M 41-10 Page 6-2336-13 Structural Earth Walls
6-13.1 Description
This Work consists of constructing structural earth walls (SEW).
6-13.2 Materials
Materials shall meet the requirements of the following sections: Cement 9-01 Aggregates for Concrete 9-03.1 Gravel Borrow for Structural Earth Walls 9-03.14(4) Premolded Joint Filler 9-04.1(2) Steel Reinforcing Bar 9-07.2 Epoxy-Coated Steel Reinforcing Bar 9-07.3 Mortar 9-20.4 Concrete Curing Materials and Admixtures 9-23 Fly Ash 9-23.9 Water 9-25 Other materials required shall be as specified in the Special Provisions.
6-13.3 Construction Requirements
Proprietary structural earth wall systems shall be as specified in the Special Provisions.
6-13.3(1) Quality Assurance
The structural earth wall manufacturer shall provide a qualified and experienced representative to resolve wall construction problems. The structural earth wall manufacturer’s representative shall be present at the beginning of wall construction activities, and at other times as needed throughout construction. Recommendations made by the structural earth wall manufacturer’s representative shall be followed by the Contractor. The completed wall shall meet the following tolerances:
1.Deviation from the design batter and horizontal alignment, when measured along a 10-foot straightedge, shall not exceed the following:
a.Welded wire faced structural earth wall: 2 inches
b.Precast concrete panel and concrete block faced structural earth wall: ¾ inch
2.Deviation from the overall design batter of the wall shall not exceed the following per 10 feet of wall height:
a.Welded wire faced structural earth wall: 1½ inches
b.Precast concrete panel and concrete block faced structural earth wall: ½ inch
3.The maximum outward bulge of the face between welded wire faced structural earth wall reinforcement layers shall not exceed 2 inches. The maximum allowable offset in any precast concrete facing panel joint shall be ¾ inch. The maximum allowable offset in any concrete block joint shall be ¾ inch.
4.The base of the structural earth wall excavation shall be within 3 inches of the staked elevations, unless otherwise accepted or specified by the Engineer.
5.The external structural earth wall dimensions shall be placed within 2 inches of that staked on the ground.
6.The backfill reinforcement layers shall be located horizontally and vertically within 1 inch of the locations shown in the structural earth wall Working Drawings. Structural Earth Walls 6-13 Page 6-234 M 41-10At least 5 working days prior to the Contractor beginning any structural earth wall Work at the site, a structural earth wall preconstruction conference shall be held to discuss construction procedures, personnel, and equipment to be used, and other elements of structural earth wall construction. Those attending shall include:
1.(representing the Contractor) The superintendent, on site supervisors, and all foremen in charge of excavation, leveling pad placement, concrete block and soil reinforcement placement, and structural earth wall backfill placement and compaction.
2.(representing the Structural Earth Wall Manufacturer) The qualified and experienced representative of the structural earth wall manufacturer as specified at the beginning of this section.
3.(representing the Contracting Agency) The Engineer, key inspection personnel, and representatives from the WSDOT Construction Office and State Geotechnical Office.
6-13.3(2) Submittals
The Contractor, or the supplier as the Contractor’s agent, shall furnish a Manufacturer’s Certificate of Compliance certifying that the structural earth wall materials conform to the specified material requirements. This includes providing a Manufacturer’s Certificate of Compliance for all concrete admixtures, cement, fly ash, steel reinforcing bars, reinforcing strips, reinforcing mesh, tie strips, fasteners, welded wire mats, backing mats, construction geotextile for wall facing, drainage geosynthetic fabric, block connectors, and joint materials. The Manufacturer’s Certificate of Compliance for geogrid reinforcement shall include the information specified in Section 9-33.4(4) for each geogrid roll, and shall specify the geogrid polymer types for each geogrid roll. A Type 1 Working Drawing of all test results performed by the Contractor or the Contractor’s supplier, which are necessary to ensure compliance with the specifications, shall be submitted along with each Manufacturer’s Certificate of Compliance. Before fabrication, the Contractor shall submit a Type 1 Working Drawing consisting of the field construction manual for the structural earth walls, prepared by the wall manufacturer. This manual shall provide step-by-step directions for construction of the wall system. The Contractor, through the license/patent holder for the structural earth wall system, shall submit Type 2E Working Drawings consisting of detailed design calculations and details. If not prepared by the license/patent holder for the structural earth system, the design calculation and working drawing submittal shall include documentation that the design calculation and working drawing submittal has been reviewed by, and received the concurrence of, the headquarters organization of the structural earth wall manufacturer as identified in the Special Provisions. Review and concurrence by a sales representative office is not acceptable.
