause the increased vertical stress induced by longitudinal shaking. In addition, the dilative behavior of the backfill soil in the reinforced zone as shown in Fig. 2(b) might also result in the upward movement and the downward interface friction between the abutment facing and the reinforced fill, thus increasing the vertical stress close to the abutment facing.

abutments showed similar distributions. The maximum modified tensile forces in the upper geogrid layers happened under the center of the beam seat. For the lower geogrid layers, however, the maximum modified tensile forces happened at the abutment facing. Zheng et al. (2017, 2018c, and 2019b) reported similar results. The self-weight of the bridge beam had more effect on the tensile forces in the upper portion of the abutment and its effect decreased with the depth from the top of the abutment; therefore, larger tensile forces developed in the upper geogrid layers under the center of the beam seat. On the other hand, the increased lateral earth pressure and the change of soil arching near the abutment facing as well as the dilative behavior of the backfill soil as discussed previously had more significant effects on the tensile forces at the bottom portion of the abutment; therefore, larger tensile forces occurred in the lower geogrid layers at the abutment facing. The residual modified tensile forces were smaller than the peak ones, especially within the upper portion of the abutment. The modified tensile forces in the geogrids in the right GRS abutment was approximately half of those in the left GRS abutment. Considering the fact that the reinforcement spacing used in the right GRS abutment was also half of that used in the left abutment, the total modified tensile forces in all the geogrid layers were approximately the same for both the left and

3.7. Tensile force in the geogrid reinforcement Fig. 17 shows the distribution of the modified tensile forces in the geogrid layers induced by earthquake motions. The tensile force in the geogrid reinforcement was calculated as the reinforcement stiffness multiplied by the global strain. The modified tensile force is defined as the calculated tensile force divided by the PGA modification factor shown in Eq. (1). Fig. 17 indicates that both the left and right GRS 14

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right GRS abutments. The use of small reinforcement spacing resulted in a more uniform distribution of tensile forces in the geogrid layers.

the bridge beam vertical displacements (i.e., the difference between the maximum and minimum values) were no larger than 30 mm, which corresponded to a vertical strain of 2.5%. The average vertical displacements of the bridge beam were no larger than 8 mm, which corresponded to a vertical strain of 0.7%. Overall, the GRSIBS was able to withstand the seismic load and did not experience obvious structure failure and significant displacements. (5) Generally, the lateral earth pressures within the upper portion of the abutment were lower than those within the lower portion of the abutment. The lateral earth pressure induced by earthquake motions with large PGAs was significantly higher than the theoretical calculated static pressure induced by the self-weight of the abutment and the bridge beam. Most of the lateral earth pressure induced by earthquake motions recovered after shaking. (6) Shaking in the longitudinal direction of the bridge beam increased the vertical stress in the reinforced soil zone. Generally, the vertical soil stress decreased with the increase of the elevation. Most of the vertical soil stresses induced by earthquake motions did not recover after shaking due to the dilative behavior of the backfill soil in the reinforced zone and the change of soil arching in the backfill soil next to the abutment facing. (7) The maximum tensile forces in the upper geogrid layers happened under the center of the beam seat while the maximum tensile forces in the lower geogrid layers happened at the abutment facing. The total tensile forces in the geogrid layers were approximately the same for both the left and right GRS abutments. The use of small reinforcement spacing resulted in a more uniform distribution of tensile forces in the geogrid layers.

