Geosynthetic Reinforced Soil Bridge Abutments Research Articles

Cumulative deformation behavior of GRS bridge abutments under cyclic traffic loading

This paper presents an experimental study on reduced scale geosynthetic reinforced soil (GRS) abutment models subjected to cyclic traffic loading, aimed at investigating the influences of cyclic load amplitude, self-weight of bridge superstructure, and reinforcement vertical spacing on the cumulative deformations. The GRS abutment models were constructed using sand backfill and geogrid reinforcement. A static load was first applied to account for the self-weight of bridge superstructure, and then the cyclic loads were applied in several phases with increasing amplitude. The results indicate that significant cumulative footing settlement under cyclic loading mainly occurs within the first few hundred loading cycles, and the settlement increases with increasing cyclic load amplitude. The cyclic load amplitude and reinforcement vertical spacing have significant impacts on the cumulative deformations of GRS abutments under cyclic loading. The maximum facing displacement under cyclic loading occurs near the top of the wall. The cyclic load has a greater impact on the reinforcement strains near the upper middle reinforcement layers, while it has a smaller impact on the lower reinforcement layers.

Comparative assessment of stability of GRS abutments through 1 g physical model tests for field implementation

Geosynthetic reinforced soil (GRS) abutments have emerged as innovative improvement measures over the conventional GRS walls. Being an internally stabilized composite structure subjected to heavy stresses adjacent to facing, proper selection of GRS abutments in field is very important. Over the years, various design philosophies have been formulated in respect of GRS abutments but proper selection to a specific problem remains undiscussed. The present study attempts to conduct comparative analysis of stability of 5 types of chronologically evolved GRS bridge abutments (BA) namely BA I, BA II, BA III, BA IV and BA V through 1 g model tests (5 types are defined later) with special emphasis given to the influence of type of facing and configuration of reinforcements. A total of 75 model tests on 1/5th (N = 5) scaled down abutments have been performed to evaluate the effects of footing width (B), footing offset (x), facing type and abutment type on serviceable bearing capacity, ultimate bearing capacity, footing settlement, horizontal displacement of facing, tilting of footing, rotation and buckling of facing. The serviceability criteria based on FHWA recommendation has been chosen to ascertain field suitability of the model. An interesting mechanism correlating footing tilt (positive and negative) with movement of facing has been hypothesized and validated by the failure mode observed at the facing of the abutments. The abutments with modular facing were found to be more stable as compared to continuous facing. The footing width ratio (B/H) > 0.2 with footing offset ratio (x/H) > 0.3 (where, H is height of abutment) was found to be more suitable for field application. The degree of tilt, facing rotation, buckling behavior and differential settlement of footing were minimum for BA V. Based on all response parameters, BA V having modular facing with secondary reinforcements in the bearing bed performed exceedingly well in withstanding serviceable bearing pressures while sustaining larger footing settlements and resisting horizontal displacements of facing, followed by BA IV, BA III, BA II and BA I.

Experimental study on the load bearing behavior of geosynthetic reinforced soil bridge abutments on yielding foundation

This paper presents an experimental study of the load bearing behavior of geosynthetic reinforced soil (GRS) bridge abutments constructed on yielding clay foundation. The effects of two different ground improvement methods for the yielding clay foundation, including reinforced soil foundation and stone column foundation, were evaluated. The clay foundation was prepared using kaolin and consolidated to reach desired shear strength. The 1/5-scale GRS abutment models with a height of 0.8 m were constructed using sand backfill, geogrid reinforcement, and modular block facing. For the GRS abutments on three different yielding foundations, the reinforced soil zone had relatively uniform settlement and behaved like a composite due to the higher stiffness than the foundation layers. The wall facing moved outward with significant movements near the bottom of facing, and the foundation soil in front of facing showed obvious uplifting movements. The vertical stresses transferred from the footing load within the GRS abutment and on the foundation soil are higher for stiffer foundation. The improvement of foundation soil using geosynthetic reinforced soil and stone columns could reduce the deformations of GRS abutments on yielding foundation. Results from this study provide insights on the practical applications of GRS abutments on yielding foundation.