6-13.3(2)A Design Calculation Content Requirements
The design calculation submittal shall include detailed design calculations based on the wall geometry and design parameters specified in the Plans and Special Provisions. The calculations shall include detailed explanations of any symbols, design input, materials property values, and computer programs used in the design of the walls. All computer output submitted shall be accompanied by supporting hand calculations detailing the calculation process. If MSEW 3.0, or a later version, is used for the wall design, hand calculations supporting MSEW are not required. The design calculations shall be based on the current AASHTO LRFD Bridge Design Specifications , including current interims, the current WSDOT Bridge Design Manual LRFD (BDM), and the WSDOT Geotechnical Design Manual (GDM), and also based on the following:
6-13 Structural Earth Walls
M 41-10 Page 6-2351. The wall design calculations shall address all aspects of wall internal stability for the service, strength, and extreme event limit states.
2.The wall surcharge conditions (backfill slope) shown in the Plans.
3.If a highway is adjacent to and on top of the wall, a 2-foot surcharge shall be used in the design.
4.If the Plans detail an SEW traffic barrier or SEW pedestrian barrier on top of the wall, the barrier shall be designed for a minimum TL-4 impact load, unless otherwise specified in the Plans or Special Provisions.
5.If the Plans detail an SEW traffic barrier or SEW pedestrian barrier on top of the wall, the wall shall be designed for the impact load transferred from the barrier to the wall.
6.The geotechnical design parameters for the wall shall be as specified in the Special Provisions.
7.The soil reinforcement length shall be as shown in the Plans. If the Plans do not show a length, the length shall be either 6 feet or 0.7 times the wall design height H, whichever is greater. If there are differences in design requirements between the AASHTO LRFD Bridge Design Specifications and the BDM or GDM, the BDM and GDM requirements shall govern.
6-13.3(2)B Working Drawing Content Requirements
All design details shown in the working drawings shall be selected from the design details and products specified for the specific structural earth wall manufacturer in the Preapproved Wall Appendix in the current WSDOT Geotechnical Design Manual (GDM). Geosynthetic reinforcement shown in the working drawings shall be selected from the products listed in the current WSDOT Qualified Products List (QPL). Substitution of design details and products not listed in the current WSDOT GDM or QPL will not be allowed. The working drawing submittal shall include all details, dimensions, quantities, and cross sections necessary to construct the wall based on the wall geometry and design parameters specified in the Plans and Special Provisions, and shall include, but not be limited to, the following items:
1.A plan and elevation sheet or sheets for each wall, containing the following:
a.An elevation view of the wall that includes the following:
i.The elevation at the top of the wall, at all horizontal and vertical break points, and at least every 50 feet along the wall; ii. Elevations at the base of welded wire mats or the top of leveling pads and foundations, and the distance along the face of the wall to all steps in the welded wire mats, foundations, and leveling pads; iii. The designation as to the type of panel, block, or module; iv. The length, size, and number of geogrids or mesh or strips, and the distance along the face of the wall to where changes in length of the geogrids or mesh or strips occur; or
v.The length, size, and wire sizes and spacing of the welded wire mats and backing mats, and the distance along the face of the wall to where changes in length, size, and wire sizes and spacing of the welded wire mats and backing mats occur; and vi. The location of the original and final ground line. Structural Earth Walls 6-13 Page 6-236 M 41-10b. A plan view of the wall that indicates the offset from the construction centerline to the face of the wall at all changes in horizontal alignment; the limit of the widest module, geogrid, mesh, strip, or welded wire mat, and the centerline of any drainage structure or drainage pipe that is behind or passes under or through the wall.
c.General notes, if any, required for design and construction of the wall.
d.All horizontal and vertical curve data affecting wall construction.
e.A listing of the summary of quantities provided on the elevation sheet of each wall for all items, including incidental items.
f.A cross section showing limits of construction. In fill sections, the cross section shall show the limits and extent of select granular backfill material placed above original ground.
g.Limits and extent of reinforced soil volume.
