140P2022R0045-0004_Att01a-Q36_RevSpecSect323223_01-MechStabilizedEarthWall_220803_0004.pdf

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MECHANICALLY STABILIZED EARTH WALL

SECTION 323223.01 - MECHANICALLY STABILIZED EARTH WALL

PART 1 - GENERAL

1.1 SUMMARY

A. Section Includes:

1. Furnishing certified design calculations and shop drawings.

2. Fabrication, furnishing and installation of steel facing units, soil reinforcement elements, wrapping the select backfill, joint materials and coping.

3. Technical representatives.

4. Wall construction.

5. Excavation and backfill for the wall.

6. Other services necessary for construction of the modified mechanically stabilized earth

(Modified MSE) geogrid supported wall.

B. Related Requirements:

1. Section 312000 "Earth Moving" for excavation and backfill execution requirements.

2. Section 315000 "Excavation Support and Protection" for excavation temporary supports and protections.

3. Section 313719: Boulders

1.2 DEFINITIONS

A. Modified Mechanically Stabilized Earth (Modified MSE) Wall: A retaining wall system that consists of reinforced soil, soil reinforcement, and facing elements connected to the soil reinforcement.

B. Soil Reinforcement: A material placed within a soil mass to provide wall stability and increase the strength of the soil. Soil reinforcement for this Modified MSE Wall will consist of geogrid.

C. Reinforced Soil: Backfill soil placed in the reinforced zone meeting the material requirements detailed in Part 2 of this specification and placement following the procedures detailed in Section 312000 “Earth Moving”.

D. Reinforced Zone: Practical limit for placement of reinforced soil. Limit begins near the termini of the bottom layer of soil reinforcement and extends at a slope determined by OSHA regulations and the in-situ soils.

E. Retained Soil: Soil retained by the Modified MSE Wall mass behind the reinforced zone and meeting the material requirements detailed in Part 2 of this specification and placement following the procedures detailed in Section 312000 “Earth Moving”.

F. Foundation Soil: Soil below the top of the leveling pad elevation and beneath the reinforced zone and meeting the material requirements detailed in Part 2 of this specification and placement following the procedures detailed in Section 312000 “Earth Moving”.

Srour, Chadi (USCS686173) Cloud

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G. Facing Panels: Galvanized steel wire formed baskets that will contain stone drainage at the face of the wall.

H. Connection Device: The item may be used to connect the soil reinforcement to the facing natural stone.

I. Geotextile Filter: Material placed behind the stone drainage layer which prevents migration of fines, yet still allows for drainage of water through the joints.

J. Wedges: Temporary supports used to position the facing units during construction.

K. MSE Wall Supplier: The vendor that is responsible for supplying the MSE system including the soil reinforcement, facing panels, and connections. The MSE Wall Supplier also designs the MSE system for internal stability and the components of the MSE Wall and prepares the shop drawings, and provides on-site assistance during construction.

L. Design Height: For wall with level fill, the design height is the distance from the top of the leveling pad to the top of the pavement, sidewalk, or soil (if unpaved) supported by the wall.

1.3 MSE WALL DESIGNER/SUPPLIER REQUIREMENTS

A. The wall designer shall be a professional Engineer licensed by the State of Maine and shall prepare, sign, and date the design calculations, shop drawings, for the Modified MSE Wall in the contract.

1. The wall designer shall have experience in the design and construction of a minimum of five MSE Wall projects of similar type. This experience shall include MSE Walls of equivalent complexity and similar height to the wall being designed as part of this contract. A letter certifying the wall designer’s previous design experience shall be submitted to the Contracting Officer.

2. The wall designer shall thoroughly check the design calculations and shop drawings to verify compliance with the specifications and shall also sign and date each design pages.

1.4 SUBMITTAL REQUIREMENTS

A. The Contractor shall be responsible for reviewing all available geotechnical investigation reports and conduct his own investigations if more information is required.

1. The Contractor’s signature on the proposal shall certify that this review has been performed and that the designer has all relevant geotechnical information and the MSE Wall Supplier of the Modified MSE Wall.

