Geosynthetically Reinforced Soil-Integrated Bridge Systems (GRS-IBS) Specification Development for PennDOT Publication 447

DRAFT PRODUCT REPORT (revised)

Approved Products for Low Volume Local Roads

December 14, 2012 By Steve Bloser, David Shearer, Ken Corradini and Barry Scheetz The Thomas D. Larson Pennsylvania Transportation Institute COMMONWEALTH OF PENNSYLVANIA DEPARTMENT OF TRANSPORTATION

CONTRACT No. 355I01 PROJECT No. 100604

Technical Report Documentation Page

Form DOT F 1700.7 (8-72) Reproduction of completed page authorized

1. Report No.

2. Government Accession No.

3. Recipient’s Catalog No.

4. Title and Subtitle Geosynthetically Reinforced Soil-Integrated Bridge Systems (GRS-IBS) Specification Development for PennDOT Publication 447

5. Report Date December 14, 2012 6. Performing Organization Code

7. Author(s) Steve Bloser, David Shearer, Ken Corradini and Barry Scheetz

8. Performing Organization Report No. LTI 2013-05

9. Performing Organization Name and Address Thomas D. Larson Pennsylvania Transportation Institute Transportation Research Building The Pennsylvania State University University Park, PA 16802-4710

10. Work Unit No. (TRAIS) 11. Contract or Grant No. 355I01, Project 100604

12. Sponsoring Agency Name and Address Pennsylvania Department of Transportation Bureau of Planning and Research Commonwealth Keystone Building 400 North Street, 6th Floor Harrisburg, PA 17120-0064

13. Type of Report and Period Covered Draft Product Report 4/1/12 – 10/31/12 14. Sponsoring Agency Code

15. Supplementary Notes COTR: Randy Albert, galbert@pa.gov, 814-765-0408 16. Abstract Geosynthetic reinforced soil (GRS) technology consists of closely-spaced layers of geosynthetic reinforcement and compacted granular fill material for supporting bridge abutments on low-volume roads. This method is being presented as a potential alternative to conventional concrete bridge abutments. GRS bridge abutments have been proven to cut both the time and cost of bridge construction by at least 50% compared to traditional abutments. The technology has been used to build over 50 bridges since its implementation in 2005. The purpose of this project was to develop a Pennsylvania-specific specification for PennDOT Publication 447, “Approved Products for Low-Volume Roads,” so that municipalities in Pennsylvania can begin to implement this technology. 17. Key Words Geosynthetic reinforced soil, low-volume road, concrete bridge abutment, compacted granular fill, reinforced soil foundation, geotextile fabric, bearing capacity

18. Distribution Statement No restrictions. This document is available from the National Technical Information Service, Springfield, VA 22161

19. Security Classif. (of this report) Unclassified

20. Security Classif. (of this page) Unclassified

21. No. of Pages 22

22. Price

Table of Contents page

1. Executive Summary………………………………………………………………………. 1

2. Literature Review and Case Studies / Testing……………………………………….. 2 2.1. Introduction ………………………………………………………………………….… 2

2.2. Advantages of GRS ………………………………………………………………….. 2

2.3. National GRS Guidelines …………………………………………………………….. 3

2.4. Case Studies ………………………………………………………………………….. 3

2.4.1. Defiance County, Ohio ……………………………………………………….. 4

2.4.2. FHWA Turner Fairbanks Highway Research Center ……………………… 6

2.4.3. Mt. Pleasant Road Bridge, Clearfield County, Pennsylvania ………….…. 7

2.4.4. Buchannon County, Iowa ………………………………………………….…. 9

2.5. Summary of Literature Review and Testing …………………………………….…. 9

3. Speciation Development & Review of PennDOT Resources ……………………... 10 3.1. Site Visits …………………………………………………………………………….... 10

3.2. Testing …………………………………………………………………………………. 12

3.3. Specification Development …………………………………………………………... 12

4. Draft GRS-IBS Specification for PennDOT Publication 447 ……………………..... 13

References ……………………………………………………………………….….…….. 19

ACKNOWLEDGEMENTS

Special thanks are extended to the following people who contributed significantly to the development of this report and specification: Randy Albert, PennDOT Bureau of Municipal Services, District 2; Mike Adams and Jennifer Nicks, Federal Highway Administration; and Warren Schlatter, Defiance County, Ohio. This work was sponsored by the Pennsylvania Department of Transportation and the U.S. Department of Transportation, Federal Highway Administration. The contents of this report reflect the views of the authors, who are responsible for the facts and the accuracy of the data presented herein. The contents do not necessarily reflect the official views or policies of either the Federal Highway Administration, U.S. Department of Transportation, or the Commonwealth of Pennsylvania at the time of publication. This report does not constitute a standard, specification, or regulation.

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1. Executive Summary 1 2 Overview: Geosynthetic reinforced soil (GRS) technology consists of closely-spaced layers of 3 geosynthetic reinforcement and compacted granular fill material for supporting bridge abutments 4 on low-volume roads. This method is being presented as a potential alternative to conventional 5 concrete bridge abutments. GRS bridge abutments have been proven to cut both the time and 6 cost of bridge construction by at least 50% compared to traditional abutments. The technology 7 has been used to build over 50 bridges since its implementation in 2005. The purpose of this 8 project was to develop a Pennsylvania-specific specification for PennDOT Publication 447, 9 “Approved Products for Low-Volume Roads,” so that municipalities in Pennsylvania can begin to 10 implement this technology. 11 12 Literature and Testing Review: As part of the background research for development of this 13 specification, an extensive literature review was conducted. The literature review focused on 14 existing bridges and the monitoring data that has been recorded to date. Settlement has been 15 monitored at several bridges in Ohio, Pennsylvania, and Iowa. Settlement data on these 16 bridges, even when projected out to 100 years, was well within accepted tolerances. In addition 17 to the literature review, several experts were consulted in the development of the specification. 18 This included a visit to Defiance County, Ohio, where more than 25 GRS-IBS bridges have been 19 constructed; a visit to the Federal Highway Administration (FHWA) Turner-Fairbank Highway 20 Research Center to meet with several of the authors of the GRS-IBS Implementation Guide; 21 and continual collaboration with the PennDOT Bureau of Municipal Services. 22