2.All details, including steel reinforcing bar bending details. Bar bending details shall be in accordance with Section 9-07.1 .
3.All details for foundations and leveling pads, including details for steps in the foundations or leveling pads.
4.All modules and facing elements shall be detailed. The details shall show all dimensions necessary to construct the element, all steel reinforcing bars in the element, and the location of reinforcement element attachment devices embedded in the precast concrete facing panel or concrete block.
5.All details for construction of the wall around drainage facilities, sign, signal, luminaire, and noise barrier wall foundations, and structural abutment and foundation elements shall be clearly shown.
6.All details for connections to SEW traffic or pedestrian barriers, coping, parapets, noise barrier walls, and attached lighting shall be shown.
7.All details for the SEW traffic or pedestrian barrier attached to the top of the wall (if shown in the Plans), including interaction with bridge approach slabs.
6-13.3(3) Excavation and Foundation Preparation
Excavation shall conform to Section 2-09.3(3) . Foundation soils found to be unsuitable shall be removed and replaced in accordance with Section 2-09.3(1)C. The foundation for the Structure shall be graded level for a width equal to or exceeding the length of reinforcing as shown in the structural earth wall Working Drawings and, for walls with geogrid reinforcing, in accordance with Section 2-12.3 . Prior to wall construction, the foundation, if not in rock, shall be compacted as accepted by the Engineer. At the foundation level of the bottom course of precast concrete facing panels and concrete blocks, an unreinforced concrete leveling pad shall be provided as shown in the Plans. The leveling pad shall be cured a minimum of 12 hours and have a minimum compressive strength of 1,500 psi before placement of the precast concrete facing panels or concrete blocks.
6-13.3(4) Precast Concrete Facing Panel and Concrete Block Fabrication
Precast concrete facing panels shall conform to Section 6-02.3(9), except as modified in this section. Concrete for precast concrete facing panels shall meet the following requirements:
1.Have a minimum 28-day compressive strength of 4,000 pounds per square inch, unless otherwise specified in the Special Provisions for specific proprietary wall systems.
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M 41-10 Page 6-2372. Contain a water-reducing admixture meeting AASHTO M194 Type A, D, F, or G.
3.Be air-entrained, 6 percent ± 1½ percent.
4.Have a maximum slump of 4 inches, or 6 inches if a Type F or G water reducer is used. Concrete for dry cast concrete blocks shall meet the following requirements:
1.Have a minimum 28-day compressive strength of 4,000 psi.
2.Conform to ASTM C1372, except as otherwise specified.
3.The lot of blocks produced for use in this project shall conform to the following freeze-thaw test requirements when tested in accordance with ASTM C1262. Minimum acceptable performance shall be defined as weight loss at the conclusion of 150 freeze-thaw cycles not exceeding 1 percent of the block’s initial weight for a minimum of four of the five block specimens tested.
4.The concrete blocks shall have a maximum water absorption of 1 percent above the water absorption content of the lot of blocks produced and successfully tested for the freeze-thaw test specified in item 3 above. The precast concrete facing panels and concrete blocks shall be considered acceptable regardless of curing age when compressive test results indicate that the compressive strength conforms to the 28-day requirements and when the visual inspection is satisfactorily completed. Testing of dry cast concrete blocks shall conform to ASTM C140. All precast concrete facing panels shall be 5 feet square, except:
1.for partial panels at the top, bottom, and ends of the wall; and
2.as otherwise shown in the Plans. All precast concrete facing panels shall be manufactured within the following tolerances:
1.All dimensions ± 3⁄16 inch.
2.Squareness, as determined by the difference between the two diagonals, shall not exceed ½ inch.
