505PILING

330

Payment will be made for each additional stage of loading described in Subarticle 505.04(b). Payment will be the percentage of the contract price for a Loading Test given in the following table.

Factored Load Shown on Plans

Percentage of Contract Price for a Loading Test Up to 75 {45} 50% Over 75 {45} to 125 {70} 75% Over 125 {70} 100%

Accepted dynamic loading tests will be paid for at the contract unit price for Dynamic Loading Tests per each, complete in place, which shall be payment in full for all equipment and labor incidental to aiding the Engineer in the performance of this test and for all costs associated with down time while setting up equipment, making dynamic measurements, and down time while waiting to perform a restrike dynamic test.

The quantity of acceptable sheet piling in place after all cut-offs have been made will be paid for at the respective contract price for the type of sheet piling listed. The contract unit price bid for this item shall also include any necessary excavation unless an item of excavation is provided in the contract.

Pile Points will be paid for at the contract unit price per each. This payment shall be full compensation for furnishing the points and all materials, labor and incidentals necessary to install the points.

Where hard marl, solid rock or other conditions are encountered that make it necessary or desirable to place piles in concrete pedestal foundations, the net length of piling so placed in the structure will be paid for at the contract unit price for the respective kinds of piling. The additional work required for construction of the pedestal foundations will be paid for as extra work as outlined in Article 104.03, Extra Work.

The contract unit price per linear foot {meter}, measured as noted above, shall be payment in full for all materials, equipment and labor required to excavate the pilot hole. It shall also be payment in full for the disposal of excavated material and for filling the voids in pilot holes around the piles with sand or concrete.

The quantity of temporary steel sheet piling acceptably placed, measured as noted above, will be paid for at the unit bid price which includes furnishing the design and piling, driving, bracing, and removing the piling. The piling, after removal, shall remain the property of the Contractor.

The accepted lengths of steel piling in the finished structure will be paid for at the respective contract price for steel piling furnished and driven. The extra length (beyond estimated length) of steel pile that may be required to complete a structure will be paid for at the contract price for steel piling furnished and driven. No payment will be made for cut-offs or splices of steel piling.

The approved lengths of concrete piling (lengths approved by the Engineer for casting) will be paid for at the respective contract price for concrete piling furnished. Non-driven pile build-ups and cut-offs will be paid for at the designated rate for concrete piling furnished.

The approved casting lengths of concrete piling remaining in the finished structure (casting lengths minus any cut-offs) will be paid for at the respective contract price for concrete piling driven. No payment for build-ups, either driven or non-driven, will be made under this item.

505-A Type Test Piles (*)(****) – per each 505-B Static/Dynamic Loading Tests (*) (**) – per each DRILLED SHAFT CONSTRUCTION 331

505-E Permanent Steel Sheet Piling - per linear foot {meter} 505-F Permanent Concrete Sheet Piling (width) – per linear foot {meter} 505-G Pile Points (***) – per each 505-H Pilot Holes – per linear foot {meter} 505-I Temporary Steel Sheet Piling – per square foot {square meter} 505-M Steel Piling Furnished and Driven (*)(****) – per linear foot {meter} 505-N Concrete Piling Furnished (*) – per linear foot {meter} 505-O Concrete Piling Driven (*) – per linear foot {meter} * Pile Designation/Size ** Driving or Restrike (if required) *** Type/Size of Pile Point, Example: 505-G Pile Points (Type A 10”) **** Galvanized (If Required) DRILLED SHAFT CONSTRUCTION

506.01Description

This work shall consist of all labor, materials, equipment and services necessary to perform all operations to complete a drilled shaft installation in accordance with these Specifications and the details and dimensions shown on the plans.

506.02Materials

All materials shall conform to requirements set forth in Division 800, Materials. The requirements provided for Structural Portland Cement Concrete, Section 501, shall apply in all respects to drilled shafts, except where otherwise indicated by specific requirements given hereinafter in this Section or noted by plan details.

Portland cement concrete used in construction of drilled shafts shall hereinafter be referred to as either "Class DS1", "Class DS2" or "Class DS3" concrete. The specific class of concrete that is required will be shown in the Pay Item Description for Drilled Shaft Construction. The concrete producer shall establish the proportion of materials for each class of drilled shaft concrete following the guidelines described in ALDOT-170, "Method of Controlling Concrete Operations for Structural Portland Cement Concrete", and the criteria outlined hereinafter in this Subarticle. The concrete supplier shall submit for approval the proposed concrete mixture design to the State Materials and Test Engineer following the requirements in ALDOT-170. The distribution of the approved concrete mixture design and re-approval of concrete mixture designs will be as per ALDOT-170 respectively. Any changes of the materials and/or proportions of the mixture design will require a concrete mixture resubmittal.

Minimum Compressive Strength at 28 days shall be 4000 psi {30 MPa}. The amount of cementitious material shall be a minimum of 600 pounds {360 kg} and a maximum of 800 pounds per cubic yard {475 kg per cubic meter} of concrete. The range of total air content shall be 2.5 % to 6.0 % by volume except for concrete that is completely embedded below the ground line or mud line. An air content less than 2.5 % will be acceptable for shafts that are completely embedded below the ground line or mud line. The maximum water to total cementitious material ratio shall be 0.40. Slump requirements:

from 6 inches to 9 inches {150 mm to 230 mm}. - The minimum consistency slump for all of the concrete placed in an individual shaft shall be no less than 4 inches {100 mm} at the end of the concrete placement in that shaft. The temperature of the concrete, at the time of placement in the shaft, shall not be less than 50 °F {10 °C} nor more than 95 °F {35 °C}. DRILLED SHAFT CONSTRUCTION 332

Gradation of the coarse aggregate used shall meet the requirements for either ALDOT Size No. 57, No. 67 or No. 7. All materials used in manufacturing the concrete shall conform to the requirements of the Specifications.