2. Prepare a Field Construction Manual in compliance with the approved wall design and this specification.

B. Shop Drawings and Calculation Submittals

a. Plan shop drawing for the full length of the cross-section drawings at 50-foot intervals or at each change of wall height exceeding 18 inches.

b. Elevation view in equal horizontal and vertical scale for the full length of the wall.

c. Horizontal and vertical curve data affecting the wall.

d. Match lines or other details related to wall centerline stationing.

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e. Connection details and dimensions between natural stone block facing, embedded devices and soil reinforcement.

f. Details for construction.

g. Architectural details, including surface details, and the natural stone finish.

h. Name of MSE Wall Supplier and their QA/QC documents for wall design, facing fabrication, soil reinforcement fabrication, and wall construction.

i. Test panel construction, if specified.

j. General notes, in accordance with Contracting Officer specifications, required for constructing the wall.

k. Copy of calculations.

PART 2 - PRODUCTS

2.1 MATERIALS

A. Acceptance of Materials

1. Unless stated otherwise, at least three weeks prior to construction of the Modified MSE

Wall, the Contractor shall furnish the Contracting Officer Certificates of Compliance for each material listed below, certifying that all materials comply with the applicable contract specifications, including a copy of all test results. All tests shall be performed by an independent testing laboratory unless noted otherwise. A Certificate of Compliance shall be provided by the Contractor for each material source. A new Certificate of Compliance shall be provided any time the Contractor changes the source of materials.

Refer to the material information below for additional specific requirements of each Certificate of Compliance.

2. Acceptance will be based on the Certificate of Compliance, accompanying test reports, visual inspection, and/or tests ordered or performed independently by the Contracting Officer. The Contracting Officer retains the right to order or perform independent tests to verify information.

B. Reinforced Soil

1. Material shall meet the following requirements:

a. Screened virgin aggregate material meeting the design requirements.

b. Sieve Analysis.

1) Sieve analysis tests shall be performed according to the applicable ASTM Standards.

c. Angle of Friction Requirements based on ASTM D Shear test method.

d. Electrochemical Requirements for Wall with Geosynthetic Reinforcements:

Base Polymer TEST SPEC.

RANGE

TEST

METHOD

TESTING

RATE

High Density Polyethylene (HDPE) and Polypropylene (PP) pH 3≤ pH AASHTO T 289 1/5,000 cu. Yd.

per source

Polyester (PET) pH 3≤ pH ≤ 8 AASHTO T 289 1/5,000 cu. Yd.

per source

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2. Contractor Certificate of Compliance for Reinforced Soil

a. A Certificate of Compliance shall be provided by the Contractor for each source at a rate of 1 per 5,000 cubic yards with a Certificate of Compliance for sieve analyses provided at a rate of 2 per 5,000 cubic yards. A new Certificate of Compliance shall be provided any time the Contractor changes the source of the reinforced soil materials or the material within a given source changes.

C. Soil Reinforcement

1. The contractor shall check and verify with the Contracting Officer if the Buy American is applicable to Geogrid and its accessories, and follow the Park Service guidelines.

2. Geogrid reinforcement shall be approved by the CO prior to the start of construction and shall consist of a high-density polyethylene (HDPE) geogrid reinforcement with an ultimate tensile strength greater than two tons per foot and maximum allowable design strength greater than 0.8 tons per foot.

3. Geogrid reinforcement shall be oriented, drawn, long chain high-density polyethylene containing stabilizers and inhibitors added to the base plastic for resistance to ultraviolet and heat degradation. Geogrid reinforcements and their connection devices shall be the same connection devices. Geogrid reinforcement manufacturer’s certification shall include ultimate tensile strength ASTM D6637 quality assurance test results, at a minimum rate equal to, or greater than, the sampling rate defined in Table 2411-10 (ASTM D4354) for each type of geogrid used.