23 Specification Development for PennDOT Publication 447: The goal in developing the GRS 24 specification for Publication 447 was to keep the actual specification as simple as possible while 25 making reference to the best available resources that exist. The standard resource for GRS-26 IBS bridges is a publication by the FHWA titled GRS-IBS Interim Implementation Guide (FHWA-27 HRT-11-026). The Pennsylvania specification was written in reference to the FHWA 28 implementation guide. The purpose of developing this Pennsylvania specification was to: 29 incorporate PennDOT materials and terminology into the GRS-IBS process; more clearly define 30 materials and processes specifically for use in Pennsylvania; and create a brief and user-31 friendly specification with the end user, municipalities, in mind. The end result is a specification 32 that, with reference to the FHWA implementation guide and in conjunction with sound 33 engineering, can be used by municipalities in Pennsylvania to begin implementing GRS-IBS 34 technology on local roads when site conditions allow. 35 36 37

2

2. Literature Review and Case Studies / Testing 38

39

2.1 Introduction 40 41 As defined by the Federal Highway Administration, Geosynthetic reinforced soil 42

technology consists of closely-spaced layers of geosynthetic reinforcement and compacted 43 granular fill material for supporting bridge abutments on low-volume roads. (1) GRS-IBS is a fast, 44 cost-effective method of bridge support that integrates the roadway and bridge superstructure to 45 create a jointless interface between the two surfaces (Figure 1). It consists of three main 46 components: the reinforced soil foundation (RSF), the abutment, and the integrated approach. 47 The RSF is composed of granular fill material that is compacted and encapsulated with a 48 geotextile fabric. It provides embedment and increases the bearing width and capacity of the 49 GRS abutment. It also prevents water from infiltrating underneath and into the GRS mass from 50 a river or stream crossing. This method of using geosynthetic fabrics to reinforce foundations is 51 a proven alternative to deep foundations on loose granular soils, soft fine-grained soils, and soft 52 organic soils. (2) The abutment uses alternating layers of compacted fill and closely spaced 53 geosynthetic reinforcement to provide support for the bridge, which is placed directly on the 54 GRS abutment without a joint and without cast-in-place (CIP) concrete. GRS is also used to 55 construct the integrated approach to transition to the superstructure that allows for a smooth 56 changeover from the roadway to bridge surface. The use of GRS-IBS in Pennsylvania must 57 consider site-specific factors such as appropriate soil pH, stream velocities, scour potential and 58 other factors detailed in Section II of the attached GRS-IBS specification. 59

60

61 Figure 1.Typical GRS-IBS cross section. 62

63 2.2 Advantages of GRS 64

65 GRS bridges have several advantages over conventional reinforced concrete: (3 & 7) 66

• GRS abutments are more flexible, hence more tolerant to foundation settlement. 67

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• When properly designed and constructed, GRS abutments are remarkably stable 68 and also have higher ductility (i.e., are less likely to experience a sudden 69 catastrophic collapse) than conventional reinforced concrete abutments. 70

• When properly designed and constructed, GRS abutments can alleviate 71 differential settlement between the bridge and the approach roadway, thus 72 reducing "the bump at the end of the bridge" problem. 73

• GRS abutments do not require embedment into the foundation soil for stability. 74 This advantage is especially important when an environmental problem such as 75 excavation into previously contaminated soil is involved. Some soil conditions, 76 such as low soil pH (acidity), can deteriorate geosynthetics. Varying 77 environmental conditions should be considered when using geosynthetics. 78

• The lateral earth pressure behind a GRS abutment wall is much smaller than that 79 in a conventional reinforced concrete abutment. 80

• Construction of GRS abutments is rapid and requires only "ordinary" construction 81 equipment and workers with moderate construction skills. 82

• GRS abutments are generally much less expensive to construct than their 83 conventional counterparts. 84

85 2.3 National GRS Guidelines 86

87 The FHWA has established national guidelines for the construction of GRS-IBS bridges. 88

These guidelines are as follows: (1) 89 • Vertical height of less than 30 feet. 90 • Maximum span length of 140 feet. 91 • Reinforcement layer spacing less than 12 inches. 92 • FHWA policy that the AASHTO Load and Resistance Factor Design methodology 93

be conducted for all projects receiving Federal aid. 94 • Depth of excavation for the RSF: 95

o One-quarter of the total width of the base of the GRS abutment including 96 the block face. 97

o Engineer design recommendations may require deeper excavations. 98 • Scour potential: 99

o FHWA Hydraulic Engineering Circulars, (HEC) 23 – for smaller, more culvert-100 like structures where flow length through the structure is longer than the 101 structure width. 102

o FHWA Hydraulic Engineering Circulars, HEC 18 and 20 – for more bridge-like 103 structures where the opening length is greater than the flow distance through 104 the structure. 105

106 2.4 Case Studies 107

As of 2010, 45 bridges utilizing GRS abutments had been built in the United States. Of 108 these bridges, IBS had been employed on 28 bridges, all built over water crossings.(1) The 109 hydraulic environments at these locations is such that scour is shallow, making the system 110

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feasible for these sites. For the purposes of this literature review and testing summary, several 111 case studies are highlighted. 112

