This specification sets up requirements for the design, materials, manufacture, and construction of precast, reinforced concrete retaining wall system.Contract work consists of furnishing materials and installing retaining wall in accordance with details shown on project plans.
Bidders attention is called to the fact that EVERGREEN retaining wall units are the basis for this specification.
Section 2: Design of Wall System
Evergreen Units: The wall consists of precast concrete elements with a face vertical or battered 3 to 5 vertical to 1 horizontal. Wall components are all monolithic and do not consist of individual elements, except for board units near top of wallSuch monolithic type elements are of variable width, wider elements used at the bottom, and smaller elements at the topIn case of high vertical walls, a wide base of wall is needed made with two side-by-side units
Resets: Using smaller elements on top of wider elements produces offsets, which will be either on the front side or on the rear, depending on specific wall design. This configuration contributes to improve structural integrity and safety at each joint. In cases, planting is desirable at intermediate levels; such horizontal resets at the outer surface provide rooms for plants and improve plant growth.
Topsoil: In case of planting such resets are to be filled with 8 to 10 inches of topsoil, preferably enriched with nutrients to expedite plant growth.
Design of Units: Evergreen wall components are specifically designed and manufactured for each individual application. Site-specific soil design parameters and traffic loads directly affect the size of Evergreen Maxi units and required steel reinforcement.The Evergreen franchise includes in-depth Evergreen computer design software and trained staff engineers for specific design of each wall section.
Specific Location of Units: Each type of units is reinforced for resisting a certain range of loading conditions and position of unit beneath the crest of the wall, to be verified by the designer. In most cases, these units are reversible. However, in case of specific design, heavier steel reinforcement may be necessary. In case of wall corners or turns in the alignment of the wall, front panels must be shortened to fit. These units are to be marked individually at the time of manufacture indicating number of stack and number of layer to fit.
Fill Requirement: Units are designed to withstand pressures created by a certain type of backfill within the wall. Wall fill material to be utilized within precast units can be ordinary borrow material, provided water content iswithin plus minus 2% of optimum water content and friction angle phi’ = minimum 32° at cohesion c’ = o (zero), and moist density after compaction, gamma = min. 18 kNjm3. A standard relative compaction is not a requirement, since this is not a pavement, but a gravity wall in which density is the key issue. Do notover compact to avoid over stress on units. Fill material shall have 10 to 25% fines passing sieve #200, (0.074 mm); if fill contains 15 to 25% fines, then PL must be below 6 and fraction below 15 microns shall not exceed 15%. This means silt and c1ay material are not suited for filling