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Table 2411-10 ASTM D4354 Geosynthetic Manufacturer Quality Assurance Testing Rates

Number of Rolls in Lot* Number of Tests 1 to 2 1 3 to 8 2 9 to 27 3 28 to 64 4 65 to 125 5 126 to 216 6 217 to 343 7 344 to 512 8 513 to 729 9 730 to 1000 10

1001 or more 11

* A lot is defined as a group of rolls from an individual production run.

1. Contractor Certificate of Compliance for Soil Reinforcement

a. For metallic wall reinforcement, a mill test report containing the yield and ultimate tensile strength for the soil reinforcement shall be provided along with test results for the galvanizing.

b. A new Certificate of Compliance shall be provided with each additional shipment of reinforcement and any time the Contractor changes the source of reinforcement.

The Certificate of Compliance shall contain all applicable mill test reports for each shipment.

D. Geotextile

1. Type 1 Geotextile for use to cover the drainage layer and shall overlap the underlying reinforced soil and overlaying drainage layer by a minimum of 6 inches (as shown in the construction drawings).

2. Certificate of Compliance

a. Certificate of Compliance shall include a manufacturer’s certificate stating the furnished geotextile meets the requirements of the specifications, as evaluated by the manufacturer’s quality control program.

1) Geotextile manufacturer’s certification shall include quality assurance test results at a rate equal to or greater than the sampling rate defined in (ASTM D4354).

E. Welded Wire Facing Units

1. Wall facing material shall consist galvanized steel facing forms consisting of minimum

1.78-in x 12.75-in (0.192”x 0.225”) x 9.1-ft galvanized steel bars or dimensions approved by the CO.

2. Forms that contain visible defects such as, but not limited to, vertical or horizontal seams, conspicuous stains, or color streaks shall be repaired to the satisfaction of the Contracting Officer or removed and replaced at the Contractor’s expense.

a. All units shall be cut/supplied within the following tolerances:

1) Position of facing connection device shall be within 1 inch of the shop drawing position.

3. Facing units may be rejected at the project site because of failure to meet any of the requirements specified above. In addition, any or all of the following defects shall be sufficient cause for rejection:

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a. Defects that indicate imperfect cutting,

b. Bending or misalignment of connections, if used.

c. Defects indicating excessive weathering, cracks.

d. Any damage that would prevent making a satisfactory joint or will not retain drainage layer material.

PART 3 - DESIGN REQUIREMENTS

3.1 The Modified MSE Wall(s) shall be designed using LRFD methodology (AASHTO LRFD 2018). The Contractor shall provide the MSE Wall designer with a complete set of project plans and specifications, geotechnical reports and all other necessary information to design the wall.

The Contractor shall ensure that the wall design is compatible with all other project features that may impact the design and construction of the wall.

3.2 The design shall consider the internal and external stability of the wall mass including eccentricity, sliding, and bearing pressure, including temporary construction slopes or stockpiles. The design shall be in accordance with any restrictions listed in wall design and construction provisions of the AASHTO LRFD Bridge Design Specifications, 2018, or the latest with all interim revisions. The design shall also be in accordance with the Federal Highway Administration requirements as reported in publication Nos. FHWA-NHI-10-024 and FHWA-NHI-10-025, entitled "Design and Construction of Mechanically Stabilized Earth Wall and Reinforced Soil Slopes - Volumes I and II". If the provisions of the above documents conflict, the designer shall follow the most stringent requirement as determined by the Contracting Officer. The internal stability design shall be performed using the Simplified Method as defined by the AASHTO LRFD Bridge Design Specifications (2018).

3.3 The design shall meet the following requirements:

A. For design of Modified MSE wall, the reinforced soil shall have a unit weight of 0.120 kcf and a maximum friction angle of 34 degrees. Retained soil (outside of the reinforced zone) properties are defined in the Geotechnical report(s), but not to exceed a friction angle of 30 degrees for design.

