Section 574 — Geosynthetic Reinforced Soil-Integrated Bridge System

SYSTEM

Description

574.01This work consists of constructing geosynthetic reinforced soil -integrated bridge system s (GRS - IBS).

Material

574.02Conform to the following Subsections: GRS reinforcement geosynthetic 714.06 GRS open -graded backfill 703.20 Segmental retaining wall units 720.01(a) Select borrow 704.02

Construction Requirements

574.03Qualifications. Submit one of the following for approval at least 30 days before starting GRS -IBS work: (a)On-site supervisor and installation personnel . A résumé for each individual describing at least five constructed projects of similar size and complexity. Include project names, locations, contact information for project owners , and at least two photographs of each of the completed projects ; or (b)Manufacturer’s representative. Submit a list of five previously constructed projects of similar size and complexity assisted by the manufacturer’s representative. Provide at least two photographsof each of the completed projects. Include project names, locations, and cont act information for project owners.

574.04Submittals. At least 30 days before starting GRS -IBS work, submit the following according to Subsection 104.06: (a)Plan and elevation drawings for the structure containing the following: (1)A plan view of the structure showing: (a)Horizontal offset from the construction centerline to the face of the structure at defining points along the base. Include start and end roadway stations, and start and end wall stations,if different; (b)Location, l ength, coverage ratio, and type of reinforcement; (c)Centerline and size of drainage structure or drainage pipe behind, passing through, or passing under the structure; and(d)Location, length, and offset from the face of wall to guardrail, guardwall, and parapet structures. 653 (2) An elevation view of the structure showing:

(a)Elevation and station at horizontal and vertical break points and at least every 20 feet along the top of the structure face;

(b)Elevation and station at the top of the reinforced soil foundation (RSF) and at least every 20 feet along the structure base;

(c)Length and type of reinforcement;

(d)Location and elevation of each layer of geosynthetic;

(e)Distance and elevation along the structure face to all steps of the RSF;

(f)Distance along the structure face to where change in reinforcement lengths occur;

(g)Construction joints; and

(h)Original and final ground -lines.

(b)A typical cross- section view showing:

(1)Type and depth of facing elements and structural connections to reinforcing elements;

(2)Structure batter and angle of slopes below and above wall, if any;

(3)Length, spacing and type of reinforcement, and corresponding limits of excavation and reinforced fill placement zones;

(4)Location of guardrail, guardwall, and parapet structures. Include embedment depths, offset from structure facing, and connection details with structure reinforcement;

(5)Original and final ground -lines, including right-of- way limits;

(6)Estimated or known location of subsurface soil and rock units;

(7)Beam seat and beam seat retention details; and

(8)Top of abutment cap or coping details.

(c)General construction notes.

(d)Horizontal and vertical curve data and superelevation affecting the structure. Include match lines or other details to relate structure stationing to centerline stationing.

(e)Material list and summary of quantities.

(f)Details and dimensions for the RSF. Include steps and step encapsulation details.

(g)Details for the installation of structure drainage features. Include strip, sheet, edge, blanket, and underdrain systems, and associated piping if shown in the plans. 654 (h) Details for constructing the structures around drainage features, utilities, lighting foundations, traffic barriers, and other obstructions.

(i)Details for end of wall construction and transition to adjacent ground.

(j)Details for architectural treatment.

(k)Details for corners and curves.

(l)Details and dimensions of SRWU.

(m)Proposed compaction equipment. Include light -weight equipment for use within 3 feet of the wall face and methods for stabilizing the face during compaction. Include a checklist showing each of the items specified have been addressed. If revisions are required, make corrections and resubmit.

574.05General. Survey according to Section 152 and verify the limits of the GRS -IBS installation . Perform excavation and dewatering according to Section 209. Excavate wall foundations to within 4 inches horizontally and vertically from the staked location.