Type I, Type II, Type IL, Type IP, or Type IS cement shall be used. The cementitious content may be composed of up to 30% by weight {mass} substitution of either Class C or Class F fly ash additive. In lieu of fly ash, ground granulated blast furnace slag may be substituted for cement up to a minimum substitution rate of 25% and a maximum substitution rate of 50% by weight {mass}.

Type II,Type IL, Type IP, or Type IS cement containing a maximum of 8% C3A shall be used. The cementitious content shall be composed of no less than 20% nor more than 30% by weight {mass} of Class F fly ash additive. In lieu of fly ash, ground granulated blast furnace slag may be substituted for cement up to a minimum substitution rate of 35% and a maximum substitution rate of 50% by weight {mass}.

Type II, Type IL, Type IP, or Type IS cement containing a maximum of 8% C3A shall be used. The cementitious content shall be composed of 20% by weight {mass} of Class F fly ash and 10% by weight {mass} of microsilica additives. In lieu of the percentages of fly ash and microsilica, the cementitious content may be composed of 50% by weight {mass} substitution of ground granulated blast furnace slag and 5% by weight {mass} addition of microsilica additives.

When use of slurry is either shown to be required in the contract documents or selected by the Contractor, mineral slurries shall be used unless another type of slurry is proposed for use by the Contractor and approved by the Engineer. The following minimum requirements apply to material components used in slurries:

Sodium Bentonite or Attapulgite shall be used as the principal mineral constituents of slurry. The Engineer may approve use of other minerals upon receipt of demonstrated proof that the requested alternate mineral ensures shaft stability at the applicable shaft construction site.

Mixing water shall be capable of meeting drinking water standards as outlined in Section 807.

Clean, locally available sand meeting the requirements of Section 802 (not to exceed four (4) percent by volume) may be mixed in drilling slurries.

At the Contractors discretion, additives may be used to control the consistency and/or yield of slurries subject to the limitation that the type and amount of additives used shall not exceed the recommendation(s) of the principal mineral manufacturer.

When use of casing is either specified by the contract documents or selected by the Contractor, casings shall be smooth, non-corrugated, clean, watertight steel of ample strength to withstand both handling and driving stresses and the pressures of concrete and the surrounding earth materials. Where permanent casing is required, serviceable used casing may be installed with the approval of the Engineer. The Contractor is responsible for insuring that all casing, new or used, is capable of withstanding the aforementioned stress and pressure requirements.

Unless otherwise noted on the contract documents, all steel reinforcement shall be Grade 60 {420} billet steel meeting the requirements of Section 502, sized and installed in accordance with the contract plans as applicable. Welding of the reinforcing steel will not be permitted without the written approval of the Bridge Engineer. Welding to the main vertical reinforcing steel will not be permitted. DRILLED SHAFT CONSTRUCTION 333

506.03Construction Methods and Equipment

The Contractor shall perform excavations required for shafts through whatever materials are encountered, to the dimensions and elevations shown in the plans or otherwise required by the specifications and special provisions. The Contractor's methods and equipment shall be suitable for the site conditions and materials encountered. The permanent casing method shall be used only at locations shown on the plans or authorized by the Bridge Engineer. Actual cores recovered from the test borings are available for inspection at the Bureau of Materials and Tests.

The Contractor shall submit descriptions of the drilled shaft construction projects completed in the last three years to serve as evidence of the capability to construct drilled shafts. The descriptions of the drilled shaft projects shall contain names and telephone numbers of owners' representatives who can verify the Contractor's participation on those projects. These descriptions shall be submitted with the Installation Plan and will be evaluated by the Engineer. The evaluation of the Contractor's capability for constructing drilled shafts will have a bearing on the decision by the Engineer to require the construction of a Trial Drilled Shaft.

No later than 30 days after the date of the Notice to Proceed, the Contractor shall submit an installation plan for review by the Engineer. This plan shall provide information on the following items as applicable: o Name and experience record of the drilled shaft superintendent in charge of drilled shaft operations for this project; o List of proposed equipment to be used including cranes, drills, augers, bailing buckets, final cleaning equipment, desanding equipment, slurry pumps, core sampling equipment, tremies, concrete pumps, casing, etc.; o Details of the overall anticipated construction operation sequence and the proposed sequence of shaft construction; o Details of planned shaft excavation methods; o Details of the methods to be used to ensure shaft stability (i.e. prevention of caving, bottom heave, etc., using temporary casing, slurry or other means) during excavation and concrete placement. This shall include a review of method suitability to the anticipated site and subsurface conditions. If casings are proposed or required, casing dimensions and detailed procedures for permanent casing installation, and temporary casing installation and removal shall be provided. o When use of slurry is required or proposed, details of the methods for mixing, circulating and desanding slurry; o Details of methods to clean the shaft excavation; o Details of reinforcement placement including support and centralization methods; o Details of concrete placement method required or proposed including operational procedures for free fall, tremie or pumping as appropriate; and o The method used to fill or eliminate all voids between the plan shaft diameter and excavated shaft diameter, or between the shaft casing and surrounding soil, if permanent casing is specified. o Details of the material, equipment, and procedures proposed to accomplish the required load testing.