2.4.1 Defiance County, Ohio (4 & 5) 113

From 2005-2011, Defiance County, located in northeastern Ohio, completed 26 GRS-114 IBS projects at a cost of $3,513,484. Of these completed projects, 15 were built entirely with a 115 county crew, seven structures with abutments were built by the county with the superstructure 116 by a contractor, and three structures were built entirely by a contractor. Although initially the 117 cost of construction was similar to traditional deep-foundation bridges, current construction is 118 generally half the cost or less, while construction time is twice as fast with a standard abutment 119 construction time of 3 days. A variety of superstructure types have been utilized in the 120 construction of the GRS-IBS bridges. These include adjacent pre-stressed box beams with 121 waterproofing and overlay, adjacent and spread pre-stressed box beams with composite 122 concrete deck, steel beams with composite concrete deck, cast in place slabs, and fiberglass 123 box beams. Note that fiberglass beams or adjacent pre-stressed box beams without a 124 composite deck are not permitted on projects with state funding in Pennsylvania. 125

Of the 26 completed GRS-IBS bridges, 5 have current monitoring to measure vertical 126 and lateral deformations. These bridges were built between 2005 and 2009 and have been 127 monitored for a minimum of 1.5 years to 3.2 years. A summary of these five bridges is included 128 in Table 1. 129

Table 1. Defiance County, Ohio bridge information summary. 130

Bridge Date Built Abutment

Abutment Height

(ft) Dead Load

(kips/ft2)

Span Length (COB to COB)

(ft)

Width of Bridge

(ft)

Monitoring Length

(yrs)North 12.36South 10.36North 13.22South 12.8North 17.3South 16.16East 16.91West 16.47North 20.52South 18

COB = Center of bearing.

Tiffin River

Vine Street Glenburg Road Huber Road Bowman Road

36

October 2006May 2006August 2007October 2005July 2009

32.67

28

28

34

3.69

50.0

30.6

28.0

79.0

134.0

2.37

4.53

1.53

3.46

1.5

3.2

3.6

2.4

1.5

131 132

Vertical deformation was measured for each of the bridges using either the standard 133 survey level and rod system or an electronic distance measurement (EDM) survey referenced 134 off a permanent survey pole and benchmarks. Table 2 provides a summary of the vertical 135 movement for each bridge. Over the various monitoring periods for each bridge, the maximum 136 bridge differential settlement was 0.033 ft at the Tiffin River Bridge. The average total settlement 137 ranged from -0.175 to -0.004 ft and the average GRS settlement ranged from 0.015 to 0.106 ft 138 (Table 3). 139

5

140

Table 2. Defiance County movement information summary. 141

North 12.36 0.024 0.0007South 10.36 0.015 0.0005North 13.22 0.02 0.0006South 12.8 0.008 0.0002North 17.3 0.011 0.0004South 16.16 0.021 0.0008East 16.91 0.022 0.0007West 16.47 0.003 0.0001North 20.52 0.003 0.0001South 18 0.005 0.0003

Tiffin River 0.033 0.00025

Huber Road 0.01 0.00036Bowman Road 0.019 0.00024

0.009 0.00018Glenburg Road 0.012 0.00039

AbutmentDifferentialSettlement

(∆ Sabut)(ft)

Uniformity ofAbutmentSettlement

(∆ Sabut/width of bridge)

BridgeDifferentialSettlement

(∆ S)(ft)

AngularDistortion

(∆ S/span

length)Bridge Abutment

AbutmentHeight

(ft)

Vine Street

142

Table 3. Defiance County vertical settlement and strain information summary. 143

Bridge

AverageAbutment

Height(ft)

AverageTotal

Settlement(ft)

AverageTotal

VerticalStrain

(percent)

AverageGRS

Settlement(ft)

AverageGRS Vertical

Strain(percent)

Vine Street 11.36 -0.035 0.31 0.023 0.2Glenburg Road 13.01 -0.107 0.82 0.083 0.64Huber Road 16.73 -0.004 0.024 0.015 0.09Bowman Road 16.69 -0.07 0.42 0.047 0.28Tiffin River 19.26 -0.175 0.91 0.106 0.55 144

A log-time scale was used to forecast long-term settlement for Bowman Road Bridge 145 over its expected service life (100 years). The average predicted creep settlement was 146 calculated at 0.09 ft for the bridge and 0.035 ft for the abutment walls. The GRS abutment creep 147 distance, 0.055 ft, was defined as the difference between the two average predicted creep 148 settlement values. 149

Due to difficulties in obtaining accurate long-term measurements and the fact that GRS 150 walls and abutments have performed as expected, theoretical calculations to determine lateral 151 deformation are commonly used. Lateral deformation testing was performed on the Tiffin River 152 Bridge. The results of theoretical calculations that determine the lateral deformation and strain 153 based on an assumption of a zero loss of volume are shown in Table 4. For the Tiffin River 154 Bridge, the theoretical calculations had only an error of ±0.005 ft when compared to the 155 measured lateral deformation. 156

157

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Table 4. Defiance County predicted lateral deformations summary. 158

Bridge

AverageAbutment

HeightH

(ft)

Width ofBridge BearingArea + Setback

b + ab(ft)

AverageGRS MassSettlement

Dv(ft)

Calculated LateralDeformation

DL = (2(b + ab)*Dv)/H(ft)

CalculatedLateralStrain

eLVine Street 11.36 2.64 0.023 0.011 0.004Glenburg Road 13.01 2.14 0.083 0.027 0.013Huber Road 16.73 2.64 0.015 0.005 0.002Bowman Road 16.69 3.64 0.047 0.02 0.005Tiffin River 19.26 5.14 0.089 0.047 0.009159

160

Thermal cycles based on daily temperature fluctuations can affect the expansion and 161 contraction of a bridge. Through the monitoring of in-service GRS-IBS bridges with spans up to 162 140 feet, thermal cycles do not affect bridge performance. GRS-IBS bridges are designed to 163 minimize thermal cycle-related movement through the integrated transition behind the beam 164 ends. 165

The 140-ft Tiffin River Bridge has been monitored since its construction. Through daily 166 and seasonal thermal cycles, the average lateral earth pressure changed in magnitude. 167 Although the monitoring after one thermal cycle indicated that the lateral pressure is nonlinear 168 with temperature and displays hysteretic behavior, additional monitoring is being carried out to 169 determine the effect of multiple thermal cycles. 170