B. For design purposes, passive pressure in front of the wall mass shall be assumed to be zero.

C. The design life for the wall system, other than soil reinforcement and connections, shall be 75 years. The design life for steel soil reinforcement and connections, including corrosion protection, shall be 100 years. The design life for geosynthetic reinforcement and connections used in the wall system, including long term creep, degradation, and installation damage, shall be 100 years. For analysis of corrosion degradation life, follow the requirements of “Corrosion/Degradation of Soil Reinforcements for Mechanically Stabilized Earth Wall and Reinforced Soil Slopes” (FHWA-NHI-09-087)

D. A surcharge load to account for snow loads, future maintenance operations, parking or future re-grading shall be applied. The surcharge load shall be 250 psf and placed directly behind the top panel with a maximum load factor of 1.35 and a minimum load factor of 1.0 for internal and external stability.

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Differential settlement shall be less than 1/100 along the length of the wall and normal to the wall alignment. Adequate joint width/or slip joints shall be provided to accommodate movements without facing panel cracking. The wall shall be designed and detailed to accommodate differential movements and loads from adjacent structure or structures intercepting the wall panels, if /where applicable.

E. Details shall be provided for post or corner element panels to the NPS for review. The design shall include the attachment of soil reinforcement to the corner element. Corner elements shall be one piece. Acute corner angles shall not be less than 70 degrees.

F. The minimum soil reinforcement length shall be 70% of the wall height (see Definitions) and not less than 8.0 ft. unless the reinforcement length is governed by overall stability. If the length of soil reinforcement is governed by overall stability, the designer shall meet the requirement of overall stability. The length of soil reinforcement for the wall shall be constant for all layers unless approved in writing by NPS. The maximum vertical spacing of soil reinforcement layers shall be 18 inches.

G. If the placement of an obstruction in the soil reinforcement zone, such as a light post foundation or guiderail post, the design of the wall near the obstruction shall be modified using one the of the following alternatives:

a) Splay the reinforcement around the obstruction, however geogrid reinforcement may not be splayed unless the connection has been specifically fabricated to accommodate a splay and the connection detail has been approved by NPS. Horizontal deviation is referred to as splay.

If used, the splay is limited to 15 degrees.

b) Assuming reinforcement layers must be partially or fully severed in the location of the obstruction, design the surrounding reinforcement layers to carry the additional load which had been carried by the severed reinforcements. The portion of the wall facing in front of the obstruction shall be made stable against a toppling or sliding failure.

c) Place a structural frame around the obstruction capable of carrying the load from the reinforcements in front of the obstruction to reinforcements connected to the structural frame behind the obstructions. The steel frame and connections shall be designed in accordance with Section 6 of the AASHTO Bridge Design Specifications. The steel frame and connections shall be galvanized, and long-term nominal strength shall consider corrosion losses. If a steel frame is used, an Impervious Layer (Geomembrane) is required above the steel frame regardless of the system or geogrid reinforcement manufacturer.

H. The Modified MSE wall shall be set on compacted foundation soil. If a bedrock, or a boulder is encountered along the footing, vertical steps can be formed to avoid rock excavation. Vertical steps in the footing shall not be greater than 2.5 feet, and the length of wall between vertical steps shall not exceed 9 feet.

I. The ground on the exposed side of the wall shall slope away from the wall. The surface water on the backfill side shall be drained away from the wall to prevent runoff next to the facing panels and ponding above the reinforced zone. Surface run-off shall not be permitted to pass over the top of the wall. A wall coping, drainage system, or a properly designed ditch (swale) shall be used to carry run-off water along the wall to be properly infiltrated.

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J. During the construction of the Modified MSE wall, utilities are to be placed minimum 10 feet outside the wall limits when possible. If relocation is impractical or impossible, new utilities installed within 10 feet limits require NPS approval. However, no new wet utilities (except for utilities that are used for wall drainage) may be placed longitudinally (i.e., parallel to the wall).

New utilities placed within 10 feet may be placed transversely (i.e., perpendicular to the wall) All pipes and conduits must be designed for any surcharge loading due to soil or structure bearing pressures and possible resulting deformations. All wet utilities (except for utilities that are used for wall drainage) must be cased; if facilities are too large or cannot be cased effectively, a site specific design is required. Utility owners may choose to case dry utilities to allow for future maintenance or access; however, casing is not required for dry utilities. Future open trench excavation is prohibited in order to protect the wall from potential undermining.