The Engineer will evaluate the drilled shaft installation plan for conformance with the plans and specifications. Within 15 days following receipt of the installation plan, the Construction Engineer will return the plan for corrections, distribute the plan for construction inspection, or contact the Contractor to establish a mutually agreeable date and time for a meeting to discuss the installation plan. If a meeting is held to discuss the installation plan the Contractor and his drilled shaft project superintendent shall be in attendance. The Contractor will be notified of changes in the submitted installation plan deemed necessary by the Construction Engineer within seven days after the aforementioned meeting. Shaft construction shall not begin until DRILLED SHAFT CONSTRUCTION 334

the installation plan has been distributed by the Construction Engineer for construction inspection. Distribution of the installation plan for construction inspection shall not relieve the Contractor of the responsibility to satisfactorily complete the work as detailed on the plans and in the specifications.

Any proposed modification of the installation plan during construction shall be submitted to the Construction Engineer for review and distribution.

The Contractor shall control his operations to prevent damage to existing structures and utilities as outlined in Article 107.12. Preventive measures shall include, but are not limited to, selecting construction methods and procedures that will prevent caving of the shaft excavation, monitoring and controlling the vibrations from construction activities such as the driving of casing or sheeting, drilling of the shaft, or from blasting, if permitted.

begins unless otherwise noted in the contract documents or approved by the Engineer. Any disturbance caused by shaft installation to a planned drilled shaft area shall be repaired by the Contractor prior to the shaft construction.

Contractor shall construct drilled shafts after the placement of fills unless shown otherwise in the contract documents or approved by the Engineer.

reaches a minimum of 80% of the required 28-day compressive strength and until all CSL test results (when required) are accepted and the CSL tubes have been dewatered and grouted.

The dry construction method shall be used only at sites where the groundwater level and soil conditions are suitable to permit construction of the shaft in a relatively dry excavation, and where the sides and bottom of the shaft may be visually inspected by the Engineer prior to placing reinforcement and concrete. The dry method consists of drilling the shaft excavation, removing accumulated water and loose material from the excavation, placing the reinforcing cage, and concreting the shaft in less than 3 inches of water.

The wet construction method may be used at sites where a dry excavation can not be maintained for placement of the shaft concrete. This method consists of using water or mineral slurry to maintain stability of the hole perimeter while advancing the excavation to final depth, placing the reinforcing cage, and concreting the shaft. Where drilled shafts are located in open water areas, exterior casings shall be extended from above the water elevation into the ground to protect the shaft concrete from water action during placement and curing of the concrete. The casing shall be installed in a manner that will produce a positive seal at the bottom of the casing so that no seepage of water or other materials occurs into or from the shaft excavation.

Permanent or temporary casing may be used when shown on the plans or at sites where the dry or wet construction methods are inadequate to prevent caving or excessive deformation of the hole. In this method the casing may be either placed in a predrilled hole or advanced through the ground by twisting, driving or vibration before being cleaned out. Casing which is going to be installed by predrilling and permanently left in rock for the purpose of shielding voids, shall be installed in not more than a 2 inch {50 mm} oversized drill hole. When downsizing of permanent casing is required, no more than six feet of overlap of casing will be allowed. When the casing method is required but not shown on the plans, the Contractor shall submit details of the proposed casing method (including casing lengths and diameters) and the proposed procedures of casing installation to the Bridge Engineer for review in the installation plan. If the need is determined after work on the shafts has begun, a revised plan proposing this method must be submitted for review. DRILLED SHAFT CONSTRUCTION 335

Shaft excavations shall be made at locations and to the elevations, geometry and dimensions shown in the contract documents or as directed by the Engineer. A shaft shall not be excavated as long as an adjacent shaft in the same substructure unit is open unless authorized in writing by the Construction Engineer. Blasting and vibrating casings in place will not be allowed until the concrete in adjacent shafts has reached 80 % of the required 28-day compressive strength. Once the excavation of a shaft has been started, the excavation shall be conducted in a continuous operation until the excavation is completed. When an excavation is performed with any type of drilling fluid (i.e. slurry, water, etc.) used to stabilize the excavation, the placement of concrete shall begin within 36 hours from the start of excavation and within 12 hours from the start of the excavation of the bottom 5 feet {1.5 m} of the shaft. If the Contractor exceeds these time limits, additional work may be required to insure that the condition of the excavation is adequate to result in an acceptable load carrying capacity in the completed drilled shaft. The Contractor may be required to over ream the entire depth of excavation (or the bottom 5 feet {1.5 m} if the 12 hour time limit is exceeded), increase the depth of the excavation or perform other work that may be required by the Engineer to provide an acceptable excavation. There will be no compensation for this additional work. The minimum width of over reaming shall be 1/2 inch {13 mm} and the maximum width shall be 3 inches {75 mm}.

The Contractor shall maintain an excavation log during shaft excavation. The log shall contain information such as: the description and approximate top and bottom elevation of each soil or rock material encountered during shaft excavation, elevations at which seepage or groundwater flow are encountered, and remarks. The type of tools used for the excavation shall be shown on the log. All changes in the type of tools used for excavation shall be shown on the log. The Engineer will monitor these operations and the logs will be used as a basis of measurement for payment. The Contractor shall resolve all discrepancies on the log noted by the Engineer at the end of each work day. Two copies of the legible, final log shall be furnished to the Engineer within 24 hours after a shaft excavation is completed and accepted.

