SECTION DRILLED CONCRETE PIERS AND SHAFTS

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1 1 PART ONE - GENERAL 1.1 COORDINATION SECTION DRILLED CONCRETE PIERS AND SHAFTS A. The General, Supplementary, and Special Conditions of these specifications shall all be considered as a part of this Section insofar as they may be termed applicable, whether attached or not. B. Cooperation by Contractor for work of this Section of the specifications with all other trades is mandatory, so that all phases of work may be properly coordinated, without delays or damage to any parts of any work. 1.2 DESCRIPTION OF WORK A. Furnish all labor, materials, services, equipment and appliances required in conjunction with drilled pier foundations complete, including, but not limited to the following: 1. Layout of drilled piers. 2. Excavation for drilled piers. 3. Furnishing and placing reinforcing steel. 4. Furnishing and placing concrete. 5. Removal of spoil (excavated material) resulting from drilled pier excavations. B. Extent of drilled piers is shown on Drawings including locations, diameters of shafts, estimated bottom elevations, top elevations, reinforcement, and details of construction. C. Related Sections: 1. Testing Laboratory Services: Section Reinforcement Material Properties: Section Concrete: Section QUALITY CONTROL A. Comply with American concrete Institute ACI 336.3R, Suggested Design and Construction Procedures for Pier Foundations. B. Testing Laboratory Services: 1. Refer to Section for additional information concerning laboratory services in conjunction with drilled pier work. 2. Laboratory Services on Site: a. Laboratory representative shall monitor all pier drilling operations and shall maintain an accurate and complete pier log showing diameter, top and bottom elevations of each pier, casing required or not required, actual penetration into bearing stratum, elevation of top of bearing

2 stratum, volume of concrete used, and deviations from specified tolerances. Provide copies to Architect and Contractor. b. Contractor shall give a minimum of two days notice to laboratory for services in conjunction with drilled piers. C. Contractor shall be responsible for layout of all drilled pier work. 1.4 SUBMITTALS A. Shop Drawings: Submit shop drawings for drilled pier work including dimensioned plan layout, dowel setting plans, shaft sizes, top elevation, and details of reinforcement. B. Drilled Pier Log: Submit drilled pier log for Architect s record. C. Concrete design mix, see Section JOB CONDITIONS A. Subsurface Information: 1. Reference Document Geotechnical Information for boring log information obtained from the Owner s geotechnical investigation report. 2. 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 is made available for convenience of contractor and is not guaranteed to represent conditions that may be encountered. 3. Additional test borings and other exploratory operations may be conducted by Contractor at no additional cost to Owner. B. Existing Utilities: 1. Locate existing underground utilities before starting drilled pier excavation operations. If utilities are to remain in place, provide protection from damage during drilled pier operations. 2. Should uncharted or incorrectly charted piping or other utilities be encountered during drilling 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. 3. 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. 1.6 UNIT PRICES FOR DRILLED PIERS A. Contract price shall be based on base lengths of piers as shown on Drawings. In addition, bidders shall quote unit prices for the following:

3 1. Unit price per linear foot excluding casings for piers longer or shorter than base lengths. Deduct unit price shall be two-thirds of the add unit price. 2. Unit prices per linear foot of casing used. Measurement for payment shall be from top of pier to top of bearing stratum. B. Unit prices shall include all labor, materials, equipment, overhead and fee for drilled piers complete. Adjustments to Contract shall be based on total linear feet of each pier size greater than or less than the sum of base lengths of each size. C. Cost of providing casings is not to be included in Base Proposal for drilled piers. If casings are required, cost will be added to contract based on unit price. 2 PART TWO - PRODUCTS 2.1 MATERIALS A. Reinforcing Steel: Refer to Section B. Concrete Materials: Refer to Section FABRICATION OF REINFORCEMENT A. Refer to Drawings and Section CONCRETE MIX DESIGN A. Refer to Section CONCRETE PRODUCTION AND DELIVERY A. Refer to Section PART THREE - EXECUTION 3.1 INSPECTION A. Inspect areas and conditions under which drilled pier work is to be performed and notify Architect any Geotech Lab representative of any unsatisfactory conditions. 3.2 EXCAVATION FOR DRILLED PIERS A. Excavate for drilled piers, of required diameters, to bearing strata indicated on Drawings and as confirmed by laboratory representative at site. B. Excavate into bearing strata required penetration depths indicated on Drawings