171

2.4.2 FHWA’s Turner-Fairbank Highway Research Center (4) 172

FHWA’s Turner-Fairbank Highway Research Center (TFHRC) performed a 12-year 173 settlement study of a GRS-IBS abutment. A tunnel was constructed within the abutment to 174 serve as a monitoring point. This tunnel had an overburden (3,800 lb/ft2) equivalent to a typical 175 bridge load. The abutment and embankment sides had differing reinforcement strengths of 176 4,800 lb/ft geotextile and 2,100 lb/ft geotextile, respectively. Even with these differences, 177 settlement measurements indicated that the settlement difference was nearly identical, with a 178 difference of about 0.0024 ft. A log-time scale plot predicted a vertical deformation settlement 179 after 100 years at 0.033 ft on the abutment side and 0.030 ft on the embankment side. 180

Short-term testing was completed on five concrete box beam GRS bridges. The Cecil 181 Creek, Big Lake, and Cut Off Creek bridges are typically submerged under water for 6 months 182 per year. After 147 days of testing, the settlement performance of these bridges was well within 183 acceptable criteria. The average total settlement ranged from -0.098 to 0.078 ft (Table 5). 184

185

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Table 5. Turner-Fairbank concrete box beam bridge settlement information summary. 186

Bridge DateBuilt

Bridge Span (ft) Abutment

AverageTotal

Settlement(ft)

DifferentialSettlement

(ft)

Uniformity ofAbutmentSettlement(∆Sabut)/

width of bridge)

AngularDistortion

(∆S/span length)

A -0.098 0.013 0.0007B -0.02 0.002 0.0001A 0.007 0.040 0.002B -0.029 0.075 0.004A 0.078 0.050 0.003B 0.072 0.001 0.00006

-0.021 at 6 days No data No data No data

Lake Mamie

Fall 2000 Both

-0.013 at 3 days

0.001Big Lake

June 2005 0.0005

No data No data No data Twin Lake

Fall 2000 Both

Cut Off Creek

June 2005 0.0001

67

71

76

76

76

Cecil Creek

June 2005

187 188

2.4.3 Mt. Pleasant Road Bridge in Huston Township, Clearfield County, Pa. (6 & 7) 189

The Mount Pleasant Road bridge in Huston Township, Clearfield County, Pa. was 190 completed in late 2011 at a cost of $101,893.91. Due to the fact that the bridge was in poor 191 shape and along a school bus route, construction time had to be kept to a minimum. Through 192 the implementation of GRS-IBS, the entire project took just 36 days to complete. 193

The construction details of the Mount Pleasant Road bridge are as follows: 194 • Depth of footing = 4 ft 195 • Materials used: timber superstructure, concrete blocks, geotextile, 2RC and 196

AASHTO #8 coarse aggregate, riprap (scour countermeasure), bituminous 197 paving, guide rail 198

• Facing wall: Concrete Masonry Units (CMUs) utilized; top three rows grouted 199 along with all corners 200 201

The bridge was constructed with local forces except for a rented excavator and guide rail 202 contractor. An adjacent local municipality paved where applicable. All equipment was township 203 owned or locally rented. The excavator work was subcontracted due to the reach requirements. 204 Comparable PennDOT, local, and contracted box culvert and bridge beam projects for District 2 205 range in cost from $150,000 to $500,000+. 206

Bridge settlement monitoring was implemented in December 2011. Two nails in a utility 207 pole used as benchmarks and the elevations for 17 individual bridge locations were recorded. 208 Through July 2012 there had been nominal settlement, with an initial average bridge elevation 209 of 995.20 ft and an average bridge elevation through July 2012 of 995.19 ft (Table 6). Figure 2 210 provides a schematic of the bridge structure and of the 17 monitoring points shown in Table 6. 211

212

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Table 6. Clearfield County GRS bridge vertical settlement summary. 213

10/20/2011 12/7/2011 2/3/2012 4/13/2012 7/23/2012A 993.85 993.85 993.81 993.82 993.83 NE Top of GRS Block RowB 996.09 996.09 996.08 996.08 Ne Top of CapC 994.16 994.16 994.16 994.15 NE Top of Sill PlateD 993.82 993.81 993.77 993.78 993.82 SE Top of GRS Block RowE 996.07 996.03 996.06 996.06 SE Top of CapF 994.14 994.15 994.15 994.14 SE Top of Sill PlateG 993.87 993.87 993.83 993.84 993.86 SW Top of GRS Block RowH 996.11 996.09 996.10 996.09 SW Top of CapI 994.20 994.20 994.21 994.19 SW Top of Sill PlateJ 993.88 993.89 993.85 993.87 993.87 NW Top of GRS Block RowK 996.12 996.11 996.11 996.12 NW Top of CapL 994.21 994.21 994.20 994.19 NW Top of Sill PlateM 996.38 996.36 996.36 996.35 NW Top of DeckN 996.35 996.32 996.32 996.32 NE Top of DeckO 996.34 996.32 996.31 996.32 SE Top of DeckP 996.36 996.36 996.36 996.36 SW Top of DeckQ 996.41 996.41 996.41 996.40 Center of DeckNote: 10/20/11 was during construction.

