513Retaining Walls

513.01DESCRIPTION

This Section describes the requirements for constructing cast-in-place retaining walls, prefabricated modular wall systems, mechanically stabilized earth (MSE) wall systems, and other alternate retaining wall systems.

513.02MATERIALS

.01 Materials

Provide materials as specified: Coarse Aggregate (No. 57) ................................ ................................ ................................ ............................ 901.03 Soil Aggregate (I-9) ................................ ................................ ................................ ................................ ...... 901.11 Soil Aggregate (I-15) ................................ ................................ ................................ ................................ .... 901.11 Concrete ................................ ................................ ................................ ................................ ....................... 903.03 Mortar ................................ ................................ ................................ ................................ ..................... 903.08.01 Curing Materials ................................ ................................ ................................ ................................ ........... 903.10 Precast Concrete Units ................................ ................................ ................................ ................................ .. 904.02 Reinforcement Steel ................................ ................................ ................................ ................................ ...... 905.01 Welded Wire Reinforcement ................................ ................................ ................................ .................... 905.01.03 Structural Steel Plates and Bars ................................ ................................ ................................ ................ 905.01.04 High-Strength Steel Bolts ................................ ................................ ................................ .............................. 908.02 Coal Tar Epoxy Paint ................................ ................................ ................................ ............................... 912.01.03 Preformed Joint Filler ................................ ................................ ................................ ................................ ... 914.01 Joint Sealer (Hot-Poured) ................................ ................................ ................................ .............................. 914.02 Subsurface Drainage Geotextile................................ ................................ ................................ ..................... 919.01 HDPE Geomembrane ................................ ................................ ................................ ................................ .... 919.05 Waterstops ................................ ................................ ................................ ................................ .................... 919.06 Provide soil reinforcement strips according to ASTM A 572, Grade 65. Provide tie strips according to ASTM A 1011, Grade 50. For MSE Walls, use either Soil Aggregate, I-15 or Coarse Aggregate, No. 57. For Prefabricated Modular Retaining Walls and T-Wall, use either Soil Aggregate, I-9 or Coarse Aggregate, No. 57.

.02 Equipment

Provide equipment as specified: Vibrator ................................ ................................ ................................ ................................ ...................... 1005.04 Concrete Batching Plant ................................ ................................ ................................ .............................. 1010.01 263 Concrete Trucks ................................ ................................ ................................ ................................ .......... 1010.02

513.03CONSTRUCTION

.01 Retaining Walls

at a minimum, the following:

precast units and related components.

horizontal alignment.

6 Typical sections of the wall indicating how internal drainage and surface drainage behind the wall is handled. Typical cross sections of cut and fill sections. Limits and extent of select granular backfill material placed above original ground. Location of proposed ground line.

location of reinforcement steel in the member; and th e location of reinforcement attachment devices that are embedded in the panels.

treatment.

bearing pressure.

drainage facilities, sign footings, or any other element.

and backfill.

the minimum 28 day compressive strength before shipping. Provide galvanized handling devices according to ASTM A 123. Store, transport, hoist, and handle units to prevent cracking or damage. After galvanizing, coat attachment surfaces not to be embedded in concrete with coal tar epoxy paint. Replace or repair units damaged by improper storing, transporting, or handling.

firm, even surface. Obtain RE approval before finishing excavation. If the RE determines that the bottom of the excavation is unstable, undercut, backfill, and compact as directed by the RE. Grade the foundation for the structure level for a width that exceeds the length of the soil reinforcement by at least 2 feet. Place concrete, as specified in 504.03.02.D, for an unreinforced concrete leveling footing, or provide a precast concrete leveling pad according to the manufacturer’s recommendations. Before placing wall units, install underdrains and drainage pipes. 264

cast-in-place, construct the section as specified 504.03.02.D. Obtain RE approval of the foundation for the structure before beginning erection. Install the units according to the manufacturer’s recommendations. For erection, handle units with lifting devices set into the upper edge of the panels. Place units in a horizontal course. Do not place the subsequent course until the previous course is backfilled within 2 inches of the top of the course. Provide external bracing for the initial course. While erecting each course, examine line, and grade, and correct deviations to prevent cumulative inaccuracies in alignment. Ensure vertical tolerance and horizontal ali gnment tolerance does not exceed 1/2 inch, when measured along a straightedge. Install joint filler and rubber pads according to the manufacturer’s recommendations. Close joints at corners or angle points. Ensure that all wall units above the first cours e interlock with the lower courses. Ensure vertical joint openings on the wall’s front face do not exceed 3/4 inch. Ensure the front face vertical joints has 12 inch wide strips of subsurface drainage geotextile behind each joint starting 2 feet below grade.

underdrain pipe as shown on the Plans. When constructing weep holes, place ports or vents for equalizing hydrostatic pressure below low water. Use 4 inch PVC or unreinforced concrete drain pipe as forms for weep holes through concrete.

the Plans or directed. Before placing soil reinforcement, compact the backfill material as specified in 513.03.01.G. For modular bin walls, fill wall units 4 feet o r less in height in 1 lift and then thoroughly compact with a vibratory tamping device. Fill wall units more than 4 feet in height in 2 approximately equal lifts and thoroughly compact after each layer is placed. Backfill after erecting each course of wal l units. Verify that the reinforcements and wall units are not damaged, disturbed, or misaligned while backfilling. Correct misalignment and remove and replace damaged units of the wall units before placing the next course. Backfill using one of the following materials:

Decrease this lift thickness to obtain the specified density. The ME will determine the optimum moisture content as specified in AASHTO T 99, Method C. Ensure that the moisture content of the backfill is uniform throughout each layer and has a placement moisture content that is less than or equal to the optimum moisture content. Remove and rework backfill that has a placement moisture content in excess of the optimum moisture content until the moisture content is uniformly acceptable throughout the entire layer. Ensure that backfill placed within 1 foot of a drainage structure or utility does not have any particle greater than 3 inches in maximum dimension.

geotextile at the interface of the coarse aggregate and regular roadway materials and embankments. At each reinforcement strip level, level and compact the coarse aggregate before placing the reinforcement.

the next block level. Roughly level each course of backfill to an elevation approximately 2 inches above the level of the next course of units. Compact in a direction parallel to the wall.. For MSE walls, do not use sheepsfoot or grid-type rollers for compacting backfill within the limits of the soil reinforcement. Compact for the specified material as follows:

large, smooth drum, vibratory rollers using the density control method as specified in 203.03.02.B.4. Within 5 feet of the wall, use small, single or double drum, hand operated, walk -behind vibratory rollers, or walk-behind vibrating plate compactors. Make at least 3 passes.

with a vibratory roller that has a total operating weight of 8 to 10 tons. Set the roller in the vibratory mode between 1.5 and 2.5 miles per hour.