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   PART 1 - GENERAL

    01 SECTION INCLUDES

    A. Extent of caissons is shown on drawings, including locations, diameters of shafts, diameters of bells where required, estimated bottom elevations, top elevations, and details of construction.

    02 QUALITY ASSURANCE

    A. ACI 301 - Specifications for Structural Concrete for Buildings.

    B. ASTM C31 - Practices for Making and Curing Concrete Test Specimens in the Field.

    C. ASTM C39 - Test Method for compressive Strength of Cylindrical Concrete Specimens.

    D. ASTM C94 - Specifications for Ready Mix Concrete.

    E. ASTM C143 - Test Method for Slump of Portland Cement Concrete.

    F. ASTM C172 - Method of Sampling Freshly Mixed Concrete.

    1.02 QUALITY ASSURANCE

    A. Codes and Standards: Comply with provisions of American Concrete Institute (ACI) "Standard Specification for the Construction of End Bearing Drilled Piers" (ACI 336.1), and as herein specified.

    B. Where provisions of above standard conflict with building regulations in effect for this project, building regulations will govern, but only to establish minimum requirements.

    C. Caisson Installer Qualifications: Not less than three successfully completed contracts with similar soil conditions, shaft sizes, depths and volumes of work contained in this project. Submit satisfactory proof of compliance to Architect.

    D. Survey Work: Engage a registered surveyor to perform surveys, layouts, and measurements for caisson work. Conduct layout work for each caisson to lines and levels required before excavation, and actual measurements of each caisson's horizontal axial location, shaft diameter, bottom and top elevations, deviations from specified tolerances, and other data as required.

    E. Record and maintain information pertinent to each caisson and cooperate with other testing and inspection personnel to provide data for required reports.

    F. Certificates of material properties and compliance with specified requirements may be submitted in lieu of testing, when acceptable to Architect. Certificates of compliance must be signed by materials producer and Contractor.

    1.03 SUBMITTALS

    A. Reports: Submit following reports directly to Architect, with copy to others as designated.

    B. Certified Caisson Report for each caisson, recording actual elevation at bottom and top, elevation of rock (if any), final centerline location at top, variation of shaft from plumb, result of tests performed, actual allowable bearing capacity of bottom, levelness of bottom, seepage of water, still water level (if allowed to flood), elevation of bottom and top of any casing left in place, any unusual conditions, variation of bell dimensions from original design, dates of starting excavation, completion of excavation, inspection, testing, and placement of concrete (include any delays in concreting and location of construction joints in shafts).

    1.04 JOB CONDITIONS

    A. Site Information: Data on indicated subsurface conditions are not intended as representations or warranties of continuity of such conditions. It is expressly understood that Owner will not be responsible for interpretations or conclusions drawn therefrom by Contractor. Data are made available for convenience of Contractor and are not guaranteed to represent conditions that may be encountered.

    B. Existing Utilities: Locate existing underground utilities by careful hand excavation before starting caisson excavation operations. If utilities are to remain in place, provide protection from damage during caisson operations.

    C. Should uncharted or incorrectly charted piping or other utilities be encountered during excavation, consult Architect immediately for directions as to procedure. Cooperate with Owner, and public or private utility companies in keeping their respective service and facilities in operation. Repair damaged utilities to satisfaction of utility owner.

    D. Do not interrupt existing utilities serving facilities occupied and used by Owner or others, except when permitted in writing by Architect and then only after acceptable temporary utility services have been provided.

   PART 2 - PRODUCTS

    03 CONCRETE AND RELATED MATERIALS

    A. Concrete and related materials are specified in Division 3 sections.

   PART 3 - EXECUTION

    04 CAISSON EXCAVATION

    A. General: Excavate holes for caissons to required bearing strata or elevation as shown on drawings. Excavate holes for closely spaced caissons, and those occurring in fragile or sand stratas, only after adjacent holes are filled with concrete and allowed to set. The first 16' of the excavated material shall be hauled off site and landfilled at a special waste landfill.

    B. Caisson design dimensions shown are minimums. The design of caissons is based on assumed strata bearing capacity. If bearing strata is not capable of maintaining bearing capacity assumed, foundation system will be revised as directed by Architect. Revisions will be paid for in accordance with contract conditions relative to changes in work.

    C. If required, install casings as excavation proceeds so that earth walls are maintained without spilling into shaft. When assumed elevation of top of bell portion is reached, casing may be stopped, with a smaller inner section, if required for safety of personnel, carried down to bearing strata. Do not extend inner section beyond actual top of bell, to maintain designed caisson shaft diameter.

    D. Construction Tolerances: Locate centerline of caissons within the following tolerances:

    1. Maximum permissible variation of location not more than 1/24th of shaft diameter or 3", whichever is less.

    2. Shafts out of plumb, not more than 1.5% of length nor exceeding 12.5% of shaft diameter or 15", whichever is less.

    3. Concrete cut-off elevation, plus 1/2" to minus 1-1/2".

    B. If above tolerances are exceeded, provide additional or corrective construction to compensate for excessive eccentricity. Submit proposed corrective construction methods to Architect for review before proceeding.