4 C. If flowing water or caving soil is encountered, provide and place temporary steel casings to seal off caving soil and/or flowing water. Install casings a sufficient distance into bearing stratum to ensure watertight seals. Steel casings shall be 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). Drilling of bearing strata shall be done in-the-dry. All water shall be removed from the hole prior to and during scheduled drilling penetrations. D. Tolerances: Locate center lines of drilled piers to be on center lines of bearing construction, unless otherwise indicated. Do not exceed the following tolerances: 1. Shaft Center Line Location: 1/24 of shaft diameter or 3 inches, whichever is less. 2. Shaft Variation to Plumb: 1 percent of length. 3. Top of Pier Elevation: Plus 1 inches to minus 3 inches. 4. If above tolerances are exceeded, provide additional or corrective construction methods to Architect for review before proceeding. E. Obstructions: Work of this Section may include demolition and removal of rock, boulders, concrete, masonry, and other subsurface materials in order to drill piers, and such work will not be considered a change in work. F. Dewatering: 1. Provide and maintain pumping equipment to keep excavations free of water during drilling and before placing concrete. If excessive water is encountered and drilling operations must be halted, consult with Architect before using alternate methods of construction. Do not use water to aid drilling. 2. 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. G. Over excavation: No payment will be made for extra length, when shafts are excavated to a greater depth than required or authorized by Architect, due to over drilling by Contractor. Complete drilled pier and fill extra depth with concrete, if other conditions are satisfactory. Over excavated shafts will be measured and paid for to original design or authorized depth. H. Safety: Workmen shall not be permitted to enter pier hole due to potential for caving soil. I. Excavated Material: Remove excavated material and dispose off site. 3.3 REINFORCING STEEL AND DOWELS A. Before placing, clean reinforcing steel and dowels of loose rust, scale, dirt, grease, and other material which could reduce or destroy bond

5 B. Fabricate and erect reinforcing cages in shafts as one continuous unit. Place reinforcement accurately and symmetrically about axis of hole and hold securely in position during concrete placement. C. Tie dowels in place before placing concrete. Provide blocking and holding devices to maintain required position during concrete placement. D. Protect exposed ends of dowels from mechanical damage and exposure to weather. 3.4 CONCRETE PLACEMENT A. Fill drilled pier excavations with concrete immediately after inspection and approval, and within time limit stated on Drawings. If holes are left open longer than stated time limit, drill an additional scheduled penetration length below the bottom of the hole and comply with time limit. B. Place concrete continuously and in a smooth flow without segregating mixed materials. Direct concrete down center of shaft so that it does not contact sides of shaft or reinforcing cage. Provide mechanical vibration for consolidation of at least top 5'-0" of each shaft. C. Place concrete by means of a bottom discharge bucket with downpipe or flexible drop chute, elephant trunk hopper, or tremie. Use drop chute or tremie for placing concrete to limit free fall of concrete to a maximum of 25 feet, or pump concrete into place. D. Place concrete in-the-dry. If water occurs, pier hole shall be pumped dry immediately before concreting. No more than 2 inches of standing water is permitted at time of pouring. E. Maintain a sufficient head of concrete to prevent reduction in diameter of pier 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 feet above casing bottom until top of fresh concrete reaches cut-off elevation shown. 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 from top section above grade and extend shaft to required elevation. G. Interrupted placing operations of over one hour duration, requires a cold joint installation. Leave resulting shaft surface approximately level and rough. At resumption of concrete placing, clean off surface laitance and soil particles and slush with one part sand to one part cement grout before remainder of concrete is placed. H. Protect concrete work from physical damage or reduced strength which could be caused by frost, freezing actions, or low temperatures, in compliance with ACI 306R, Cold Weather Concreting, and as herein specified. When air

6 temperature has fallen to, or is expected to fall below 40 degrees F, uniformly heat water and aggregates before mixing, to obtain a concrete mixture temperature of not less that 50 degrees F and not more than 80 degrees F, at point of placement. I. During hot weather temperature of mix delivered to site shall not exceed 95 degrees F. All work shall be in accordance with ACI 305R, Hot Weather Concreting. J. Place concrete immediately upon delivery. Keep exposed concrete surfaces and formed shaft extensions moist by fog sprays, wet burlap, or other effective means. 3.5 CLEANUP A. Clean up all debris caused by the work of this Section, keeping the area clean and neat at all times. B. Remove excavated soils from building pad and site. C. Provide select fill to fill depressions in building pad as may be caused by drilling equipment and operations. Compact to required densities. END OF SECTION