Future excavation within 10 feet in any direction is prohibited.

K. No drilling or driving of posts (sign, guardrail, etc.) or other roadside hardware in the reinforced zone shall occur after placement of the reinforced soil. If such roadside hardware is required, the design and plans shall include details such as sleeves to accommodate it.

L. Stability Analysis shall be conducted. All appurtenances behind, in front of, under, mounted on, or passing through the wall such as drainage structures, utilities, noise wall, barrier and moment slab, footings, traffic, slope surcharge or other appurtenances shown on the plans shall be accounted for in the stability analysis.

M. The Resistance Factors, Φ, for Tensile and Pullout Resistance for MSE Wall shall be according to AASHTO LRFD Bridge Design Manual (2018).

PART 4 - EXECUTION

4.1 GENERAL REQUIREMENTS

A. A modified MSE Wall Preconstruction Meeting shall be held at least 15 days before wall construction begins and after the Contracting Officer has completed the review of the shop drawings and design calculations.

1. At a minimum, this meeting shall be attended by the Contracting Officer

Representative(s), Contractor, the Contractor crew chief or foreman who will erect the wall, and a technical representative from the MSE Wall Supplier.

2. The Contractor shall provide a complete written sequence of MSE Wall construction at the meeting and review the sequence, any construction issues, the specifications and the MSE Wall requirements and determine any issues that need to be resolved prior to construction.

B. The MSE Wall Supplier shall provide a documented Field Construction Manual describing in complete detail the sequence of construction steps. The MSE Wall Supplier shall also provide an experienced technical representative on the project site during the erection of the first full height section, and the following sections if needed until the Contracting Officer determines that the Contractor has demonstrated the ability to construct the wall system on his own while meeting all project construction requirements. The MSE Wall Supplier technical representative shall be available to provide instructions, guidance in pre-construction activities, and on-site technical assistance anytime during construction at no additional cost to NPS. Every step in the sequential construction of the Modified MSE Wall shall comply with the construction

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requirements and tolerances. All instructions from the MSE Wall supplier that are not contrary to these special provisions shall be followed unless otherwise directed in writing by the Contracting Officer.

C. The Contractor shall be solely responsible to coordinate construction of the MSE Wall with adjacent roadway work and other construction and ensure that resulting or existing obstructions shall not impact the construction or performance of the wall.

D. Wall Bedding

1. The bedding for the wall structure shall be graded level for a width equal to the length of the soil reinforcement element plus 20 inches or as shown on the plans. The entire graded area shall be compacted according to ASTM D 698 to 95 Percent of the subgrades dry density before wall construction begins.

2. Prior to wall construction and subsequent to clearing and grubbing any unsuitable foundation material shall be excavated and replaced with granular fill (consist of clean coarse aggregate (AASHTO no 57 stone, or other material approved by the Contracting Officer per these specifications) and compacted with a smooth wheel steel vibratory drum roller.

3. Excavation for the Modified MSE Wall foundation and reinforcement will include soils containing boulders. If large boulders are encountered within the reinforced zone or bearing pad excavation, the contractor shall clean the area expose the bedrock/large boulder and place bedding stone meeting the top of the foundation elevation. The thickness of the bedding stone should be so selected its top is flush with the top of the rock/ large boulder.

4. The contractor shall examine the reinforced zone or bearing pad to determine its adequacy to receive natural stone wall system work. Evidence of inadequate base shall be brought to the immediate attention of the Landscape Architect or the Contracting Officer.

E. Reinforced and Backfill Soil Placement

1. Soil placement shall closely follow erection of each facing unit. Soil shall be placed in a way that does not cause damage or disturbance to the wall or soil reinforcement. Soil reinforcement shall be maintained in a horizontal position along its length and shall be placed perpendicular to the wall face, except as shown in the plans.

