EXCAVATION AND BACKFILL FOR STRUCTURES 501.01 295 SECTION 501
501.01 Description
A.General This work consists of excavating material for the construction of major structures and backfilling, stockpiling, or disposing of excess excavated material. If not otherwise provided for in the Contract, provide equipment, a nd construct and remove necessary cofferdams, shoring, and water control systems for the excavation work. If the Contract does not include a separate pay item for such work, excavation work will include all necessary clearing and grubbing and the removal of existing structures within the area to be excavated. When backfilling, place necessary backfill material, stockpile excavated material that will be used in the backfill, and dispose of excess excavated material that will not be used in the project, unle ss otherwise specified in the Contract. Excavate and backfill in reasonably close conformity with the lines, grades, and typical cross sections shown on the Contract or as directed by the Engineer. Comply with applicable environmental regulations, includin g the United States Army Corp of Engineers 404 Permit, and Section 220, “Management of Erosion, Sedimentation, and Storm Water Pollution Prevention and Control.”
B.Classification The Department classifies excavation and backfill as follows: Unclassified Excavation Material, of whatever nature, removed to construct box culverts, channels, ditches at culvert inlets and outlets, and other ditches shown in the Plans in accordance with Section 202, “Earthwor k.” Structural Excavation, Unclassified Material, of whatever nature, removed below the level of Unclassified Excavation to construct box culverts. Substructure Excavation, Common Material removed to construct substructures, piers, and abutments, except ma terial classified as Substructure Excavation, Rock. Substructure Excavation, Rock Solid rock, redbed, shale, slate, or hard material that requires loosening or breaking by blasting, sledging, or drilling for the construction of substructures, piers, and ab utments. The Department will classify rock ledges above the foundation material and boulders or pieces of concrete with a volume of at least ½ yd³ [½ m³] as Substructure Excavation, Rock. Unclassified Backfill , Select Backfill , and Granular Backfill Suppl ying, placing, and compacting unclassified borrow, select borrow, and granular backfill material in accordance with Section 202, “Earthwork.”
501.04 Exca Vation and Backfill for Structures
296 Controlled Low -Strength Material (CLSM) Backfill Supplying and placing CLSM in excavati ons, or confined or formed spaces.
C.Obstructions The Department will consider the removal and disposal of obstructions (buried natural or man - made objects) to be additional work and will pay the Contractor in accordance with Subsection 501.06, “Basis of Payment.” The Department defines obstructions as objects meeting the following conditions: Requiring the introduction of methods or equipment not already used on the Project; Not shown on the Plans; Not ascertainable b y investigation, including contact with identified utilities; and The Contractor notifies the Engineer in writing within 24 hr of discovering the obstruction and before its removal.
501.02 Materials
Provide backfill materials with no frozen lumps or degradable or hazardous matter, and a gradation that can be consistently compacted. Provide materials in accordance with the following sections and subsections: Material: Section or Subsection: Unclassified Excavation 202.01.A Select Borrow 705 Granular Backfill not for Mechanically Stabilized (MSE) Walls 703.07 Granular Backfill for MSE Walls 510.02.D Standard Bedding Material 703.08 Controlled Low -Strength Material (CLSM) 701.19
501.03 Equipment — Vacant
501.04 Construction Methods
A.Excavation
1.Depth of Footings The bottom of footing elevations shown on the Plans are approximate. The Engineer may issue written orders to change the footing dimensions or elevations. Boring logs shown on the Plans were made for designing the foundation. Interpret and confirm the b oring information for construction as needed.
