853 – RETAINING WALL SYSTEM
700 and approved by the Engineer. Finish the MBW as specified in the Contract Documents. Screed the rear face of the MSEW precast panel or the non-exposed faces of the MBW to eliminate open pockets of aggregate and surf ace distortions in excess of 1/4 inch.
MSEW Precast Panel: Manufacture all units within the following tolerances: Dimensions: Lateral position of tie strips, within 1 inch. All other dimensions, within 3/16 inch. Squareness: As determined by the difference between the two diagonals, not exceeding ½ inch. Surface defects of formed surfaces measured on a length of 5 feet: not exceeding 1/8 inch.
MBW: Manufacture all units within 1/8 inch of the length and width plan dimension. Manufacture the units within 1/16 inch of the specified height and connection slots within 3/16 inch of plan dimension. Provide MBW units with a minimum of: 1.0 sq ft of face area each for full units. 0.5 sq ft of face area for each cap unit. Provide a MBW system with angled sides capable of concave or convex alignm ent curves with minimum radius of 4.5 to 6 feet.
compressive strength will be determined on a production lot basis. A lot consists of each 40 production panels or 10,000 production blocks or fraction thereof produced in 1 day. MSEW: Prepare a minimum of 6 standard 6 x 12-inch cylinders from samples selected at random from concrete used in the production lot and in accordance with Ka nsas Test Methods. Cure 3 cylinders in accordance with Kansas Test Methods and test at 28 days. Cure at least 3 of the cylinders in the same manner as the panels and test at 7 days or later. Additional sets of 3 cylinders cured in th e same manner as the panels may be tested at other dates beginning at 7 days. A test result will be the average compre ssive strength of a set of cyli nders. Acceptance of the lot will be made if the average of any set of 3 is greater than 4,000 psi and no single cylinder has a compressive strength less than 3600 psi. MBW: Select no less than 3 units at random from each lot to represent the production lot. Acceptance of the lot for compressive strength will be made if the average of any set of 3 is greater than 4000 psi and no single unit has a compressive strength less than 3600 psi.
following defects: Defects that indicate imperfect molding Honeycombed or open texture concrete surfaces Any damage that would prevent making a satisfactory joint Chipped facing panel/unit edges Discolored panels or blocks beyond reasonable variances in the opinion of the Engineer.
MSEW Precast Panel: Prominently scribe the date of manufacture on the rear face of each panel. MBW: Prominently display the date of manufacture and lot number on each production lot stored at the casting plant in a manner acceptable to the Engineer.
danger of staining, chipping, cracks, fractures, and excessive bending stresses. Support blocks or panels in storage on firm foundations in a manner that will protect the exposed exterior finish.
of materials test, compliance with dimensional requirements and visual inspection at the point of usage.
Leveling pads. Commercial Grade (AE) concrete complying with SECTIONS 401, 402 and 1102 . 853 – RETAINING WALL SYSTEM
Cast-in-Place copings. Grade 3.0 (AE) concrete complying with SECTIONS 401, 402 and 1102 . Pre-cast Cap Blocks for MBW. Meet the requirements of subsection 853.2b. of this specification.
Use tie strips of shop fabricated hot rolled steel that complies with the minimum requirements of ASTM A570, Grade 50, or equivalent. Use reinforcing strips that complies with the following: hot rolled from bars to the required shape and dimensions. Physical and mechanical properties that complies with ASTM A572, Grade 65, or equivalent. Cut to lengths and tolerances shown in the Contract Documents. Punch holes for bolts in the locations shown. Galvanize the reinforcing and tie strips to comply to ASTM A123 after fabrication is completed. Inspect all reinforcing and tie strips so that they are true to size and free from defects that may impair their strength and durability. The reinforcing and tie strips will be accepted on the ba sis of a Type A Certification and visual inspection.
with the minimum requirements of ASTM A82 and weld into the finished me sh fabric in accordance with ASTM A185. Form loops or weld connection plates so the variati on in length between the longest and the shortest longitudinal wire in a reinforcing mesh panel is no more than 1/8 inch when measured from the cross- wire nearest the end of the reinforcing mesh panel. Loop fabricati on must permit a 5/8 inch diameter rod to pass through all loops on each piece of mesh. Galvanize reinforcing mesh in acco rdance with ASTM A123. The mesh w ill be accepted on the basis of a Type A Certification and visual inspection.
polyethylene or polypropylene containing stabilizers and inhibitors added to the base plastic for resistance to ultraviolet and heat de gradation. Use the geogrid material as de signated in the approved wall system. The designated soil reinforcing geogrid will be accepted on the basis of a Type A Certification. (4) Soil Reinforcing Geosynthetic. Use soil reinforcing of woven, high tenacity polyester yarns coated with polyvinyl chloride to maintain the integrity of the geosynthetic during handling and placement and to protect it during construction. Use the geosynthetic material as designated in the approved wall system. The designated soil reinforcing geosynthetic will be accepted on the basis of a Type A Certification.
