Design and Construction Guidelines for Geosynthetic-Reinforced Soil Bridge Abutments with a Flexible Facing (2006) / Chapter Skim
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From page 11... ...
. Despite their success, the rigid facing GRS bridgesupporting structures have found applications only in Japan, mostly because of their higher cost and longer construction time compared with GRS walls with flexible facings.
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The maximum reinforcement length was 15 m. The backfill material, a fine sand, was compacted to at least 95 percent Standard Relative Density to have a design friction angle of 32 deg.
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Cross-section of the Black Hawk bridge abutments (Wu et al., 2001)
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From page 14... ...
The upper tier reinforced soil mass was built to support the strip footing and the approach ramp. The abutments were constructed with the onsite soil, classified as SM-SC per ASTM D2487, and reinforced with layers of a woven geotextile at vertical spacing of 0.3 m.
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The lateral movement was reduced by a factor of 2.5 to 3 at 150 kPa. • After the first reloading cycles, there was no significant reduction of lateral and vertical displacements of GRS abutments in the subsequent reloading cycles.
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From page 16... ...
, the leveling pad settled vertically almost 5 mm during the construction of the front GRS wall up to the bridge foundation elevation and settled another 6 mm when the bridge and approaching roadway structures were placed. Post-construction performance of the Founders/Meadows bridge abutment was evaluated by Abu-Hejleh et al.
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17 The Colorado DOT provided the following guidelines for design and construction of GRS abutments: 1. The foundation soil for these abutments should be firm enough to limit the post-construction settlement of the bridge sill to 75 mm.
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Figure 2-7. Cross-section of the Feather Falls Trail bridge abutments, California (Keller and Devin, 2003)
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The GRS abutments have performed well since construction. Field Experiments of Bridge-Supporting Structures The test conditions and measured performance of six field experiments of GRS bridge abutments and piers are described below.
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The pier was constructed with modular concrete blocks as the facing and was reinforced with a polypropylene woven geotextile, Amoco 2044, at vertical spacing of 0.2 m. Because the geotextile was stronger in the cross-machine direction (38 kN/m at 5 percent strain)
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From page 21... ...
The maximum dry unit weight was 21.2 kN/m3, Figure 2-10. Cross-section of the Havana Yard GRS bridge pier and abutment, Denver, Colorado, (Ketchart and Wu, 1997)
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From page 22... ...
The maximum lateral creep displacement was 59.5 mm in the outer pier and 14.3 mm in the abutment. • A significant part of the maximum vertical and lateral creep displacements of the pier and the abutment occurred in the first 15 days.
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From page 23... ...
The measured maximum vertical settlement and lateral displacement of the embankment face were about 16 cm and 11 cm, respectively. Case B6: Trento Test Wall, Italy (Benigni et al., 1996)
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Synthesis of Performance Characteristics The main performance characteristics of the 12 case histories reviewed in this study, including six in-service GRS bridge abutments and six full-scale field experiments, are 24 summarized in Table 2-1. The performance characteristics include wall height, backfill, reinforcement type, reinforcement spacing, facing type and connection, ratio of reinforcement length to wall height, maximum settlement of loading slab, maximum lateral movement of the wall face, maximum reinforcement strain, and failure pressure.
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Description of Test Sections The full-scale bridge abutments in the experiments consisted of two test sections. The two test sections were in a backto-back configuration, as shown in Figure 2-15.
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w = 12% (2% dry of optimum) Amoco 2044, polypropylene woven geotextile with Tult = 70 kN/m @ε = 18% 0.3 m Natural rocks, with friction connection 0.7 to 1.2 Initial Loading: 4.9 to 28 mm @ 150 kPa; Reloading: 2.5 to 4.5 mm @ 150 kPa Initial Loading: 1.5 to 13 mm @ 150 kPa; Reloading: 0.6 to 4.5 mm @ 150 kPa 0.2% @ 80 kPa Not loaded to failure Preloading reduced differential settlements from 21.6 mm to less than 1.0 mm; sill clearance distance = 1.5 m Founders / Meadows Bridge Abutments (Case A4)
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Strain Failure Pressure Note Feather Falls Trail Bridge Abutments (Case A5) 1.5 m and 2.4 m On-site rocky soil (95% of T-99)
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Wall Height Ratio Maximum Settlement of Loading Slab Maximum Lateral Movement of Wall Face Maximum Reinf. Strain Failure Pressure Note Havana Yard GRS Bridge Pier and Abutment (Case B3)
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From page 29... ...
