504BRIDGE EXCAVATION

New Hampshire Department of Transportation Standard Specifications – 2016 Description

1.1This work shall consist of the excavation, satisfactory disposal, and backfill of all materials encountered in the construction

of bridges as shown on the plans or ordered. Classification of Materials

2.1Common bridge excavation shall consist of all materials not classified as rock. Glacial till or boulder clay will be considered

as common bridge excavation.

2.2Rock bridge excavation shall consist of solid rock which cannot be removed without blasting or ripping. It shall also consist

of boulders and parts of masonry structures when found to measure 1/2 cy or more. Construction Requirements

3.1Preparation of a Foundation on Earth.

3.1.1 In areas of excavation where pumping is not required, material shall be removed and maintained a minimum of 1 ft. outside the neat lines of the footing. 3.1.2 In areas of excavation where pumping is required, material shall be removed and maintained to such limits as will provide for carrying water outside all footing forms, with the water level maintained slightly lower than the elevation of the bottom of all footings. Suitable sumps shall be constructed and maintained. 3.1.2.1 Where materials are encountered which are susceptible to softening or displacement when inundated, pumping shall begin prior to removal of material to grade and shall continue on a 24-hour basis until masonry has been placed. 3.1.2.2 When blasting is required, the provisions of 203.3.2 and 203.3.3 shall apply as though contained in this Section. 3.1.3 The final removal of the foundation material to grade shall be made in such a manner that the foundation material below grade will not be disturbed or loosened and a uniform foundation will be obtained. Removal shall be made by hand unless the use of power equipment for this pur pose performs satisfactorily. This portion of the excavation shall be made in as short a time as possible before the masonry is to be placed. 3.1.4 When ordered, a layer of structural fill of sufficient depth to stabilize the foundation material shall be applied prior to placing either forms, reinforcing steel, or masonry.

3.2Preparation of a Foundation on Rock.

3.2.1 Care shall be taken to avoid undue overbreakage in the drilling and blasting of rock. 3.2.1.1 When blasting is required, the provisions 203.3.2 shall apply as though contained in this Section. 3.2.2 The surfaces to receive the footings shall be level, stepped, roughened, doweled, or any combination thereof as directed. When the use of dowels is ordered, holes shall be drilled to the depth required and the dowels grouted with cement mortar conforming to Section 707. The surfaces shall be cleaned and maintained clean until the masonry is placed. 3.2.3 All loose rock and fragments shall be removed as directed. 3.2.4 Seams shall be cleaned and grouted when ordered.

3.3Inspection. After each excavation is completed, and prior to placing forms for concrete, the Contractor shall secure approval

of the depth of excavation and the character of the foundation material.

3.4Backfill.

3.4.1 Where masonry is to rest on a rock surface, all space resulting from excavating rock within vertical planes through the neat lines of the footings shall be backfilled with concrete of the same class as that in the footings, unless otherwise shown or ordered. 3.4.2 All spaces resulting from excavation adjacent to the structure shall be backfilled to the level of the surrounding ground with suitable material from the excavation, free from rock, lumps, wood, or other foreign matter, unless otherwise shown or ordered. 3.4.3 Backfilling around footings shall be done immediately after form removal. Backfilling adjacent to and over arch rings or rigid frame structures shall not be performed until 21 days after the concrete has been placed, or the test cylinders prepared from the fresh concrete and cured in the laboratory have attained 80 percent of the minimum compressive strength of the class of concrete shown on the plans. Backfill material shall not exceed the optimum moisture content by more than 2 percentage points. The material shall be placed in layers not more than 12” loose depth and compacted. To avoid unequal pressures, the material shall be

New Hampshire Department of Transportation Standard Specifications – 2016 placed and compacted evenly on both sides of arches and other frame type structures. All required material shall be placed in front of walls and abutments prior to beginning fills behind these structures. Unless otherwise permitted, backfilling behind brid ge abutments shall be made to the elevation of the bridge seat before the structural steel is erected. Mechanical tamping or vibrating devices must be used where the use of rollers and the like are impracticable. 3.4.4 Density requirements shall conform to 203.3.8. 3.4.5 Adequate drainage shall be provided at all times. Water shall be used only in sufficient amounts to obtain the required compaction. Under abnormal conditions where there is no possibility of developing a liquid pressure on the structure and it is impossible or difficult to use power tamping or vibrating devices, the Engineer may order the use of water in such amounts as may be necessary to assist in placing and compacting the backfill.

3.5Approaches. When the plans for a bridge or culvert structure require the construction of an approach, the fill shall be

constructed in accordance with 203.3.7.

3.6Cofferdams. When the work prescribed in Section 503 is subsidiary, the construction methods included in Section 503 shall

apply as though contained herein. Method of Measurement

4.1Common bridge excavation will not be measured, but shall be the cubic yard final pay quantity in accordance with 109.11 .

