SECTION 506—RETAINING W ALLS
506.01 Description
This work shall consist of constructing rubble and hydraulic cement concrete retaining walls in accordance with the plans and these specifications and in conformity to the lines and grades shown on the plans or as established by the Engineer.
506.02 Materials
b.Hydraulic cement concrete retaining walls shall be constructed of concrete conforming to Section 217.
c.Reinforced concrete crib walls shall be constructed of precast concrete units. Concrete shall conform to Section 217 except that No. 7 aggregate may be used in lieu of No. 57 aggregate. Crib units shall be free from cracks, depressions, spalls, patched or plastered surfaces or edges, and any other defects that might impair their strength or durability.
d.Drain pipe shall conform to Section 232.02.
e.Reinforcing steel shall conform to Section 223, Grade 40 or 60.
f.Porous backfill shall conform to Section 204.02(c).
g.Granular backfill within crib walls shall be constructed of precast concrete units. Concrete shall conform to Section 217 except that No. 7 aggregate may be used in lieu of No. 57 aggregate. Crib units shall be free from cracks, depressions, spalls, patched or plastered surfaces or edges, and any other defects that might impair their strength or durability.
h.Piles shall conform to Section 403.
506.03 Procedures
The Contractor shall perform excavation, backfill, and foundation exploration according to Section 401. The Contractor shall perform concrete construction of retaining walls in accordance with Section 404. Immediately following finishing operations, concrete shall be cured and protected according to Section 404.03.
a.Dry Rubble and Mortar Rubble Retaining Walls: The Contractor shall not place stones in freezing weather or when stone contains frost. Each stone shall have a thickness of at least 8 inches; a width of at least 1 1/2 times the thickness; and, except for headers, a length at least equal to 1 1/2 times the width. The thickness of courses, if varied, shall diminish from the bottom to the top of the wall. Header stones in the heart of the wall shall be the same size as in the face and shall extend at least 12 inches into the core or backing. They shall occupy at least 1/5 of the face area of the wall and shall be evenly distributed. Header stones in walls 2 feet or less in thickness shall extend entirely through the wall. Stones shall be roughly squared on joints, beds, and faces. The Contractor shall use selected stone, roughly squared and pitched to line, at angles and the ends of walls. Stones shall be placed to line and in courses roughly leveled. Bottom or foundation courses shall be composed of large, selected stones. Courses shall be placed with bearing beds parallel to the natural bed of the material. The Contractor shall perform any shaping or dressing of stone before stone is placed in the wall. The Engineer will not allow any dressing or hammering that will loosen the stone after placement. 506.04
1.Dry rubble retaining walls: Face joints shall be not more than 1 inch in width. Each stone shall have a firm bearing on the underlying course at no fewer than three points of contact. Open joints, both front and rear, shall be chinked with spalls fitted to take firm bearing on their top and bottom surfaces so as to result in a firm bearing throughout the length of the stone.
2.Mortar rubble retaining walls: The Contractor shall clean and thoroughly wet each stone with water before it is placed. The bed that is to receive the stone shall also be cleaned and moistened. Stones shall be bedded in freshly prepared mortar. Mortar joints shall be full, and stones shall be carefully settled into place before the mortar has set. The Engineer will not permit the use of spalls in beds. Joints and beds shall not have an average thickness of more than 1 inch. Whenever possible, face joints shall be properly pointed before mortar has set. Joints that cannot be pointed shall be prepared for pointing by raking them out to a depth of 2 inches before mortar has set. Face surfaces of stones shall not be smeared with mortar forced out of joints. Vertical joints in each course shall offset joints of adjoining courses by at least 6 inches. The Contractor shall not locate a vertical joint directly above or below a header. If a stone is moved or a joint is broken after it has been set, the Contractor shall remove the stone, the mortar shall be thoroughly cleaned from the bed and joints, and the stone shall be reset in fresh mortar. Joints that are not pointed at the time stone is placed shall be thoroughly wetted with clean water and filled with mortar. Mortar shall be forced into joints and finished with an approved pointing tool. The wall shall be kept wet while pointing is being done. In hot or dry weather, freshly pointed masonry shall be protected from the sun and kept wet by saturated burlap for at least 3 days after completion. After pointing is completed and mortar has set, the Contractor shall thoroughly clean the wall and leave it in a neat, orderly condition.
c.Reinforced Concrete Crib Walls: Crib units that are damaged during storage or erection shall be removed and replaced at the Contractor’ s expense. Granular backfill shall be used inside and approximately 2 feet in back of and beyond each end of a crib. Backfilling for the crib wall shall follow closely the erection of successive tiers of units. The wall shall not be placed higher than 3 feet above the backfilled portion. Backfill shall be placed carefully to avoid distorting the crib wall.
506.04 Measurement and Payment
Standard retaining walls will be measured in cubic yards within the limiting dimensions shown on the plans, and will be paid for at the contract unit price per cubic yard. This price shall include rubble stone, concrete, joint material, and weep holes. Concrete and reinforcing steel for special design retaining walls will be measured and paid for according to Sections 404.08 and 406.04, respectively.
Referenced in this section
Sections that cite this one
Retaining Walls in other states
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Source: Road and Bridge Specifications, 2020 Edition. Pages 699–701 of 1,065. View official source ↗