the minimum requirements of ASTM A 1011, Grade 50 or equivalent. Galvanize connectors after fabrication in accordance with ASTM A123. Use configured reinforcing strips (SINEstrips) that comply with the following: Cold formed from coils to the required shape and dimensions. Depict the strip widths and dimensions on the shop drawings. Physical and mechanical properties that comply with ASTM A 1011, Grade 65, or equivalent. Bolt strips to the connectors usi ng ASTM A325 bolts and ASTM A563 nuts galvanized in accordance with ASTM A153. Galvanize reinforcing strips after fa brication in accordance with ASTM A1 23. The strips will be accepted on the basis of a Type A Certification and visual inspection.
or equivalent, and hot-dip ga lvanized in accordance with ASTM F 2329. Provi de fasteners 1/2 inch in diameter, 1-1/4 inch in length with 3/4 inch thread length. The specified fasteners will be accepted on the basis of a Type A Certification.
with ASTM A82 and welded in accordance with ASTM A185 and galvanized in accordance with ASTM A153, or 853 – RETAINING WALL SYSTEM 800-122 approved equal. Place connectors with in 1/2 inch from the dimensions shown on the Contract Documents or approved shop drawings.
accordance with ASTM A153.
and galvanized in accor dance with ASTM A153.
inspection.
adhesive to temporarily attach the fabric material to the r ear of the facing panels as approved by the retaining wall system manufacturer. Cover each side of the joint with a minimum of 6 inches of filter fabric.
approved by the Engineer. (3) Bearing Pads. Use bearing pads made of high-density polyethylene LR73400 with a shore hardness of 66 or as approved by the re taining wall system manufacturer. Cover for horizontal and vertical joints between pa nels with a Fiber Bond filter fabric complying with AASHTO M 288 surface drainage with less than 15% soil passing No. 200 square mesh sieve, or equal as approved by the retaining wall system manufacturer. Use adhesive to te mporarily attach the fabric ma terial to the rear of the facing panels as approved by the re taining wall system manufacturer.
853.3CONSTRUCTION REQUIREMENTS
initial erection and be available during construction of a ll retaining walls at no additional cost to KDOT. The representative must spend suffici ent time with both the Contractor and the Engineer so they are familiar with the proper erection procedures.
excavation for the wall with the underdrain construction so that drainage pipes will be constructed as specified. Maintain stable sides at all excavations by providing reasonable cut back slopes or shoring where necessary.
strengthened earth or MSE structure volume level with the top of the leveling pad for a width equal to or exceeding the length of the reinforcing mesh, reinforcing strips or geogrid plus 12 inches or to the limits shown in the Contract Documents. Compact the foundations prior to wall construction, with a smooth wheel vibratory roller with a minimum static weight of 8 tons to recompact any loose material the excavation proce ss created to Type AA, MR 3- 3 requirements. Remove and replace any foundation soils found to be unstabl e or unsatisfactory. Construct an unreinforced concrete leveling pad at foundation level as shown in the Contract Documents. Cure the pad for a minimum of 12 hours before placement of wall panels or blocks. Install the wall drainage system concurrently with the bottom layer of reinforcement and se lect granular backfill. Do not proceed past the bottom layer of reinforcement until the drainage system is installed and outletted away from the wall.
allowable. If one gap is more than 4 inches, remove the le veling pad and re-cast in that location. If there are more than 3 gaps greater than 4 inches in a wall, remove the leveling pad and re-cast in all locations that have gaps regardless of the width of the gap. Cover gaps less than 4 inches in width with a separation geotextile on the inside of the wall face. No gaps between the leveling pad and a modular block is allowed.
to erection of the next panel or modular block row. Shou ld any panels/modular blocks be out of tolerance, remove the fill and reset the panels/modular blocks to their proper tolerances. Do not drape geosynthetic reinforcement over the face of the wall. Do not place more than one row of blocks at one time.
handle panels by means of a lifting insert precast into th e upper edge of the panels. Place panels in successive 853 – RETAINING WALL SYSTEM 800-123 horizontal lifts in the sequence shown in the Contract Documents as backfill placement proceeds. Maintain in vertical position as fill material is placed behi nd a panel, by means of temporary wooden wedges placed on the external side of the wall in the joint between adjacent panels. External bracing is required fo r the initial lift. Vert ical tolerances and horizontal alignment tolerance shall not ex ceed ¾-inch when measured with a 10-fo ot straight edge. Offset each panel from the panel below it as shown in the Contract Docume nts, with a maximum allowable offset of ¾-inch. The maximum vertical overall tolerance of the wall is ½-inch pe r 10 feet of wall height. Remove the wedges as the erection proceeds. Make horizontal and vertical joint openings between panel’s uniform, and between ½-inch and 1 ¼-inch. Check the plumbness and tolerances of each panel row at the face prior to erection of the next panel row. Should any panels be out of tolerance, remove the fill and reset the panels to their proper tolerances.