PointElevation (ft)

Description

214 215

216

Figure 2. Mount Pleasant Road GRS bridge schematic; letters 217 relate to measured elevation points in Table 6. 218

219

BM#7 (nail in utility pole)

Road Surface

GRS-IBS Structure

Stream Flow Stream Flow

GRS-IBS Structure

BM#31 (nail in utility pole)

A,C BN

Q

MKJ,LP

H G,I

OE D,F

9

2.4.4 Buchanan County, Iowa (8) 220

The Center for Earthworks Engineering Research at Iowa State University evaluated two 221 GRS-IBS in Buchanan County, Iowa. These GRS-IBS bridges were found to be 50%-60% 222 lower in cost when compared to traditional bridges. The first bridge, located on Olympic 223 Avenue, is a 73-ft Railroad Flat Car (RRFC) bridge on a reinforced concrete spread footing and 224 had a GRS bridge abutment with flexible wrapped geosynthetic and grouted riprap facing. The 225 total cost was approximately $49,000. Field observations showed that the grouted riprap 226 installed over the wrapped geosynthetic facing for erosion protection was intact. The average 227 settlement was about 0.7 inches for the north abutment footing and 0.4 inches for the south 228 abutment footing. No transverse differential settlement was observed at either abutment. 229

The second bridge, located on 250th Street, is a 68.5-ft RRFC bridge that used existing 230 concrete bridge abutments along with some existing fill, which were left in place as GRS facing. 231 Sheet piling was used as scour protection and the total cost was approximately $43,000. In-situ 232 bridge abutment settlement monitoring was conducted for roughly 1 year after bridge 233 construction. The monitoring results found an average settlement of about 0.4 inches with a 234 transverse maximum differential settlement of about 0.2 inches. Monitoring indicated that most 235 of the settlement occurred within the first 2 months after completion of construction. Lateral 236 ground movements monitored during the 1-year monitoring period showed minimal movements. 237

238

2.5 Summary of Literature Review and Testing 239

Over 50 GRS bridges have been constructed in the United States since 2005. The 240 technology has proven to be time saving, cost effective, and reliable. In general, GRS bridges 241 have seen a cost and construction time savings of at least 50% over conventional bridges. The 242 monitoring data outlined above has shown that settlement has been minimal and that even the 243 100 year settlement projections are well within acceptable tolerances. It should be noted that 244 Pennsylvania’s only GRS bridge in Clearfield County, built utilizing a township workforce and 245 PennDOT-specified materials, has performed extremely well, with an average settlement of only 246 0.01 ft over the first year after construction. 247

248

249

250

251 252

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3. Specification Development & Review of PennDOT 253

Resources 254

Center for Dirt and Gravel Road Studies staff employed a variety of strategies in the 255 development of the GRS specification for Pennsylvania. These included site visits to many 256 existing GRS structures and gathering of information from experts in the field of GRS bridge 257 construction. The Center also adapted existing GRS guidelines and construction materials to 258 make a “Pennsylvania-specific” specification that references existing PennDOT-approved 259 materials, practices, and standards where possible. 260

261

3.1 Site Visits 262 263 Site visits were conducted in Defiance County, Ohio, at the Turner-Fairbank Highway 264

Research Center in Washington D.C., and at the Mt. Pleasant Road GRS bridge in 265 Pennsylvania. The purpose of these site visits was not to simply see the bridges, but to interact 266 with the GRS experts at these various locations. 267

268 3.1.1 Defiance County, Ohio 269

270 On July 1-3, 2012, Center staff visited Defiance County, Ohio. Defiance County is 271

nationally recognized as the leader in GRS-IBS implementation, with over 26 bridges completed 272 using the technology from 2005 through 2011. Center staff met with Warren Schlatter (Defiance 273 County Engineer), and visited a dozen completed GRI-IBS bridges. Mr. Schlatter proved to be 274 an extremely knowledgeable and valuable resource during the visit. Center staff visited GRS-275

IBS bridges ranging from 2005 to 2011 in time of construction, 11 ft to 130 ft in span length, and 276 5 ft to 25 ft in GRS height. All bridges and GRS abutments were in excellent condition and 277 functioning well. Many of the abutments had been completely submerged since their 278 construction with no detrimental effects (Figure 5). There was no evidence of scour or erosion 279 around the GRS structures of any of the bridges. Several of these bridges were used in long-280

Figure 4. A small 11-ft span GRS bridge on Flory Road (west) in Defiance County, OH, completed in 2011.

Figure 3. Under the 74-ft length Bowman Road Bridge, the first GRS-IBS bridge in Defiance County, OH, completed in 2005.

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term monitoring and assessment studies of the GRS-IBS concept. Much of this data was 281 presented in the Literature Review/Testing section of this document. 282

283 284 3.1.2 Turner-Fairbank Highway Research Center, Washington D.C 285 286 On August 15, 2012, Center staff visited the Federal Highway Administration’s Turner-Fairbank 287 Highway Research Center in McLean, Virginia. Center staff met with three of the authors of the 288 FHWA GRS-IBS Implementation Guide: Michael Adams, Jennifer Nicks, and Jonathan Wu. 289 The purpose of the meeting was to receive feedback and input that would help in the creation of 290 the GRS specification for Pennsylvania. The visit proved to be invaluable, as it answered many 291 questions previously raised by several parties about the potential GRS specification for 292 Pennsylvania. FHWA staff continue to be in contact and have offered any assistance they can 293 provide in the creation of a GRS specification for Pennsylvania. 294 295 296 3.1.3 Mt. Pleasant Road, Clearfield County, Pennsylvania 297 298 The Mt. Pleasant Road Bridge is located just 299 North of Pennfield in Clearfield County, Pa. It is 300 currently the only modern GRS bridge in 301 Pennsylvania. It was built in the fall of 2011 by a 302 township crew at a total cost of ~$100,000. This 303 represented a significant cost savings over 304 standard bridge alternatives. The GRS abutments 305 were constructed in 6 days and the entire bridge, 306 including paving, was done in 36 days. The 307 Center had made several visits to the Mt. Pleasant 308 Bridge. In September of 2012, the Center used 309

Figure 5. Under the Tiffin River Bridge, the longest span to date at 130 ft, completed in 2009. Note the debris stuck under the bridge, indicating total flooding of the GRS structure.

Figure 6. Unbroken pavement (no bump) over the 20-ft span Flory Road (east) bridge in Defiance County, OH, completed in 2008.

Figure 7. The 26-ft span Mount Pleasant Road Bridge constructed in Clearfield County, PA, in 2011.