Chemie Linz Full-Scale GRS Embankment (Case B5) 2.4 m Silty gravelly sand c = 20 kPa φ = 21° γ = 19.3 kN/m3 Polyfelt TS 400, polypropylene needle-punched nonwoven geotextile (Tult = 16 kN/m @ = 80%, weight = 350 g/m2)
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From page 30... ...
5.75 7.34 0.15 4.57 Sill Hydraulic jack 0.91 0.60 0.40 Wing wall Wing wall A b u tm e n t w a ll A b u tm e n t w a ll Section 2-2 Section 1-1 Load cell Hydraulic jack Sill Reaction plate Main loading beam Transverse loading beam Intermediate reinforcement sheet Facing blocks Reinforcement sheet Dywidag steel rod Strong concrete floor Anchor plate Units are in meters Mirafi test sectionAmoco test section Section 1-1 4.65 Section 2-2 Figure 2-15. Configuration of the NCHRP full-scale test abutments.
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From page 31... ...
These soil property tests indicate that the fill is deemed acceptable by the current backfill selection criteria. Geotextile Reinforcement Everything was essentially the same for the two test sections except for the geotextile reinforcement: one test section used Amoco 2044 (referred to as the Amoco test section)
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The top surface Amoco Test Section Mirafi Test Section Abutment height 4.65 m (15.25 ft)
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From page 33... ...
Three-dimensional movement of the abutment wall and one of the wing walls for each test section were traced by using a laser displacement measurement device. A total of 74 high-elongation strain gauges (MicroMeasurement Type EP-08-250BG-120)
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The Mirafi test section at 414 kPa had approached a bearing failure condition while the Amoco test Figure 2-17. Sill settlement versus applied pressure relationships of the Amoco test section.
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Figure 2-19. Average sill settlement versus applied pressure relationships of the Amoco and Mirafi test sections.
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Figures 2-22 and 2-23 show the lateral movements of the abutment and wing-walls, respectively, of the Mirafi test section. For the abutment wall, the maximum lateral movement also occurred near the top of the wall under smaller loads.
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Figure 2-22. Lateral movement of abutment wall: Mirafi test section.
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From page 38... ...
The most likely cause was that the gauges were damaged by the lengthy delay between mounting of strain gauges and actual loading experiments. Figures 2-25 and 2-26 show the measured reinforcement strain versus applied pressure of the Amoco test section and Mirafi test section, respectively.
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(a) y = 1.17x 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 Measured Strain from Strain Gauge (%)
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Figure 2-26. Reinforcement strains in the Mirafi test section.
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Contact Pressures on the Rigid Foundation Figure 2-27 shows the measured contact pressures under different applied pressures at three selected points on the rigid floor of the Mirafi test section. The three points are located along the centerline of the abutment and are 0.25 m, 1.72 m, and 3.13 m from the wall face.
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From page 42... ...
When analyzing the results, the settlement of footing, rotation of the footing, lateral deformation of abutment wall, maximum shear stress levels in the GRS soil mass, ultimate load carrying capacity of the abutment, and potential failure mechanisms were emphasized. TABLE 2-3 Summary of measured performance and observed behavior of the NCHRP test abutments Amoco Test Section Mirafi Test Section Reinforcement Amoco 2044,Tult = 70 kN/m Mirafi 500x, Tult = 21 kN/m Upon termination of loading: Average Applied Pressure 814 kPa 414 kPa Sill Settlement (front)
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From page 43... ...
These parameters, termed herein "performance parameters," are the vertical displacement at the abutment seat (where the girder load is applied) , the horizontal displacement at the abutment seat, the maximum displacement of the segmental facing, and sill distortion.
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44 Figure 2-29. Three-dimensional representation of the base case.
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Judging from the same criteria, the vertical and horizontal displacements of the abutment seat for the base case at 400 kPa are unacceptable (barely acceptable) : the vertical displacement is 10.3 cm, and the horizontal displacement is 4.6 cm (Figure 2-31)
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From page 46... ...
The effect of increasing φ on the horizontal displacement of the abutment seat was similar in trend but with smaller magnitudes as shown in Figure 2-32b. As shown in Figure 2-32c, at 200 kPa of applied pressure, the maximum lateral displacement of the segmental facing decreased roughly linearly with increasing φ, with a total reduction of 45 percent at φ = 40° as compared with the base case.
