CRITICAL ANALYSIS OF INTERNAL STABILITY METHODS FOR ANALYSIS OF REINFORCED SOIL WALLS (original) (raw)
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Geosynthetic Reinforced Soil Structures are widely deployed in variety of applications around the world. And the evaluation of these structures in special loading conditions such as point and linear loads over abutments and also special geometrical conditions such as the nearness to adjacent structures, for example soil nailed wall, may be frequently necessary. There are several guidelines and softwares that are normally being used for design of the above-mentioned structures, However, most of them (if not all) do not make any recommendation for critical conditions and miscellaneous details such as connection of reinforcing element to the wall facade and to the retained zone, while those can jeopardize the whole structure stability. In this article, in order to evaluate the above mentioned topics, results of some parametric studies for an assumed abutment structure are presented. These analysis are based on various guidelines such as FHWA (NHI-10-024., 2009), BS (8006. 2010), Iranian national Code (No. 308, 2005), and guideline of Road Congress India 2014. Also several softwares such as PLAXIS, FLAC2D, MSEW and ReSSA are used. Finally a comparison between results is made and the advantages and limitations of each code and software are addressed.
Engineering Structures, 2014
This paper presents the results of a parametric study conducted to investigate the effect of different reinforcement types on required minimum reinforcement length and governing design criteria of mechanically stabilized earth walls. There are several reinforcement types with varying properties used in these walls. The reinforcement should be long enough to satisfy both external and internal stability criteria. The minimum reinforcement length criteria vary throughout the world; however most specifications and guidelines require that minimum length should be equal to 70% of wall height. A natural rock formation behind the wall or manmade shoring system may cause limitations on the reinforcement length. The focus of this paper is to investigate the required minimum reinforcement length and the criteria governing the design length for four different reinforcement types; geogrids, geotextiles, metal strips, and metal bar mats. Effect of different parameters on the required minimum reinforcement length and the governing design criteria were investigated for these four reinforcement types. The parameters considered included wall height, surcharge, reinforcement vertical spacing, reinforced soil properties, backfill/ retained soil properties, and foundation soil properties. The results indicate that, depending on the parameters involved, the reinforcement type can affect both the required reinforcement length and the governing design criteria. The study also shows that reinforcement lengths shorter than 70% of wall height, as low as 50%, are possible in some cases. Among the four reinforcement types considered, the metal strips usually require the longest lengths; however, it is possible to reduce the required minimum reinforcement lengths of the metal strips by increasing the coverage ratio.
Global Stability Analysis of Reinforced Earth Wall Using Basal Reinforcement
International Journal for Science and Advance Research In Technology (IJSART), 2020
The analysis of global stability of retaining structures has become a crucial aspect to consider before construction. Global stability relies on geometry of soil and is primarily dependent on soil conditions. Geotextiles with high tensile strength can contribute to the load carrying capacity of soil that is poor in tension and good in compression and thus help improve global stability of structures. This project is focusses on improving the safety factor of the reinforced earth wall by providing ParaWeb Geogrids between the soil layers as reinforcement and conducting a Global Stability Analysis on Slide 5.0 software. The model is designed on the slope stability software that depicts 8 layers of soil having different soil properties. ParaWeb Geogrid strips are provided between two walls and compacted after each layer. Each strip is having a specific tensile strength and is on a measured height. On the top-most layer of the soil, a Uniformly Distributed Load (UDL) is applied a basal reinforcement is placed at the bottom. The research paper shows how the safety factor can be improved by changing the tensile strengths of reinforcements in an earth wall so as to make it safe for construction and thus, save the structure from unforeseeable hazards.
Geotextiles and Geomembranes, 2011
A mechanically stabilized earth (MSE) wall behaves as a flexible coherent block able to sustain significant loading and deformation due to the interaction between the backfill material and the reinforcement elements. The internal behaviour of a reinforced soil mass depends on a number of factors, including the soil, the reinforcement and the soil/structure interaction and represents a complex interaction sol/ structure problem. The use of parameters determined from experimental studies should allow more accurate modelling of the behaviour of the MSE structures. In this article, a reference MSE wall is modelled from two points of view: serviceability limit state "SLS" and ultimate limit state "ULS". The construction of the wall is simulated in several stages and the soil/ interface parameters are back analysed from pullout tests. An extensive parametric study is set up and permits to highlight the influence of the soil, the reinforcement and the soil/structure parameters. The behaviour of MSE walls with several geosynthetic straps is compared with the metallic one. Several constitutive models with an increasing complexity have been used and compared. The results obtained from stress-deformation analyses are presented and compared. The use of geosynthetic straps induces more deformation of the wall but a higher safety factor. To design theses walls the important parameters are: the soil friction, the cohesion, the interface shear stiffness and the strip elastic modulus. It is shown that for wall construction that involves static loading conditions, the modified DuncaneChang model is a good compromise but induces slightly lower strip tensile forces due to the fact that it do not take into account of dilatancy before failure.
