40-Sec 31 20 00 - EARTHWORK.pdf

EARTHWORK

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SECTION 31 20 00

PART 1 - GENERAL

1.01 SECTION DESCRIPTION:

A. Site grading, removal of topsoil and subsoil, building excavating and backfill.

B. Preparing of subgrade for site structures, walks and pavements.

1.02 RELATED INFORMATION

A. Related Work Specified Elsewhere:

1. Section 01 57 13: Soil Erosion and Sediment Control

2. Section 31 11 00: Clearing and Grubbing

3. Section 31 23 33: Excavation, Backfill and Compaction

4. Section 32 12 00: Bituminous Concrete Paving

5. Section 32 93 00: Landscaping

1.03 QUALITY ASSURANCE

A. Testing Agency

1. Any required compaction testing for this Project shall be performed by a soils testing agency engaged and paid for by Contractor. Quality assurance testing shall be coordinated with Resident Project Representative.

B. Reference Standards:

1. Pennsylvania Department of Transportation

Publication 408 Specifications

2. American Society for Testing and Materials (ASTM):

ASTM D422 Test Method for Particle-Size Analysis of Soils

ASTM D1557 Test Method for Laboratory Compaction Characteristics of Soil Using

Modified Effort (56,000 ft.-lbf/ft3)

ASTM D2922 Standard Test Method for Density of Soil and Soil Aggregate in

Place by Nuclear Methods (Shallow Depth)

ASTM D4318 Test Method for Liquid Limit, Plastic Limit, and Plasticity Index of

Soils

C. Compaction Testing:

1. Conduct compaction tests at locations as directed by the Resident Project Representative during grading operations.

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1.04 SUBMITTALS

A. Submit certified test reports on borrow material. Test reports shall include grain size distribution (ASTM D422), Atterberg limits (ASTM D4318) and moisture density relationship

(ASTM D1557).

B. Submit certified compaction testing results from the soils testing agency for any required compaction testing.

1.05 JOB CONDITIONS

A. All earthwork shall be performed in accordance with conditions outlined in Section 01 57 13, Soil Erosion and Sediment Control and the Drawings.

B. Site disturbance and earth moving shall proceed in accordance with the sequence shown on the Drawings.

C. Contractor may conduct earthwork activities within the contract limit lines as shown on the Drawings.

D. Prior to earth moving activities, all topsoil shall be stripped and stockpiled in accordance with the Project Drawings.

E. Classification of Excavation:

1. All excavation work performed under this contract is UNCLASSIFIED.

PART 2 - PRODUCTS

2.01 SOIL MATERIALS

A. Topsoil: Excavated or imported friable loam that is reasonably free of subsoil, clay lumps, brush, roots, weeds, other objectionable vegetation, stones or other foreign material.

B. Subbase Material: Naturally or artificially graded mixture of natural or crushed gravel, crushed stone, and natural or crushed sand.

C. Drainage Fill: Washed, evenly graded mixture of crushed stone, or crushed or uncrushed gravel, with 100 percent passing a 1-1/2 inch sieve and not more than 5 percent passing a No. 8 sieve. PennDOT No. 2B or AASHTO No. 57 coarse aggregate, Table C, Section 703.2, Publication 408 Specifications.

D. Fill Materials: Satisfactory on-site soil materials comprised of less than 40% by weight larger than 3/4 inches in diameter, free of particles larger than 4 inches, and free of debris, slag, waste, frozen material, excessive moisture, organics, or other deleterious material.

PART 3 - EXECUTION

3.01 STORAGE OF EXCAVATED MATERIALS

A. Stockpile excavated materials acceptable for backfill and fill. Place, grade and shape stockpiles for proper drainage.

1. Locate and retain soil materials away from edge of excavations. Do not store within drip line of trees indicated to remain.

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2. Dispose of excess excavated soil material and materials not acceptable for use as backfill or fill.

3.02 EXCAVATION FOR SITE STRUCTURES

A. Conform to elevations and dimensions shown within a tolerance of plus or minus 0.10 foot, and extending a sufficient distance from site structures to permit placing and removal of concrete formwork, installation of services, and other construction and for inspection. In the event that fill deposits or other unsuitable bearing materials are encountered at the given elevations, they shall be over-excavated and replaced with structural backfill as specified hereinafter.

