Section 257 — Contractor-Designed Retaining Structures

Description

257.01This work consists of designing various types of retaining structures, including walls, reinforced soil slopes, and rockeries.

Material

257.02Conform to the following Sections:

Driven piles

Gabions and revet mattresses

Mechanically stabilized earth w

Micropiles Permanent ground anchors Reinforced concrete retaining w Reinforced soil slopes Rockery, special rock embankmSoldier pile retaining walls

Soil nail retaining walls alls

alls ent, and rock buttress 551 253 255 567 256 258 261 252 254 259

Construction Requirements

257.03Qualifications. Provide a wall designer who is a professional engineer proficient in the applicable design field and licensed in the state where the project will be constructed. At least 30 days before starting the design of retaining structures, submit examples of at least three similar retaining structures designed by the wall designer. Submit photos of each retaining structure with narrative descriptions of design method used, materials used, proprietary systems used (if any), constructability issues, and other pertinent information . Include the name, address, and telephone number for project owners.

257.04Submittals. At least 30 days before starting Contractor- designed retaining structure construction, submit the following according to Subsection 104.06:

(a)Plan and elevation drawings for each structure containing the following:

(1)A plan view of the structure showing:

(a)Horizontal offset from the construction centerline to the face of the structure at defining points along the base. Include begin and end stations;

(b)Location, length, coverage ratio, and type of reinforcement or anchorage as applicable (such as strip, mesh, grid, geosynthetic fabric, and anchor); (c) Centerline and size of drainage structures, drainage pipe, and other utilities behind, passing through, or passing under the structure; and (d) Location, length, and offset from the face of wall to guardrail, guardwall, or parapet structures.

(2)An elevation view of the structure showing:

(a)Elevation and station at horizontal and vertical break points and at least every 50 feet along the top of the structure at the face;

(b)Elevation and station at the top of leveling pads and footings, at the top and tip of piling, and at least every 50 feet along the structure base;

(c)Length and type of reinforcement, anchorage, structure module, and lagging;

(d)Distance and elevation along the structure face to all steps in the base, footings, leveling pads, or lagging; (e) Distance along the structure face to where changes in reinforcement or anchor lengths occur; (f) Construction joints;

(g)Original and final ground -line;

(h)1H:1V scale; and

(i)Location, length, minimum slope for drainage, and type of structure underdrain system.

(3)A typical cross- section view showing:

(a)Type and depth of facing elements and structural connections to reinforcing and anchorage elements; (b) Structure batter or face slope;

(c)Length, spacing, and type of reinforcement, anchorage, structure module and corresponding limits of excavation, and reinforced fill placement zones; (d) Location of guardrail or guardwall features or parapet structures. Include embedment depths, offset from structure facing, connection details with structure reinforcement or anchorage, and blockouts or other provisions to prevent damage to wall elements during guardrail construction;

(e)Original and final ground- line, including right- of-way limits; and

(f)Estimated or known location of subsurface soil and rock units.

(4)General construction notes;

(5)Horizontal and vertical curve data affecting the structure, including match lines or other details to relate structure stationing to centerline stationing; and

(6)Material list and summary of pay item quantities.

(b)Dimensions and schedules of reinforcing steel. Include reinforcing bar bending details, dowels, studs, or both for attaching the facing;

(c)Details and dimensions for foundations and leveling pads. Include steps in the footings or leveling pads; (d) Details and dimensions for: (1) Panels, modules, soldier piles, and lagging necessary to construct the structure;

(2)Reinforcing steel in structural elements;

(3)Details of proposed splices in reinforcements;

(4)Location of mesh, strip attachment, or anchor devices embedded in facing panels;

(5)Anchor no- load lengths, anchor bond lengths, anchor spacing, anchor angles and skews, centralizers, and anchor sheathing and corrosion pr otection; and,

(6)Piles, pile spacing, pile embedment depth, pile installation method, and pile corrosion protection.

(e)Details for the installation of structure drainage and underdrain systems;

(f)Details for constructing structures around drainage features, utilities, lighting foundations, traffic barriers, and other obstructions; (g) Details for terminating structures and adjacent slope construction;

(h)Architectural treatment details;

(i)Design notes, a description of symbols, terminology, and computer programs used in the design of the structure; specify the bearing pressure beneath the structure footing, reinforced soil zone, or piles; (j) Design criteria, loads, load and resistance factors, and soil, rock, and reinforcement parameters for each structure.; and (k) Design calc ulations, assessment of temporary excavation stability, internal and external stability of earth retaining structures and reinforced soil slopes, joint, splice, and facing connection capacities, and relevant references for data used in the design. Submit a checklist showing that each item specified in these requirements has been addressed in the design. Update drawings when plan dimensions are revised due to field conditions or for other reasons. 257.05 General . Ensure that the wall designer and wall material suppliers take full responsibility for the success of the components provided by each party, and do not qualify the responsibility for the design information or calculations provided by the wall designer. Indemnify the Government from claims for infringement of proprietary rights by others without the consent of the patent holders or licensees. Survey according to Section 152 and verify the limits of structure installation. Arrange and conduct a pre -design conference following selection of the structure designer or supplier and before design work starts to discuss structure selection, constructability, design parameters, methods, and limitations. Include the CO, subcontractors, supplier, and the supplier’s design engineer.

257.06Design and Construction. Unless otherwise stated, design retaining structures according to AASHTO, LRFD Bridge Design Specifications . Design and construct retaining structures according to the approved drawings, and the following as applicable:

(a)Rockeries. Conform to Section 252. Design according to FHWA -CFL/TD -06-006, Rockery Design and Construction Guidelines , November 2006.

(b)Gabions. Conform to Section 253.

(c)Soldier pile retaining walls. Conform to Section 254.

(d)MSE walls. Conform to Section 255.

(e)Permanent ground anchors. Conform to Sections 256 and 552.

(f)Reinforced concrete retaining walls. Conform to Section 258.

(g)Soil nail retaining walls. Conform to Section 259.

(h)Reinfo rced soil slopes. Conform to Section 261. Design according to FHWA -NHI-10-025, Design and Construction of Mechanically Stabilized Earth Walls and Reinforced Soil Slopes – Volume II. (i) Micropiles. Conform to Section 567.

257.07Acceptance . Design of the retaining structures will be evaluated under Subsection 106.02 and the applicable Sections listed in Subsection 257.06. Survey will be evaluated under Section 152.

Measurement

257.08Measure the Section 257 pay items listed in the bid schedule according to Subsection 109.02 .

Payment

257.09The accepted quantities will be paid at the contract price per unit of measurement for the Section 257 pay items listed in the bid schedule. Payment will be full compensation for the work prescribed in this Section. See Subsection 109.05 . Progress payments for Contractor- designed retaining walls by the lump sum will be paid as follows:

(a)50 percent of the pay item amount will be paid after the design submittal is approved.

(b)An additional 25 percent of the pay item amount will be paid after 50 percent of the retaining wall construction is completed.

(c)The remaining portion of the pay item amount will be paid after retaining wall construction is completed.