2.Foundation Preparation and Control of Water
a.General Construct substructures in open excavations. Ensure safe excavations by using cofferdams, shoring, or bracing in accordance with Subsection 502.04.D “Temporary Retaining Structures.” EXCAVATION AND BACKFILL FOR STRUCTURES 501.04 297 If cofferdams are unnecessary, the Department will allow omission of footing backforms and filling of the excavation with concrete, as approved by the Engineer. Construct temporary wa ter control systems in accordance with Subsection 502.04.E, “Temporary Water Control Systems.” Cut or step excavations vertically adjacent to abutments, wings, and retaining walls before backfilling. Remove existing structures in accordance with Subsection 619.04.B, “Removal of Bridges, Culverts, and Other Existing Structures.”
b.Excavation in Channels Clear the right -of-way in accordance with Sectio n 201, “Clearing and Grubbing,” for the full length of the bridge, unless otherwise required by the Contract. Avoid encroaching into creeks and riverbanks, and maintain the existing natural condition. The Department will not allow excavating or cutting of banks unless required by the Contract. Submit proposed work road locations for Engineer’s approval, and construct only in the approved location. Restore bank cuts and work roads to the original shape, density, and condition, unless otherwise required by the Contract. Obtain approval from the Engineer before excavating or dredging outside caissons, cribs, cofferdams, steel piling, or sheeting, and before disturbing the natural streambed. Backfill and compact excavation outside these structures in accorda nce with Subsection 501.04.B, “Backfilling, ” at no additional cost to the Department. Remove excess excavated material within the stream area, and restore the stream to the existing condition.
c.Foundations on Rock Excavate solid rock or other hard foundation material to the depth shown on the Plans or as directed by the Engineer. Remove loose and disintegrated material from the excavation. Level the final surface or make level steps as shown on the Plans, or as d irected by the Engineer. Do not disturb solid rock outside the neat lines of the footing. Clean seams and fill with concrete or CLSM before placing the footing. Remove and replace loose, fractured rock caused by overbreak where when blasting is necessary to reach footing elevation below the bearing level with concrete at no additional cost to the Department.
d.Foundations Not on Rock Do not disturb the bottom of the excavation if placing a foundation on an excavated surface other than rock. Remove fou ndation material to grade just before placing the footing reinforcing steel and concrete. Remove disturbed material at the bottom of footings not supported by piles. Fill the area with concrete or CLSM, at no additional cost to the Department. Replace an d compact disturbed material at the bottom of footings supported by piles as directed by the Engineer. Remove unsuitable foundation material below the footing bottom slab and aprons for box culvert excavation and replace with approved bedding material. Re place material removed
501.04 Excavation and Backfill for Structures
298 below designed elevation with approved bedding material. Open outlets for the effective width of the structure before constructing slab and aprons of box culverts to allow for drainage.
e.Approval of Foundation Notify the Engineer when the excavation is ready for inspection. Place the footing concrete after the Engineer approves the excavation and foundation material. Unless otherwise approved by the Engineer, do not place concrete under water.
B.Backfilling
1.General Place an d compact backfill (to the existing ground line) and embankments in accordance with Section 202, “Earthwork,” unless modified by Subsection 501.04.B(1) . If excavation does not yield enoug h suitable material for backfill, provide additional backfill material in accordance with Subsection 501.02, “Materials.” Backfill excavated spaces unoccupied by permanent structures up to the surface of the surrounding ground and allow for settlement unless otherwise required by the Contract. Uniformly backfill around the sides of the structure to ensure equal density of the surrounding ground, and neatly grade its top surface. Do not place rocks larger than 3 in [75 mm] against concrete surfaces. Place and compact fill for retaining walls, abutments, wingwalls, and bridge bents in layers no greater than 6 in [150 mm] thick. Uniformly backfill around the sides of the structure to ensure equal loading. Compact backfil l within, or beneath, embankments within roadways in excavated areas, or in front of abutments and retaining walls or wingwalls to the same density required for the embankments. Unless otherwise required by the Contract, compact fill in embankments to at least 95 percent of maximum density in accordance with AASHTO T 99. Place backfill against structure concrete only when the concrete reaches the required compressive strength in accordance with Subsection 509.04.I, “ Application of Loads Including Bridge Decks and Approach Slabs .” Place backfill on the outside faces before backfilling the inside faces to prevent horizontal movement of abutments and wingwalls. The Department will not allow jetting the backfill behind abutments or wingwalls. Operate rollers, vibrators, or other compactors parallel to the outside lines of box culverts and cross -drain wingwalls. Compact areas inaccessible to rolling equipment with mechanical tampers.
