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Geosynthetic-Reinforced Soil (GRS) mass, comprising soil and layers of geosynthetic reinforcement, is not a uniform mass. To examine the behavior of a GRS mass by a laboratory test, a sufficiently large-size specimen of soil and reinforcement is needed to produce a representative soil-geosynthetic composite. This paper presents a generic test, refe...
Citations
... In an element test, the aim would be to determine the "properties of the material" being tested; whereas, determination of the "behavior of a structure" would be the aim of a model test. For the former, the stresses (Wu et al., 2012). ...
... They proposed an analytical model to predict the load carrying capacity for closely-spaced reinforced soil based on a semiempirical factor (i.e., W factor) considering the effect of reinforcement spacing S v and the maximum particle diameter of the backfill soil d max . The model proposed by Wu and Pham (2013) was verified using results of a series of large scale model tests (Elton and Patawaran, 2004;Adams et al., 2007Adams et al., , 2014Wu et al., 2012). The common point among these large scale model tests is that d max was larger than 10 mm. ...
... The smooth surface of the polytef membrane could reduce the friction between the soil and the box, thus ensuring that the model tests conducted in this study were under a plane strain condition. Similar methods have been successfully used in laboratory plane strain model tests to reduce the friction and the results were satisfactory (Huang and Tatsuoka, 1990;Kongkitkul et al., 2007;Wu et al., 2012). ...
... However, if course-grained soil was used as backfill soil and the maximum particle size was larger than 10 mm, the influence of the value of 0. 7 S S ( / ) v ref became less significant and Eq. (2) was verified to be able to reasonably predict the bearing capacity of the GRS mass (Wu et al., 2012). ...
Geosynthetic reinforced soil (GRS) structures have gained popularity in replacing concrete rigid piles as abutments to support medium or small-spanned bridge superstructures in recent years. This study conducted 13 model tests to investigate the ultimate bearing capacity of the GRS mass when sand was used as backfill soil. The GRS mass was constructed and loaded to failure under a plane strain condition. Test results were compared with two analytical solutions available in literature. This study also proposed an analytical model for predicting the ultimate bearing capacity of the GRS mass based on the Mohr-Coulomb failure criterion. The failure surface of the GRS mass was described by the Rankine failure surface. The effects of compaction and reinforcement tension were equivalent to increased confining pressures to account for the reinforcing effects of the geosynthetic reinforcement. The proposed model was verified by the results of the model tests conducted in this study and reported in literature. Results indicated that the proposed model was more capable of predicting the ultimate bearing capacity of the GRS mass than the other two analytical solutions available in literature. The proposed model can be used to predict the ultimate bearing capacity of GRS structures when sand was used as backfill material. In addition, a parametric study was conducted to investigate the effects of friction angle of backfill soil, reinforcement spacing, reinforcement strength, and reinforcement stiffness on the ultimate bearing capacity of the GRS mass calculated with and without compaction effects. Results showed that the ultimate bearing capacity of the GRS mass was significantly affected by the friction angle of backfill soil, reinforcement spacing and strength. Compaction effects resulted in an increase in the ultimate bearing capacity of the GRS mass.
... The behavior of geosynthetic reinforced soil mass has been the subject of many studies. The significant benefit of small reinforcement spacing (on the order of 0.1 to 0.3 m) for increased stiffness and strength of a reinforced soil mass has been investigated analytically by Wu and Pham [17] and verified by many full-scale experiments (e.g., [3,8,10,12,16]) as well as hundreds of walls in actual construction [4,5]. The ultimate load-carrying capacity of a reinforced soil mass has been found to be well over 1,000 kPa with medium strength geosynthetic reinforcement at 0.2-m spacing and a well-compacted granular backfill. ...
There have been ongoing arguments whether heavy blocks and/or facing connection enhancement elements, such as pins, lips, or keys, are needed for facing stability of segmental reinforced soil walls with geosynthetic reinforcement. This study was undertaken to examine facing connection forces for vertical or near vertical segmental reinforced soil walls with purely friction connections. In the study, the lateral earth pressure was assumed to be the Rankine active earth pressure—an assumption that has been employed by most current design methods of reinforced soil walls with extensible reinforcement. Based on force equilibrium, the driving forces and resisting forces at facing connections are derived for situations where reinforcement is at every course of facing blocks and at every three courses of facing blocks. For the latter, both the connection forces at geosynthetic–block interface and at block–block interface are considered. Based on these connection force equations, generalized equations of driving and resisting forces for any number courses of blocks between adjacent reinforcement layers are developed. Using the generalized connection force equations, comparisons of driving and resisting forces for some common parameter values and under typical conditions of reinforced soil walls were performed. The significance of reinforcement spacing, as well as the need, or lack thereof, for heavy facing blocks and/or additional connection measures on facing stability is discussed. The benefit of small reinforcement spacing is demonstrated. A common perception that a higher wall is more susceptible to connection failure is true only for segmental walls with larger reinforcement spacing.