Experimental study on the load bearing behavior of geosynthetic reinforced soil bridge abutments with different facing conditions

This paper presents an experimental study on reduced-scale model tests of geosynthetic reinforced soil (GRS) bridge abutments with modular block facing, full-height panel facing, and geosynthetic wrapped facing to investigate the influence of facing conditions on the load bearing behavior. The GRS abutment models were constructed using sand backfill and geogrid reinforcement. Test results indicate that footing settlements and facing displacements under the same applied vertical stress generally increase from full-height panel facing abutment, to modular block facing abutment, to geosynthetic wrapped facing abutment. Measured incremental vertical and lateral soil stresses for the two GRS abutments with flexible facing are generally similar, while the GRS abutment with rigid facing has larger stresses. For the GRS abutments with flexible facing, maximum reinforcement tensile strain in each layer typically occurs under the footing for the upper reinforcement layers and near the facing connections for the lower layers. For the full-height panel facing abutment, maximum reinforcement tensile strains generally occur near the facing connections.

Influence of backfill type on the load-bearing performance of GRS bridge abutments

The influence of backfill type and material properties on the performance of field-scale geosynthetic reinforced soil (GRS) abutment models is investigated. Two alternative types of backfill as recommended in the Federal Highway Administration (FHWA) guidelines (called open-graded and well-graded) were used to build two field-scale model abutments and compare their load-bearing performance under a loading beam. Results are presented and discussed relative to the loading beam settlement, facing deformation and reinforcement strains. The well-graded backfill was found to result in smaller beam settlements and facing lateral deformations, especially at smaller loads that were comparable to service load levels. However, it was significantly faster and easier to compact the open-graded aggregate to the unit weight recommended in the guidelines. Nevertheless, performances of both abutment models were found to be satisfactory relative to the limiting requirements on the beam settlement and facing deformations at service load levels.

2D and 3D simulations of static response of a geosynthetic reinforced soil bridge abutment

This paper presents two-dimensional (2D) and three-dimensional (3D) numerical simulations of a half-scale geosynthetic reinforced soil (GRS) bridge abutment during construction and bridge load application. The backfill soil was characterized using a nonlinear elastoplastic model that incorporates a hyperbolic stress–strain relationship and the Mohr–Coulomb failure criterion. Geogrid reinforcements were characterized using linearly elastic elements with orthotropic behavior. Various interfaces were included to simulate the interaction between the abutment components. Results from the 2D and 3D simulations were compared with physical model test measurements from the longitudinal and transverse sections of a GRS bridge abutment. Facing displacements and bridge seat settlements for the 2D and 3D simulations agree well with measured values, with the 2D-simulated values larger than the 3D-simulated values due to boundary condition effects. Results from the 3D simulation are in reasonable agreement with measurements from the longitudinal and transverse sections. The 2D simulation can also reasonably capture the static response of GRS bridge abutments and is generally more conservative than the 3D simulation.

A Study of the Effects of Geosynthetic Reinforced Soil and Reinforcement Length on GRS Bridge Abutment

The geosynthetic reinforced soil (GRS) bridge abutment with a staged-construction full height rigid (FHR) facing and an integral bridge (IB) system was developed in Japan in the 2000s. This technology offers several advantages, especially concerning the deformation behavior of the GRS-IB abutment. In this study, the effects of GRS in the bridge abutment with FHR facing and the effects of geosynthetics reinforcement length on the deformation behavior of the GRS–IB are presented. The numerical models are analyzed using the finite element method (FEM) in Plaxis 2D program. The results showed that the GRS–IB model exhibited the least lateral displacements at the wall facing compared to those of the IB model without geosynthetics reinforcement. The geosynthetics reinforcement in the bridge abutment with FHR facing has reduced the vertical displacement increments by 4.7 times and 1.3 times (maximum) after the applied general traffic loads and railway loads, respectively. In addition, the numerical results showed that the increase in the length-to-height (L/H) ratio of reinforcement from 0.3H to 1.1H decreases the maximum lateral displacements by 29% and the maximum vertical displacements by 3% at the wall facing by the end of construction. The effect of the reinforcement length on the wall vertical displacements is minimal compared to the effect on the wall lateral displacements.