2.Placing CLSM Fill the excavation with approved CLSM uniformly around the structure to the elevation shown on the Plans. Place CLSM in lifts no deeper than 4 ft [1.2 m]. Begin placing specified fill material over the CLSM when the water is gone from the surface of the CLSM, or as directe d by the Engineer.
3.Disposal of Surplus Clean construction areas in accordance with Subsection 104.10, “Final Cleanup.” Do not place excess material in the streambed. Remove obstructions that may collect drift, ind uce scour, or EXCAVATION AND BACKFILL FOR STRUCTURES 501.05 299 endanger the work as approved by the Engineer. Dispose of excess excavated and removed materials.
501.05 Method of Measuremen T
A.General The Engineer will measure the volume of excavation for structures based on the following: Quantities sh own on the Plans, A calculation of the actual quantities removed, or Quantities directed by the Engineer. The Engineer will not measure additional volumes of excavation resulting from slips, slides, cave - ins, silting, or filling due to the action of the el ements or carelessness that is the responsibility of the Contractor. The Department will not classify water as excavated material. The Department will not measure and separately pay for the disposal of excess material. The Department considers the dispo sal of excess material as incidental to the various classes of excavation and removal. The Department will not measure or separately pay for the disposal of excess material. The Department will consider the disposal of excess material as incidental to th e various classes of excavation and removal. The Department will not measure for payment any additional concrete necessary to fill excavation outside the neat lines shown on the Plans. The Engineer will measure the volume of backfill for structures in acc ordance with Subsection 501.05.E, “Backfilling.”
B.Excavation for Box Culverts
1.Unclassified Excavation For box culverts, the Engineer will calculate the theoretical volume of the trapezoidal prism of Unclassified Ex cavation in accordance with the following: The depth using the difference between the elevation of the existing ground line and the elevation of the flow line shown on the Plans; The base width of the excavation 4 ft [1.2 m] wider than the outside dimensio ns of each side of the barrel of the box culvert as shown on the Plans; The top width using 2H:1V side slopes from the limits of the design flow line to the existing ground line; and The length along the centerline of the box culvert between a point on a l ine connecting the wingwall ends on each side of the culvert, plus 15 ft [5 m] on each end of the structure.
2.Structural Excavation, Unclassified The Engineer will calculate the volume of Structural Excavation, Unclassified based on the volume of the bo x culvert base slab (the volume of box culvert slab below the flow line shown on the Plans) using the width and thickness shown on the Plans, and the length along the centerline of the box culvert between a point on a line connecting the wingwall (outer) e nds on each side of the culvert. The Engineer will not measure additional volumes of excavation for curtain walls, wingwall
501.05 Excavation and Backfill for Structures
300 footings, aprons, sheeting, shoring, or Contractor convenience beyond the theoretical dimensions defined above. If the Contractor encounters and removes soft and yielding material at the bottom of the footing and replaces it with suitable bedding material at the direction of the Engineer, the Engineer will measure the volume of unsuitable material removed and pay fo r it in accordance with Subsection 501.06, “Basis of Payment. ”
C.Excavation for Substructures Supported on Piling The Engineer will measure excavation for substructures, piers, and abutments supported on piling as Subs tructure Excavation, Common . The Engineer will calculate the excavation volume in accordance with the following: The depth from the existing ground line to the bottom of the substructure footing; The width 6 ft [2 m] wider than the width of the substructu re shown on the Plans; and The length 6 ft [2 m] longer than the length of the substructure shown on the Plans. If the Contract requires channel excavation, the Department will consider the existing ground line to be the bottom of the excavated channel.
D.Excavation for Substructures Supported on Natural Foundation Materials The Engineer will measure excavation for substructures, piers, and abutments supported on natural foundation materials as Substructure Excavation, Common or Substructure Excavation, Ro ck. The Engineer will calculate volumes of excavation for substructures and piers in accordance with Subsection 501.05.C, “Excavation for Substructures Supported on Piling,” except the Engineer will calculate the vol ume of excavation below the top of the approved foundation material based on the neat lines of footings shown on the Plans or directed by the Engineer. The Engineer will calculate the volume of excavation for abutments based on the abutment dimensions sho wn on the Plans.
