Outline

  • Abstract
  • Keywords
  • 1. Introduction
  • 2. Overview of Current Design Practice
  • 3. Minimum Reinforcement Length Required for Failure Modes
  • 3.1. External Stability
  • 3.2. Internal Stability
  • 4. Parametric Study
  • 4.1. Method of Approach
  • 4.2. Parameter Value Ranges and Baseline Case
  • 5. Results
  • 5.1. Summary
  • 5.2. Effect of Wall Height
  • 5.3. Effect of Backfill/retained Soil
  • 5.4. Effect of Reinforcement Vertical Spacing
  • 5.5. Effect of Reinforced Soil
  • 5.6. Effect of Surcharge
  • 5.7. Effect of Foundation Soil
  • 6. Sensitivity Analyses
  • 7. Summary and Discussion of Results
  • 8. Conclusions
  • References

رئوس مطالب

  • چکیده
  • کلیدواژه ها
  • 1. مقدمه
  • 2. مروری بر شیوه طراحی کنونی
  • 3. حداقل طول آرماتور مورد نیاز برای حالات شکست
  • 3. 1. پایداری خارجی
  • 3. 2. پایداری داخلی
  • 4. مطالعه پارامتری
  • 4. 1. روش رویکرد
  • 4. 2. محدوده مقادیر پارامتر و مورد پایه
  • 5. نتایج
  • 5. 1. خلاصه
  • 5. 2. تاثیر ارتفاع دیوار
  • 5. 3. تأثیر خاک سطحی/انباشته
  • 5. 4. تاثیر فاصله عمودی تقویت
  • 5. 5. تأثیر خاک مسلح
  • 5. 6. تاثیر اضافه بار
  • 5. 7. تأثیر خاک پایه
  • 6. تحلیل حساسیت
  • 7. چکیده نتایج و بحث در مورد آن
  • 8. نتیجه گیری

Abstract

Current design practice of reinforced soil retaining walls is based on the limit equilibrium approach. The walls are designed for both external and internal stability criteria. Design reinforcement length should be such that minimum required safety factors are fulfilled for all failure modes. Most agencies require minimum reinforcement length equal to 70 percent of wall height. However, it is not always possible to have enough space behind a wall to accommodate these required reinforcement lengths due to an existing natural rock formation, man-made shoring system, or the presence of another reinforced soil retaining wall. This study was performed to investigate governing failure mode in determining the required minimum reinforcement length and also to investigate the possibility of shortening the specified minimum reinforcement lengths. Effect of different parameters involved in the design of reinforced soil retaining walls on the required minimum reinforcement length and the governing failure mode were studied. Parameters considered included wall height, surcharge, reinforcement vertical spacing, reinforced soil properties, backfill/retained soil properties, and foundation soil properties. Results indicated that both external and internal failure modes can be governing criteria in determining the required minimum reinforcement length depending on the parameters involved for a specific wall. In addition, it may be possible to use reinforcement lengths as low as almost 50 percent of the wall height, instead of 70 percent as required by many agencies around the world. This paper presents the results of parametric studies conducted, including the effect of different parameters on the required minimum reinforcement length and the governing failure criteria.

Keywords: - - - - - - - -

Conclusions

Governing failure mode in determining the minimum design reinforcement length for various parameters involved in the design of reinforced soil retaining walls has been studied. A series of equations were derived using current design practice to calculate the required minimum reinforcement length for each performance criterion. Governing failure modes determining the reinforcement lengths and shortest possible lengths that can be used for walls under varying conditions were investigated. Based on the variables and ranges considered for the parametric study performed during this study, the following conclusions are drawn:

• The minimum required reinforcement length can be governed by both external and internal failure modes, based on the parameter values involved and would be case specific. • The pullout, internal stability mode, is the most common failure mode that generally governs the minimum reinforcement length in geogrid reinforced walls. However, designers should be aware that the governing failure mode may shift from pullout to eccentricity or bearing capacity failure modes (external stability) depending on the parameters involved.

• Friction angle of soils involved, especially in the reinforced zone, has the most influence on the minimum reinforcement length. By using soils with higher friction angle in the reinforced zone, it is possible to reduce reinforcement lengths up to 30 percent for some conditions.

• The minimum reinforcement length required usually ranges between 0:5H to 0:7H, depending on the properties involved.

• It is possible to use reinforcement lengths less than 0:7H, usually specified by the codes.

Reinforcement lengths approximately 0:5H are possible with the current performance criteria, if favorable conditions exist. If lower safety factors are allowed, it may be possible to reduce the reinforcement lengths even further. When shorter reinforcement lengths are used, special attention should be given to wall deformations, as the wall deformations increase as reinforcement lengths decrease.

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