3.Surface defects on smooth formed surfaces measured on a length of 5 feet shall not exceed ⅛ inch. Surface defects on textured-finished surfaces measured on a length of 5 feet shall not exceed 5⁄16 inch. All concrete blocks shall be manufactured within the following tolerances:
1.Vertical dimensions shall be ± 1⁄16 inch of the Plan dimension, and the rear height shall not exceed the front height.
2.The dimensions of the grooves in the top and bottom faces of the concrete blocks shall be formed within the tolerances specified by the proprietary wall manufacturer, for the fit required for the block connectors.
3.All other dimensions shall be ± ¼ inch of the Plan dimension. Tie attachment devices, except for geosynthetic reinforcement, shall be set in place to the dimensions and tolerances shown in the Plans prior to casting. The forms forming precast concrete facing panels, including the forms for loop pockets and access pockets, and the forms forming the concrete blocks, shall be removed in accordance with the recommendations of the wall manufacturer, without damaging the concrete. The concrete surface for the precast concrete facing panel shall have the finish shown in the Plans for the front face and an unformed finish for the rear face. The rear face of the precast concrete facing panel shall be roughly screeded to eliminate open pockets of aggregate and surface distortions in excess of ¼ inch. Structural Earth Walls 6-13 Page 6-238 M 41-10The concrete surface for the front face of the concrete block shall be flat, and shall be a conventional “split face” finish in accordance with the wall manufacturer’s specifications. The concrete surface of all other faces shall be Class 2 in accordance with Section 6-02.3(14)B. The finish and appearance of the concrete blocks shall also conform to ASTM C1372. The color of the concrete block shall be concrete gray, unless otherwise shown in the Plans. The date of manufacture, production lot number, and the piece-mark, shall be clearly marked on the rear face of each precast concrete facing panel, and marked or tagged on each pallet of concrete blocks. All precast concrete facing panels and concrete blocks shall be handled, stored, and shipped in accordance with Sections 6-02.3( 9) to prevent chipping, cracks, fractures, and excessive bending stresses. Precast concrete facing panels in storage shall be supported on firm blocking located immediately adjacent to tie strips to avoid bending the tie strips.
6-13.3(5) Precast Concrete Facing Panel and Concrete Block Erection
Precast concrete facing panels shall conform to Section 6-02.3(9), except as modified in this section. The precast concrete facing panels shall be placed vertically. During erection, precast concrete facing panels shall be handled by means of a lifting device set into the upper edge of the panels. Concrete blocks shall be erected in a running bond fashion in accordance with the wall manufacturer’s field construction manual, and may be placed by hand. The top surface of each course of concrete blocks, including all pockets and recesses, shall be cleaned of backfill and all extraneous materials prior to connecting the reinforcing strips or geosynthetic reinforcing, and placing the next course of concrete blocks. Concrete blocks receiving geosynthetic reinforcement shall be connected as specified in the Special Provisions. Cap block top courses shall be bonded to the lower course of concrete blocks as specified below. All other concrete blocks shall be connected with block connectors or pins placed into the connector slots. Precast concrete facing panels and concrete blocks shall be placed in successive horizontal lifts as backfill placement proceeds in the sequence shown in the structural earth wall Working Drawings as approved by the Engineer. External bracing is required for the initial lift for precast concrete facing panels. As backfill material is placed behind the precast concrete facing panels, the panels shall be maintained in vertical position by means of temporary wooden wedges placed in the joint at the junction of the two adjacent panels on the external side of the wall. Reinforcing shall be placed normal to the face of the wall, unless otherwise shown in the Plans or directed by the Engineer. Prior to placement of the reinforcing, backfill shall be compacted. Geosynthetic reinforcing shall be placed in accordance with Section 2-12.3 and as follows:
1.The Contractor shall stretch out the geosynthetic in the direction perpendicular to the wall face to remove all slack and wrinkles, and shall hold the geosynthetic in place with soil piles or other methods as recommended by the geosynthetic manufacturer, before placing backfill material over the geosynthetic to the specified cover.
