REPORT

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Publication Number: FHWA-HRT-13-066 Date: August 2013

Publication Number: FHWA-HRT-13-066
Date: August 2013

Geosynthetic Reinforced Soil Performance Testing - Axial Load Deformation Relationships

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FOREWORD

The use of geosynthetic reinforced soil (GRS) for load bearing applications such as bridge abutments and integrated bridge systems (IBS) has expanded among transportation agencies looking to save time and money while delivering a better and safe product to the traveling public. GRS has been identified by the Federal Highway Administration (FHWA) as a proven, market-ready technology, and is being actively promoted through its Every Day Counts (EDC) initiative. FHWA interim design guidance for GRS abutments and IBSs is presented in Publication No. FHWA-HRT-11-026. The guidance includes the procedure and use of the GRS performance tests, also termed a mini-pier experiment. This report presents a database of nineteen performance tests performed by the FHWA, largely at the Turner-Fairbank Highway Research Center. It also presents findings, conclusions, and suggestions regarding various design parameters related to the performance of GRS, such as backfill material, reinforcement strength, reinforcement spacing, facing confinement, secondary reinforcement, and compaction.

A reliability analysis for load and resistance factor design (LRFD) was performed based on the results of this performance testing to determine a calibrated resistance factor for the soil-geosynthetic capacity equation. The results of this analysis can also be used by bridge designers to estimate capacity and deformation of GRS. In addition, an insight into the behavior of GRS as a new composite material due to the close reinforcement spacing is described.

Jorge E. Pagán-Ortiz
Director, Office of Infrastructure
Research and Development

Notice

This document is disseminated under the sponsorship of the U.S. Department of Transportation in the interest of information exchange. The U.S. Government assumes no liability for the use of the information contained in this document. This report does not constitute a standard, specification, or regulation.

The U.S. Government does not endorse products or manufacturers. Trademarks or manufacturers' names appear in this report only because they are considered essential to the objective of the document.

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The Federal Highway Administration (FHWA) provides high-quality information to serve Government, industry, and the public in a manner that promotes public understanding. Standards and policies are used to ensure and maximize the quality, objectivity, utility, and integrity of its information. FHWA periodically reviews quality issues and adjusts its programs and processes to ensure continuous quality improvement.

Technical Report Documentation Page

1. Report No. FHWA-HRT-13-066	2. Government Accession No.		3 Recipient's Catalog No.
4. Title and Subtitle Geosynthetic Reinforced Soil Performance Testing-Axial Load Deformation Relationships			5. Report Date August 2013
			6. Performing Organization Code
7. Author(s) Nicks, J.E., Adams, M.T., Ooi, P.S.K., Stabile, T.			8. Performing Organization Report No.
9. Performing Organization Name and Address Turner-Fairbank Highway Research Center 6300 Georgetown Pike McLean, VA 22101			10. Work Unit No.
			11. Contract or Grant No. N/A
12. Sponsoring Agency Name and Address Office of Infrastructure R&D FHWA Research, Development and Technology 6300 Georgetown Pike McLean, VA 22101			13. Type of Report and Period Covered Technical
			14. Sponsoring Agency Code
15. Supplementary Notes The FHWA Contracting Officer's Technical Representative (COTR) was Mike Adams, HRDI-40.
16. Abstract The geosynthetic reinforced soil (GRS) performance test (PT), also called a mini-pier experiment, consists of constructing alternating layers of compacted granular fill and geosynthetic reinforcement with a facing element that is frictionally connected, then axially loading the GRS mass while measuring deformation to monitor performance. This large element load test provides material strength properties of a particular GRS composite built with unique combinations of reinforcement, compacted fill, and facing elements. This report describes the procedure and provides axial load-deformation results for a series of PTs conducted in both Defiance County, OH, as part of the Federal Highway Administration's (FHWA) Every Day Counts (EDC) GRS Validation Sessions and in McLean, VA, at the FHWA's Turner-Fairbank Highway Research Center as part of a parametric study. The primary objectives of this research report are to: (1) build a database of GRS material properties that can be used by designers for GRS abutments and integrated bridge systems; (2) evaluate the relationship between reinforcement strength and spacing; (3) quantify the contribution of the frictionally connected facing elements at the service limit and strength limit states; (4) assess the new internal stability design method proposed by Adams et al. 2011 for GRS; and (5) perform a reliability analysis of the proposed soil-geosynthetic capacity equation for LRFD calibration. ^(1,11)
17. Key Words Geosynthetic reinforced soil, performance test, mini-pier experiment, abutment, integrated bridge system, geotextile, capacity, deformation		18. Distribution Statement
19. Security Classification (of this report) Unclassified	20. Security Classification (of this page) Unclassified		21. No. of Pages 169	22. Price