Proceedings of the Third International Conference on Sustainable Innovation 2019 – Technology and Engineering (IcoSITE 2019), 2019
Geotextile is a geosynthetic constructed for embankment functioning as reinforcement to support tension force from the loading design and decrease the failure potential of embankments. In accordance with the Federal Highway Administration (FHWA) standard, geotextiles are designed under static and dynamic loading on a 7.5 m-high earth wall at Pondok Hijau, Bandung. The reinforced earth wall is known as a mechanically stabilized earth wall. The FHWA design calculation uses the simplified coherent gravity method, while the final analysis is based on the limit equilibrium and finite element methods. The FHWA calculation produces a preliminary design of a 6.5 m-long geotextile with 200 kN/m ultimate tensile strength placed at every 30 cm at the first layer, 50 cm from the second to the seventh layer, and 30 cm from the eighth to the twenty-first layer. The maximum horizontal deformations of the geotextile because of static and dynamic loading are 2.94 and 4.6 cm, respectively. The wall itself also deforms by as much as 5.07 and 7.93 cm owing to static loading and dynamic loading, respectively. The allowable deformation of the geotextile and the wall are 27.3 and 10 cm, respectively. Hence, the preliminary design is valid according to the deformation requirements.
Can Geotech J, 2007
In this paper the K-stiffness method is extended to the case of c-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-soil backfills when compared to the current American Association of State Highway and Transportation Officials simplified method.
Numerical Study of the Behavior of Back-to-Back Mechanically Stabilized Earth Walls
Geotechnics, 2021
Back-to-back mechanically stabilized earth (MSE) walls can sustain significant loadings and deformations due to the interaction mechanisms which occur between the backfill material and reinforcement elements. These walls are commonly used in embankments approaching bridges, ramps, and railways. The performance of a reinforced wall depends on numerous factors, including those defining the soil, the reinforcement, and the soil/reinforcement interaction behavior. The focus of this study is to investigate the behavior of back-to-back mechanically stabilized earth walls considering synthetic and metallic strips. A two-dimensional finite difference numerical modeling is considered. The role of the soil friction angle, the distance of the reinforcement elements, the walls’ width to height ratio, and the quality of the soil material are investigated in a parametric study. Their effects on the critical failure surface, shear displacements, wall displacements, and tensile forces on the reinfo...
PARAMETRIC STUDY FOR NARROW MECHANICALLY STABILIZED EARTH WALLS
Previous studies defined Narrow Mechanically Stabilized Earth, NMSE, walls as a retaining wall with aspect ratio (wall width to its height, L/H) less than 0.70 as in traditional walls. Some studies investigated its behavior and its failure planes compared to those of traditional walls. In this paper, parametric study using finite element analysis PLAXIS, 8.2 has been introduced to discuss global factor of safety, FS, maximum horizontal displacement, Ds, maximum tension force of reinforcement element, Tmax, and active earth pressure coefficient, ka, as a function of different aspect ratio of NMSE wall, L/H, reinforcing elements spacing, S, elastic axial stiffness of reinforcement element, EA, wall batter, 1/m, soil friction angle, φ, and wall height, H. The results indicated that increasing aspect ratio increases the factor of safety, maximum horizontal displacement, maximum tensile force and active earth pressure. Increasing elastic axial stiffness increases factor of safety, maximum tension force of reinforcement element while decreasing the maximum horizontal displacement.
Evolution of the Stability Work from Classic Retaining Walls to Mechanically Stabilized Earth Walls
Institutul Politehnic din Iasi. Buletinul. Sectia …, 2008
For the consolidation of soil mass and the construction of the stability works for roads infrastructure it was studied the evolution of these kinds of works from classical retaining walls-common concrete retaining walls, to the utilization in our days of the modern and competitive methods-mechanically stabilized earth walls. Like type of execution the variety of the reinforced soil is given by the utilization of different types of reinforcing inclusions (steel strips, geosynthetics, geogrids) or facing (precast concrete panels, dry cast modular blocks, metal sheets and plates, gabions, and wrapped sheets of geosynthetics).