675SOIL NAIL WALL

677.04 Materials The Contractor shall be responsible for the purchase or

manufacture of the precast concrete facing panels, reinforcing mesh or strips, panel/reinforcement connections, bearing pads, joint filler, an d all other necessary components. The Contractor shall furnish to the Resident the a ppropriate Certificates of Compliance certifying that the applicable wall materials meet t he requirements of the project specifications. All materials used in the construction of the MSE retaining walls shall meet the requirements specified in the following subsections of the Maine Standard Specifications and as specified herein. Materials not conforming to this section of the specifications , or from sources not listed in the contract documents, shall not be used without wri tten consent from the Resident. 677.041 Reinforced Concrete Facing Panels Reinforced concret e facing panels shall meet the requirements specified in the following subsections: Structural Precast Concrete Units 712.061 Drainage Geotextile 722.02 677.042 Precast Panel Tolerances and Surface Finish Concrete surface for the front face shall have a smooth steel formed finish, or as noted on th e plans. The rear face shall have an unformed surface finish. The rear face of the panel sh all be roughly screeded to eliminate open pockets of aggregate and surface distortions in excess of ¼ in. All uncoated steel projecting from the panel unit shall be galvanized in acc ordance with ASTM A 123/A 123M (AASHTO M 111) with a minimum coating thickness of 2 oz/ft2. Defects Defects which may cause rejection of precast units in clude, but are not limited to, the following: Any discontinuity (crack, rock pocke t, etc.) of the concrete wh ich could allow moisture to reach the reinforcing steel. Rock pockets or honeycomb over 6 square inches in area or over 1 inch deep. Edge or corner breakage exceeding 12 inches in length or 1 inch in depth. Any other defect that clearly and substantially impacts the qua lity, durability, or maintainability of the structure, as determined by the Fabricat ion Engineer. Repair honeycombing, ragged or irregular edges and other non-st ructural or cosmetic defects using a patching materia l from the MaineDOT Qualified P roducts List (QPL). The repair, including preparation of the repair area, mixing and ap plication and curing of the patching material, shall be in accordance with the manufacturer 's product data sheet. Corners that are not exposed in the final product may be ground smooth with no further repair necessary if the depth of the defect does not exceed 1/2 inch. Remove form ties and other hardware to a depth of not less than 1 inch from the face of the concrete and patch the holes using a patching material from the MaineDOT QPL. 6-211 Repair structural defects only w ith the approval of the Fabrica tion Engineer. Submit a nonconformance report (NCR) to the Fabrication Engineer with a proposed repair procedure. Do not perform struct ural repairs without an NCR tha t has been reviewed by the Fabrication Engineer. Structural defects include, but are not b e limited to, exposed reinforcing steel or strand, cracks in bearing areas, through c racks and cracks 0.013 inch in width that extend more than 12 inches in length in any directio n. Give the QAI adequate notice prior to beginning any structural repairs. Precast panel tolerances shall comply with the following; unit s that do not meet the listed tolerances will be rejected.

677.06 Submittals

677.07 Delivery, Storage and Handling

677.08 Wall Excavation The excavation and use as fill dispos al of all excavated

material shall meet the requirements of Section 203 - Excavatio n and Embankment, except as modified herein. Temporary excavation support as required s hall be the responsibility of the contractor.

677.09 Foundation Preparation. The foundation for the struct ure shall be graded

level for a width equal to the length of reinforcement elements plus 5 ft, or as shown on the plans. Prior to wall construction the foundation shall be comp acted with at least 10 passes of a smooth wheel vibratory r oller weighing at least 10,000 lbs . Any foundation soils found to be unsuitable or incapable of sustaining the required compac tion shall be removed and 6-217 replaced with Special Borrow Material. The foundation for the structure shall be approved by the Resident before erection is started. A concrete leveling pad shall be constructed as indicated on t he submitted plans. The leveling pad shall be cast to the design elevations as show n on the plans. Allowable elevation tolerances are +0.01 ft and -0.02 ft from the design elevations. Placement of wall panels may begin after 24 hours curing time of the concrete lev eling pad.

677.10 Wall Erection A field representative from the proprie tary wall system being

used shall be available, as needed, during the erection of the wall. The services of the representative shall be at no additional cost to the project. Precast concrete panels shall be placed so that their final po sition is vertical or battered as shown on the plans. The vendor representative shal l specify the required back- batter so that the final position of the wall is vertical. Ear th berms at the footing shall be placed to maintain the desired position of panels. For erectio n, panels are handled by means of lifting devices connected to the upper edge of the panel. P anels should be placed in successive horizontal lifts in the sequence shown on the approv ed shop drawings as backfill placement proceeds. As backfill material is placed behind the panels, the panels shall be maintained in position by means of temporary wedges or bracing according to the wall supplier’s recommendations. Concrete facing vertical tolerances and horizontal alignment tolerances shall not exceed ¾ inch when measured with a 10 ft straightedge (¼ in/yd) . During construction, the maximum allowable offset in any panel joint shall be ¾ in. The overall vertical tolerance of the wall (from top to bottom) shall not exceed ½ inch per 10 ft of wall height.