2. The soil reinforcements shall wrap fully the front face of the wall

3. Soil within the reinforcement zone shall be placed in nine inch lifts and compacted to a density of not less than 95 percent of maximum density using the specified density method in accordance with ASTM D 698. The maximum lift size shall be nine inches loose.

4. Compaction within 3 feet of the back face of the natural stone blocks shall be achieved by means of a minimum of 3 passes with a lightweight mechanical tamper, roller or vibratory system. The number of passes needed for the compaction within the 3-foot zone shall be determined using a test strip with the proposed compactor and lift height(s) for this zone. The maximum lift size within 3 feet of the back face shall be 8 inches loose and fill shall be compacted to a density of not less than 95 percent of maximum density using the specified density method in accordance with ASTM D 698

5. Sieve analysis testing for quality control shall be performed according to the relevant section of this specification. Sieve analysis testing for quality assurance shall be performed according the ASTM D 422, or other approved equivalent.

6. The MSE Wall Supplier may require the Contractor to perform quality control density tests beyond the quality assurance tests required by the Contracting Officer. The

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contractor shall perform the MSE Wall suppliers required tests and submit the test results to the Contracting Officer.

7. No drilling or driving of piles, posts (sign, guardrail, etc.) or other roadside hardware through the reinforced soil shall occur after placement of fill.

8. At the end of each day’s operations, slope the last lift of reinforced soil to direct surface runoff away from the wall. Do not allow surface runoff from adjacent areas to enter the wall construction area.

9. The area in front of the wall and around the leveling pad should be backfilled as soon as practically possible. Tamping type (sheep’s foot) rollers shall not be used for compaction of the reinforced soil.

10. At no time shall construction equipment come in direct contact with the soil reinforcement. A minimum reinforced soil thickness of 6 inches geosynthetic soil reinforcement shall be required prior to operation of vehicles. Each course or layer shall be compacted up to or slightly above (-0.0 inches, + 2.0 inches) the location of the next connection for the soil reinforcement prior to placing the next layer of reinforcement as designated in the erection sequence provided by the manufacturer of the wall system.

11. If the reinforced soil material changes or a new source or material is used, construction of the modified MSE Wall shall be halted until the Contractor provides a new Certificate of Compliance and accompanying test reports.

F. Wall Erection

1. If water has ponded in the reinforced soil zone during construction; pump the water out and obtain Contracting Officer’s approval prior to constructing the wall and reinforced zone.

Generally, construction should begin from existing structures toward the open end of the wall.

Facing units vertical and horizontal alignment tolerances shall not exceed 3/4 inch per 10 feet. Do not construct any unit more than 1/2 inch out of vertical or horizontal alignment from the adjacent blocks. The completed wall shall have (cap or top of wall) overall horizontal and vertical tolerance not to exceed 1/2 inch per 10 feet of the planned location.

Facing elements out of alignment shall not be pulled or pushed into proper place, as that may cause damage to the facing element or soil reinforcement. If misalignment occurs, the reinforced soil and the soil reinforcement shall be removed and the facing panels reset to the proper alignment.

2. Embedment depth of the wall shall be a minimum 48 inches feet below ground surface;

to accommodate estimated frost penetration depths in Mount Desert, ME.

G. Soil Reinforcement Installation

1. Soil reinforcement shall be placed in accordance with the shop drawings and manufacturer recommendations. Reinforcement shall consist of HDPE geogrid, generally installed perpendicular to the back of wall, with at least 3 feet of overlap between pieces.

When backfilling, the geogrid shall be pulled in tension to remove any slack in non-bolted connections. Bar mat soil reinforcement shall not be skewed, unless the panel connector is specifically fabricated for such. No alteration or cutting of reinforcement is permitted unless clearly detailed in the approved shop drawings. Connections must be made in accordance with the manufacturer’s recommendations.

2. Any wall system material that becomes damaged or disturbed during the installation of the wall system shall be removed, replaced or corrected at the Contractor’s expense, as directed by the Contracting Officer. Wall may be rejected due to failure to meet any of

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the requirements of the above specifications that will require future maintenance or will impact aesthetics, function, performance or life of the wall.

END OF SECTION 323223.01