Reinforced Soil Retaining Wall Testing, Modeling and Design (original) (raw)
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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 ...
Application of the Simplified Stiffness Method to Design of Reinforced Soil Walls
Journal of Geotechnical and Geoenvironmental Engineering, 2018
A new design methodology for estimating reinforcement loads in reinforced soil walls, termed the K 0-Stiffness Method, has been developed. This new method has been demonstrated to more accurately estimate reinforcement loads and strains in reinforced soil walls than do current design methodologies. Step-by-step procedures are provided to lead the designer through the reinforced soil wall internal stability design process using this new methodology. These step-by-step design procedures have been developed with a limit states design approach consistent with current design codes (in North America this is termed Load and Resistance Factor Design, or LRFD). Specifically, consideration has been given to strength and serviceability limit states. Load and resistance factors, based on statistical data where feasible, have been developed for use with this method. The results of examples from actual wall case histories were summarized and analyzed to assess how well the new methodology performs relative to current design practice. From this analysis of the design examples, the following was observed: • For geosynthetic walls, the K 0-Stiffness Method has the potential to reduce required backfill reinforcement capacity relative to current design methodology by a factor of 1.2 to 3. • For steel reinforced soil walls, the reduction in reinforcement capacity relative to what is required by current design methodology is more modest, on the order of 1.0 to 2.1. Given these findings, use of the K 0-Stiffness Method can result in substantial cost savings, especially for geosynthetic walls, because of reduced reinforcement needs.
Prediction of reinforcement loads in reinforced soil walls
Proper estimation of soil reinforcement loads and strains is key to accurate design of the internal stability of geosynthetic and steel reinforced soil structures. Current design methodologies use limit equilibrium concepts to estimate reinforcement loads for internal stability design, with empirical modifications to match the prediction to observed reinforcement loads at working stresses. This approach has worked reasonably well for steel reinforced walls but appears to seriously overestimate loads for geosynthetic walls. A large database of full-scale geosynthetic walls (16 fully instrumented, full-scale geosynthetic walls and 14 walls with limited measurements) and 24 fully instrumented, full-scale steel reinforced wall sections was utilized to develop a new design methodology based on working stress principles, termed the K-Stiffness Method. This new methodology considers the stiffness of the various wall components and their influence on reinforcement loads. Results of simple statistical analyses to evaluate the ratio of predicted to measured peak reinforcement loads in geosynthetic walls were telling: the AASHTO Simplified Method results in an average ratio of measured to predicted loads of 0.45 with a coefficient of variation (COV) of 91 percent, whereas the proposed method results in an average of 0.99 and a COV of 36 percent. The proposed method remains accurate up until the point at which the soil begins to fail (approximately 3 to 5 percent strain). For steel reinforced MSE walls the improvement was more modest: AASHTO's Simplified Method results in an average ratio of predicted to measured loads of 1.12 with a (COV) of 45 percent, whereas the new K-Stiffness Method results in an average of 0.95 and a COV of 32 percent. The objective of the method is to design the wall reinforcement so that the soil within the wall backfill will not reach a state of failure consistent with the notion of working stress conditions. This soil failure limit state is not considered in the design methods currently available, yet, given the research results presented herein, is likely to be a controlling limit state for geosynthetic structures. The fruit of this research is a more accurate method for estimating reinforcement loads, thereby reducing reinforcement needs and improving the economy of reinforced soil walls. The scope of this research was limited to reinforced soil walls that utilize granular (non-cohesive, relatively low silt content) backfill.
Static Response of Reinforced Soil Retaining Walls with Nonuniform Reinforcement
International Journal of Geomechanics, 2001
The structural response of reinforced-soil wall systems with more than one reinforcement type (nonuniform reinforcement) is investigated using a numerical approach. The selected reinforcement types and mechanical properties represent actual polyester geogrid and woven wire mesh products. The model walls are mainly of wrapped-face type and have different reinforcement lengths, arrangements, and stiffness values. Additional wall models with tiered and vertical gabion facings are included for comparison purposes. The numerical simulation of wall models has been carried out using a finite difference-based program and includes sequential construction of the wall and placement of reinforcement at uniform vertical spacing followed by a sloped surcharge. The wall lateral displacements and backcalculated lateral earth pressure coefficient behind the facing in all nonuniform reinforcement wall models show a clear dependence on relative stiffness values of reinforcement layers at different elevations. An equation is proposed that can be used to predict the maximum reinforcement load in nonuniform reinforced wrappedface walls of given backfill types and reinforcement configurations similar to those investigated in this study.