... Verification of the analytical model [Eq. (17)] for predicting the load-carrying capacity of a GRS composite is carried out by comparing the model calculation results with measured data from (1) a series of generic soil-geosynthetic composite (GSGC) tests (Pham 2009;Wu et al. 2011Wu et al. , 2012, (2) unconfined compression tests (Elton and Patawaran 2004), and (3) available field-scale tests (as of 2011). The soils involved in the comparisons described previously range from uniform fine sand to crushes gravel, the geosynthetic reinforcement varies from lightweight nonwoven to heavyweight woven geotextiles, and the reinforcement spacing ranges from 0.15 to 0.3 m. ...
In current design methods for reinforced soil walls, it has been tacitly assumed that reinforcement strength and reinforcement spacing play an equal role. This fundamental design assumption has led to the use of larger reinforcement spacing (0.3-1.0 m) in conjunction with stronger reinforcement to reduce construction time. Recent studies, however, have clearly indicated that the role of reinforcement spacing is much more significant than that of reinforcement strength. With closely spaced (reinforcement spacing <= 0.3 m) reinforcement, the beneficial effects of geosynthetic inclusion is significantly enhanced, and the load-deformation behavior can be characterized as that of a composite material. A reinforced soil mass with closely spaced geosynthetic reinforcement is referred to as geosynthetic-reinforced soil (GRS). In this study, an analytical model is developed for predicting the ultimate load-carrying capacity and required reinforcement strength of a GRS mass. The model was developed based on a semiempirical equation that reflects the relative roles of reinforcement spacing and reinforcement strength in a GRS mass. Using measured data from field-scale experiments available to date, it is shown that the analytical model is capable of predicting the ultimate load-carrying capacity and required reinforcement strength of a GRS mass with good accuracy. (C) 2013 American Society of Civil Engineers.
... (6,7) Several large scale tests have also been conducted. (7,8,9) For the aggregates recommended by FHWA for bridge support, large scale tests are required to adequately predict performance of a full-scale GRS abutment. (1) The proposed FHWA PT has been shown to accurately predict both the strength limit and the service limit for GRS abutments. ...
FOREWORD The use of geosynthetic reinforced soil (GRS) for load bearing applications such as bridge abutments and integrated bridge systems (IBS) has expanded among transportation agencies looking to save time and money while delivering a better and safe product to the traveling public. GRS has been identified by the Federal Highway Administration (FHWA) as a proven, market-ready technology, and is being actively promoted through its Every Day Counts (EDC) initiative. FHWA interim design guidance for GRS abutments and IBSs is presented in Publication No. FHWA-HRT-11-026. The guidance includes the procedure and use of the GRS performance tests, also termed a mini-pier experiment. This report presents a database of nineteen performance tests performed by the FHWA, largely at the Turner-Fairbank Highway Research Center. It also presents findings, conclusions, and suggestions regarding various design parameters related to the performance of GRS, such as backfill material, reinforcement strength, reinforcement spacing, facing confinement, secondary reinforcement, and compaction. A reliability analysis for load and resistance factor design (LRFD) was performed based on the results of this performance testing to determine a calibrated resistance factor for the soil-geosynthetic capacity equation. The results of this analysis can also be used by bridge designers to estimate capacity and deformation of GRS. In addition, an insight into the behavior of GRS as a new composite material due to the close reinforcement spacing is described.
The Federal Highway Administration (FHWA) has recently developed a new bridge abutment system, known as Geosynthetic-Reinforced Soil-Integrated Bridge System (GRS-IBS). The term “GRS” refers to a soil mass that is reinforced internally by closely spaced (reinforcement spacing not more than 0?3 m) horizontal layers of geosynthetic sheets. The design protocol of GRS-IBS recommends a “performance test” be conducted to estimate the load-deformation behavior of a GRS-IBS system. The performance test involves a cuboidal block-faced GRS mass that is subjected to increasing axial loads. More than 100 GRS-IBS have been constructed in the US since its introduction in 2011. In light of the rapid development of the new bridge abutment system, an analytical model is developed for predicting the load-deformation behavior of the performance test up to the ultimate load-carrying capacity that is determined from the “W-equation.” This paper presents the analytical model and validation of the analytical model. Validation of the model was accomplished by comparing the analytical results with measured data of four sets of performance tests. The paper also presents a new interpretation of the W-equation, an equation that has been shown to be capable of predicting the ultimate load-carrying capacity of a GRS mass with very good accuracy. The analytical model is seen to give very good predictions of the load-deformation behavior of the performance tests up to the ultimate load-carrying capacity; hence may be used to supplement or replace the FHWA performance test that is rather laborious and time-consuming to conduct.