Numerical Analyses on the Behavior of Geosynthetic-Reinforced Soil: Integral Bridge and Integrated Bridge System

Geosynthetic-reinforced soil (GRS) technology has been used worldwide since the 1970s. An extension to its development is the application as a bridge abutment, which was initially developed by the Federal Highway Administration (FHWA) in the United States, called the GRS—integrated bridge system (GRS-IBS). Now, there are several variations of this technology, which includes the GRS Integral Bridge (GRS-IB) developed in Japan in the 2000s. In this study, the GRS-IB and GRS-IBS are examined. The former uses a GRS bridge abutment with a staged-construction full height rigid (FHR) facing integrated to a continuous girder on top of the FHR facings. The latter uses a block-faced GRS bridge abutment that supports the girders without bearings. In addition, a conventional integral bridge (IB) is considered for comparison. The numerical analyses of the three bridges using Plaxis 2D under static and dynamic loadings are presented. The results showed that the GRS-IB exhibited the least lateral displacement (almost zero) at wall facing and vertical displacements increments at the top of the abutment compared to those of the GRS-IBS and IB. The presence of the reinforcements (GRS-IB) reduced the vertical displacement increments by 4.7 and 1.3 times (max) compared to IB after the applied general traffic and railway loads, respectively. In addition, the numerical results revealed that the GRS-IB showed the least displacement curves in response to the dynamic load. Generally, the results revealed that the GRS-IB performed ahead of both the GRS-IBS and IB considering the internal and external behavior under static and dynamic loading.

Experimental study of a geosynthetic-reinforced soil bridge abutment

The article presents an experimental study of a geosynthetic-reinforced soil (GRS) bridge abutment (BA). The BAs are seated on a saturated soft foundation layer and support a 16 m long concrete bridge. Laboratory tests were conducted on the foundation soil, geogrid, and fill material. The BA is constructed from 14 geogrids and has a total height of 4.2 m. The strain values in the geogrids were measured and recorded during the construction of the abutments and after installation of the bridge structure. The test results show that more than 50% of the total strain in the geogrids was developed during the construction of the BAs, mostly embedded in the ground. The remainder of the measured strain was a consequence of installing the prefabricated bridge girders, back fill placement, concreting the top slab, and placing the asphalt concrete. The strain distribution along the geogrids shows that the maximum strain was recorded below the sill, and was 50% higher than at the center of the BA. Based on an analysis of the construction costs, it can be concluded that conventional reinforced concrete abutments could cost up to five times the amount of optimally designed GRS-BAs.

Numerical study of geosynthetic reinforced soil bridge abutment performance under static and seismic loading considering effects of bridge deck

Although the use of Geosynthetic Reinforced Soil (GRS) bridge abutments has been increasing, the seismic performance of such structures has remained a significant concern due to their unknown behavior in load-bearing and stress distribution under bridge load and seismic conditions simultaneously. This paper investigates the static and dynamic response of GRS bridge abutment. A series of numerical models representing the realistic field conditions of these structures, including two reinforced soil walls and a single span deck that restrains the top of walls, rather than equivalent surcharge load, was developed. The calibrated numerical model in FLAC program was used to evaluate the effects of horizontal restraint from the deck on the GRS wall displacements and reinforcement loads at the end of construction and under harmonic base acceleration up to 0.5 g. Results indicated that the restraint mobilized from the bridge deck presence, considerably affected the results at both the end of construction and after the dynamic load was applied. Moreover, a series of the parametric studies were performed to investigate the influences of backfill soil relative compaction, reinforcement stiffness, reinforcement length, and reinforcement vertical spacing on the response of GRS abutments at the end of construction and post dynamic state.

