31 30 00 STRUCTURAL BACKFILL AND COMPACTION

Owned by Former user (Deleted)
Last updated: Aug 01, 2017 by Former user (Deleted)
6 min read
.01 General
  1. Summary
    1. Section Includes:  Backfill and compaction requirements for building, structures, roads, sidewalks, etc.
  2. References
    1. American Society for Testing and Materials (ASTM):
      1. ASTM C 295:  Guide to Petrographic Examination of Aggregates for Concrete.
      2. ASTM C 1580:  Standard Test Method for Water-Soluble Sulfate in Soil
      3. ASTM D 698:  Standard Test Methods for Laboratory Compaction of Soil Using Standard Effort.
      4. ASTMD 2922:  Density of Soil and SOil-Aggregate in Place by Nulcear Methods (Shallow Depth).
    2. Pennsylvania Department of Transportation (PENNDOT), Standard Specifications Publication 408, as supplemented.
      1. PENNDOT Section 703, Coarse Aggregate.
    3. American Association of State Highway and Transportation Officials (AASHTO):
      1. AASHTO R 18-97, Establishing and Implementing a Quality System for Construction Materials Testing Laboratories.
    4. Pennsylvania Department of Transportation Directive:
      1. "Acid Bearing Rock Policy" by Tucker Ferguson P.E.; Director, Bureau of Construction and Materials; September 30, 2009.
  3. Submittals
    1. Aggregate:  Submit samples and lab tests to Professional for approval as specified below in Quality Control.
    2. Field Test Reports:  Submit copies of all field tests performed to confirm that backfill materials have been compacted to the specified density.
    3. Testing Laboratory:  Submit for approval the AASHTO Materials Reference Laboratory (AMRL) certification of the proposed testing laboratory.
  4. Quality Control
    1. Provide advance examination and testing according to methods referenced, or as required by the Professional, for aggregate materials.
      1. Conduct aggregate quality tests in accordance with requirements of PENNDOT Section 703.
      2. Conduct petrographic examination of aggregate samples representative of proposed materials according to procedure defined in ASTM C 295.
        1. Examination shall be performed by an experienced petrographer.
        2. The selected aggregate material shall meet these additional restrictions:
          • Less than 0.5% pyrite (i.e. 0.3% S).
          • Contain less than 2% deletrious materials.
          • Limit the sulfur content to 0.1% if it is in the form of framboidal pyrite in a carbonaceous shale (Antes Member of the Reedsville Formation and parts of the Coburn Formation) or as whisker pyrite in veins.
          • Less than 15% thin, elongate, or platy pieces for Type A, 20% for Type B.
      3. Conduct chemical analysis of aggregate samples representative of proposed materials according to procedures defined in ASTM C 1580.
      4. Professional reserves the right to accept aggregate materials based on certification from supplier that aggregate originates from a source approved by PENNDOT and that aggregate complies with specified PENNDOT requirements and the additional requirement included in this specification.
    2. Independent Testing Agency shall perform testing of aggregate samples prior to the start of the work and every three months thereafter.  Testing results must be resubmitted for review each time the source material is changed.  Testing shall include soundness, abrasion, petrographic examination and chemical analysis.
  5. Quality Assurance Testing
    1. The Quality Assurance Agency will perform tests related to backfill compaction density, moisture content, and inspection of the subgrade.
    2. Testing shall be performed and approved for each subgrade and each fill layer before proceeding to the next layer.  Any area which does not meet density, percent moisture, or other requirements at any time shall be suitably reworked by the Contractor and retested at the expense of the Contractor.
  6. Project Conditions
    1. Environmental Requirements:
      1. Pumping:  Keep excavations free from water.  Build dams and other devices necessary for this purpose, including lowering water table below excavation bottom by deep wells, well points, and pumping.  Provide and operate pumps of sufficient capactiy for dewatering excavations.  Dispose of water removed from excavations in a manner not to cause injury to public health, public or private property, work of other trades or contractors, portions of work completed or in progress, or produce an impediment to highway, road, lane, or street usage by public.  No additional payment will be made for pumping or other difficulties encountered due to water.
      2. Maintain water table elevation sufficiently below excavation levels so that slopes remain stable and bottoms of excavations do not become loosened by water flow.
    2. Explosives and Blasting:  Not permitted in performance of structural excavating.
    3. Responsibility for Condtion of Excavation:  Assume responsibility for condition and results of excavations.  Remove slides and cave-ins without extra compensation at whatever time and under whatever circumstances they occur.
    4. Protection:
      1. At no additional expense, sustain in places, and protect from direct or indirect injury, pipes, walls, buildings, and other structures or property in vicinity of work, whether above or below ground, or that may appear in or adjacent to excavation.
      2. Adequately support pipes and underground conduits exposed as a result of operations.  Provide adequate support along entire exposed length by timber or planking, install in a manner that anchorage of supporting members is not disturbed or weakened during backfilling operation.  Carefully ram and tamp specified backfill materials under and around supports and leave in place as a guard against breakage of supported structure due to backfill settlement.  No additional payment will be made for material left in place or for labor of installing and maintaining supports.
      3. Assume risks attending presence or proximity of pipes, conduits, and other items of every kind and description, in or over excavation, or in vicinity of work, whether above or below ground surface.  Assume responsibility for damages and expenses for direct or indirect injury, caused by work, to persons or property by reason of them or by reason of injury to them whether structures are or are not indicated on Drawings.
    5. Removal of Obstructions:
      1. Should a pipe, conduit, or other structure, above or below ground be in a position in opinion of Professional, to require its removal, realignment, or change due to work to be done under Contract, work of removal, realignment, or change will be done as extra work, or will be done by the owner of obstructions, without cost to Contractor.  The Contractor is required to uncover and sustain structures, at no additional expense, before removal and before and after realignment or change as constituting part of Contract; and no claim for damage or extra compensation on account of presence of structure, or on account of delay in removal or rearrangement of structure.
    6. Dewatering:  Contractor is responsible for keeping groundwater levels at least 2 feet below working subgrades.  Contractor shall provide adequate pumps and piping to maintain groundwater levels at this level without an increase in the contract price.  Subgrades damaged by groundwater infiltration will be overexcavated and replaced as required by the Professional at no increase in the contract price.