Excavated materials which are removed from shaft excavations shall be disposed of by the Contractor in accordance with Subarticle 215.03(g).

The Contractor shall not permit workers to enter the shaft excavation for any reason unless: suitable casing has been installed, the water level has been lowered and stabilized below the level to be occupied, and adequate safety equipment and procedures have been provided to protect workers entering the excavation. The Contractor is responsible for compliance with applicable State and Federal safety regulations.

The excavation of the shaft using conventional earth drilled shaft excavation tools will be designated as "drilled shaft excavation".

The excavation of the shaft requiring rock tools and/or procedures to accomplish hole advancement will be designated as "special drilled shaft excavation". This excavation will be for the removal of rock or other hard material within the planned shaft.

Excavation and drilling equipment shall have adequate capacity including power, torque and down thrust to excavate a hole of both the maximum specified diameter and to a depth of twenty

DRILLED SHAFT CONSTRUCTION 336

When the material encountered cannot be drilled using conventional earth drilling tools and equipment, the Contractor shall provide rock drilling equipment including air tools, approved blasting materials, and other equipment as necessary to construct the shaft excavation to the size and depth required. Concurrence of the Engineer shall be obtained prior to switching from earth to rock drilling tools and equipment. Approval of the Engineer is required before excavation by blasting is permitted.

either softened due to excavation methods, swollen due to delays in concreting, or degraded because of slurry cake buildup. Overreaming thickness shall be a minimum of 1/2 inch {13 mm} and a maximum of 3 inches {75 mm}.

approved equipment. The thickness and extent of sidewall overreaming shall be as directed by the Engineer. The Contractor shall bear all costs associated with both sidewall overreaming and additional shaft concrete placement.

Drilling tools which are lost in the excavation shall not be considered obstructions and shall be promptly removed by the Contractor without compensation. All costs due to lost tool removal shall be borne by the Contractor including costs associated with correcting hole degradation due to removal operations and time delays.

The Contractor will be required to perform some type of exploratory shaft excavation (soil samples, rock cores or drilling or probing) below the bottom elevations shown on the plans unless this requirement is noted on the plans as being deleted. The Contractor shall extend drilled shaft tip elevations when the Engineer determines that the material encountered during this exploratory excavation is unsuitable and/or differs from that anticipated in the design of the drilled shaft.

The Contractor shall take 2.0 inch {51 mm} minimum diameter rock cores and/or soil samples at locations as designated on the plans or as directed by the Engineer to determine the character of the material directly below the completed shaft excavation. The soil samples shall be extracted with a split spoon sampler or undisturbed sample tube in accordance with AASHTO T 206 and T 207. The methods and equipment used for the rock coring shall be those given in Subarticle

506.10(b) for the core drilling of drilled shaft concrete. The cores and/or soil samples shall be

taken to a minimum of 10 feet {3 m} below the bottom of the drilled shaft excavation unless otherwise noted on the plans or directed by the Geotechnical Engineer. The Engineer may require this depth to be extended up to a total depth of 20 feet {6 m} below the bottom of the shaft. The Contractor may choose to take these cores and/or soil samples prior to excavating for the drilled shafts, however, payment will only be considered for that portion of the cores taken below the bottom elevation of the shafts shown on the plans. Rock core and soil test samples shall be measured, visually identified and described on the Contractor's log. The samples shall be placed in suitable containers, identified by shaft location, elevation and project number and delivered to the Central Laboratory in Montgomery with the Contractor's field logwithin 24-hours after the exploration is completed. The Engineer will inspect the samples/cores and determine the final depth of required excavation based on his evaluation of the sampled materials suitability.

At all drilled shaft locations where rock cores and/or soil samples are not designated, the Contractor will be required to drill or probe an exploratory holebelow the bottom elevation of the shaft to determine if any voids or crevices are present. The exploratory hole shall be taken to a depth of 10 feet {3 m}, unless noted otherwise on the plans. Exploratory drilling or probing will not be required if it is noted on the plans that this requirement is not necessary. No direct payment will be made for this operation. DRILLED SHAFT CONSTRUCTION 337

Surface and subsurface obstructions at drilled shaft locations shall be removed by the Contractor. Such obstructions may include man-made materials such as old concrete foundations and natural materials such as boulders. Special procedures and/or tools shall be employed by the Contractor in the event the hole cannot be advanced using conventional augers fitted with soil or rock teeth, drilling buckets and/or underreaming tools. Special procedures/tools may include but are not limited to: chisels, boulder breakers, core barrels, air tools, hand excavation, temporary casing, and increasing the hole diameter. Blasting shall not be permitted unless specifically approved in writing by the Engineer. Removal of obstructions will be classified as "special drilled shaft excavation".

The Engineer will require the construction of a trial shaft if the submittal of descriptions of previous drilled shaft construction projects does not, in the opinion of the Engineer, substantiate the Contractor's capability for constructing the drilled shafts on this project. The Engineer may also require the construction of a trial shaft to verify the adequacy of unusual construction methods and/or equipment proposed for use in the construction of the production shafts. The trial drilled shaft shall be constructed if required by special note on the plans.

The trial shaft(s) shall be positioned as indicated on the plans or as directed by the Engineer. Unless otherwise indicated, shafts shall be drilled to the maximum depth of any production shaft shown on the plans.