Form DOT F 1700.7 (8-72)

Reproduction of completed page authorized

SI* (Modern Metric) Conversion Factors

Appendix A. Soil Testing Data

Appendix B. Nuclear Density Testing for TFHRS PTS

Appendix C. Deformation Instrumentation Layouts for PTS

Appendix D. Raw Data for PTS

Acknowledgements

References

LIST OF FIGURES

Figure 1	Photo. Vegas mini-pier experiment
Figure 2.	Illustration. Plan view of Vegas mini-pier experiment
Figure 3.	Illustration. Face view of Vegas mini-pier experiment
Figure 4.	Illustration. Side view of Vegas mini-pier experiment
Figure 5.	Illustration. Reinforcement schedule for Vegas mini-pier experiment
Figure 6.	Illustration. Plan view of Defiance County experiment
Figure 7.	Illustration. Elevation view of Defiance County (DC) test
Figure 8.	Equation. Ultimate vertical capacity for a GRS composite
Figure 9.	Equation. W factor
Figure 10.	Equation. Required reinforcement strength
Figure 11.	Equation. Confining stress (Wu et al. 2010)
Figure 12.	Graph. Predictive capability of the soil-geosynthetic composite capacity equation
Figure 13.	Graph. Predictive capability of the required reinforcement strength equation
Figure 14.	Graph. Reinforced backfill gradations
Figure 15.	Graph. LSDS testing results
Figure 16.	Photo. DC-1 GRS PT (before testing)
Figure 17.	Illustration. Concrete footing on GRS composite, inset from facing
Figure 18.	Photo. Hollow core hydraulic jacks for PT assembly
Figure 19.	Photo. TF-1 PT setup with reaction frame
Figure 20.	Photo. TF-6 PT setup with reaction frame
Figure 21.	Photo. TF-10 PT setup with reaction frame
Figure 22.	Photo. TF-9 at failure with reaction frame
Figure 23	Photo. Spherical bearing to apply load to the footing on the GRS composite
Figure 24.	Illustration. Instrumentation layout for DC tests and TF-1
Figure 25.	Illustration. General additional instrumentation layout TF PT series
Figure 26.	Graph. Load-deformation behavior for the Defiance County PTs
Figure 27.	Graph. Load-deformation behavior for the Turner Fairbank PTs
Figure 28.	Photo. Tilting of the footing during TF-4 testing
Figure 29.	Graph. TF-4 results
Figure 30.	Graph. TF-1 results
Figure 31.	Graph. TF-5 results
Figure 32.	Graph. TF-6 results
Figure 33.	Graph. Repeatability of PT at TFHRC
Figure 34.	Photo. TF-11 at failure with S_v = 3-13/16 inches, T_f = 1,400 lb/ft, and 21A material
Figure 35.	Photo. TF-3 at failure with S_v = 7⅝ inches, T_f = 2,400 lb/ft, and 21A material
Figure 36.	Photo. TF-13 at failure with S_v = 11¼ inches, T_f = 3,600 lb/ft, and 21A material
Figure 37.	Photo. TF-10 at failure with S_v = 15¼ inches, T_f = 4,800 lb/ft, and 21A material
Figure 38.	Photo. Rupture pattern for geotextiles in TF-6 (q_ult,emp = 43,828 psf); the lowest layer of reinforcement is the closet fabric in the picture
Figure 39.	Photo. Post-test picture of TF-6 (S_v = 7⅝ inches, T_f = 4,800 lb/ft)
Figure 40.	Equation. Mohr-Coulomb shear strength
Figure 41.	Equation. Ultimate capacity of an unconfined GRS PT
Figure 42.	Equation. Ultimate capacity of a strip footing on slope
Figure 43.	Equation. Ultimate capacity of a strip footing on a vertical GRS abutment