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Figure 2-34. Effects of geosynthetic stiffness for s = 20 cm.
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From page 48... ...
The effects of sill clear distance on the performance of the GRS abutment is shown in Figure 2-36 for geosynthetic spacing s = 20 cm and in Figure 2-37 for s = 40 cm. Figure 2-36a shows that the vertical displacement of the abutment seat of the base case is 4.7 cm for an applied pressure of 200 kPa.
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49 Figure 2-36. Effects of sill clear distance for s = 20 cm.
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At 300 kN/m of applied load (corresponding to 200 kPa of applied pressure for the 150-cm-wide sill, and 300 kPa for the 100-cm-wide sill) , the vertical displacement at the abutment seat increased 21 percent when the width decreased from 150 cm (base case)
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From page 51... ...
It is suitable to think about shear strain in the soil mass as a measure of distress in a GRS abutment. Thus, a simple failure criterion based on the maximum shear strain is proposed herein in order to estimate the allowable bearing pressure of a spread footing.
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From page 52... ...
The variables in the analyses included the following: • Sill type: integrated sill and isolated sill; • Sill width: 0.8 m, 1.5 m, and 2.5 m; • Reinforcement spacing: 0.2 m and 0.4 m; • Soil friction angle: 34°, 37°, and 40°; and • Foundation: 6-m-thick medium sand foundation and rigid foundation. Of the 72 analyses, one-half were for a GRS abutment situated over a medium sand foundation (with its stiffness representing a lower-bound "competent" foundation)
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From page 53... ...
General observations of the performance characteristics follow: • For reinforcement spacing of 0.2 m, none of the abutments suffered from any stability problems up to an applied pressure of 1,000 kPa. φ = 34° Reinforcement Spacing = 20 cm 225 kPa 280 kPa 360 kPa Reinforcement Spacing = 40 cm 120 kPa 200 kPa 280 kPa φ = 37° φ = 40° TABLE 2-4 Allowable bearing pressures based on the critical shear strain distribution criterion (text continues on page 60)
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From page 54... ...
54 Figure 2-42. Configuration of a GRS abutment with integrated sill, sill width = 0.8 m.
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55 Figure 2-43. Configuration of a GRS abutment with integrated sill, sill width = 1.5 m.
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56 Figure 2-44. Configuration of a GRS abutment with integrated sill, sill width = 2.5 m.
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57 Figure 2-45. Configuration of a GRS abutment with isolated sill, sill width = 0.8 m.
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58 Figure 2-46. Configuration of a GRS abutment with isolated sill, sill width = 1.5 m.
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59 Figure 2-47. Configuration of a GRS abutment with isolated sill, sill width = 2.5 m.
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From page 60... ...
to improve the performance characteristics is more efficient for soils with a lower friction angle than for soils with a higher friction angle. • The effect of reinforcement spacing on sill settlement and maximum lateral displacement of wall face was significant, especially at applied pressure greater than 200 kPa.
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From page 61... ...
61 Figure 2-48. Relationship between applied pressure and sill settlement: integrated sill, s= 0.2 m, and medium sand foundation.
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62 Figure 2-49. Relationship between applied pressure and sill settlement: integrated sill, s = 0.4 m, and medium sand foundation.
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From page 63... ...
63 Figure 2-50. Relationship between applied pressure and sill settlement: isolated sill, s = 0.2 m, and medium sand foundation.
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From page 64... ...
64 Figure 2-51. Relationship between applied pressure and sill settlement: isolated sill, s = 0.4 m, and medium sand foundation.
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From page 65... ...
65 Figure 2-52. Relationship between applied pressure and maximum lateral wall displacement: integrated sill, s = 0.2 m, and medium sand foundation.
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From page 66... ...
Relationship between applied pressure and maximum lateral wall displacement: integrated sill, s = 0.4 m, and medium sand foundation.
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From page 67... ...
Figure 2-54. Relationship between applied pressure and maximum lateral wall displacement: isolated sill, s = 0.2 m, and medium sand foundation.
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From page 68... ...
Relationship between applied pressure and maximum lateral wall displacement: isolated sill, s = 0.4 m, and medium sand foundation.
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From page 69... ...