Seismic behaviour of rigid-faced reinforced soil retaining wall models: reinforcement effect
Geosynthetics International, 2009
This paper presents the results of shaking table tests on geotextile-reinforced wrapfaced soil-retaining walls. Construction of model retaining walls in a laminar box mounted on a shaking table, instrumentation, and results from the shaking table tests are discussed in detail. The base motion parameters, surcharge pressure and number of reinforcing layers are varied in different model tests. It is observed from these tests that the response of the wrap-faced soil-retaining walls is significantly affected by the base acceleration levels, frequency of shaking, quantity of reinforcement and magnitude of surcharge pressure on the crest. The effects of these different parameters on acceleration response at different elevations of the retaining wall, horizontal soil pressures and face deformations are also presented. The results obtained from this study are helpful in understanding the relative performance of reinforced soil-retaining walls under different test conditions used in the experiments.
Mechanical performance and sustainability assessment of reinforced soil walls
2023
Soil reinforced retaining wall structures are materially more efficient than competing construction solutions such as gravity and cantilever walls. Nevertheless, the behaviour and interactions between the component materials are complex and not fully understood. Current design methods are typically limited to simple cases with respect to material properties, geometry, and boundary conditions. Advanced numerical models using finite element and/or finite difference methods offer the possibility to extend the understanding of these systems and to predict wall performance under operational conditions. Mechanical Performance and Sustainability Assessment of Reinforced Soil Walls Abstract / Resum / Resumen social/functional) as judged by different stakeholders. Reinforced soil walls turned out to be the best choice in most cases analyzed, based on a quantitative end score. The models and analysis methodologies developed as part of this Thesis work have improved understanding of the behavior of these structures, and offered possibilities to improve and optimize designs in the future.
Field Performance of a 17 m-High Reinforced Soil Retaining Wall
Geosynthetics International, 2001
A 17 m-high steel strip reinforced soil retaining wall was instrumented to compare field measurements with predictions given by the design guidelines of the American Association of State Highway and Transportation Officials (AASHTO) 1996 Standard Specifications and the AASHTO 1999 Interim Revisions. The AASHTO models were conservative with respect to external lateral earth pressures and lateral earth pressures on the facing panels. On average, the AASHTO 1996 and 1999 models overestimated lateral pressure at the facing by 94 and 142%, respectively. Measured values of foundation bearing stress were generally in good agreement with values calculated using soil unit weight and depth, except that the average force from the facing panels on the leveling pad was twice that of the weight of the panels themselves. This discrepancy is attributed to shear stress on the back of the facing panels and vertical loads transferred to the panels through the strip connection clips. The location of the zone of maximum strip tension was in good agreement with the assumed failure surface. On average, the AASHTO 1996 and 1999 models underestimated maximum strip tensions by 17 and 8% and overestimated strip connection tensions by 127 and 154%, respectively. Finally, the apparent soil-reinforcement friction coefficient for the ribbed steel strips exceeded values specified in the AASHTO models by an average of 132%.
Seismic Response of Rigid Faced Reinforced Soil Retaining Walls
2012
Reinforced soil walls offer excellent solution to problems associated with earth retaining structures under seismic conditions. Among different types of reinforced soil walls, rigid faced walls are widely used in various infrastructure projects. Presented is the seismic response of such rigid faced reinforced soil retaining walls through numerical models. Development of numerical model for simulating the shaking table tests on rigid faced reinforced soil retaining walls and its application in investigating the seismic response of wall models are presented. These models are discussed in depth in the article. The results obtained from the numerical simulations are validated with that of experimental studies reported in the literature. Sensitivity analyses are conducted to understand the affect of different material properties like backfill friction angle, backfill dilation angle and stiffness of reinforcement on model response.
Numerical Model for Reinforced Soil Segmental Walls under Surcharge Loading
Journal of Geotechnical and Geoenvironmental Engineering, 2006
The construction and surcharge loading response of four full-scale reinforced-soil segmental retaining walls is simulated using the program FLAC. The numerical model implementation is described and constitutive models for the component materials ͑i.e., modular block facing units, backfill, and four different reinforcement materials͒ are presented. The influence of backfill compaction and reinforcement type on end-of-construction and surcharge loading response is investigated. Predicted response features of each test wall are compared against measured boundary loads, wall displacements, and reinforcement strain values. Physical test measurements are unique in the literature because they include a careful estimate of the reliability of measured data. Predictions capture important qualitative features of each of the four walls and in many instances the quantitative predictions are within measurement accuracy. Where predictions are poor, explanations are provided. The comprehensive and high quality physical data reported in this paper and the lessons learned by the writers are of value to researchers engaged in the development of numerical models to extend the limited available database of physical data for reinforced soil wall response.