Failure of the Contractor to demonstrate the adequacy of his equipment, methods and/or expertise shall be reason for the Engineer to require alterations necessary to eliminate unsatisfactory results. Additional trial shafts required to demonstrate correction of deficiencies shall be at the Contractor's expense.

Once approval has been given to construct production shafts, no changes will be permitted in the personnel, methods or equipment that were used to construct the satisfactory trial shaft without written approval of the Engineer.

Unless otherwise shown in the contract documents, the trial shaft holes will be filled with non-reinforced concrete in the same manner that production shafts will be constructed. The concreted trial shafts shall be cutoff 2 feet {600 mm} below finished grade or at the mudline if in water. The disturbed areas at trial shaft holes shall be restored as nearly as practical to their original condition. No direct payment will be made for cutting off the top of the trial shaft or for the site restoration.

506.04Encased Excavations

The outside diameter of casings shall not be less than the specified shaft size. No extra compensation will be allowed for concrete required to fill an oversized casing or excavation. All casings, except permanent casing, shall be removed from shaft excavations.

All casing shall be considered temporary unless specifically shown as permanent casing in the contract documents. The Contractor will be required to remove temporary casing before completion of concreting the drilled shaft. Telescoping, predrilling with slurry, and/or overreaming to beyond the outside diameter of the casing may be required to install casing.

If the Contractor elects to remove a specified diameter or length of casing and substitute a longer or larger diameter casing through caving soils, the excavation shall be either stabilized with slurry or backfilled before the new casing is installed. Other methods, as approved by the Engineer, may be used to control the stability of the excavation and protect the integrity of the foundation soils. DRILLED SHAFT CONSTRUCTION 338

Temporary casings which become bound or fouled during shaft construction and cannot be practically removed shall constitute a defect in the drilled shaft. The Contractor shall be responsible for correcting such defective shafts to the satisfaction of the Engineer. Correction may consist of, but is not limited to: removing the shaft concrete and extending the shaft deeper to compensate for loss of frictional capacity in the cased zone, providing straddle shafts to compensate for capacity loss, or providing a replacement shaft. All corrective measures including redesign of shafts caused by defective shafts shall be done to the satisfaction of the Engineer without compensation or an extension of the completion date of the project. In addition, no compensation will be paid for casing remaining in place.

When the shaft extends above ground or through a body of water, the portion exposed above ground or through a body of water may be formed with suitable, removable casing except when permanent casing is specified. Removable casing shall be stripped from the shaft in a manner that will not damage the concrete. Casings can be removed when the concrete has attained a compressive strength of not less than 2500 psi {20 MPa} as determined from concrete cylinder breaks provided: curing of the concrete is continued for the full period in accordance with specifications and the shaft concrete is not exposed to salt water or moving water for seven days.

Permanent casing shall be used when shown in the contract documents. The casing shall be continuous between top and bottom elevations prescribed in the plans. After installation is complete, the permanent casing shall be cut off at the prescribed elevation and the shaft completed by installing necessary reinforcing steel and concrete in the casing. Exterior surfaces of permanent casings shall be cleaned and coated with the prime coat only of a System 1A Coating in accordance with the requirements given in Section 521 and as shown on the plans. The exterior surfaces shall be coated prior to the installation of the casings. After the installation of the casings, all damage to the coated surfaces of the casings exposed to the air shall be repaired by a repeated application of the same prime coat. When not shown in the contract documents, permanent casing may be used if determined to be necessary by the Engineer and if approved by the Bridge Engineer.

In cases where special temporary casings are shown on the plans or authorized in writing by the Engineer, the Contractor shall maintain alignment of both the temporary outer and permanent inner casing, and a positive, watertight seal between the two casings during excavation and concreting operations.

506.05Use of Slurry

Slurries shall have a mineral grain size that will remain in suspension and sufficient viscosity and gel characteristics to transport excavated material to a suitable screening system. The percentage and specific gravity of the material used to make the suspension shall be sufficient to maintain stability of the excavation and allow proper concrete placement.

The mineral slurry shall be premixed thoroughly with clean fresh water and adequate time allotted for hydration prior to introduction into the shaft excavation. Slurry tanks of adequate capacity will be required for slurry circulation, storage, and treatment. Excavated slurry pits will not be allowed in lieu of slurry tanks without the written permission of the Engineer.

Desanding equipment shall be provided by the Contractor as necessary to control slurry sand content at less than 4 percent by volume at any point in the borehole. Desanding will not be required for setting temporary casing, signpost, or lighting mast foundations unless required by the plans or special provisions. DRILLED SHAFT CONSTRUCTION 339

During construction, the level of the slurry shall be maintained at a height sufficient to prevent caving of the hole. In the event of a sudden significant loss of slurry in the hole, the construction of that foundation shall be stopped until methods to stop slurry loss or an alternate construction procedure have been approved by the Engineer.

Mineral slurry in a shaft excavation shall be maintained at a level not less than 4 feet {1.2 m} above the highest expected static water surface along the depth of the shaft. If at any time the Engineer determines the slurry construction method fails to produce the desired final results, the Contractor shall discontinue this method and propose an alternate method for approval of the Engineer.

The Contractor shall take all steps necessary to prevent the slurry from "setting up" in the shaft. Such methods may include but are not limited to: agitation, circulation and/or adjusting the properties of the slurry.