2.The geosynthetic reinforcement shall be continuous in the direction perpendicular to the wall face from the back face of the concrete panel to the end of the geosynthetic or to the last geogrid node at the end of the specified reinforcement length. Geosynthetic splices parallel to the wall face will not be allowed.
6-13 Structural Earth Walls
M 41-10 Page 6-239At the completion of each course of concrete blocks and prior to installing any block connectors or geosynthetic reinforcement at this level, the Contractor shall check the blocks for level placement in all directions, and shall adjust the blocks by grinding or rear face shimming, or other method as recommended by the structural earth wall manufacturer’s representative and as approved by the Engineer, to bring the blocks into a level plane. For concrete block wall systems receiving a cap block top course, the cap blocks shall be bonded to the lower course either with mortar conforming to Section 9-20.4(3) , or with an adhesive capable of bonding the concrete block courses together.
6-13.3(6) Welded Wire Faced Structural Earth Wall Erection
The Contractor shall erect the welded wire wall reinforcement in accordance with the wall manufacturer’s field construction manual. Construction geotextile for wall facing shall be placed between the backfill material within the reinforced zone and the coarse granular material immediately behind the welded wire wall facing, as shown in the Plans and the structural earth wall Working Drawings. Geosynthetic reinforcing, when used, shall be placed in accordance with Sections 2-12.3 and 6-13.3(5) .
6-13.3(7) Backfill
Backfill placement shall closely follow erection of each course of welded wire mats and backing mats, precast concrete facing panels, or concrete blocks. Backfill shall be placed in such a manner as to avoid any damage or disturbance to the wall materials or misalignment of the welded wire mats and backing mats, precast concrete facing panels, or concrete blocks. Backfill shall be placed in a manner that segregation does not occur. Construction equipment shall not operate directly on the wall reinforcement. A minimum backfill thickness of 6 inches over the reinforcement shall be required prior to operation of vehicles or equipment. The Contractor shall place wall backfill over geosynthetic reinforcement, or construction geotextile for wall facing, in accordance with Section 2-12.3 . Misalignment or distortion of the precast concrete facing panels or concrete blocks due to placement of backfill outside the limits of this Specification shall be corrected in a manner acceptable to the Engineer. The moisture content of the backfill material prior to and during compaction shall be uniformly distributed throughout each layer of material. The moisture content of all backfill material shall conform to Sections 2-03.3(14)C and 2-03.3(14)D. Backfill shall be compacted in accordance with Method C of Section 2-03.3(14)C , except as follows:
1.The maximum lift thickness after compaction shall not exceed 10 inches.
2.The Contractor shall decrease this lift thickness, if necessary, to obtain the specified density.
3.The Contractor shall not use sheepsfoot rollers or rollers with protrusions for compacting backfill reinforced with geosynthetic layers, or for compacting the first lift of backfill above the construction geosynthetic for wall facing for each layer of welded wire mats. Rollers shall have sufficient capacity to achieve compaction without causing distortion to the face of the wall in accordance with the tolerances specified in Section 6-13.3(1) .
4.The Contractor shall compact the zone within 3 feet of the back of the wall facing panels without causing damage to or distortion of the wall facing elements (welded wire mats, backing mats, construction geotextile for wall facing, precast concrete facing panels, and concrete blocks) by using a plate compactor. No soil density tests will be taken within this area. Structural Earth Walls 6-13 Page 6-240 M 41-105. For wall systems with geosynthetic reinforcement, the minimum compacted backfill lift thickness of the first lift above each geosynthetic reinforcement layer shall be 6 inches. At the end of each day’s operation, the Contractor shall shape the last level of backfill to permit runoff of rainwater away from the wall face. In addition, the Contractor shall not allow surface runoff from adjacent areas to enter the wall construction site.