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the bridge as a tour stop as part of the 2012 Annual Maintenance Workshop. More than 150 310 conservation and road maintenance professionals from around Pennsylvania toured the site. 311 The Center has also been working closely with project supervisor Randy Albert, of PennDOT 312 BMS District 2, in the development of the GRS specification. Previously unpublished monitoring 313 data from the Mt. Pleasant Road Bridge is also included in the Literature Review/Testing section 314 of this document. 315 316 3.2 Testing 317 318

As outlined in the Center’s proposal, actual testing of GRS structures was not within the 319 scope of the Center’s work. Instead, monitoring and testing data from existing sources has 320 been summarized. This data is presented in Section 2 of this report. 321

322 3.3 Specification Development 323 324

GRS-IBS bridges are a much more complicated practice than many of the products and 325 practices typically included in PennDOT Publication 447. The goal in developing the GRS 326 specification for Publication 447 was to keep the actual specification as simple as possible while 327 making reference to the best available resources that existed for the bulk of the guidance. This 328 proved to be the Geosynthetic Reinforced Soil Integrated Bridge System—Interim 329 Implementation Guide, published by FHWA. This extensive guide outlines the GRS-IBS 330 process in detail and includes specifications for materials to be used. 331

The goal of developing the GRS specification for PennDOT Publication 447 was to 332 incorporate PennDOT-approved materials, testing methods, and practices into the existing GRS 333 Implementation Guide. Based on feedback received from various sources, the Center also 334 incorporated several guidelines into the Publication 447 GRS specification that are more 335 conservative than FHWA guidelines. Center staff also met with the authors of the FHWA 336 implementation guide to assist in developing the Pennsylvania specification. 337

Maintenance and protection of traffic must be considered during construction. The road 338 may need to be closed or a realignment may be necessary since this type of construction is 339 typically not conducive to a phased construction environment. (PennDOT Publication 408, 340 Section 901) 341

342 343 344

345

13

4. Draft GRS-IBS Specification for PennDOT Publication 447 346

NP-0050 347

Geosynthetically Reinforced Soil – Integrated Bridge System 348

(GRS-IBS) 349

350

I. DESCRIPTION – This work consists of designing and constructing an Integrated Bridge System 351 (IBS) using Geosynthetically Reinforced Soil (GRS) technology on a Reinforced Soil Foundation 352 (RSF). GRS technology consists of closely spaced layers of geosynthetic reinforcement and 353 compacted granular fill material. GRS-IBS is a fast, cost-effective method of bridge support that 354 blends the roadway into the superstructure. GRS-IBS includes an RSF, a GRS abutment, and an 355 Integrated Approach (IA). Designers must utilize the design and construction specifications 356 provided as follows: 357

A. Federal Highway Administration: 358 1. FHWA-HRT-11-026: “Geosynthetic Reinforced Soil Integrated Bridge Systems 359

Implementation Guide.” 360 2. FHWA-HRT-12-051: “Sample Guide Specifications for Construction of 361

Geosynthetic Reinforced Soil-Integrated Bridge Systems (GRS-IBS).” 362 B. Guidelines in this document provide additional information to FHWA-HRT-11-026 and 363

FHWA-HRT-12-051. In instances where guidelines differ between the sources, this 364 document takes precedence. 365

C. PennDOT current and applicable design standards, including, but not limited to 366 PennDOT Publication 15M, Design Manual Part 4 on structures. 367

D. PennDOT standard drawings (PennDOT Publications 72M, 218M, and 219M). 368 369

370 II. GRS-IBS DESIGN GUIDELINES 371

(in accordance with: FHWA-HRT-11-026 and FHWA-HRT-12-051) 372 A. SITE LIMITATIONS 373

1. GRS-IBS is limited to bridges with simple plan structures. 374 2. GRS-IBS is limited to span lengths up to 70 feet. 375 3. GRS-IBS is limited to bridges with GRS abutment heights up to 30 feet. 376 4. GRS-IBS is limited to sites with low scour potential. 377 5. GRS-IBS is limited to streams with a 100 year storm maximum allowable stream 378

velocity of: 379 1. < 7 fps: 380

a. Conventional GRS construction utilizing Standard CMUs (8” x 381 8” x 16”) with friction connection. 382

383 2. 7-10 fps: 384

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a. Complete concrete fill with rebar on Standard CMUs. 385 3. 10-12 fps: 386

a. Large CMUs (24” x 24” x 72”) with intermediate layers of 387 geotextile wrap-faced at 8” intervals. 388

6. GRS-IBS is limited to sites with soil pH between 5 and 9. 389 7. Outlet pipes through the GRS-IBS are not permitted. 390

391 B. SITE EVALUATION 392

A site evaluation shall be performed in accordance with FHWA-HRT-11-026, 393 Section 4.3.2. 394

395 C. SCOUR 396

1. Scour Depth: 397 1. Footings are to be designed based on the total scour depth obtained from 398

a scour design flood. The scour design flood is defined as a 100 year 399 flood, the flood of record (if available), or the overtopping flood (if less 400 than the 100 year flood), whichever results in the worst-case scour 401 condition in accordance with PennDOT Publication 15M Section 7.2.2. 402

2. The reinforced soil foundation shall be placed below this calculated 403 depth in accordance with Hydraulic Engineering Circular 18 (HEC-18) 404 –or- PennDOT Publication 15M Section 7.2.4. 405

2. Scour Protection: 406 1. A properly designed scour countermeasure shall be placed to protect 407

against local scour in accordance with FHWA-HRT-11-026, Section 408 4.3.3. Riprap protection shall be sized appropriately for the class of 409 stone specified in accordance with PennDOT Publication 15M Section 410 7.2.5. It is recommended that CMU blocks which are solid be used at the 411 bottom of the GRS wall for reinforcement, and CMU blocks of a 412 different color be used to indicate scour as per FHWA-HRT-11-026, 413 Section 6.4. 414