Control tests using suitable apparatus shall be carried out on the mineral slurry by the Contractor to determine density, viscosity and pH. An acceptable range of values for these physical properties is shown in the following table: MINERAL SLURRY (Sodium Bentonite or Attapulgite in Fresh Water) Acceptable Range of Values Property (Units) At Time of Slurry Introduction In Hole at Time of Concreting Test Method Density (pounds per cubic foot) {kg/m3} 64.3** – 69.1** {1030** – 1110**} 64.3** – 75.0** {1030** – 1200**} Density Balance Viscosity (seconds / quart) {seconds / liter} 28 – 45 {30 – 48} 28 – 45 {30 – 48} Marsh Cone pH 8-11 8-11 pH paper, pH meter ** Increase by 2 pounds per cubic foot {32 kg/m 3} in salt water

hole as determined by the American Petroleum Institute sand content test.

Tests to determine density, viscosity and pH value shall be done during the shaft excavation to establish a consistent working pattern. A minimum of four sets of tests shall be made during the first 8 hours of slurry use. When the results show consistent behavior the testing frequency may be decreased to one set every four hours of slurry use.

Reports of all tests required above, signed by an authorized representative of the Contractor, shall be furnished to the Engineer on completion of each drilled shaft.

All slurry and contaminated spoils shall be captured and contained to the maximum extent practicable. All slurry and contaminated spoils shall be disposed offsite by the Contractor or as directed by the Engineer.

506.06Excavation Measurement and Cleaning

The Contractor shall provide equipment and personnel for checking the dimensions and alignment of each permanent shaft excavation. The dimensions, depth and alignment shall be determined under the direction and to the satisfaction of the Engineer after final cleaning. DRILLED SHAFT CONSTRUCTION 340

Unless otherwise stated in the contract, a minimum of 50 percent of the base of each shaft will have less than 1/2 inch {13 mm} of sediment at the time of concrete placement. The maximum depth of sediment or any debris at any place on the base of the shaft shall not exceed 1.5 inches {40 mm}. Shaft cleanliness will be determined by sounding with an airlift pipe, a tape with a heavy weight attached to the end of the tape, a borehole camera with visual sediment depth measurement gauge, or other means acceptable to the Engineer. For dry excavations the maximum depth of water covering the bottom of the excavation shall not exceed 3 inches {75 mm} prior to concrete pour.

506.07Reinforcing Steel Construction and Placement

The reinforcing steel cage, consisting of longitudinal and transverse bars, ties, cage stiffeners, spacers, centralizers, and other necessary appurtenances, shall be completely assembled and placed as a unit immediately after the shaft excavation is inspected and accepted, and prior to concrete placement. The reinforcing steel in the shaft shall be securely tied and supported so that the reinforcing steel will remain within allowable tolerances given in Subarticle 506.11(c) of this Specification.

intervals near the bottom, and at intervals not exceeding 10 feet up the shaft, to ensure concentric spacing for the entire cage length.

specified for the shaft. The spacers shall be of adequate dimension to ensure the proper annular space between the outside of the reinforcing cage and the side of the excavated hole and/or permanent casing as detailed on the plans or proposed in the installation plan. If not detailed on the plans, a minimum 4 inch {100 mm} annular space will be required.

Cylindrical concrete feet (bottom supports) shall be provided to ensure that the bottom of the cage is maintained at the proper distance above the base as specified by the project plans.

If the drilled shaft excavation is extended to an elevation lower than the plan bottom elevation, reinforcing cage length shall also be extended by the same amount. Cages may be extended at the plan bottom elevation by lap splicing additional longitudinal bars, per planned cage requirements, of sufficient length to provide a compression splice, 4.17 feet {1270 mm} in length, plus the required extension. Hoops for the extension shall be spaced the same as shown for other hoops. Any additional splices of the cage above the plan bottom elevation and not shown on the plans, must have prior approval of the Bridge Engineer. Stiffeners, spacers and other appurtenances shall also be extended as required.

506.08Concrete Placement Requirements

Concrete used for drilled shaft construction shall meet the requirements of Subarticle 506.02(b). After the reinforcing steel has been placed and before the concrete is ordered, the bottom of the drilled shaft must be resounded to verify cleanliness.

Concrete shall be placed as soon as possible after the reinforcing steel has been placed and the bottom of the shaft has been resounded. The concrete placement shall be continuous from the bottom to the top elevation of the shaft. The elapsed time from the beginning of concrete placement in the shaft to the completion of placement shall not exceed 2 hours except as allowed by the Engineer. The Engineer may allow the concrete placement time to exceed 2 hours if the Contractor adequately demonstrates that the slump of the concrete will not be less than 4 inches {100 mm} during the entire time of concrete placement. DRILLED SHAFT CONSTRUCTION 341

The Contractor may choose either a laboratory test or a field test to demonstrate the slump loss/time relationship. Adjustments to chemical admixture dosages will be allowed for the sole purpose of extending the time of concrete placement provided that the admixtures are included in the approved concrete mix design. A new slump loss test will be required if changes are made to the concrete mix, including adjustments to chemical admixtures.

The Contractor shall demonstrate by trial mix and slump loss tests that the slump of the concrete will not be less than 4 inches {100 mm} during the longer placement time. These tests shall be conducted by an independent testing laboratory, approved by the Department as per ALDOT-405, and in the presence of a Department representative. The slump loss tests shall be performed at intervals not to exceed 30 minutes and shall be made from a trial mix proportioned from the approved concrete mix design. The temperature of the trial mix shall be kept at a level representative of construction site conditions.