6-13.3(8) Guardrail Placement
Where guardrail posts are required, the Contractor shall not begin installing guardrail posts until completing the structural earth wall to the top of wall elevation shown in the Plans. The Contractor shall install the posts in a manner that prevents movement of the precast concrete facing panels or concrete blocks, and prevents ripping, tearing, or pulling of the wall reinforcement. The Contractor may cut welded wire reinforcement of welded wire faced structural earth walls to facilitate placing the guardrail posts, but only in the top two welded wire reinforcement layers and only with the permission of the Engineer in a manner that prevents bulging of the wall face and prevents ripping or pulling of the welded wire reinforcement. Holes through the welded wire reinforcement shall be the minimum size necessary for the post. The Contractor shall demonstrate to the Engineer prior to beginning guardrail post installation that the installation method will not rip, tear, or pull the wall reinforcement. The Contractor shall place guardrail posts between the reinforcing strips, reinforcing mesh, and tie strips of the non-geosynthetic reinforced precast concrete panel or concrete block faced structural earth walls. Holes through the reinforcement of geosynthetic reinforced walls, if necessary, shall be the minimum size necessary for the guardrail post.
6-13.3(9) SEW Traffic Barrier and SEW Pedestrian Barrier
The Contractor, in conjunction with the structural earth wall manufacturer, shall design and detail the SEW traffic barrier and SEW pedestrian barrier in accordance with Section
6-13.3(2) and the above ground geometry details shown in the Plans. The barrier Working
Drawings and supporting calculations shall be Type 2E and shall include, at a minimum, the following:
1.Complete details of barrier cross section geometry, including the portion below ground, and accommodations necessary for bridge approach slabs, PCCP, drainage facilities, underground utilities, and sign support, luminaire pole, traffic signal standard, and other barrier attachments.
2.Details of the steel reinforcement of the barrier, including a bar list and bending diagram in accordance with Section 6-02.3(24), and including additional reinforcement required at sign support, luminaire pole, traffic signal standard, and other barrier attachment locations.
3.Details of the interface of, and the interaction between, the barrier and the top layers of structural earth wall reinforcement and facing.
4.When the Plans specify placement of conduit pipes through the barrier, details of conduit pipe and junction box placement. SEW traffic barrier and SEW pedestrian barrier shall be constructed in accordance with Sections 6-02.3(11)A and 6-10.3(2), and the details in the Plans and in the structural earth wall Working Drawings as approved by the Engineer. The moment slab supporting the SEW traffic or pedestrian barrier shall be continuously wet cured for 3 days in accordance with Section 6-02.3(11).
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M 41-10 Page 6-2416-13.4 Measurement Structural earth wall will be measured by the square foot of completed wall in place. The bottom limits for vertical measurement will be the bottom of the bottom mat, for welded wire faced structural earth walls, or the top of the leveling pad (or bottom of wall if no leveling pad is present) for precast concrete panel or concrete block faced structural earth walls. The top limit for vertical measurement will be the top of wall as shown in the Plans. The horizontal limits for measurement are from the end of the wall to the end of the wall. Gravel borrow for structural earth wall including haul will be measured by the cubic yard in place determined by the limits shown in the Plans. SEW traffic barrier, and SEW pedestrian barrier will be measured as specified in Section
6-10.4 for cast-in-place concrete barrier.
6-13.5 Payment
Payment will be made for each of the following Bid items when they are included in the Proposal: “Structural Earth Wall”, per square foot. The unit Contract price per square foot for “Structural Earth Wall” shall be full payment for all costs to perform the Work in connection with constructing structural earth walls, including leveling pads and copings when specified. “Gravel Borrow for Structural Earth Wall incl. Haul”, per cubic yard. The unit Contract price per cubic yard for “Gravel Borrow for Structural Earth Wall incl. Haul” shall be full payment for all costs to perform the Work in connection with furnishing and placing backfill for structural earth or geosynthetic retaining wall, including hauling and compacting the backfill, and furnishing and placing the wall- facing backfill for retaining walls. “SEW Traffic Barrier”, per linear foot. “SEW Pedestrian Barrier”, per linear foot. The unit Contract price per linear foot for “SEW ___ Barrier” shall be full pay for constructing the barrier on top of the structural earth wall, except that when these Bid items are not included in the Proposal, all costs in connection with performing the Work as specified shall be included in the unit Contract price per square foot for “Structural Earth Wall”. Structural Earth Walls 6-13
Source: Washington Standard Specifications for Road, Bridge, and Municipal Construction, 2024 Edition. Pages 587–595 of 1,151.