4. Limitation It is important to acknowledge that the boundary conditions of the shaking table tests presented in this study are different from those in the field. Particularly, the length of the whole GRS-IBS investigated in this study was limited by the size of the shaking table, thus resulting in a smaller retained soil zone as compared to that in the field. Unfortunately, this is a common limitation for shaking table tests, which also existed in the previous studies (Helwany et al., 2012; Zheng et al., 2017, 2018, 2019 a, b). Nevertheless, the results of this study provided valuable insights into the seismic performance of a whole GRS-IBS, especially the effects of the bridge beam on the distribution of the peak acceleration amplitudes in the two GRS abutments at opposite ends of the bridge. 5. Conclusions This paper documented a scaled shaking table test on a whole Geosynthetic Reinforced Soil – Integrated Bridge System (GRS-IBS) with a full-length bridge beam resting on two GRS abutments at opposite ends under a plane strain condition. A series of input earthquake motions with different peak ground accelerations (PGA) (up to 1.0 g) were applied to the model GRS-IBS in the longitudinal direction of the bridge beam. A poorly-graded quartz sand was used as the backfill soil and biaxial geogrids with or without removed ribs were used as reinforcement material. An aluminum plate was used to simulate the bridge beam and modular blocks were used to simulate the abutment facing. The left and right GRS abutments had reinforcement layers with vertical spacing Sv of 0.10 and 0.05 m respectively. The tensile strengths Tf of the geogrids used in the left and right GRS abutments were 10 and 5 kN/m respectively. The tensile stiffness values at 2% tensile strain J@2% of the geogrids used in the left and right GRS abutments were 170 and 80 kN/m respectively. Therefore, the ratios of Tf/Sv and J@2%/Sv were kept approximately the same for the left and right GRS abutments. This study aimed to investigate the seismic responses of the whole GRS-IBS. Reinforcement spacing and tensile stiffness were considered as two influence factors that would affect the performance of the system. Based on the test results, the following conclusions can be drawn from this study:

Acknowledgements This study was financially supported by the National Natural Science Foundation of China (Grant No. 41772284) and the Key Research and Development Project of the Chinese Ministry of Science and Technology (Grant No. 2016YFE0105800). The authors would like to appreciate these supports. References Adams, M.T., Nicks, J., Stabile, T., Wu, J.T.H., Schlatter, W., Hartmann, J., 2011. Geosynthetic Reinforced Soil Integrated Bridge System Synthesis Report. the US Federal Highway Administration, McLean, VA, USA Report No., FHWA-HRT-11-027. Adams, M., Nicks, J., 2018. Design and Construction Guidelines for Geosynthetic Reinforced Soil Abutments and Integrated Bridge Systems. the US Federal Highway Administration, McLean, VA, USA Report No., FHWA-HRT-17-080. Bathurst, R.J., Allen, T.M., Walters, D.L., 2002. Short-term strain and deformation behavior of geosynthetic walls at working stress conditions. Geosynth. Int. 9 (5–6), 451–482. El-Emam, M., Bathurst, R.J., 2007. Influence of reinforcement parameters on the seismic response of reduced-scale reinforced soil retaining walls. Geotext. Geomembranes 25 (1), 33–49. Guler, E., Selek, O., 2014. Reduced-scale shaking table tests on geosynthetic-reinforced soil walls with modular facing. J. Geotech. Geoenviron. Eng. 140 (6), 04014015. Helwany, S.M.B., Wu, J.T.H., Kitsabunnarat, A., 2007. Simulating the behavior of GRS bridge abutments. J. Geotech. Geoenviron. Eng. 133 (10), 1229–1240. Helwany, S.M.B., Wu, J.T.H., Meinholz, P., 2012. Seismic Design of GeosyntheticReinforced Soil Bridge Abutments with Modular Block Facing. NCHRP Web-Only Document 187. Transportation Research Board, Washington, DC, USA. Huang, C.C., 2000. Investigations of soil retaining structures damaged during the chi-chi (Taiwan) earthquake. J. Chin. Inst. Eng. 23 (4), 417–428. Huang, C.C., Chou, L.H., Tatsuoka, F., 2003. Seismic displacements of geosynthetic-reinforced soil modular block walls. Geosynth. Int. 10 (1), 2–23. Iai, S., 1989. Similitude for shaking table tests on soil-structure-fluid models in 1 g gravitational fields. Soils Found. 29 (1), 105–118. Jiang, Y., Han, J., Parsons, R.L., Brennan, J.J., 2016. Field instrumentation and evaluation of modular-block MSE walls with secondary geogrid layers. J. Geotech. Geoenviron. Eng. 142 (12), 05016002. Ling, H.I., Leshchinsky, D., Chou, N.N.S., 2001. Post-earthquake investigation on several geosynthetic-reinforced soil retaining walls and slopes during the Ji-Ji earthquake of Taiwan. Soil Dyn. Earthq. Eng. 21, 297–313. Ling, H.I., Leshchinsky, D., Mohri, Y., Wang, J., 2012. Earthquake response of reinforced segmental retaining walls backfilled with substantial percentage of fines. J. Geotech. Geoenviron. Eng. 138 (8), 934–944. Ling, H.I., Mohri, Y., Leshchinsky, D., Burke, C., Matsushima, K., Liu, H., 2005. Large-