1. Excavations for site structures: Do not disturb bottom of excavation. Excavate by hand to final grade just before concrete reinforcement is placed. Trim bottoms to required lines and grades to leave solid base to receive other work.

B. In the event bedrock is encountered at the footing subgrade elevation, it shall be over-excavated to a level 12 inches below the plan site structure subgrade elevation and 12 inches beyond the perimeter of the site structure on all sides. Bedrock encountered within four (4) inches of the base of the site structure shall be removed to at least six (6) inches below the base elevation for the site structure. The over-excavations specified above shall be restored to the subgrade elevation with PA No. 2A or 2RC processed aggregate which is placed and compacted as specified hereinafter.

C. Any soft, weak and/or unstable soil encountered at the footing subgrade elevation shall be overexcavated to satisfactory bearing material. Subsequently, the overexcavation shall be backfilled to the plan subgrade elevation with either lean concrete or PA No. 2A or 2RC processed aggregate.

3.03 EXCAVATION FOR PAVEMENTS

A. Cut surface under pavements to comply with cross-sections, elevations and grades as indicated.

3.04 COLD WEATHER PROTECTION

A. Protect excavation bottoms against freezing when atmospheric temperature is less than 35 degrees F.

3.05 BACKFILL AND FILL

A. General: Place soil material in layers to required subgrade elevations, for each area classification listed below, using materials specified in Part 2 of this Section.

1. Under grassed area, use satisfactory excavated or borrow material.

2. Under walks and pavements, use subbase material, satisfactory excavated or borrow material, or a combination.

3. Under steps, use subbase material.

4. Under site structures, use drainage fill material for 6” or 8" drainage course as shown on the Drawings. Below drainage course, provide satisfactory soil material.

5. For utility and pipe trenches see Section 31 23 33.

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B. Backfill site structure excavation as promptly as work permits, but not until completion of the following:

1. Acceptance of construction below finish grade including, where applicable, dampproofing, water-proofing and perimeter insulation.

2. Removal of concrete formwork.

3. Removal of shoring and bracing, and backfilling of voids with satisfactory materials.

Cut off temporary sheet piling driven below bottom of structure and remove in manner to prevent settlement of the structure, or leave in place if required.

4. Removal of trash and debris from excavation.

5. Permanent or temporary horizontal bracing is in place on horizontally supported walls.

3.06 PLACEMENT AND COMPACTION

A. Ground Surface Preparation: Remove vegetation, debris, unsatisfactory soil materials, obstructions, pavement sections, topsoil and organic and deleterious materials from ground surface prior to placement of fills (See Section 31 11 00). Plow, strip, or break up sloped surfaces steeper than 1 vertical to 4 horizontal so that fill material will bond with existing surface.

1. When existing ground surface has a density less than that specified under 3.06.E. for particular area classification, break up ground surface, pulverize, moisture-condition to optimum moisture content, and compact to required depth and percentage of maximum density.

2. After stripping and rough excavation grading, areas to provide support for the foundations, floor slab, structural fill and pavement shall be carefully inspected for soft surficial soils and proofrolled with a fully loaded triaxle dump truck or similar approved equipment. Proofrolling shall be performed under the observation of the soils testing agency. The proofroller shall make at least eight passes over each location, with the last two passes perpendicular to the first two. Any areas which wave, rut or deflect excessively and continue to do so after several passes of the proofroller shall be undercut to stable soils or as directed by the geotechnical engineer. The undercut areas shall be backfilled in thin lifts with suitable compacted refill materials.

3. The stripping and proofrolling operations shall be delayed in areas where the construction will not proceed immediately to a finished surface so that the exposed subgrade will not deteriorate under the effects of weather and construction traffic.

B. Place backfill and fill materials in layers not more than 8 inches in loose thickness for material compacted by heavy compaction equipment, and not more than 6 inches in loose thickness for material compacted by hand-operated tampers.

C. Before compaction, moisten or aerate each layer as necessary to provide optimum moisture content. Compact each layer to required percentage of maximum dry density or relative dry density for each area classification. Do not place backfill or fill material on surfaces that are muddy, frozen or contain frost or ice.

D. Place backfill and fill materials evenly adjacent to structures to required elevations. Prevent

31 20 00-5 wedging action of backfill against structures by carrying material uniformly around structure, piping or conduit to approximately same elevation in each lift.