2. Potential for channel migration shall be evaluated. The effect of lateral 415 channel movement on abutments may be mitigated by providing 416 abutment setback or providing wingwalls that extend beyond the 417 estimated channel migration distance. The RSF shall be protected from 418 scour. In all cases, wingwall height and length shall be constructed to 419 adequately protect the reinforced fill from channel scour and 420 undermining from surface drainage. 421

D. BEAM SEAT: 422 1. The maximum Service I Bearing Pressure on the GRS beam seat shall be limited 423

to 4,000 lb/ft2. 424

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2. A cast-in-place or precast beam seat with a concrete end diaphragm is required 425 for concrete girders, steel/timber superstructure elements, or other similar 426 superstructures without backwall support. 427 428

III. MATERIAL (in accordance with: FHWA-HRT-11-026 and FHWA-HRT-12-051) Materials must 429 be obtained from a manufacturer listed in Bulletin 15 for projects with state or Federal funding 430 and conforming to the following requirements: 431 432

A. FACING ELEMENTS 433 1. Concrete Masonry Unit (CMU): PennDOT Publication 408, Section 713.2 and 434

ASTM C1372, and conforming to the following requirements: 435 1. Class A concrete (PennDOT Publication 408, Section 704). 436 2. Water absorption limit < 5%. 437 3. Freeze thaw testing in accordance with ASTM C1262-10. 438 4. “Standard CMUs” with nominal dimensions of 8” x 8” x 16”. 439 5. “Large CMUs” with nominal dimensions of 24” x 24” x 72”. 440

2. Existing Abutments: GRS structures can be constructed behind existing bridge 441 abutments, subject to PennDOT approval. In these cases, the existing bridge 442 abutments effectively become part of the facing element of the GRS structure. 443 The GRS shall be wrapped-faced using geotextile fabric against the existing 444 abutment in accordance with FHWA-HRT-11-026, Section 7.3.3. 445

3. Other Facing Elements: Other facing materials may be used with District 446 Bridge Engineer approval. 447

B. BACKFILL MATERIAL: 448 1. All backfill material shall consist of sound crushed durable particles, fragments 449

of stone gravel free from organic matter or other deleterious material, with a 450 minimum friction angle of 38 degrees. 451

1. Reinforced Soil Foundation (RSF) Backfill: PennDOT 2A coarse 452 aggregate with a maximum Plasticity Index value of 6 (PennDOT 453 Publication 408, Section 703.2) -or- Driving Surface Aggregate (DSA) 454 with a maximum Plasticity Index value of 6. (PennDOT Pub 447, MS-455 0450-0004) 456

2. GRS Abutment Backfill: AASHTO #8 is the preferred abutment 457 backfill. Backfill may also consist of coarse aggregate conforming to 458 AASHTO #8, #57, #67, or a combination thereof. All backfill 459 aggregates must be Type A. (PennDOT Publication 408, Section 703.2) 460

3. Integrated Approach Backfill: PennDOT 2A coarse aggregate with a 461 maximum Plasticity Index value of 6 (PennDOT Publication 408, 462 Section 703.2) -or- Driving Surface Aggregate (DSA) with a maximum 463 plasticity index value of 6. (PennDOT Pub 447, MS-0450-0004) 464

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C. GEOSYNTHETICS (Geotextiles) 465 1. Geosynthetic Reinforcement in Abutment, Reinforced Soil Foundation and 466

Integrated Approach: Biaxial geotextiles with Ultimate Tensile Strength = 467 4,800 lb/ft as determined by ASTM D 4595 (woven geotextiles). Geotextile 468 reinforcement tensile strength at 2 percent strain shall be greater than the 469 calculated required reinforcement strength in the direction perpendicular to the 470 abutment wall face as outlined in FHWA-HRT-11-026, Section 4.3.7. The design 471 requirement may call for a Geotextile with higher strength. Geosynthetics shall 472 conform to PennDOT Publication 408, Section 212. 473

D. Concrete (Block Wall Fill and Wet Cast Coping): Class A cement concrete with 3,000 474 psi compressive strength. (PennDOT Publication 408, Section 704.1) 475

E. Reinforcement Bars: Deformed #4 rebar (0.5” diameter), epoxy coated in accordance 476 with PennDOT Publication 408, Section 1002. 477

F. Aluminum Flashing: Flashing, such as 4” x 1.5” aluminum fascia or equivalent, may be 478 used to serve as a drip edge under the superstructure to shed potentially corrosive fluids 479 off the dry cast block and to prevent animals from burrowing into the abutment. 480

G. Preformed Cellular Polystyrene: A durable foam board, such as expanded polystyrene 481 filler or equivalent, having a compressive strength >10 psi as defined in PennDOT 482 Publication 408 Section 516.2. Total thickness of the foam board shall be 4 inches or 483 greater depending on the abutment height. 484

H. Asphaltic (bitumen) Coating: An asphaltic coating shall be shop installed on the 485 concrete beam ends where it will be embedded between the GRS abutment and the wing 486 wall to seal the embedded concrete. 487

J. Rip-rap Scour Countermeasure: Rip-rap as defined in PennDOT Publication 408, 488 Section 850. Rip-rap scour countermeasures shall be sized according to Hydraulic 489 Engineering Circular 23 (HEC-23). 490

491 IV. CONSTRUCTION (in accordance with: FHWA-HRT-11-026 (Chapter 7), and FHWA-HRT-12-492

051, Section 3) 493 A. Equipment: Use equipment that produces the completed GRS-IBS and maintain all 494

equipment in a satisfactory operating condition as specified in PennDOT Publication 495 408, Section 108.05(c). 496

1. Compaction Equipment: Rollers and other compaction equipment as described 497 in PennDOT Publication 408, Section 108.05(c)3,4. 498