Figure 2-56. Relationship between applied pressure and sill lateral movement: integrated sill, s = 0.2 m, and medium sand foundation.
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From page 70... ...
Relationship between applied pressure and sill lateral movement: integrated sill, s = 0.4 m, and medium sand foundation.
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From page 71... ...
Figure 2-58. Relationship between applied pressure and sill lateral movement: isolated sill, s = 0.2 m, and medium sand foundation.
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Relationship between applied pressure and sill lateral movement: isolated sill, s = 0.4 m, and medium sand foundation.
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φ = 40° (Sill Width = 0.8 m) φ = 37° (Sill Width = 0.8 m)
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(facing failure @ 969 kPa) φ = 37° (Sill Width = 0.8 m)
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From page 75... ...
φ = 40° (Sill Width = 1.5 m) φ = 34° (Sill Width = 2.5 m)
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(facing failure @ 937 kPa) φ = 34° (Sill Width = 1.5 m)
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From page 77... ...
Figure 2-64. Relationship between applied pressure and sill settlement: integrated sill, s = 0.2 m, and rigid foundation.
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Relationship between applied pressure and sill settlement: integrated sill, s = 0.4 m, and rigid foundation.
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From page 79... ...
Figure 2-66. Relationship between applied pressure and sill settlement: isolated sill, s = 0.2 m, and rigid foundation.
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From page 80... ...
Relationship between applied pressure and sill settlement: isolated sill, s = 0.4 m, and rigid foundation.
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From page 81... ...
Figure 2-68. Relationship between applied pressure and maximum lateral wall displacement: integrated sill, s = 0.2 m, and rigid foundation.
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From page 82... ...
82 Figure 2-69. Relationship between applied pressure and maximum lateral wall displacement: integrated sill, s = 0.4 m, and rigid foundation.
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From page 83... ...
83 Figure 2-70. Relationship between applied pressure and maximum lateral wall displacement: isolated sill, s = 0.2 m, and rigid foundation.
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From page 84... ...
84 Figure 2-71. Relationship between applied pressure and maximum lateral wall displacement: isolated sill, s = 0.4 m, and rigid foundation.
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From page 85... ...
85 Figure 2-72. Relationship between applied pressure and sill lateral movement: integrated sill, s = 0.2 m, and rigid foundation.
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From page 86... ...
86 Figure 2-73. Relationship between applied pressure and sill lateral movement: integrated sill, s = 0.4 m, and rigid foundation.
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From page 87... ...
87 Figure 2-74. Relationship between applied pressure and sill lateral movement: isolated sill, s = 0.2 m, and rigid foundation.
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From page 88... ...
88 Figure 2-75. Relationship between applied pressure and sill lateral movement: isolated sill, s = 0.4 m, and rigid foundation.
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From page 89... ...
89 Figure 2-76. Relationship between applied pressure and rotation of sill: integrated sill, s = 0.2 m, and rigid foundation.
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From page 90... ...
90 Figure 2-77. Relationship between applied pressure and rotation of sill: integrated sill, s = 0.4 m, and rigid foundation.
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From page 91... ...
91 Figure 2-78. Relationship between applied pressure and rotation of sill: isolated sill, s = 0.2 m, and rigid foundation.
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From page 92... ...
φ = 37° (Sill Width = 0.8 m) (facing failure @ 500 kPa)
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From page 93... ...
A more detailed explanation of the critical shear strain distribution criterion is in the parametric study in this chapter. Tables 2-7 and 2-8 show the values of the bearing pressures corresponding to the 1 percent H settlement criterion and the critical shear strain distribution criterion for all 36 analyses with a medium sand foundation.
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From page 94... ...
Reinforcement Spacing (m) Applied Pressure at Settlement = 1%H (kPa)
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From page 95... ...
(kPa) 34 281 37 3750.2 40 500 34 156 37 281 0.8 0.4 40 406 34 167 37 2170.2 40 283 34 117 37 167 1.5 0.4 40 233 34 150 37 2000.2 40 267 34 100 37 150 Integrated 2.5 0.4 40 217 34 188 37 2500.2 40 313 34 125 37 156 0.8 0.4 40 219 34 150 37 2000.2 40 250 34 83 37 133 1.5 0.4 40 167 34 133 37 1670.2 40 233 34 67 37 117 Isolated 2.5 0.4 40 150 TABLE 2-8 Allowable bearing pressures based on the critical shear strain distribution criterion
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