Rock bridge excavation will be measured by the cubic yard within the following limits: 4.1.1 The upper limit will be the original ground except as provided under 203.5.1.6 . 4.1.2 The lateral limits shall be vertical planes, 1 ft. outside the neat lines of the footings and parallel thereto unless otherwise noted. 4.1.2.1 When bridge excavation is required in order to place portions of the structure outside of the lateral excavation limits specified above, as may be the case in beams and cantilever walls, payment planes will be parallel to the structure, 1 ft. away from the structure, measured normally. 4.1.3 The lower limits shall be as follows: 4.1.3.1 When excavation for masonry that is to rest on a surf ace other than rock is required down to a depth of 1 ft. below the elevations shown on the plans, the material actually removed to such 1 ft. depth will be measured for payment. When such excavation is required deeper than 1 ft. below the elevations shown on the plans, the quantity of all excavation required below such limit will be paid for at 150 percent of the bid price of the appropriate bridge excavation. 4.1.3.2 Unless otherwise shown on the plans, when masonry is to rest on existing rock either undisturbed or prepared in accordance with 3.2, the lower limit shall be either the surface of the existing undisturbed rock or the firm surface prepared in accordance with 3.2, but any rock removed below an elevation 1 ft. lower than the required elevation will be considered as excess removal and will not be measured. The quantity of any common excavation removed more than 1 ft. below the assumed elevation of the existing rock shown on the plans will be paid for at 150 percent of the bid price of the appropr iate bridge excavation. 4.1.3.3 Unless otherwise shown on the plans, when the masonry is to rest on a foundation at a plan elevation within rock, all material actually removed above a plane 1 ft. below the plan elevation will be measured for payment. When such excavation is required and ordered deeper than 1 ft. below the plan elevation, the quantity of all excavation below such limit will be paid for at 150 percent of the bid price of the appropriate bridge excavation. But any rock removed that was not o rdered, below an elevation 1 ft. lower than the required elevation will be considered excess removal and will not be measured.

4.2Material removed from existing structures will be considered as bridge excavation if it is not to be paid for under 502, and is

either:

to such elevations as are noted on the plans or ordered.

4.3Blast vibration control and monitoring, preblast condition surveys, postblast surveys, blasting precautions and other

protective measures will not be measured.

4.4When both classes (common and rock) are present in the bridge excavation the final pay quant ity of common bridge

excavation will be adjusted by the difference between the estimated and accepted quantity of rock bridge excavation. Basis of Payment

5.1Common bridge excavation is a final pay quantity item and will be paid for at the Cont ract unit p rice per cubic yard in

accordance with 109.11. The accepted quantity of rock bridge excavation will be paid for at the Contract unit price per cubic yard.

New Hampshire Department of Transportation Standard Specifications – 2016 5.1.1 No payment will be made for unauthorized material removed except that actual overbreakage of rock will be paid for, not to exceed 1 ft. below the elevations shown or ordered, within the same lateral limits specified in 4.1.2.

5.2Concrete necessary to replace material classified as excess removal will not be pai d for; other concrete within the neat lines

will be paid for under Section 520.

5.3Payment for drilling dowel holes ordered and cleaning and grouting seams be paid as provided for in 109.04; the dowels will

be paid for under Section 544.

5.4Structural fill ordered under 3.1.4 will be paid for under Section 508.

5.5When common bridge excavation is the only class included in the Contract, any rock bridge encountered will be paid for at

5 times the Contract unit price for the common bridge excavation under Item 504.2.

5.6The cost of all blast vibration control and monitoring, preblast condition surveys, postblast surveys, blasting precautions and

other protective measures necessary to prevent damage and subsequent creation of claims in connection with blasting shall be subsidiary to Item 504.2. Pay items and units:

504.1Common Bridge Excavation (F) Cubic Yard

504.2Rock Bridge Excavation Cubic Yard

New Hampshire Department of Transportation Standard Specifications – 2016

Description

This work shall consist of furnishing and placing permanent timber or steel sheet piling as shown on the plans or ordered.

Materials

Steel sheet piling. The steel sheet piling shall conform to AASHTO M 202. Used steel sheet piling in good condition as

determined by the Department is acceptable. Construction Requirements

Steel Sheet Piling.

3.1.1 The sections when assembled in place shall be practically watertight at the joints. 3.1.2 The tops of the piles shall be cut off to a straight line at the elevation indicated.

Defective piles. The procedure incident to the driving of piles shall not subject them to excessive and undue abuse producing

deformation of the steel. Manipulation of piles to force them into proper position, considered by the Engineer to be excessive, will not be permitted. Any pile damaged by reason of internal defects or by improper driving, driven out of its proper location, or driven below the elevation fixed by the plans or by the Engineer shall be corrected at the Contractor’s expense. Method of Measurement

Steel sheet piling will be measured by the pound.

Only the lengths shown on the plans or ordered will be measured.

Basis of Payment

The accepted quantity of piling will be paid for at the Contract unit price per pound for steel piling, as measured.

Pay items and units:

506.2Steel Sheet Piling Pound