574.06Reinforced Soil Foundation Construction. RSF consists of GRS open- graded backfill encapsulated in geosynthetic reinforcement. Provide a smooth, uniform foundation surface without protruding objects. Place geosynthetic reinforcement perpendicular to the abutment and wingwall faces. Overlap geosynthetic reinforcement so the upstream geosynthetic sheet overlies the downstream sheet (such as shingled). Overlap geosynthetic joints at least 3 feet in all directions. Pull the geosynthetic taut, remove wrinkles, and lay flat before placing the GRS open-graded backfill. Do not operate equipment directly on the geosynthetic reinforcement. Place at least a 6-inch lift of GRS open- graded backfill over the geosynthetic reinforcement before operating equipment over the reinforcement. Compact GRS open- graded backfill according to Subsection 574.09. Grade and level the top of the RSF before final encapsulation. Construct the top of the RSF to within 1 inch of plan elevation. Final encapsulation includes the following:

(a)Fold the geosynthetic from the back of the RSF at the top finish elevation, then fold over the geosynthetic from the front of the RSF so it overlies the geosynthetic at the back of the RSF and secure. (b) Secure geosynthetic firmly against the backfill, wrapping and securing the geosynthetic tight around the corners of the RSF. (c) Do not leave exposed backfill or loose geosynthetic.

574.07Segmental Retaining Wall Units Requirements. Provide SRWUs that have smooth upper and lower bearing surfaces. Do not use SRWUs with finished faces containing chips larger than 1 inch in any direction, finished faces having cracks in any orientation wider than 0.02 inch and longer than 25 percent of the nominal height of the unit, or SRWUs that are broken. Remove without damaging the SRWUs protrusions and loose material from the SRWU surfaces that come in contact with one another or the 655 geosynthetic reinforcement to achieve full contact between the geosynthetic reinforcement and the SRWU surfaces.

574.08Erection Procedures. Erect the GRS -IBS according to the approved drawings and manufacturer’s recommendations and to the tolerance requirements in Table 574-1. Table 574-1

Construction Tolerance

Facing Type Vertical ,

inch(1) (±) Horizontal , inch(2) (±) Horizontal

Straightedge

Point Check ,

inch(3) (±) SRWUs 0.6 0.6 0.6

(1)Wall vertical tolerance at top of wall for every 10 feet of wall height. For example, 65 feet wall height multiply 6.5×value.

(2)Wall horizontal tolerance at top of wall for every 10 feet of wall height.

(3)Maximum horizontal deviation at a point in the wall from a 10 -foot metal straightedge placed horizontally or vertically on the theoretical plane of the design face. Place the first course of SRWUs so that they are level, even, and within 1 inch of planned horizontal and vertical locations. Fill SRWUs with u nit fill as shown in the approved drawings. Construct the external face of the first row of SRWUs in the abutment face and wingwalls to within 1 inch of the horizontal location shown in the approved drawings. Place SRWUs side by side for the full length of the wall such that adjoining blocks are located according to the manufacturer’s recommendations. Sweep the top of the SRWU clean of debris and fill material before placement of geosynthetic reinforcement and SRWUs. Plac e each SRWU tightly against the adjacent SRWU so that vertical joints of each course have less than a ¼ -inch gap and the joint is midway between those of the underlying course. Remove SRWUs that have become cracked, chipped, or broken. Complete each course of SRWUs before starting the next course. Pull layers of geosynthetic reinforcement taut, remove wrinkles, and lay flat. Use pins, stakes, fill piles, or the manufacturer’s recommended method to anchor the reinforcement before placing backfill to prevent wrinkles and ensure full contact between the reinforcement and top of the RSF backfill. Place the geosynthetic within 1 inch of elevations shown in the approved drawings. Where placing geosynthetic reinforcement between SRWUs place the reinforcement so that no less than 85 percent of the full depth (front to back) of the SRWU is covered by the reinforcement as measured to the front face of the wall. Cut excess geosynthetic reinforcement that extends past the front face of the SRWUs clean and flush with the wall face. Construct subsequent courses following the same procedure. Check the GRS wall for plumbness at least every other lift. Correct deviations greater than 1 inch when measured vertically with a 10 -foot metal straightedge. Correct high areas by grinding or shimming with manufacturer recommended shims. Do not use shims over ⅟ 16 inch in stack thickness or within 1 inch of the face. Check every other row of SRWU alignment before placing backfill. Construct corners according to the approved drawings. In the bearing bed zone, place secondary geosynthetic reinforcement as shown in the plans. No connection between the SRWUs and secondary geosynthetic is required. When seams are necessary, butt adjacent rolls together without overlap. Stagger seams at least 24 inches apart on subsequent lifts and only in the 656 direction parallel to bridge centerline. Trim geosynthetic reinforcement overlaps in contact with the surfaces between the SRWUs to avoid varying the geotextile reinforcement thicknesses between the SRWUs.