B. Excavation: Construct embankments and/or cut existing grade to the bottom of footing 499 elevations. Excavate and backfill foundation areas as specified in PennDOT Publication 500 408 Section 204.3 and compact using a mechanical tamper. If unsuitable foundation 501 material is encountered, remove all unsuitable material at least 12” or as specified or 502 directed below the bottom of the RSF elevation and backfill with compacted No. 2A 503

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Coarse Aggregate or DSA as specified or directed. No additional payment shall be made 504 if rock is encountered during excavation. 505

C. Compaction of Backfill (RSF, Abutment, and Integrated Approach): Hand-operated 506 compaction equipment as specified above is required within 3 ft of the front of the 507 abutment wall face. 508

1. Compaction of Open-Graded Backfill in Abutment: Compact to non-509 movement or no appreciable displacement with compaction equipment specified 510 above and assess with visual inspection (minimum of 4 vibratory passes per lift). 511 Abutment backfill is to be placed at a maximum compacted depth of 4 inches per 512 lift. 513

2. Compaction of Well-Graded Backfill in Reinforced Soil Foundation and 514 Integrated Approach: Compact well-graded backfill to not less than 100% of 515 the determined dry-weight density. Dry-weight density for material in place in 516 the field will be determined, in accordance with Pennsylvania Testing Method 517 (PTM) No. 106, Method B. In-place density or compaction will be determined, in 518 accordance with PTM No. 402 where directed. At the time of compaction, 519 maintain the material's moisture content not more than 2 percentage points above 520 optimum moisture for that material. Backfill is to be placed and compacted in 521 lifts shallow enough to achieve 100% compaction, not to exceed 8 inches (loose) 522 in a single lift. 523

D. GRS Abutment 524 1. Reinforcement of Facing-wall/Wing-wall Corners for Flows <7 fps Velocity 525

During 100 year Storm: 526 1. The top three courses of Standard CMU block shall be filled with Class 527

A cement concrete (PennDOT Publication 408, Section 704) with one #4 528 epoxy coated reinforcement bar of sufficient length to engage all three 529 courses of block, embedded with a minimum of 2” cover, and provided 530 with a wet-cast cap in accordance with FHWA-HRT-11-026, Section 531 7.7.7. 532

2. All courses of hollow CMU blocks on the facing-wall/wing-wall corners 533 shall be filled as described in Section 1.1 above. This shall include a 534 minimum of 3 block columns comprised of the corner unit, and one unit 535 on each side of the corner unit. 536

2. Reinforcement of Facing-wall/Wing-wall for Flows of 7-10 fps Velocity 537 During 100 year Storm: 538

1. All courses of hollow Standard CMU blocks on the facing-wall and 539 wing-walls shall be filled with Class A cement concrete (PennDOT 540 Publication 408, Section 704), #4 epoxy coated reinforcement bars of 541 sufficient length to engage all courses of block, and embedded with a 542

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minimum of 2” cover and provided with a wet-cast cap in accordance 543 with FHWA-HRT-11-026, Section 7.7.7. 544

3. Construction of Facing-wall/Wing-wall for Flows of 10-12 fps Velocity 545 During 100 year Storm: 546

1. Large CMUs (24” x 24” x 72”) shall be used. In addition to horizontal 547 geotextile layers between blocks, two additional intermediate layers of 548 geotextile shall be used behind each block, wrap-faced against the GRS 549 wall so that geotextile spacing is at 8” intervals. 550

E. Site Drainage 551 All GRS structures shall include consideration for surface drainage both during and after 552 construction in accordance with FHWA-HRT-11-026, Section 7.1,1 and Section 8.2. 553

554 V. MEASUREMENT AND PAYMENT – Lump Sum. Includes all excavation required for GRS-555

IBS placement, the Reinforced Soil Foundation (RSF), the GRS abutments, the integrated 556 approach, geotextile, backfill material, CMUs, and scour protection. Does not include the beam 557 seat (when required), superstructure, removal of the existing structure as defined in the contract 558 drawings, temporary shorings, dewatering, maintenance and protection of traffic, or approach 559 roadway items. 560

561

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References 562

563 1. Adams, M., Nicks, J., Stabile, T., Wu, J., Schlatter, W., and Hartmann, J. (2011). 564

Geosynthetic Reinforced Soil Integrated Bridge System—Interim Implementation Guide. 565 Report No. FHWA-HRT-11-026, Federal Highway Administration, McLean, VA. 566

567 2. Geo-Institute, Committee on Shallow Foundations. (1999). Shallow Foundations on 568

Reinforced Soil, American Society of Civil Engineers, Reston, VA. 569 570

3. Wu, J.T., Lee, K., Helwany, S., Ketchart, K. (2006). Design and Construction Guidelines 571 for Geosynthetic-reinforced Soil Bridge Abutments with a Flexible Facing, NCHRP 572 Report 556, Transportation Research Board, Washington, D.C. 573

574 4. Adams, M. T., Nicks, J. E., Stabile, T., Wu, J. T. H., Schlatter, W., and Hartmann, J. 575

(2011). Geosynthetic Reinforced Soil Integrated Bridge System—Synthesis Report. 576 Report No. FHWA-HRT-11-027, Federal Highway Administration, McLean, VA. 577

578 5. Schlatter, W. (2011). "GeoSynthetic Reinforced Soil Integrated Bridge System (GRS-579

IBS)." Powerpoint Presentation, Defiance, Ohio. 580 581

6. Albert, G. R. (2011). "Huston Township, Clearfield County Mount Pleasant Road Bridge." 582 Powerpoint Presentation, Clearfield, PA. 583

584 7. Albert, G. R. (2012). Unpublished monitoring data for the Huston Township, Clearfield 585

County Mount Pleasant Road Bridge. 586 587

8. Vennapusa, P., White, D., Klaiber, W., Wang, S. (2012). Geosynthetic Reinforced Soil 588 for Low-Volume Bridge Abutments, IHRB Project TR-621, Center for Earthworks 589 Engineering Research and Bridge Engineering Center, Iowa State University, Ames, IA. 590

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