Figure 44.	Equation. Ratio of plane strain capacity to PT capacity
Figure 45.	Equation. Stability Factor
Figure 46.	Graph. Ratio of plane strain capacity to PT capacity for different stability factors
Figure 47.	Graph. Mohr-Coulomb failure envelope for Pham (2009) plane strain GSGC tests
Figure 48.	Graph. Plane strain capacity to PT capacity for a stability factor of 0.29
Figure 49.	Illustration. Infinitely Long Unconfined GRS abutment
Figure 50.	Equation. Stiffness of an Infinitely Long Unconfined GRS abutment
Figure 51.	Illustration. Solution for strip footing on top of a wall
Figure 52.	Equation. Vertical displacement of a GRS abutment with a strip footing
Figure 53.	Equation. Vertical strain
Figure 54.	Equation. Stiffness of a GRS abutment supporting a strip footing
Figure 55.	Equation. Vertical displacement of a GRS abutment with a strip footing.
Figure 56.	Graph. Ratio of plane strain stiffness of a strip footing on top of a wall (S_GRS) to that of a PT (S_PT) for the case of constant stiffness with depth
Figure 57.	Graph. Comparison between compacted and uncompacted GRS composites
Figure 58.	Design service limit for uncompacted sample DC-5
Figure 59.	Graph. Comparison of compacted and uncompacted strains between the DC-1 and DC-5 tests
Figure 60.	Graph. Effect of bearing bed reinforcement for TF-7 and TF-8
Figure 61.	Graph. Measured lateral deformation at 3,600 psf applied stress for TF-7 (no bearing bed reinforcement) and TF-8 (2 courses of bearing bed reinforcement)
Figure 62.	Graph. Measured lateral deformation at 26,600 psf applied stress for TF-7 (no bearing bed reinforcement) and TF-8 (2 courses of bearing bed reinforcement)
Figure 63.	Graph. Comparison of open-graded and well-graded backfills for TF-1 and TF-2
Figure 64.	Graph. Stress-strain curves for PTs with CMUs at T_f/S_v = 3,800 psf
Figure 65.	Graph. Stress-strain curves for PTs with no CMU facing at T_f/S_v = 3,800 psf
Figure 66.	Graph. Capacity of GRS with no CMU facing at various reinforcement spacing for different T_f/S_v
Figure 67.	Graph. Capacity of GRS with CMU facing at various reinforcement spacing for different T_f/S_v Ratios
Figure 68.	Graph. Capacity of GRS with no CMU facing at various reinforcement strength for different T_f/S_v ratios
Figure 69.	Graph. Capacity of GRS with CMU facing at various reinforcement strength for different T_f/S_v ratios
Figure 70.	Graph. Stress-strain response for TF-2 (CMU facing) and TF-3 (No CMU facing) with S_v = 7⅝ inches and T_f = 2,400 lb/ft
Figure 71.	Stress-strain response for TF-6 (CMU facing) and TF-7 (No CMU facing) with S_v = 7⅝ inches and T_f = 4,800 lb/ft
Figure 72.	Graph. Stress-strain response for TF-9 (CMU facing) and TF-10 (No CMU facing) with S_v = 15¼ inches and T_f = 4,800 lb/ft
Figure 73.	Graph. Stress-strain Response for TF-12 (CMU facing) and TF-11 (No CMU facing) with S_v = 3-13/16 inches and T_f = 1,400 lb/ft
Figure 74.	Graph. Stress-strain response for TF-14 (CMU facing) and TF-13 (No CMU facing) with S_v = 11¼ inches and T_f = 3,600 lb/ft
Figure 75.	Graph. Effect of CMU facing on ultimate capacity as a function of reinforcement spacing