The Contractor shall demonstrate by construction site slump loss tests that the slump of the concrete will not be less than 4 inches {100 mm} during the longer placement time. The slump loss tests shall be performed at intervals not to exceed 30 minutes and shall be made from the first batch of concrete that is placed in a trial drilled shaft. The concrete used for these slump loss tests shall be sampled at the trial drilled shaft site and shall be kept covered during testing. If a trial shaft is not required then a field test may be performed at the construction site prior to the beginning of the work. The slump test shall be performed by the contractor’s Concrete Technician, certified by the Department as per ALDOT-405, in the presence of a Department representative.

The Contractor shall ensure that a heavily contaminated slurry suspension, which could impair the free flow of concrete, has not accumulated in the bottom of the shaft.

Prior to placing concrete in a slurry filled shaft excavation, the Contractor shall take slurry samples using a sampling tool. Slurry samples shall be extracted from the base of the shaft and at intervals not exceeding 10 feet {3 m} up the shaft, until two consecutive samples produce acceptable values for density, viscosity, pH, and sand content as noted in Subarticle 506.05(c) and Item 506.05(e)2, respectively.

When any slurry samples are found to be unacceptable, the Contractor shall take whatever action is necessary to bring the mineral slurry within specification requirements. Concrete shall not be poured until resampling and testing results produce acceptable values.

The level of fresh concrete placed into a casing shall be a minimum of 5 feet {1.5 m} above either the hydrostatic water level or the level of drilling fluid whichever is higher. As a temporary casing is withdrawn, care shall be exercised to maintain an adequate level of concrete within the casing so that fluid trapped behind the casing is displaced upward and discharged at the ground surface without contaminating or displacing the shaft concrete.

506.09Concrete Placement Methods

If a method of concrete placement has not been specifically identified in the contract documents, the Contractor may use any of the placement methods described hereafter. If a concrete pump is used to move the concrete to the drilled shaft, a standby pump shall be immediately available to pump the concrete if there is a pump failure. Details pertaining to compliance with this specification shall be presented as part of the Contractors "Installation Plan" as outlined in Item 506.03(a)2. Concrete placement shall continue after the shaft excavation is full until good quality concrete is evident at the top of the shaft. Any overflow of concrete at the top of the shaft shall be removed to maintain a uniform appearance and the proper dimensions of the shaft. DRILLED SHAFT CONSTRUCTION 342

The free fall placement of concrete shall only be permitted in dry vertical shafts where the clear opening (inside the reinforcing cage) is not less than 24 inches {610 mm} in diameter. The height of free fall placement shall not exceed 75 feet {22 m}. Concrete placed by free fall shall fall directly to the placement location without contacting either the reinforcing cage or the shaft sidewall. The Engineer will observe the falling of the concrete within the shaft. If the concrete strikes the reinforcing cage or sidewall, or if there is excessive spatter from the impact of the falling concrete, the Contractor shall reduce the rate of concrete placement, reduce the height of free fall or provide a drop chute for concrete placement as directed by the Engineer.

Drop chutes shall consist of a smooth tube of either one piece construction or sections which can be added and removed. Concrete may be placed through either a hopper at the top of the tube or side openings as the drop chute is retrieved during concrete placement.

The drop chute shall be supported so that the free fall of the concrete measured from the bottom of the chute to the point of deposition is less than 75 feet {22 m}. If concrete placement causes the shaft excavation to cave or slough, or if the concrete strikes the rebar cage or sidewall, the Contractor shall reduce the height of free fall and/or reduce the rate of concrete flow into the excavation.

If in the opinion of the Engineer, placement cannot be satisfactorily accomplished by the free fall and drop chute method, the Contractor shall change to either tremie or pumping methods to accomplish the pour.

Tremies may be used for concrete placement in either wet or dry holes.

Tremies shall consist of a tube of sufficient length, weight {mass}, and diameter to discharge concrete at the shaft base elevation. The tremie shall not contain aluminum parts which will have contact with the concrete. The tremies inside diameter shall be at least 6 times the maximum size of aggregate used in the concrete mix but shall not be less than 10 inches {250 mm}.

Inside and outside surfaces of the tremie shall be clean and smooth to permit both flow of concrete and unimpeded withdrawal during concreting. The wall thickness of the tremie shall be adequate to prevent crimping or sharp bends which restrict concrete placement.

The tremie used for wet concrete placement shall be watertight. Underwater placement shall not begin until the tremie is placed to the shaft base elevation. Valves, bottom plates or plugs may be used to ensure concrete discharge begins within one tremie diameter of the base. Plugs shall either be removed from the excavation or be made of a material which will not cause a defect in the shaft if not removed. The discharge end of the tremie shall be constructed to permit the free radial flow of concrete during placement operations.

The tremie discharge end shall be immersed at least 5 feet {1.5 m} in concrete at all times after starting the flow of concrete. The flow of the concrete shall be continuous. The concrete in the tremie shall be maintained at a positive pressure differential at all times to prevent water or slurry intrusion into the shaft concrete. DRILLED SHAFT CONSTRUCTION 343

If at any time during the concrete pour, the tremie line orifice is removed from the fluid concrete column and discharges concrete above the rising concrete level, the shaft shall be considered defective. In such case, the Contractor shall either: o remove the reinforcing cage and concrete, complete any necessary sidewall removal directed by the Engineer, and repour the shaft or, o the tremie shall be replugged, recharged with concrete and inserted a minimum of 5 feet {1.5 m} below the existing top level of concrete prior to continuing the pour. The contractor shall be responsible for correcting any defect caused by this procedure without additional compensation. All costs for replacement of defective shaft concrete shall be the responsibility of the Contractor.