(1) As compared to increasing the tensile stiffness of the reinforcement, reducing the reinforcement spacing was more beneficial to minimize the seismic effect on the abutment since no significant change of the distribution of the peak acceleration amplification coefficients occurred in the right GRS abutment with the increase of the input target PGA. (2) The existence of the bridge beam affected the distribution of the peak acceleration amplitudes near the top of both GRS abutments. The seismic inertial forces acted on the top of the left and right GRS abutments interacted with each other through the bridge beam, which led to similar peak acceleration amplitudes at the locations near the bridge beam between these two abutments. (3) Smaller lateral facing displacements happened in the right GRS abutment than those in the left abutment, indicating that reducing the reinforcement spacing was more beneficial to improve the seismic performance of the GRS abutment in terms of lateral facing displacements induced by earthquake motion as compared to increasing the tensile stiffness of the reinforcement. When the input target PGA was smaller than 0.5 g, most of the lateral facing displacements recovered after shaking. However, when the input target PGA was relatively larger, most of the lateral facing displacements induced by earthquake motions could not recover. (4) When the input target PGA was larger than 0.5 g, the amplitudes of 15

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C. Xu, et al. scale shaking table tests on modular-block reinforced soil retaining walls. J. Geotech. Geoenviron. Eng. 131 (4), 465–476. Mizuhashi, M., Sugita, H., Sasaki, T., 2008. Analytical study on geotextile-reinforced soil retaining walls damaged during the 2004 mid Niigata prefecture Japan earthquake. In: Proceedings of the 4th Asian Regional Conference on Geosynthetics, June 17 - 20, 2008, Shanghai, China. Nicks, J.E., Adams, M.T., Ooi, P.S.K., Stabile, T., 2013. Geosynthetic Reinforced Soil Performance Testing – Axial Loading Deformation Relationship. the US Federal Highway Administration, McLean, VA, USA Report No., FHWA-HRT-13-066. Nicks, J.E., Esmaili, D., Adams, M.T., 2016. Deformations of geosynthetic reinforced soil under bridge service loads. Geotext. Geomembranes 44 (4), 641–653. Perkins, S.W., Schulz, J.L., Lapeyre, J.A., 1997. Local versus global strain measurement of a polymeric geogrid. J. Test. Eval. 25 (6), 576–583. Runser, D., Fox, P.J., Bourdeau, P.L., 2001. Field performance of a 17 m-high reinforced soil retaining wall. Geosynth. Int. 8 (5), 367–391. Sabermahani, M., Ghalandarzadeh, A., Fakher, A., 2009. Experimental study on seismic deformation modes of reinforced-soil walls. Geotext. Geomembranes 27 (2), 121–136. Saghebfar, M., Abu-Farsakh, M., Ardah, A., Chen, Q., Fernandez, B.A., 2017. Performance monitoring of geosynthetic reinforced soil integrated bridge system (GRS-IBS) in Louisiana. Geotext. Geomembranes 45 (2), 34–47. Sandri, D., 1997. A performance summary of reinforced soil structures in the greater Los Angeles area after the Northridge earthquake. Geotext. Geomembranes 15, 235–253. Shen, P., Han, J., Zornberg, J.G., Morsy, A.M., Leshchinsky, D., Tanyu, B.F., Xu, C., 2019. Two and three-dimensional numerical analyses of geosynthetic-reinforced soil (GRS) piers. Geotext. Geomembranes 47 352-268. Shen, P., Xu, C., Han, J., 2018. Model tests investigating spatial tensile behavior of simulated geosynthetic reinforcement material over rigid supports. J. Mater. Civ. Eng. 30 (2), 04017288. Talebi, M., 2016. Analysis of the Field Behavior of a Geosynthetic Reinforced Soil Integrated Bridge System during Construction and Operation. The University of Delaware, DE, USA. Tatsuoka, F., Tateyama, M., Koseki, J., 1996. Performance of soil retaining walls for railway embankments. Soils Found. 36 (S1), 311–324. Wu, J.T.H., Pham, T.Q., Adams, M.T., 2013. Composite Behavior of Geosynthetic Reinforced Soil Mass. the US Federal Highway Administration, McLean, VA, USA