Figure 76.	Graph. Effect of CMU facing on ultimate capacity as a function of reinforcement strength
Figure 77.	Graph. Calculated confining pressure due to CMU facing at the ultimate capacity
Figure 78.	Graph. Comparison of predicted capacity and measured capacity
Figure 79.	Graph. Cumulative distribution function plot for DC and TF PTs
Figure 80.	Graph. Cumulative distribution function plot for all GRS composite tests
Figure 81.	Graph. Normalized applied stress versus strain for all PT
Figure 82.	Graph. Normalized load-deformation behavior for the DC and TF PTs up to 5 percent vertical strain
Figure 83.	Graph. Cumulative distribution function for proposed service limit pressure
Figure 84.	Graph. Load-deformation behavior for the Turner Fairbank PTs at low strain levels
Figure 85.	Graph. Normalized load-deformation behavior for the DC and TF PTs up to 0.5 percent vertical strain
Figure 86.	Graph. PTs strictly meeting FHWA GRS abutment design specifications
Figure 87.	Equation. Limit state function for FOSM approach
Figure 88.	Graph. Reliability index for lognormal R and Q
Figure 89.	Equation. LRFD format
Figure 90.	Equation. Resistance factor using FOSM
Figure 91.	Equation. Coefficient of variation for factored load
Figure 92.	Equation. Coefficient of variation for resistance
Figure 93.	Graph. Resistance factor for footings on GRS composites for different dead to dead plus live load ratios and target reliability indices based on PT series
Figure 94.	Graph. Resistance factor for footings on GRS composites for different dead to dead plus live load ratios and target reliability indices based on all testing to date
Figure 95.	Graph. AASHTO No. 8 LSDS test results (DC tests)
Figure 96.	AASHTO No. 8 LSDS deformation test results (DC tests)
Figure 97.	Graph. AASHTO No. 8 pea gravel LSDS test results (DC tests)
Figure 98.	Graph. AASHTO No. 8 pea gravel LSDS deformation test results (DC tests)
Figure 99.	Graph. AASHTO No. 57 LSDS test results (DC tests)
Figure 100.	Graph. AASHTO No. 57 LSDS deformation test results (DC tests)
Figure 101.	Graph. AASHTO No. 9 LSDS test results (DC tests)
Figure 102.	Graph. AASHTO No. 9 LSDS deformation test results (DC tests)
Figure 103.	Graph. AASHTO No. 8 LSDS test results (TFHRC tests)
Figure 104.	Graph. AASHTO No. 8 LSDS deformation test results (DC tests)
Figure 105.	Graph. AASHTO A-1-a (VDOT 21A) LSDS test results (TFHRC tests)
Figure 106.	Graph. AASHTO A-1-a (VDOT 21A) LSDS deformation test results (DC tests)
Figure 107.	Illustration. Instrumentation layout for DC tests and TF-1
Figure 108.	Illustration. Instrumentation layout for TF-2, TF-9
Figure 109.	Illustration. Instrumentation layout for TF-3, TF-4
Figure 110.	Illustration. Instrumentation layout for TF-5, TF-7
Figure 111.	Instrumentation layout for TF-6, TF-12
Figure 112.	Illustration. Instrumentation layout for TF-8
Figure 113.	Illustration. Instrumentation layout for TF-10
Figure 114.	Illustration. Instrumentation layout for TF-11
Figure 115.	Illustration. Instrumentation layout for TF-13
Figure 116.	Illustration. Instrumentation layout for TF-14