Limit analysis of bearing capacity and failure geometry of GRS bridge abutments

The paper presents analytical investigation of bearing capacity of geosynthetic reinforced soil (GRS) bridge abutments with vertical or nearly vertical facing batter angle. A limit analysis (LA) method is proposed using a y-shaped failure mechanism to determine the bearing capacity and the corresponding failure surface geometry within GRS bridge abutments. The proposed method is validated against results from numerical simulations and limit-equilibrium methods. Parametric analyses are subsequently carried out to examine the effects of backfill strength, reinforcement properties, and abutment geometry on the bearing capacity and failure surface geometry of GRS bridge abutments.

Physical Model Tests of Half-Scale Geosynthetic Reinforced Soil Bridge Abutments. II: Dynamic Loading

Physical Model Tests of Half-Scale Geosynthetic Reinforced Soil Bridge Abutments. II: Dynamic Loading

Geosynthetic-reinforced soil structures for railways and roads: development from walls to bridges

The development and construction of various types of geosynthetic-reinforced soil (GRS) structures for railways, roads and others, mainly for railways, for the last 35 years in Japan is described. In the 1980s, GRS retaining wall (RW) with full-height rigid (FHR) facing was developed. The FHR facing is constructed firmly connected to reinforcement layers after the reinforced backfill and subsoil has deformed sufficiently. In the early 1990s, GRS Bridge Abutment supporting one end of a simple girder at the top of the FHR facing was developed. In the early 2000s, GRS Integral Bridge was developed, which structurally integrates both ends of a continuous girder to the top of the FHR facings of a pair of GRS RWs. The total wall length of these GRS structures became about 185 km by June 2019 with no problematic case. The use of FHR facing, the staged construction of FHR facing and the structural integration for GRS Integral Bridge are the three major breakthroughs for the development of these GRS structure technologies.

Physical Model Tests of Half-Scale Geosynthetic Reinforced Soil Bridge Abutments. I: Static Loading

AbstractThis paper presents experimental results from physical model tests on four half-scale geosynthetic reinforced soil (GRS) bridge abutment specimens constructed using well-graded angular back...

Determining optimal designs for geosynthetic-reinforced soil bridge abutments

The article presents a parametric study of optimal designs for geosynthetic-reinforced soil (GRS) bridge abutments. A mixed integer design optimization model GRS-BA was developed, which is comprised of an accurate objective function of the construction costs. The cost objective function was constrained by a set of geotechnical and design conditions that were in accordance with current practice rules and recommendations. The optimal design recommendation for GRS bridge abutments was developed. A typical example of such an abutment is presented in order to compare design solutions derived from conventional design methods with solutions obtained from the proposed optimal design procedure.

Transverse shaking table test of a half-scale geosynthetic reinforced soil bridge abutment

This paper presents an experimental study on the response of a half-scale geosynthetic reinforced soil (GRS) bridge abutment subjected to shaking in the direction transverse to the bridge beam. The specimen geometry, reinforcement stiffness, soil modulus, applied surcharge stress and characteristics of the earthquake motions were scaled according to established similitude relationships for shaking table tests in a 1g gravitational field. The GRS bridge abutment was constructed using modular facing blocks, well-graded angular sand and uniaxial geogrid reinforcement, in both the longitudinal and transverse directions. Facing displacements, bridge seat settlements, accelerations, vertical and lateral soil stresses, reinforcement strains, and bridge seat and bridge beam interactions were measured during a series of input motions. The average incremental residual bridge seat settlement was 4.7 mm after the Northridge motion, which corresponds to a vertical strain of 0.22% for the lower GRS fill. After the series of motions, the maximum residual tensile strains occurred near the facing block connections for the lowermost reinforcement layer and under the bridge seat for higher reinforcement layers.