Report No., FHWA-HRT-10-077. Wu, J., Lee, K., Pham, T., 2006. Allowable bearing pressures of bridge sills on GRS abutments with flexible facing. J. Geotech. Geoenviron. Eng. 132 (7), 830–841. Xu, C., Liang, C., Shen, P., 2019. Experimental and theoretical studies on the ultimate bearing capacity of geogrid-reinforced sand. Geotext. Geomembranes 47 (3), 417–428. Xu, P., Hatami, K., Jiang, G., 2020. Study on seismic stability and performance of reinforced soil walls using shaking table tests. Geotext. Geomembranes 48 (1), 82–97. Yazdandoust, M., 2017. Investigation on the seismic performance of steel-strip reinforcedsoil retaining walls using shaking table test. Soil Dyn. Earthq. Eng. 97, 216–232. Yen, W.P., Chen, G., Buckle, I., Allen, T., Alzamora, D., Ger, J., Arias, J.G., 2011. Postearthquake Reconnaissance Report on Transportation Infrastructure Impact of the February 27, 2010, Offshore Maule Earthquake in Chile. the US Federal Highway Administration, McLean, VA, USA Report No., FHWA-HRT-11-030. Zheng, Y., Fox, P.J., 2017. Numerical investigation of the geosynthetic reinforced soilintegrated bridge system under static loading. J. Geotech. Geoenviron. Eng. 143 (6), 04017008. Zheng, Y., Fox, P.J., McCartney, J.S., 2018a. Numerical simulation of deformation and failure behavior of geosynthetic reinforced soil bridge abutments. J. Geotech. Geoenviron. Eng. 144 (7), 04018037. Zheng, Y., Fox, P.J., McCartney, J.S., 2018b. Numerical study on maximum reinforcement tensile forces in geosynthetic reinforced soil bridge abutments. Geotext. Geomembranes 46 (5), 634–645. Zheng, Y., Fox, P.J., Shing, P.B., McCartney, J.S., 2019a. Physical model tests of half-scale geosynthetic reinforced soil bridge abutments. I: static loading. J. Geotech. Geoenviron. Eng. 145 (11), 04019094. Zheng, Y., McCartney, J.S., Shing, P.B., Fox, P.J., 2018c. Transverse shaking table test of a half-scale geosynthetic reinforced soil bridge abutment. Geosynth. Int. 25 (6), 582–598. Zheng, Y., McCartney, J.S., Shing, P.B., Fox, P.J., 2019b. Physical model tests of half-scale geosynthetic reinforced soil bridge abutments. II: dynamic loading. J. Geotech. Geoenviron. Eng. 145 (11), 04019095. Zheng, Y., Sander, A.C., Rong, W., Fox, P.J., Shing, P.B., McCartney, J.S., 2017. Shaking table test of a half-scale geosynthetic-reinforced soil bridge abutment. Geotech. Test J. 41 (1), 171–192.

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