devices or by hand. Place blocks in successive horizontal lif ts in the sequence shown in the Contract Documents as backfill placement proceeds. Leave modular block unit cores void unless drainage fill material is specifically called for in the Contract Documents. Take care when placing material behind the blocks to prevent the blocks from moving outward. Vertical tolerances and horizontal alignment to lerance shall not exceed 1 ½-in ch when measured with a 10-foot straight edge. Offset each bl ock from the block below it as shown in the Contract Documents with a maximum allowable offset of 1-inch. The maximum vertical overall tolerance of the wall is 1-inch per 10 feet of the wall height. Construct uniform horizontal and vertical joint openings between modular blocks a maximum of ⅛ inch. Extend the Mesa Connector into adjoining courses with 2 Mesa standard connectors per unit. Place Anchor Lock Bar con tinuously only at elevations where geosyn thetic reinforcement is required. Place KeySystem I steel connection pins at soil re inforcing connection locations only and fiberglass alignment pins at all other pin locations. Handle and store all geogrids, geomembranes, geotextiles, and geosynth etics according to the manufacturer’s recommendations. Do not remove any geogrid, geomembrane, geotextile, or geosynthetic from its packaging and expose it to the sunlight and the elements for a period exceeding 10 days before it is placed and covered. Place a geomembrane horizonta lly above all select granular backfill that contains reinforcing strips or soil reinforcing mesh or any other metallic soil reinforcement. Extend the geomembrane 2 feet beyond the limits of the select granular backfill. Place a Class 2 geotextile for subsurface drainage above all select granular backfill that contains soil reinforcing geogrid or soil reinforcing geosynthetic or any other polymeric reinforcement. Extend the geotextile 2 feet beyond the limits of the select granular backfill.
level, roughly level backfill before placing and or attaching the reinforcement. Place reinforcing as shown in the Contract Documents normal to the face of the wall. For geos ynthetic reinforcing, the e nd of the geogrid sheet will terminate with a transverse element at the retained soil limi t to prevent curling of the sheet and aid in construction. Tightly draw the reinforcing against th e connections at the connect ors and stake the end of the geogrid sheet at the retained soil limit before backfilling is allowed, and main tain tautness during backfilling operations. Place backfill in maximum loose lift thickness of 10 inches or less as may be necessary to obtain the specified density. Construct the MSE wall lifts and reinforcement without deflecting any nearby appurtenances, such as piles, pile casings, etc. For MBW systems using sand and sand-gravel combinatio ns, provide a 3-foot wide zone immediately behind the facing composed of crushed stone backfill. Separate the crushed stone backfill from the sand or sand-gravel backfill with the use of a Class 2 geotextile for separation. Compact the entire retained earth volume to 95% of maximum laboratory dry density at a moisture requirement of MR 3-3, SECTION 205 . For backfills containing more than 30% retained on the ¾-inch sieve, use a method compaction consisting of at least 4 passes of a heav y roller. Accomplish compaction without disturbance or displacement of reinforcing and facing. Begin compaction from the area nearest the wall face to the back of the reinforcing, except for a strip 3 feet wide adjacent to the backside of the facing. Compact this 3-foot strip with light mechanical tampers after compaction of the remainder of the layer. Soil density tests will not be required within this 3- foot area. Maintain a maximum elevation difference of 3 feet between the retained fill and the select granular backfill. No shale or weathered shale is perm itted in the retained fill zone. 853 – RETAINING WALL SYSTEM
800-124At the end of each day's operations, shape the last level of backfill to permit runoff of rainwater away from the
wall face. Remove and replace any wall materials that become damaged during backfill placement at the Contractor's expense. Trim excess geogrid protru ding from the face of the wall for MBWs to match the modular block’s face. Seal any geogrid permanently exposed from exposure to the elements with the use of epoxy grout, grout, or other methods as approved by the Engineer. No construction traffic is permitted on galvanized steel reinforcing. Use only rubber tired vehicles going less than 5 mph with no turning on geosynthetic reinforcement.
853.4MEASUREMENT AND PAYMENT
The Engineer will measure Retaining Wall by the squa re foot. The Engineer will use the neat lines shown in the Contract Documents to compute the quantities. Payment for "Retaining Wall (*)" at the contract un it price is full compensation for the specified work.