837 An unreinforced concrete leveling pad sh all be provided at each foundation level as shown on the plans. The leveling pad shall be cured in accordance with 702.22 for a minimum of 12 h before placement of concrete face panels. 380
731.08 Retaining Wall Excavation The Contractor shall notify the Engineer a minimum of 7 calendar days or other time as mutually agreed upon before beginning the excavation so that measurements can be taken of the undisturbed ground.
Prior to starting excavation operations at the wall site, the area shall be cleared and grubbed to the excavation with the lim its shown on the plans and in accordance with 201.03. All timber, stumps, or debris shall be disposed of in accordance with
201.03 Excavation shall include the construction and subsequent removal of all 390
necessary bracing, shoring, sheeting, and cr ibbing. Excavation shall also include all pumping, bailing, and draining. The excavation shall be shored or braced in accordance with Stat e and local safety requirements. Excavation and related work shall be performed such that no portion of the wall is endangered by subsequent operations. Where excavation for the wall requires shoring, sheeting, or bracing, the method shall be shown on the working drawings. Excavation operations shall not begin until the Contractor receives notice that the working drawings are approved. 400 After the excavation for the wall has been performed, the Contractor shall notify the Engineer. The material beneath the leve ling pad shall be compacted in accordance with 203. Concrete for the leveling pad sh all not be placed until the Engineer has approved the depth of the excavation and the foundation material. The leveling pad shall be in accordance with 731.07. When an internal drainage system is shown on the plans, the drain pipe shall be 6 in. underdrain pipe in accordance with 715. 02(d). The remainder of the internal drainage system shall be in accordance with 718, longitudinal underdrains. Video 410 inspection will not be required. 731.09 Wall Erection Concrete face panels shall be handled by means of a lifting device set into the upper edge of each panel. Panels shall be placed in successive horizontal lifts in the sequence shown on the plans as backfill placement proceeds. As backfill material is placed behind the 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. External bracing will be required for the initial lift. 420 731.09 838 Panels shall be stored on blocking to minimize contact with the ground or being covered by standing water. Panels placed in contact with the ground or covered by standing water shall have face discoloration removed by means of a chemical wash. Plumb, vertical tolerances, and horizont al alignment tolerances shall not exceed 3/4 in. as measured with a 10 ft straightedge. The maximum allowable offset in panel joints shall be 3/4 in. For a wall of over 10 ft height, the overall plumb from top to bottom of the wall shall not exceed 0.05 in./ft of wall height. For aesthetic considerations and to make differential settlement unnoticeable, the panels shall be erected such that the horizontal site line is discontinuous at every other panel. This shall be accomplished by starti ng erection with the lower panel level of each wall by alternating full-height and half -height panels. Panels above the lowest level shall be of a uniform size, except as required to top out the wall, to be in accordance with the plan elevations. The Contractor shall perform the necessary work to verify that the foundation is at the correct elevation, that the wall is constructed to the correct alignment, and that the work is in accordance w ith the specified tolerances. The checking of alignments 440 and tolerances shall include verifying that the plumb of the face panels is in accordance with 731.10 over the entire height of the wall. Alignment shall be checked at each layer of panels after the backfill behind the panels has been compacted, and the results shall be recorded. The connections of the ground reinforcement to the panels shall be in two elevations for full height panels. The connections shall not be more than 30 in. vertically apart. To prevent out-of-plane rotation, full height face panels shall be connected to the ground reinforcement on at least three different points in two different planes. However, a preapproved system utilizing a horizontal stabilizing leg to prevent 450 rotation shall require only ground reinforcement attachments in one plane. Partial size panels shall have three different connection points, but only one plane shall be attached to the ground reinforcement. Panels located at the top of the wall shall not be attached to the coping or traffic barrier. Ground reinforcement shall be placed no rmal to the face of the wall, unless otherwise shown on the plans or as dir ected. Prior to placement of the ground reinforcement, backfill shall be co mpacted in accordance with 731.11.