Passive Force–Displacement Behaviour of GRS Bridge Abutments

Many bridge abutments suffered severe damages due to pounding of superstructure elements of the bridge during seismic excitation. Collision of the girder is resisted by passive pressures mobilised in the backfill soils. Seismic load on the bridge structure causes the bridge abutments to undergo lateral translation (Δ) and rotation. The present study focuses on the evaluation of passive force (Pp) developed in the reinforced backfills of the geosynthetic-reinforced soil (GRS) bridge abutments. The GRS abutments of nine configurations with three different geogrid spacing and three different geogrid lengths are modelled using finite element (FE) approach under lateral push. Hypoplastic soil constitutive model with inter-granular strain concept is used to model the soil behaviour. User material subroutine, VUMAT is developed to simulate the soil behaviour in Abaqus. The maximum passive resistance (Pp,ult) increases by 12% in the GRS abutments with closer geogrid spacing.

A Generic Design Protocol for Geosynthetic Reinforced Soil Foundation

This technical note presents a generic step-by-step design protocol based on consideration of bearing capacity of reinforced soil foundation (RSF) on a level ground. The technical note begins with a synopsis of notable studies on bearing capacity of geosynthetic reinforced soil (GRS) and a brief description of an analytical model for load-carrying capacity of closely-spaced soil-geosynthetic composites. The generic RSF design protocol was developed based on findings of the notable studies and the analytical model. Specifically, the design protocol determines (i) reinforcement configuration of RSF (including reinforcement depths, spacing, and width), (ii) required reinforcement stiffness and strength for selection of reinforcement in RSF, and (iii) the increase in ultimate bearing capacity of RSF if the width of RSF is increased to fulfill design requirements A design example for RSF of a GRS bridge abutment is also given to illustrate how the design protocol can be applied.

Numerical study on maximum reinforcement tensile forces in geosynthetic reinforced soil bridge abutments

This paper presents a numerical study of maximum reinforcement tensile forces for geosynthetic reinforced soil (GRS) bridge abutments. The backfill soil was characterized using a nonlinear elasto-plastic constitutive model that incorporates a hyperbolic stress-strain relationship with strain softening behavior and the Mohr-Coulomb failure criterion. The geogrid reinforcement was characterized using a hyperbolic load-strain-time constitutive model. The GRS bridge abutments were numerically constructed in stages, including soil compaction effects, and then loaded in stages to the service load condition (i.e., applied vertical stress = 200 kPa) and finally to the failure condition (i.e., vertical strain = 5%). A parametric study was conducted to investigate the effects of geogrid reinforcement, backfill soil, and abutment geometry on reinforcement tensile forces at the service load condition and failure condition. Results indicate that reinforcement vertical spacing and backfill soil friction angle have the most significant effects on magnitudes of maximum tensile forces at the service load condition. The locus of maximum tensile forces at the failure condition was found to be Y-shaped. Geogrid reinforcement parameters have little effect on the Y-shaped locus of the maximum tensile forces when no secondary reinforcement layers are included, backfill soil shear strength parameters have moderate effects, and abutment geometry parameters have significant effects.

Numerical Simulation of Deformation and Failure Behavior of Geosynthetic Reinforced Soil Bridge Abutments

This paper presents a numerical investigation of the deformation and failure behavior of geosynthetic reinforced soil (GRS) bridge abutments. The backfill soil was characterized using a nonlinear elastoplastic constitutive model that incorporates a hyperbolic stress–strain relationship with strain-softening behavior and the Mohr–Coulomb failure criterion. The geogrid reinforcement was characterized using a hyperbolic load–strain–time model. The abutments were numerically constructed in stages, including soil compaction effects, and then monotonically loaded in stages to failure. Simulation results indicate that a nonlinear reinforcement model is needed to characterize deformation behavior for high applied stress conditions. A parametric study was conducted to investigate the effects of reinforcement, backfill soil, and abutment geometry on abutment deformation and failure behavior. Results indicate that reinforcement vertical spacing, reinforcement stiffness, backfill soil friction angle, and lower GRS wall height are the most significant parameters. The shape of the failure surface is controlled primarily by abutment geometry and can be approximated as bilinear.