574.09Backfilling and Compaction. Do not operate equipment directly on the geosynthetic reinforcement. Place at least 6 inches of uncompacted GRS open- graded backfill over the geosynthetic reinforcement before operating equipment over the reinforcement e xcept in the bearing bed zone where at least 4 inches of uncompacted GRS open- graded backfill is allowed. Place GRS open -graded backfill immediately following placement of each course of SRWUs and geosynthetic reinforcement. Backfill from the front of the wall to the back and remove wrinkles that form during the backfilling operation. Correct damaged or misaligned geosynthetic reinforcement. Place and grade the GRS open -graded backfill level for areas behind the SRWUs before compacting. Except for the area within 3 feet from the SRWUs, use only light- weight mechanical tamper, plate, or roller or rubber- tire equipment for compaction. If rubber tire equipment is used, limit speeds to less than 5 miles per hour with no sudden starting, braking, or sharp turning. Use only an approved hand- operated lightweight vibrating plate or roller within 3 feet of the back of the SRWUs. Correct SRWUs that are displaced by compaction operations before placing additional rows of SRWUs. Perform a method compaction test for approval on the first two lifts to establish the number of passes, lift thickness, and quantity of wetting needed to adequately consolidate the GRS open- graded backfill until there is no visible evidence of further consolidation. Follow the approved compaction procedure for the remainder of the abutment construction without the need for density tests. Fill and compact depressions caused during compaction so that the compacted lift is level with the top of the SRWUs before constructing the next lift. At the end of the day ’s operation, slope the last lift of backfill away from the GRS -IBS structure to direct surface runoff away from the interior of the structure. Do not allow surface runoff from adjacent areas or stream flow to enter the GRS abutment construction area.

574.10Wingwall Fill Slope Side. Construct wingwalls above the RSF. Backfill in front of the wingwalls as the GRS wall advances upward. Construct the fill slope to original ground elevation that allows water to drain from wall face outward. Prevent surface water runoff on fill slopes.

574.11Superstructure Placement. After folding the final wrap in the beam seat zone, adjust the final grade to provide an even contact between the top of the reinforced beam seat zone and the bottom of the concrete beam seat. Set bridge structure elements square and level without dragging across the beam seat surface.

574.12Integrated Approach Construction. Following the placement of the superstructure, place geosynthetic reinforcement layers along the back of the superstructure and backfill according to Subsection 574.09. Place geosynthetic reinforcement with seams that are perpendicular to the abutment face.

574.13Acceptance. See Table 574-2 for samplin g, testing, and acceptance requirements. Material for GRS -IBS will be evaluated under Subsections 106.02 and 106.03. Construction of GRS -IBS will be evaluated under Subsections 106.02 and 106.04. 657 Excavation and dewatering will be evaluated under Section 209. Survey work will be evaluated under Section 152.

Measurement

574.14Measure the Section 574 pay items listed in the bid schedule according to Subsection 109.02 and the following as applicable: When measuring GRS-IBS by the square foot, measure the front face of wall, including cap units.

Payment

574.15The accepted quantities will be paid at the contract price per unit of measurement for the Section 574 pay items li sted in the bid schedule. Payment will be full compensation for the work prescribed in this Section. See Subsection 109.05 . Table 574-2 Sampling, Testing, and Acceptance Requirements

Material or

Product

(Subsection) Type of

Acceptance

(Subsection) Characteristic Category Test Methods

Specifications Tolerance Sampling

Frequency Point of

Sampling Split

Sample Reporting

Time Remarks

GRS -IBS

backfill Measured & tested for conformance (106.04) Gradation – AASHTO T 27 & T 11 – 1 per 1000 tons Each source Yes Before use in work See

Subsection

703.20

GRS -IBS

backfill Measured & tested for conformance (106.04) Quality – AASHTO T 104 – " Each source Yes " See

Subsection

703.20

Quality

Electrochemical

requirements – AASHTO T 90 – "

Each source Yes

Yes "

See

Subsection

703.20AASHTO D 5821 – " " ASTM T289 – " 24 hours Compaction – (1) – 1 for each lift In place Yes, if requested " –

(1)Do not apply density requirements as measured by AASHTO T 310 to material cannot be tested or compacted to maximum values determined by AASHTO T 99. Compact each lift, full width, until there is no visible evidence of further consolidation.