677.11 Backfill Placement Backfill shall not be placed betw een November 1st and

April 1st. Backfill placement shall closely follow erection of each course of panels. Backfill shall be placed and compacted in such a manner as to a void any damage or disturbance of the wall materials or misalignment of the facing panels or reinforcing elements. Any wall materials which become damaged during backf ill placement shall be removed and replaced at the Contractor’s expense. Any misalign ment or distortion of the wall facing panels due to placement of backfill outside the lim its of this specification shall be corrected by the Contractor a t his expense. Prior to the pl acement of the soil reinforcement, the backfill elevation after compaction shall be at the required elevation of the reinforcements. At each reinforcement level, the backfill shall be placed to the level of the connection. Backfill placement methods near the panels sha ll assure that no voids exist directly beneath the reinforcing element. Gravel borrow backfill shall be compacted in accordance with S ubsection 203.12 except that the minimum required compaction shall be 92 percent of maximum density as determined by AASHTO T180, Method C or D (with oversize correct ion, as outlined in Note 7 of that test). If 30 percent or more of the backfill ma terial is greater than 3/4 in. in size, AASHTO T180 is not applicable, and the acceptance criteri on for control of compaction shall be either a minimum of 70 percent of the relat ive density of the material as 6-218 determined by ASTM D4253 and D4254, or a method of compaction consisting of at least 4 (four) passes by a heavy roller. Where spread footings support bridge or other structural loads , the top 5 ft below the bottom of footing elevation shall be compacted to 98 percent of the maximum density as determined by AASHTO T180, Method C or D (with oversize correct ion, as outlined in Note 7 of that test). The moisture content (determined in accordance with AASHTO T18 0, Method C or D) of the backfill material prior to and during compaction shal l be uniformly distributed throughout each layer. Backfill materials shall have be placed at a moisture content not more than 2 percentage points less than or equal to the optimum moisture content. Backfill material with a placement moisture content in excess of the opt imum moisture content shall be removed and reworked until the moisture content is uniformly acceptable throughout the entire lift. At each reinforcing level, backfill shall be leveled before pl acing and bolting the reinforcing. The maximum lift thickness after compaction shall not exceed 12 in. The Contractor shall decrease this lift thickness, if necessary, to obtain the specified density. Heavy compaction equipment shall not be used to compact backfil l within 3 ft of the wall face. Compaction within 3 ft of the back face of the wall shall be achieved by at least three (3) passes of lightweight m echanical tamper, lightweight roller, or vibratory system. The specified lift thickness shall be adjusted as warranted by the type of compaction equipment actually used. No vehicular equipment shall be opera ted within 3 ft of the panels. The frequency of sampling of the backfill material necessary t o assure gradation control throughout construction shall be as directed by the Res ident. At the end of each day’s operation, the Contractor shall slope the last level of the backfill away from the wall f acing to rapidly direct runoff awa y from the wall face. In addition, the Contractor shall not allow surface runoff from ad jacent areas to enter the wall construction site.

677.12 Reinforcement Placement Prior to placing the first la yer of reinforcements

(strips, mats or grids), backfill shall be placed and compacted in accordance with Subsection 677.11, Backfill Placement. Bending of reinforcements in the horizontal plane resulting in a permanent deformation in their alignment shall not be allowed. Gradual b ending in the vertical direction that does not result in permanent deformations is all owable. Cutting of longitudinal or transverse reinforcement bars to av oid conflicts with utility obstructions or piles will not be allowed. A structura l connection (yokes) from the 6-219 wall panel to the reinforcement shall be used whenever it is ne cessary to avoid cutting or excessive skewing of reinforcement due to pile or utility confl icts. Soil reinforcements shall be placed normal to the face of the wall, unless otherwise shown on the plans or directed by t he Resident. If skewing of the soil reinforcements is required due to obstructions in the reinforced fill, rotatable bolted connections shall be used and the maximum skew angle shall not exceed 15º from the normal position except in the case of acute corner where redundant reinforcements are used. The tensile capacity of splayed reinforcement shall be reduced by the cosine of the spl ay angle.

677.13 Method of Measurement Mechanically Stabilized Earth R etaining Wall will

be measured by the square foot of face area computed using the plan dimensions. No adjustment in the pay quantity will be made if the computed qua ntity, based on the working drawings, varies from the plan quantity. Vertical dimension limits will be from the top of leveling pad to the top of the wall facing units, as shown on the plans. The horizontal dimension limits will be from the edges of the facing units at each end of a wall, as shown on the plan s. No field measurements will be made unless the Resident specifies, in writing, a change to the limits indicated on the plans. The wall surface area, as shown on the plans, includes the surf ace area of nominal panel joint openings and wall penetrations such as pipes and ot her utilities.

677.14 Basis of Payment The accepted quantity of Mechanicall y Stabilized Earth

Retaining Wall will be paid for at the contract unit price per square foot. Payment for Mechanically Stabilized Earth Retaining Wall shall be full comp ensation for:

677.20 Mechanically Stabilized Earth Retaining Wall Square foot

SECTION 678 – GEOSYNTHETIC REINFORCED MECHANICALLY STABILIZED EARTH RETAINING WALL Reserved SECTION 679 – FIELDSTONE RETAINING WALL

679.01 Description This work shall consist of supplying mater ial for and constructing a

Fieldstone Retaining Wall (FSRW) in accordance with these Speci fications and in reasonably close conformity with the lines, grades, design and dimensions shown on the Plans and Special Details or as directed by the Resident. An FSRW will consist of the following components:  Foundation Soils – Native soil mass supporting the FSRW  Drainage System – 6-inch underdrain pipe  Crushed Stone Leveling Pad - 8-inch-thick bed of Crushed Stone  Wall Stones - Hard, durable, flat fieldstones or quarried stones with flat faces in a mixture of sizes to be stacked in a compact and stable mass  Crushed Stone Drainage Layer – 12-inch vertical layer directly behind the FSRW  Geotextile - Drainage Geotextile meeting the requirements of Standard Specification 722  Backfill - Soil placed behind the FSRW