Numerical Investigation of the Performance of a Geosynthetic Reinforced Soil-Integrated Bridge System (GRS-IBS) under Working Stress Conditions

Author(s):  
Murad Abu-Farsakh ◽  
Allam Ardah ◽  
George Voyiadjis
2005 ◽  
Vol 42 (4) ◽  
pp. 1066-1085 ◽  
Author(s):  
Kianoosh Hatami ◽  
Richard J Bathurst

The paper describes a numerical model that was developed to simulate the response of three instrumented, full-scale, geosynthetic-reinforced soil walls under working stress conditions. The walls were constructed with a fascia column of solid modular concrete units and clean, uniform sand backfill on a rigid foundation. The soil reinforcement comprised different arrangements of a weak biaxial polypropylene geogrid reinforcement material. The properties of backfill material, the method of construction, the wall geometry, and the boundary conditions were otherwise nominally the same for each structure. The performance of the test walls up to the end of construction was simulated with the finite-difference-based Fast Lagrangian Analysis of Continua (FLAC) program. The paper describes FLAC program implementation, material properties, constitutive models for component materials, and predicted results for the model walls. The results predicted with the use of nonlinear elastic-plastic models for the backfill soil and reinforcement layers are shown to be in good agreement with measured toe boundary forces, vertical foundation pressures, facing displacements, connection loads, and reinforcement strains. Numerical results using a linear elastic-plastic model for the soil also gave good agreement with measured wall displacements and boundary toe forces but gave a poorer prediction of the distribution of strain in the reinforcement layers.Key words: numerical modelling, retaining walls, reinforced soil, geosynthetics, FLAC.


2019 ◽  
Vol 271 ◽  
pp. 02001
Author(s):  
Murad Abu-Farsakh ◽  
Allam Ardah ◽  
George Voyiadjis

This paper evaluates the performance of geosynthetic reinforced soil-Integrated Bridge System (GRS-IBS) in terms of lateral facing deformation and strain distribution along geosynthetics. Simulations were conducted using 2D PLAXIS program. The hardening model proposed by Schanz et al. [1] was used to simulate the behavior of backfill material; the backfill-reinforcement interface was simulated using Mohr-Coulomb model, and the reinforcement and facing block were simulated using linear elastic models. The numerical model was verified using the results of a case study conducted at Maree Michel GRS-IBS, Louisiana. Parametric study was carried out to investigate the effects of span length, reinforcement spacing, and reinforcement stiffness on the performance of GRS-IBS. The results indicate that span length have significant impact on strain distribution along geosynthetics and lateral facing deformation. The reinforcement stiffness has significant impact on the GRS-IBS behavior up to a certain point, beyond which the effect tends to decrease contradictory to reinforcement spacing that has a consistent relationship between the GRS-IBS behavior and reinforcement spacing. The results also indicate that reinforcement spacing has higher influence on the lateral facing deformation than the reinforcement stiffness for the same reinforcement strength/spacing ratio (Tf/Sv) due to the composite behavior of closely reinforcement spacing.


Author(s):  
Arshia Taeb ◽  
Phillip S.K. Ooi

When subjected to ambient daily temperature fluctuations, a 109.5 ft-long geosynthetic reinforced soil integrated bridge system (GRS-IBS) was observed to undergo cyclic straining of the superstructure. The upper and lower reaches of the superstructure experienced the highest and lowest strain fluctuation, respectively. These non-uniform strains impose not only axial loading of the superstructure but also bending. Pure axial loading in a horizontal superstructure will cause the footings to slide. However, bending in the superstructure will cause the footings to rotate thereby inducing cyclic fluctuations of the vertical pressure beneath the footing and also lateral pressure behind the end walls. Measured vertical footing pressure closest to the stream experienced the greatest daily pressure fluctuation (≈ 2,500–3,000 psf), while that nearest the end wall experienced the least. The toe pressure fluctuations seem rather large. That these large vertical pressure fluctuations are observed in a tropical climate like Hawaii when no other GRS-IBS in temperate regions has reported the same (or perhaps higher fluctuation) is indeed surprising. The larger these pressures are, the greater the likelihood of inducing cyclic-induced deformations of the GRS abutment. A finite element analysis of the same GRS-IBS was performed by applying an equivalent temperature and gradient to the superstructure over the coldest and hottest periods of a day to see if the field measured values of pressures are reasonable and verifiable, which indeed they were. This methodology is novel in the sense that the effects of axial load and bending of the superstructure are simulated using measured strains rather than measured temperatures.


Author(s):  
Milad Saghebfar ◽  
Murad Y. Abu-Farsakh ◽  
Allam Ardah ◽  
Qiming Chen ◽  
Benjamin A. Fernandez

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