LIST OF TABLES

Table 1.	Summary of PT conditions
Table 2.	PT reinforced backfill gradations
Table 3.	PT backfill gradation properties
Table 4.	Maximum dry density for PT aggregates
Table 5.	LSDS testing results
Table 6.	Geosynthetic reinforcement properties
Table 7.	PT dimensions
Table 8.	PT measured results summary
Table 9.	Parametric study on aggregate size
Table 10.	Effect of aggregate type results
Table 11.	Parametric study on compaction
Table 12.	Parametric study on bearing bed reinforcement
Table 13.	Parametric study on gradation (T_f = 2,400 lb/ft, S_v = 7⅝ inches)
Table 14.	Parametric study on gradation (T_f = 4,800 lb/ft, S_v = 7⅝ inches)
Table 15.	Parametric study on reinforcement strength with open-graded aggregates
Table 16.	Parametric study on reinforcement strength with well-graded aggregates
Table 17.	Parametric study for 3,800 lb/ft² T_f/S_v ratio (with facing)
Table 18.	Parametric study for 3,800 lb/ft² T_f/S_v ratio (with no facing)
Table 19.	T_f /S_v ratios for each PT
Table 20.	Effect of CMU facing on stiffness and capacity
Table 21.	Effect of CMU facing on strain
Table 22.	PTs meeting GRS strength and service limit design criteria
Table 23.	Predicted and measured vertical capacity for DC and TF PTs
Table 24.	Predicted and measured vertical capacity for all GRS composite tests
Table 25.	Estimation of allowable dead load to limit vertical strain to 0.5 percent using the GRS capacity equation
Table 26.	Statistics for dead and live loads
Table 27.	AASHTO No. 8 sieve analysis (DC tests)
Table 28.	AASHTO No. 8 pea gravel sieve analysis (DC tests)
Table 29.	AASHTO No. 57 Sieve analysis (DC tests)
Table 30.	AASHTO No. 9 Sieve analysis (DC tests)
Table 31.	AASHTO No. 8 Sieve analysis (TFHRC tests)
Table 32.	AASHTO A-1-a (VDOT 21A) sieve analysis (TFHRC tests)
Table 33.	Summary of AASHTO No. 8 LSDS results (DC tests)
Table 34.	Summary of AASHTO No. 8 pea gravel LSDS results (DC tests)
Table 35.	Summary of AASHTO No. 57 LSDS results (DC tests)
Table 36.	Summary of AASHTO No. 9 LSDS results (DC tests)
Table 37.	Summary of AASHTO No. 8 LSDS results (TFHRC tests)
Table 38.	Summary of AASHTO A-1-a (VDOT 21A) LSDS results (TFHRC tests)
Table 39.	TF-2 Nuclear density test results
Table 40.	TF-2 Nuclear density test results
Table 41.	TF-3 Nuclear density test results
Table 42.	TF-4 Nuclear density test results
Table 43.	TF-5 Nuclear density test results
Table 44.	TF-6 Nuclear density test results
Table 45.	TF-7 Nuclear density test results
Table 46.	TF-8 Nuclear density test results
Table 47.	TF-9 Nuclear density test results
Table 48.	TF-10 Nuclear density test results
Table 49.	TF-11 Nuclear density test results
Table 50.	TF-12 Nuclear density test results
Table 51.	TF-13 Nuclear density test results
Table 52.	TF-14 Nuclear density test results
Table 53.	DC-1 PT Data
Table 54.	DC-2 PT Data
Table 55.	DC-3 PT Data
Table 56.	DC-4 PT Data
Table 57.	DC-5 PT Data
Table 58.	TF-1 PT Data
Table 59.	TF-2 PT Data
Table 60.	TF-3 PT Data
Table 61.	TF-4 PT Data
Table 62.	TF-5 PT Data
Table 63.	TF-6 PT Data
Table 64.	TF-7 PT Data
Table 65.	TF-8 PT Data
Table 66.	Â TF-9 PT Data
Table 67.	TF-10 PT Data
Table 68.	TF-11 PT Data
Table 69.	TF-12 PT Data
Table 70.	TF-13 PT Data
Table 71.	TF-14 PT Data

LIST OF ABBREVIATIONS AND SYMBOLS

Abbreviations

AASHTO	American Association of State Highway and Transportation Officials
CMU	Concrete masonry unit
DC	Defiance County, OH
EDC	Every Day Counts initiative
FHWA	Federal Highway Administration
GP-GM	Poorly graded-silty gravel
GRS	Geosynthetic reinforced soil
IBS	Integrated bridge systems
LFD	Load factor design
LRFD	Load and resistance factor design
LSDS	Large scale direct shear
LVDT	Linear voltage displacement transducers
MARV	Minimum average roll value
POT	Potentiometer
PT	Performance test
SRW	Segmental retaining wall
TFHRC	Turner-Fairbank Highway Research Center
USCS	Unified Soil Classification System