    C. Temporary Shaft Protections: When required, provide full-length watertight steel casings of sufficient thickness to withstand compressive, displacement and withdrawal stresses and to maintain shaft walls. Temporary casings may be left in place or may be withdrawn as concrete is placed, at Contractor's option.

    D. Shoring: Provide shoring in bells as required in unstable soil conditions to preclude cave-in during hand excavation and inspection operations.

    E. Obstructions: If rock, boulders, or other unforeseen obstructions are encountered which cannot be removed by standard caisson excavation methods, and if such obstructions are not indicated by available subsurface data, removal of such obstructions will be paid for in accordance with terms of contract relative to changes in work.

    F. Remove such obstructions by hand labor using air-powered tools, or by other safe methods recognized in construction industry.

    G. Classification of Rock: Rock is defined as material which cannot be drilled with a conventional earth auger or under-reaming tool, and requires use of special rock augers, core barrels, air tools, blasting, or other methods of hand excavation. Earth seams, rock fragments, and voids included in rock excavation area will be considered rock for full volume of shaft from initial contact with rock for pay purposes.

    H. The work of this section includes demolition and removal of rock, boulders, concrete, masonry, and other subsurface obstructions which are clearly indicated by contract documents, or by available subsurface exploration data, and such work will not be considered a change in work.

    I. Dewatering: Provide and maintain pumping equipment to keep excavations free of water before placing concrete. If excessive water is encountered and drilling operations must be halted, consult with Architect before using alternate methods of construction.

    J. Conduct water to general site run-off ditches and disposal areas with discharge lines. Provide ditching as required to conduct water to site drainage facilities.

    K. Inspection: Each caisson must be inspected and tested before placing concrete.

    L. Provide facilities as required to assist inspection and testing of excavation, and cooperate with inspecting and testing personnel to expedite work.

    M. Notify Architect and testing facility at least 24 hours prior to time excavations will be ready for inspection and tests.

    N. Depth of Bearing Strata: If indicated depth of shaft excavation is reached without developing required strata bearing capacity, immediately suspend excavation operations and inform Architect. Architect will determine procedures to be followed in each instance.

    O. Where changes in indicated depth or dimensions are required, or additional soil borings are required, proceed with such work when directed in writing by Architect.

    P. Overexcavation: No payment will be made for extra length, when caisson shafts are excavated to a greater depth than required or authorized by Architect, due to overdrilling by Contractor. Complete caisson and fill extra depth with concrete, if other conditions are satisfactory. Overexcavated shafts will be measured and paid for to original design or authorized depth.

    Q. Excavated Material: Excavate and landfill the first 16' of the material at a special waste landfill. (Reference Section 02220 - Excavation, Backfilling, Compaction; 3.03., A.) Deposit and spread excavated material on site at locations as directed.

    3.02 REINFORCING STEEL AND DOWELS

    A. Fabricate and erect reinforcing cages in shafts as one continuous unit using inner ring resteel. Place reinforcement accurately and symmetrically about axis of hole and hold securely in position during concrete placement.

    B. Use templates to set anchor bolts, leveling plates and other accessories furnished under work of other sections. Provide blocking and holding devices to maintain required position during concrete placement.

    C. Protect exposed ends of dowels and anchor bolts from mechanical damage and exposure to weather.

    3.03 CONCRETE PLACEMENT

    A. General: Fill caissons with concrete immediately after inspection and approval by testing laboratory. Use protection sheets (cut out to receive concrete) over excavation openings, extending at least 12" beyond edge.

    B. Place concrete continuously and in a smooth flow without segregating the mixed materials. Provide mechanical vibration for consolidation of at least top 2.5' of each shaft.

    C. Place concrete by means of a bottom discharge bucket, flexible drop chute, elephant trunk hopper, or tremie. Use chutes or tremies for placing concrete where a drop of more than 20' is required, or pump concrete into place.

    D. Place concrete in-the-dry. If water occurs, and it is impracticable to dewater caisson excavation, and reasonable attempts to seal off water flow have failed, allow water level to attain its normal level and place concrete by tremie method. Control placement operations to ensure that tremie is not broken during continuous placing from bottom to top. Other methods of depositing concrete underwater may be used, if acceptable to Architect.

    E. Maintain a sufficient head of concrete to prevent reduction in diameter of caisson shaft by earth pressure and to prevent extraneous material from mixing with fresh concrete. Coordinate withdrawal of temporary casings with concrete placement operations to maintain a head of concrete approximately 5' above casing bottom.

    F. Stop concrete placement at cut-off elevation shown, screed level, and apply a scoured, rough finish. Where cut-off elevation is above ground elevation, form top section above grade and extend shaft to required elevation.

    G. Interrupted placing operation of over one hour duration will require a cold joint installation. Leave resulting shaft surface approximately level and insert steel dowels as shown on drawings. At resumption of concrete placing, clean off surface laitance, roughen as required, and slush with a 1 to 1 cement grout or commercial bonding agent before remainder of concrete is placed.