E. Control soil and fill compaction, providing minimum percentage of density specified for each area classification indicated below. Correct improperly compacted areas or lifts as directed by Resident Project Representative if soil density tests indicate inadequate compaction.

1. Percentage of Maximum Density Requirements: Compact soil to not less than the following percentages of maximum dry density, in accordance with ASTM D1557 (Modified Proctor):

a. Under structures, building slabs and steps, and pavements, compact top 12 inches of subgrade and each layer of backfill or fill material at 95% (Modified Effort) of the maximum density, at or near the optimum moisture content.

b. Non-structural areas which lie within five (5) feet of building, pavement and structural areas at 93% (Modified Effort) of the maximum density at or near the optimum moisture content.

c. Detention basin berms, compact each layer of fill material at 95% (Modified

Effort) of the maximum density, at or near the optimum moisture content.

d. Under lawn or unpaved areas, compact top 6 inches of subgrade and each layer of backfill or fill material at 90% (Modified Effort) of the maximum density at or near the optimum moisture content.

e. Under walkways, compact top 6 inches of subgrade and each layer of backfill or fill material at 93% (Modified Effort) of the maximum density, at or near the optimum moisture content.

2. Moisture Control: Where subgrade or layer of soil material must be moisture conditioned before compaction, uniformly apply water to surface of subgrade or layer of soil material. Apply water in minimum quantity as necessary to prevent free water from appearing on surface during or subsequent to compaction operations.

a. Remove and replace, or scarify and air dry, soil material that is too wet to permit compaction to specified density.

b. Stockpile or spread soil material that has been removed because it is too wet to permit compaction. Assist drying by discing, harrowing or pulverizing until moisture content is reduced to a satisfactory value.

3.07 GRADING

A. General: Uniformly grade areas within limits of grading under this section, including adjacent transition areas. Smooth finished surface within specified tolerances, compact with uniform levels or slopes between points where elevations are indicated or between such points and existing grades.

B. Grading Outside Building Lines: Grade areas adjacent to building lines to drain away from structures and to prevent low points as shown on the Drawings. Finish surfaces free from irregular surface changes and as follows:

1. Lawn or Unpaved Areas: Finish areas to receive topsoil to within not more than 0.10 foot above or below required subgrade elevations.

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2. Walks: Shape surface of areas under walks to line, grade and cross section, with finish surface not more than 0.10 foot above or below required subgrade elevation.

3. Pavements: Shape surface of areas under pavement to line, grade and cross section, with finish surface not more than 1/2 inch above or below required subgrade elevation.

C. Grading Surface of Fill under Site Structure Slabs: Grade smooth and even, free of voids, compacted as specified, and to required elevation. Provide final grades within a tolerance of 1/2-inch when tested with a 10-foot straightedge.

D. Compaction: After grading, compact subgrade surfaces to the depth and indicated percentage of maximum or relative density for each area classification.

3.08 SITE STRUCTURE SLAB DRAINAGE COURSE

A. General: Drainage course consists of placement of drainage fill material, in layers of indicated thickness over subgrade surface to support concrete site structure slabs.

B. Placing: Place drainage fill material on prepared subgrade in layers of uniform thickness, conforming to indicated thickness.

1. When compacted drainage course is indicated to be 6 inches thick or less, place material in a single layer. When indicated to be more than 6 inches thick, place material in equal layers, except no single layer more than 6 inches or less than 3 inches in thickness when compacted.

3.09 EROSION CONTROL

A. Provide erosion control methods in accordance with Section 01 57 13 and the Project Drawings.

3.10 MAINTENANCE

A. Protection of Graded Areas: Protect newly graded areas from traffic and erosion. Keep free of trash and debris.

B. Repair and re-establish grades in settled, eroded and rutted areas to specified tolerances.

C. Reconditioning Compacted Areas: Where completed compacted areas are disturbed by subsequent construction operations or adverse weather, scarify surface, reshape and compact to required density prior to further construction.

D. Settling: Where settling is measurable or observable at excavated areas during general project warranty period, remove surface (pavement, lawn or other finish), add backfill material, compact and replace surface treatment. Restore appearance, quality and condition of surface or finish to match adjacent work, and eliminate evidence of restoration to greatest extent possible.

3.11 DISPOSAL OF EXCESS AND WASTE MATERIALS

A. Removal from Owner's Property: Remove waste materials, including unacceptable excavated material, trash and debris, and dispose of it off Owner's property.

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END OF SECTION