731.10 Joint Spacers and Joint Covering for Wall Panels 460
Horizontal and vertical joint spacers shall be provided between adjacent face panels to prevent concrete-to-concrete contact and chipping if differential settlement occurs. Panels without an uninterrupted vertical joint shall have a minimum joint thickness of 3/4 in. Joint covering shall be provided and attached to the rear face of the panels. Geotextiles used to cover the joint behind the MSE wall facing panels shall be in accordance with 918.02(a), Type 2B. 731.10 839 731.11 Backfill Placement Backfill placement shall follow erection of each course of panels and ground reinforcement. All sheeting and bracing shall be removed as the backfilling progresses. 470 Backfill shall be placed to avoid damage or disturbance to the wall materials or misalignment of the concrete face panels. All material for backfill shall be subject to approval and shall be free from lumps, wood, or other undesirable material. Wall materials that become damaged or disturbed during backfill placement shall be removed and replaced or corrected as directed. All misalignment or distortion of the concrete face panels due to placement of ba ckfill outside the limits described herein shall be corrected as directed. B borrow shall be compacted in accordan ce with 203.23 or 203.24. For structure backfill Type 3, compaction shall consist of five passes with a vibratory roller and one 480 pass with the same roller in static mode. Compaction equipment shall be in accordance with 409.03(d). All displacemen t or rutting of the aggregate shall be repaired prior to placing subsequent material. The maximum loose lift thickness shall not exceed 9 in. Howeve r, lifts within 3 ft of the wall shall not exceed 5 in. in loose thickness. This lift thickness shall be decreased, if necessary, to ob tain the specified density. Compaction within 3 ft of the back f ace of the concrete face panels shall be achieved by means of a minimum of five passes with a lightweight mechanical tamper, 490 roller, or an alternative vibratory system. At the end of each day's operation, the last level of backfill shall be sloped away from the wall units. Surface runoff from adjacent areas shall not enter the wall construction site. Subsurface drainage for the pavement s ection shall be underdrains for MSE walls and shall be as shown on the plans. Cutting or altering of ground reinforcement in the field shall not be performed 500 unless one of the alternatives in Article 11.10.10.4 of the AASHTO LRFD Bridge Design Specifications is followed and a compensating adjustment is made in the wall design. All adjustments shall be shown on revised working drawings, signed by, and shall bear the seal of a professional engineer, and submitted to the Engineer for approval. Cutting shall be considered only if adequate additional ground reinforcement is provided to produce the required strength shown in the approved calculations. If the ground reinforcement is shortened in the field, the cut ends shall be covered with a galvanized paint or coal tar to prevent corrosion of the metal.
731.12 Method of Measurement 510
The measurement of concrete face panels and wall erection will be based on the square foot of area contained within the neat line limits of the wall envelope shown on the plans and not that of the wall system supplier. 731.12 Concrete leveling pad will be measured by the linear foot. Common excavation will be measured by the cubic yard in accordance with 203.27(a) to the neat lines shown on the plans. Structure backfill and B borrow will be measured in accordance with 211.09. Unsuitable foundation materials, if found, will be measured in accordance with 211.09. Geotextile used in conjunction with MSE wall construction will not be measured for payment. Underdrains for MSE walls and components of the 520 internal drainage system will be measured in accordance with 718.09. If unsuitable foundation material is encountered in the portion of the foundation beneath the leveling pad in a section constructed on original ground or in a cut section, the removal, replacement, and compaction of the new material will be measured in accordance with 203 and 211. Precast or cast-in-place concrete coping will not be measured.
731.13 Basis of Payment The accepted quantities of concrete face panels will be paid for at the contract unit 530
price per square foot. Wall erection will be paid for at the contract unit price per square foot. Concrete leveling pad, complete and in place, will be paid for at the contract unit price per linear foot for leveling pad. Common excavation will be paid for in accordance with 203.28. Structure backfill and B borrow will be paid for in accordance with 211.10, except that structure backfill used in the retained backfill zone will be paid for as B borrow. Unsuitable foundation materials, if found, will be paid for in accordance with 211.10. Underdrains for MSE walls and components of an internal drainage system will be paid for in accordance with 718.10. Payment will be made under: 540 Pay Item Pay Unit Symbol Face Panels, Concrete ................................................................ SFT Leveling Pad, Concrete ............................................................. LFT Wall Erection ............................................................................. SFT The cost of designing the wall system, services including the testing laboratory, certified testing personnel, and the testing and inspection of the concrete panels shall be included in the cost of face panels, concrete. 550 The cost of all wall materials including concrete face panels, ground reinforcement, tie strips, fasteners, joint materials, joint covering, precast or cast-in-place concrete coping, repair or replacemen t of face panels damaged or removed due to backfill placement, and incidentals shall be included in the cost of face panels, concrete. 731.13 841 The cost of all labor and materials required to prepare the wall foundation, place the ground reinforcement, and erect the concre te face panels shall be included in the cost of wall erection. 560 If unsuitable foundation material is encountered in the portion of the foundation beneath the reinforced backfill zone in a section constructed on original ground or in a cut section, the cost of removal, replacement, and compaction of new material will be paid for in accordance with 203 and 211. If unsuitable foundation material is encountered in the portion of the foundation beneath the reinforced backfill zone that is constructed on an embankment section that is constructed under the same contract, the cost of removal, replacement, and compaction of new material will not be considered for payment. 570 The cost for geotextile used in MSE wall construction shall be included in the cost of the pay items in this section. The cost of refilling and refinishing of the core holes from verification coring shall be included in the cost of face panels, concrete. The cost of performing the laboratory tests by a qualified geotechnical consultant for structure backfill or ACBF slag shall be included in the cost of the pay items in this section. 580 The cost of cutting, altering, or recoating the ground reinforcement at the site shall be included in the cost of wall erection.