    H. Cold Weather Placing: Protect concrete work from physical damage or reduced strength which could be caused by frost, freezing actions, or low temperatures, in compliance with ACI 306 and as herein specified.

    I. When air temperature has fallen to or is expected to fall below 40 degrees F. (4 degrees C), uniformly heat water and aggregates before mixing to obtain a concrete mixture temperature of not less than 50 degrees F. (10 degrees C), and not more than 80 degrees F. (27 degrees C) at point of placement.

    J. Do not use frozen materials or materials containing ice or snow. Do not place concrete on frozen subgrade or on subgrade containing frozen materials.

    K. Do not use calcium chloride, salt and other mineral containing anti-freeze agents or chemical accelerators, unless otherwise accepted by Architect.

    L. Hot Weather Placing: When hot weather conditions exist that would seriously impair quality and strength of concrete, place concrete in compliance with ACI 305 and as herein specified.

    M. Cool ingredients before mixing to maintain concrete temperature at time of placement below 90 degrees F. (32 degrees C). Mixing water may be chilled, or chopped ice may be used to control concrete temperature provided water equivalent of ice is calculated to total amount of mixing water.

    N. Place concrete immediately upon delivery. Keep exposed concrete surfaces, and formed shaft extensions, moist by fog sprays, wet burlap or other effective means.

    O. Do not use retarding admixtures without acceptance of Architect.

    3.04 FIELD QUALITY CONTROL

    A. Quality Control Testing During Construction: Sample and test concrete for quality control during placement, as follows:

    1. Sampling Fresh Concrete: ASTM C 172, except modified for slump to comply with ASTM C 94.

    2. Slump: ASTM C 143; one test for each concrete load at point of discharge; and one for each set of compressive strength test specimens.

    3. Compression Test Specimens: ASTM C 31; one set of 4 standard cylinders for each compressive strength test, unless otherwise directed. Mold and store cylinders for laboratory cured test specimens except when field-cure test specimens are required.

    4. Concrete Temperature: Test when air temperature is 40 degrees F (4 degrees C) and below, and when 80 degrees F (27 degrees C) and above; and each time a set of compression test specimens made.

    5. Compressive Strength Tests: ASTM C 39; one set for each 100 cu. yds. or fraction thereof, placed in one day. One specimen tested at 7 days, 2 specimens tested at 28 days, and one specimen retained in reserve for later testing if required. When strength of field-cured cylinders is less than 85% of companion laboratory-cured cylinders, evaluate current operations and provide corrective procedures for protecting and curing in-place concrete.

    B. Report test results in writing to Architect and Contractor on same day tests are made. Include in reports project identification name and number, date of concrete placement, name of Contractor, name of concrete supplier and truck number, name of concrete testing service, concrete type, location of caisson, design compressive strength at 28 days, concrete mix proportions and materials; compressive breaking strength and type of break both 7-day tests and 28-day tests.

    C. Additional Concrete Tests: Testing service may take core samples of in-place concrete when test results are such that there is reasonable doubt specified concrete strengths and other characteristics have not been attained.

    D. Complete continuous coring of caissons may be required, at Contractor's expense, where time for removal of temporary casings exceed specified limits, or where observations of placement operations indicate cause for suspicion of quality of concrete, presence of voids, segregation or other possible defects.

    E. Inspection and Tests for Caissons: The soil testing facility shall perform and report specified tests, and additional tests which may be required. Conduct tests and provide reports as soon as possible to not delay concreting operations for acceptable excavations.

    F. Bottom elevations and bearing capacities and lengths of caissons as shown on drawings are estimated from available soil data. Actual elevations, caisson lengths, and bearing capacities will be determined by soil testing facility from conditions found in excavations. Final evaluations and acceptance of data will be determined by Architect.

    3.05 MEASUREMENT AND PAYMENT

    A. Basis of Bids: Bids shall be based on number of caissons, design length from top elevation to bottom of shaft (extended through the bell, if applicable), and diameter of shaft and bell, as shown on drawings.

    B. There will be no additional compensation for excavation, concrete fill, reinforcing, casings, or other costs due to unauthorized overexcavating shafts or bells. No payment will be made for rejected caissons.

    C. Prices quoted include full compensation for labor, materials, tools, equipment, and incidentals required for excavation, trimming, shoring, casings, dewatering, reinforcement, concrete, and other items for complete installation.

    D. Unit Prices: Unit prices for the following items, as set forth in contract conditions, will apply in event additions to or deductions from work are required and authorized by a written order from Architect to Contractor.

    Soil excavation - per cu. yd.

    Rock excavation - per cu. yd.

    Permanent steel casings, installed - per lin. ft.

    Reinforcing steel and dowels, installed - per lb.

    Concrete - per cu. yd.

    E. Cassions are designed to set on rock bearing strata. Contractor shall determine actual depth of cassion based on bearing strata depth. No additional payment shall be made for Contractor assuming bearing strata depth incorrectly.

    END OF SECTION