Development of the K - stiffness method for geosynthetic reinforced soil walls constructed with c - soils (original) (raw)
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Canadian Geotechnical Journal, 2007
In this paper the K-stiffness method is extended to the case of c-ϕ soils using data obtained from a total of nine new case studies – six from Japan and three from the USA. A common feature in this new data set is that the walls were all constructed with a vertical face using backfill soils with a range of fines content. The walls varied widely with respect to facing type. This new data set together with previously published data for vertical walls is now used to isolate the effect of soil cohesion on reinforcement loads within the framework of the original K-stiffness method. The new data set is used to calibrate a modified K-stiffness method equation that includes a cohesion influence factor. The modified K-stiffness method is demonstrated to quantitatively improve the estimate of the magnitude and distribution of reinforcement loads for internal stability design of vertical-faced geosynthetic reinforced soil walls with c-ϕ soil backfills when compared to the current American Asso...
Refinement of K-stiffness Method for geosynthetic-reinforced soil walls
Geosynthetics International, 2008
The K-stiffness Method is an empirically-developed working stress method used to compute reinforcement loads for the internal stability design of geosynthetic-reinforced soil walls under serviceability conditions. In this paper, additional data from Japanese case studies for five full-scale field and three full-scale laboratory geosynthetic-reinforced soil walls are added to the database that was used to calibrate the original K-stiffness Method. One more case study from an instrumented wall in the USA is also introduced. Measured loads are compared with predicted loads using the current AASHTO Simplified Method and a modified version of the K-stiffness Method that has been adjusted by back-fitting model parameters to the extended database. The AASHTO Simplified Method is shown to be excessively conservative (on average) with respect to accurate prediction of reinforcement loads and to correlate poorly with measured values. The modified K-stiffness Method is demonstrated by statistical analysis to give ratios (bias) of average measured to predicted reinforcement load values close to 1 and coefficient of variation (COV) values for the maximum reinforcement load in a wall that are less than 25%.
Evaluation of K-Stiffness Method for Vertical Geosynthetic Reinforced Granular Soil Walls in Japan
SOILS AND FOUNDATIONS, 2007
In this paper the K-stiŠness Method as originally proposed by is re-examined using a total of six new case studies-ˆve from Japan and one from the USA. A common feature of the walls in this new data set is that the walls were all constructed with a vertical face and a granular backˆll. However, the walls varied widely with respect to facing type. This new data set together with data for vertical walls previously published by Allen and Bathurst (2002a,b) and is now used to isolate the eŠect of the facing stiŠness factor on reinforcement loads and to adjust the original equation that was developed to calculate its value. The paper also shows that predicted reinforcement loads using the current AASHTO Simpliˆed Method in the USA and the current PWRC method in Japan give the same reinforcement load predictions, and both grossly over-estimate the values deduced from measured strains. The new data set is used to slightly reˆne the estimate of the facing stiŠness factor used in the original K-stiŠness Method. The original and modiˆed K-stiŠness Method are demonstrated to quantitatively improve the estimate of the magnitude and distribution of reinforcement loads for internal stability design of vertical-faced geosynthetic reinforced soils walls with granular backˆlls when compared to the current American and Japanese methods.
CRITICAL ANALYSIS OF INTERNAL STABILITY METHODS FOR ANALYSIS OF REINFORCED SOIL WALLS
TJPRC, 2014
Due to growing restrictions on right-of-way, wetlands, or other space-limiting conditions, the demand for design and construction of Mechanically Stabilized Earth (MSE) Walls are increasing worldwide, in general and India in particular. There are two stages of analysis of reinforced earth walls, namely external stability and internal stability. Internal Stability deals with the tensile and pullout failure of the reinforcement. Different Codes/ Standards are available for analysis of reinforced earth walls. A study was undertaken to compare the approaches in these Codes. Therefore, this study emphasises on quantification and comparison of metallic reinforcements by analysis using Coherent Gravity Method as per British Standard(BS-8006) and Federal Highway Administration (FHWA-(NHI-10-024)). The results are compared and reported in this paper.
Canadian geotechnical journal, 2005
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.
Facing Effects in Geosynthetic-Reinforced Soil Structures
2004
This Paper outlines the Finite Element Method of analysis for simulating of Geosynthetic-Reinforced Soil Retaining Walls (GRS-RWs). Results of a parametric study to investigate the effect of facing including panel facing, segmental facing and wrapped facing on the behavior of GRS-RWs in terms of displacement of wall and forces in the reinforcements are presented. However this study is focused on the walls, because of the similarities to other forms of reinforced structures in facing such as slopes and abutments it can be applied to these structures too. This study shows that facing has a strong effect especially on the displacement of walls and should be taken into account in the design procedures which is not often concerned in analysis. RÉSUMÉ Ce Papier esquisse la Méthode d'Elément Finie d'analyse pour simulers de Murs De Soutènement de Sol GeosyntheticRenforcés (GRS-RWs). Les résultats d'une étude paramétrique pour examiner l'effet de revêtement y compris le pann...
Canadian Geotechnical Journal, 2006
Current limit equilibrium-based design methods for the internal stability design of geosynthetic reinforced soil walls in North America are based on the American Association of State Highway and Transportation Officials (AASHTO) Simplified Method. A deficiency of this approach is that the influence of the facing type on reinforcement loads is not considered. This paper reports the results of two instrumented full-scale walls constructed in a large test facility at the Royal Military College of Canada. The walls were nominally identical except one wall was constructed with a stiff face and the other with a flexible wrapped face. The peak reinforcement loads in the flexible wall were about three and a half times greater than the stiff-face wall at the end of construction and about two times greater at the end of surcharging. The stiff-face wall analysis using the Simplified Method gave a maximum reinforcement load value that was one and a half times greater than the measured value at ...
A simplified method for analysis of a piled embankment reinforced with geosynthetics
Geotextiles and Geomembranes, 2009
Piled embankments provide an economic solution to the problem of constructing embankments over soft soils. The piles and geosynthetic combination can alleviate the uneven surface settlements that sometimes occur in embankments supported by piles without reinforcement. The main focus of this paper is to present a new method for analysis of an embankment of granular fill on soft ground supported by a rectangular grid of piles and geosynthetic. This method is based on consideration of the arching effect in granular soil and similar to the method proposed by Low, B.]. The main refinements are: inclusion of a uniform surcharge load on the embankment fill, individual square caps were used, and taking into account the skin friction mechanism, which contributes to soil-geosynthetic interface resistance. Using this method, the influence of embankment height, soft ground depth, soft ground elastic modulus, and geosynthetic tensile stiffness on efficiency, stress concentration ratio, settlement ratio, tension of geosynthetic, and axial strain of geosynthetic are investigated. The results show that inclusion of a geosynthetic membrane can increase the fill load carried by piles. As a result, both the total and differential settlements of the embankment can be reduced. The new design method was verified against several current design methods. Theoretical solution showed that BS8006 [1995. Code of Practice for Strengthened/Reinforced Soils and other Fills. British Standards Institution, London, p. 162] and Guido, V.A., Plate loading tests on geogrid-reinforced earth slabs. In: Proceedings of the Geosynthetics '87, New Orleans, USA, IFAI, pp. 216-225] methods overpredict the vertical stress acting on the geosynthetic due to that the reaction of the soft ground on the geosynthetic is not considered in their methods. It also showed that the present method is in good agreement with Low