Symbols

β	Reliability index
β_s	Slope angle
β_T	Target reliability index
γ	Unit weight of the backfill
γ_b	Bulk unit weight of the facing block
γ_d	Maximum dry density
γ_D	Load factor for dead load
γ_L	Load factor for live load
γ_GRS	Unit weight of the GRS composite
γ_i	Load factor for load component i
δ	Interface friction angle between the geosynthetic and the facing element for a frictionally connected GRS composite
ε_@q=4000psf	Measured vertical strain at an applied load of 4000 psf
ε_@qult	Measured vertical strain at failure
ε_max	Maximum recorded vertical strain
ε_v	Vertical strain
ε_v,compact	Vertical strain for a compacted GRS composite
ε_v,uncompact	Vertical strain for an uncompacted GRS composite
λ	Bias, ratio of measured to predicted
λ_D	Bias factor for dead load
λ_L	Bias factor for live load
λ_R	Bias factor for resistance
ν_GRS	Poisson’s ratio of the GRS
ρ	Vertical displacement
σ	Applied normal stress
σ_c	External confining stress due to the facing
σ_h	Total lateral stress within the GRS composite at a given depth and location
τ	Shear strength of soil
Φ	Peak friction angle
Φ_GRS	Friction angle of the GRS composite
Ф	Resistance factor
Ф_cap	Resistance factor for capacity
ω	Optimum moisture content
a	Footing offset from the edge of the wall face (i.e., setback distance)
b	Footing width on top of the GRS composite
B	Base width of the GRS composite
B_total	Total width of the PT with the CMU facing
c	Cohesion of the backfill
c_GRS	Cohesion of the GRS composite
C_c	Coefficient of Curvature
C_u	Coefficient of Uniformity
d	Depth of the facing block unit perpendicular to the wall face
d_max	Maximum aggregate size
D₁₀	Aggregate size in which 10 percent of the sample is finer
D₃₀	Aggregate size in which 30 percent of the sample is finer
D₆₀	Aggregate size in which 60 percent of the sample is finer
D₈₅	Aggregate size in which 85 percent of the sample is finer
E_o	Initial stress-strain ratio
E_o,CMU	Initial stress-strain ratio for tests with CMU facing
E_o,noCMU	Initial stress-strain ratio for tests without any facing
E_GRS	Young's modulus of the GRS composite
E_R	Ratio of stress to strain for the reload cycle
	Mean safety margin
H	Height of the GRS composite
K_ar	Coefficient of active earth pressure for the backfill
K_pr	Coefficient of passive earth pressure for the backfill
L	Length of footing/bearing area
N_γq	Bearing capacity factor
N_cq	Bearing capacity factor
N_s	Stability factor
S_GRS	Plane strain stiffness of a strip footing on top of GRS
S_PT	Stiffness of the unconfined GRS column
S_v	Reinforcement spacing
T_f	Wide width tensile strength of the geosynthetic, expressed as the minimum average roll value (MARV)
T_req,c	Required reinforcement strength in the direction perpendicular to the wall face
q	Applied stress
q_@ε=0.5%	Applied stress at 0.5 percent vertical strain
q_{@ε=0.5%,predicted}	Predicted applied stress at 0.5 percent vertical strain
q_@ε=0.5%	Applied stress at 5 percent vertical strain
q_max	Maximum applied pressure during testing
q_ult,an,c	Ultimate capacity using semi-empirical theory
q_ult,emp	Measured failure pressure
q_{ult,emp CMU}	Measured failure pressure for tests with CMU facing
q_{ult,emp no CMU}	Measured failure pressure for tests without any facing
q_ult,PS	Ultimate capacity of strip footing under plane strain conditions
q_ult,PT	Ultimate capacity of the GRS column
Q	Load
Q_D	Dead load
Q_L	Live load
Q_i	Load component i
R	Resistance
V_dmax	Coefficient of variation of the maximum aggregate size
V_D	Coefficient of variation of the dead load
V_Kp	Coefficient of variation of the coefficient for passive earth pressure
V_L	Coefficient of variation of the live load
V_M	Coefficient of variation of the model
V_Q	Coefficient of variation of the loads
V_R	Coefficient of variation of the resistance
V_Tf	Coefficient of variation of the reinforcement strength
W	Factor accounting for the effect of reinforcement spacing and aggregate size
z	Standard normal variable

Page Owner: Office of Research, Development, and Technology, Office of Infrastructure, RDT

Topics: research, infrastructure, structures
Keywords: research, structures, Post-tensioned tendons, Bridges, Corrosion, Grout, Chlorides, Grout defects, Inspection, Sampling
TRT Terms: research, infrastructure, Facilities, Structures
Scheduled Update: Archive - No Update needed

This page last modified on 02/06/2014

Geosynthetic Reinforced Soil Performance Testing - Axial Load Deformation Relationships

FOREWORD

Table of Contents

LIST OF FIGURES

LIST OF TABLES

LIST OF ABBREVIATIONS AND SYMBOLS