E.Backfilling The Engineer will calculate the volumes of each type of backfill required by the Contract, above the existing ground line based on the neat lines shown on the Plans, or as directed by the Engineer.
F.Obstructions The Engineer will measure the volumes of removed obstructions in accordance with Subsection 501.01.C, “Obstructions.” EXCAVATION AND BACKFILL FOR STR UCTURES 501.06 301 501.06 BASIS OF PAYMENT The Department will pay for each pay item at the contract unit price per the specified pay unit as follows: Pay Item: Pay Unit:
A.STRUCTURAL EXCAVATION, UNCLASSIFIED Cubic Yard [Cubic Meter]
B.SUBSTRUCTURE EXCAVATION, COMMON Cubic Yard [Cubic Meter]
C.SUBSTRUCTURE EXCAVATION, ROCK Cubic Yard [Cubic Meter]
D.UNCLASSIFIED BACKFILL Cubic Yard [Cubic Meter]
E.SELECT BACKFILL Cubic Yard [Cubic Meter]
F.GRANULAR BACKFILL Cubic Yard [Cubic Meter]
G.CLSM BACKFILL Cubic Yard [Cubic Meter] The Department will pay for the volumes of Unclassified Excavation, calculated in accordance with Subsection 501.05.B(1), “Unclassified Excavation,” in accordance with Section 202, “Earthw ork.” Include the cost of removal and disposal of obstructions, as defined in Subsection 501.01.C, “Obstructions,” in the Contract unit price for the relevant excavation pay item, unless specifically included in other pay items. The Department will pay for volumes of removed obstructions at twice the Contract unit price for the relevant excavation pay item for which the obstruction was encountered. Include the cost of removing volumes of water, disposing of excess mat erial, and excavation for placing sway bracing, sash bracing, and bulkheads on timber substructures in the Contract unit price for the relevant excavation pay item. The Department will pay for the volume of soft and yielding material removed and a like vol ume for replacement material from the bottom of box footings as Structural Excavation, Unclassified at the Contract unit price. Include the cost of backfilling around structures below the existing ground line to be included in the contract unit price for t he relevant excavation pay item. The Department will not pay for excess concrete when the Contractor omits footing backforms and fills the excavation with concrete in accordance with Subsection 501.04.A(2)(a), “Ge neral.”
502.02 Forms , Falsework, and Temporary Works
302 SECTION 502 FORMS, FALSEWORK, AND TEMPORARY WORKS
502.01 Description
This work consists of designing, constructing, and removing temporary structures used for highway bridge structure s. The Department defines formwork, falsework, and temporary structures as follows: Temporary Structures. Falsework, formwork, temporary retaining structures, temporary water control systems, and detour bridges. Falsework. Temporary construction used to su pport a permanent structure until it becomes self-supporting. Formwork. Temporary structure or mold used to contain plastic or fluid concrete in the shape shown on the Plans until the concrete reaches the compressive strength required by the Contract. Temporary Retaining Structure. A temporary structure that holds the surrounding earth and water out of an excavation and protects adjacent property during construction of the permanent work. Temporary Water Control System. A system to divert water from and prevent it from entering an excavation. Detour Bridge. A conveyance for traffic during construction of permanent work.
502.02 Materials
A.Falsework
1.General The Department will allow the use of new or used manufactured components, or both in falsework construction. Provide materials in accordance with the following sections: Material: Section: Structural Steel 506 Structural Concrete (Class A) 509 Reinforcing Steel for Structures 511 If the Contract requires, provide certification for new materials. Perform concrete tests in accordance with Section 701, “Portland Cement Concrete. ”
2.Salvaged Steel Provide steel meeting ASTM A 6 criteria for surface imperfections at the allowable working stresses for new steel of the same grade . Provide salvaged steel in good condition with an
Source: Oklahoma Standard Specifications for Highway Construction, 2019 Edition. Pages 309–315 of 935.