.02  Products
  1. Materials
    1. Aggregate Backfill:  Coarse aggregate consisting of hard, tough, durable, and uncoated inert particles free from clay, silt, vegetation, and other deleterious material such as reactive chert, gypsum, iron sulfide, amorphous silica, and hydrated iron oxide.
      1. Stuctural Aggregate Backfill:  PENNDOT 2A Coarse Aggregate.
      2. Aggregate Fill:  AASHTO 57 conforming to gradation requirements defined in PENNDOT 703.
    2. Furnish aggregate backfill crushed and prepared from one of the following for listed materials:
      1. Limestone:
        1. Nealmont Formation (Rodman and Centre Hall members)
        2. Linden Hall Formation (Valentine, Valley View, and Stover members)
        3. Snyder Formation
        4. Hatter Formation
      2. Dolostone:
        1. Bellefonte Formation (Tea Creek and Coffee Run members)
        2. Nittany Formation
      3. Mixed limestone and dolostone:
        1. Lower Loysburg Formation
        2. Axemann Formation

.03 Execution
    1. Dewater
      1. Keep excavation free from water during the performance of the work.  Provide and operate dewatering equipment of sufficient capacity for dewatering the excavations.
        1. Dewatering efforts are to be maintained until excavations are closed or when determined by the Owner or Professional no longer necessary.
  • Subgrade Preparation and Inspection
    1. After removal of existing subbase material under floor slab to limits defined by Owner, scarify the exposed disturbed surface to a depth of 4 inches and compact to 97 percent of maximum dry density determined in accordance with ASTM D 698.
      1. Compact all subgrades in the presence of the Professional.  Provide at least 48 hours advance notice of anticipated proofrolling.
      2. Compact subgrade using walk-behind rollers and hand tampers.
    2. The Professional will evaluate subgrade acceptability and will determine the lateral and vertical limits of any unsuitable materials.  Excavate loose, soft, or otherwise unsuitable soils as directed by the Professional.
    3. Backfill the excavated areas with Aggregate Backfill Materials as directed by the Professional after approval of subgrade is received.
    4. Approved subgrades shall be protected from degradation caused by construction activities or other causes.  Subgrade that is degraded or weakened shall be reevaluated and repaired as directed by the Professional.
  1. Aggregate Backfill Placement
    1. General:
      1. Place aggregate backfill as indicated on Drawings.
      2. Perform backfilling using walk-behind rollers and hand tampers.
      3. Prior to backfilling, clean excavation free of trash and debris.
      4. Do not proceed with additional layer until density obtained.
      5. Place backfill material in such a manner that unbalanced horizontal loads will not be applied to structure, utilities, or pipelines.
      6. Do not use compaction equipment or methods that produce excessive horizontal or vertical earth pressures.
    2. Aggregate Placement:
      1. Aggregate Fill:  Place in 4-inch lifts and compact each lift with the vibratory equipment to the satisfaction of the Construction Manager based on non-movement of material under compaction equipment.
      2. Structural Aggregate Backfill:  Place in 4-inch lifts and compact to 97 percent of maximum dry density determined in accordance with ASTM D 698.
  2. Cleanup
    1. Remove and dispose of excess material that cannot be used on Project off site in a legal manner at no additional expense to the Owner.  Leave area in a clean and neat condition.
  3. Field Quality Control
    1. Compacted backfill shall be tested to verigy compliance with specified requirements in accordance with ASTM D 2922.
      1. Perform one test per 50 cubic yards.

Page Navigation

Related Files

  File Modified