Concrete pumps and lines may be used for concrete placement in either wet or dry excavations.

Pump lines shall have a minimum diameter of 4 inches {100 mm} and shall be constructed with watertight joints. Except as modified herein, requirements pertaining to tremie lines as stated in Item 506.09(c)1, also apply to pump lines and their use. The concrete pump unit shall have sufficient power to ensure continuous placement of concrete under all foreseeable placement conditions.

The discharge orifice shall remain at least 5 feet {1.5 m} below the surface of the fluid concrete. When lifting the pump line during concreting, the Contractor shall temporarily reduce the line pressure until the orifice has been repositioned at a higher level in the excavation.

If at any time during the concrete pour the pump line orifice is removed from the fluid concrete column and discharges concrete above the rising concrete level, the shaft shall be considered defective. In such case, the Contractor shall remove the reinforcing cage and concrete, complete any necessary sidewall removal directed by the Engineer, and repour the shaft. All costs for replacement of defective shaft concrete shall be the responsibility of the Contractor.

Testing Requirements For Drilled Shafts

The nondestructive testing method called Crosshole Sonic Logging (CSL) shall be used on all production and trial drilled shafts (a) when constructed with the placement of concrete underwater or through slurry, (b) when required by special note on the plans, (c) when a full length temporary casing is used to prevent water from entering the shaft, or (d) when determined to be necessary by the Engineer. The testing shall not be conducted until 72 hours after the placement of all concrete in a shaft and must be completed within 20 calendar days after placement. The CSL tests shall be conducted by an experienced independent testing consultant approved by the Engineer prior to testing. The CSL tests measure the time it takes for an ultrasonic pulse to travel from a signal source in one access tube to a receiver in another access tube. In uniform, good quality concrete, the travel time between equi-distant tubes will be relatively constant and correspond to a reasonable concrete pulse velocity from the bottom to the top of the foundation. In uniform, good quality concrete, the CSL test will also produce records with good signal amplitude and energy. Longer travel times and lower amplitude/energy signals indicate the presence of irregularities such as poor quality concrete, void, honeycomb and soil intrusions. The signal will be completely lost by the receiver and CSL recording system for the more severe defects such as voids and soil intrusions.

A number of tubes shall be installed in each shaft to permit access for CSL. The number of tubes installed will depend on the diameter of the shaft as specified below: DRILLED SHAFT CONSTRUCTION 344

Shaft Diameter D Minimum Number of Tubes D < 4.5 feet {1372 mm} 4 4.5 feet {1372 mm} < D < 5.5 feet {1676 mm} 5 5.5 feet {1676 mm} < D < 6.5 feet {1981 mm} 6 6.5 feet {1981 mm} < D < 7.5 feet {2286 mm} 7 7.5 feet {2286 mm} < D < 8.5 feet {2591 mm} 8 8.5 feet {2591 mm} < D < 9.0 feet {2743 mm} 9 9.0 feet {2743 mm} < D < 10.0 feet {3048 mm} 10 10.0 feet {3048 mm} < D < 11.0 feet {3353 mm} 11 11.0 feet {3353 mm} < D < 12.0 feet {3658 mm} 12 The tubes shall have a 1.5 inch {40 mm} inside diameter and shall be schedule 40 steel pipe. The pipes shall have a round, regular internal diameter free of defects or obstructions, including any at pipe joints, in order to permit the free, unobstructed passage of a 1.3 inch {30 mm} diameter source and receiver probes. The tubes shall be watertight and free from corrosion with clean internal and external faces to ensure passage of the probes and a good bond between the concrete and the tubes. The pipes shall each be fitted with a water tight shoe on the bottom and a removable cap on the top. The pipes shall be securely attached to the interior of the reinforcement cage with a minimum cover of 4 inches {100 mm}.The tubes shall be installed in each shaft in a regular, symmetric pattern such that each tube is equally spaced from the others around the perimeter of the cage. The Contractor shall submit to the testing organization his selection of tube size, along with his proposed method to install the tubes, prior to construction. The tubes shall be as near to parallel as possible. The tubes shall extend from 6 inches {150 mm} above the shaft bottoms to at least 3 feet {1 m} above the shaft tops. If the shaft top is sub-surface, the tubes shall extend at least 2 feet {600 mm} above the ground surface. Any joints required to achieve full length tubes shall be made watertight. Care shall be taken during reinforcement installation operations in the drilled shaft hole so as not to damage the tubes. As the cage is being lowered into the shaft, the tubes shall be checked to assure that they are vertical and parallel and that all connections are watertight. After placement of the reinforcement cage, the tubes shall be filled with clean water as soon as possible. After the tubes are filled with water, the tube tops shall be capped or sealed to keep debris out of the tubes prior to concrete placement. The pipe caps or plugs shall not be removed until the concrete in the shaft has set. Care shall be exercised in the removal of caps or plugs from the pipes after installation so as not to apply excess torque, hammering, or other stresses which could break the bond between the tubes and the concrete.

Typical CSL test equipment consists of the following components:

conversion and recording of CSL data, analysis of receiver responses and printing of CSL logs. - Ultrasonic source and receiver probes for 1.5 inch {40 mm} ID pipe, as appropriate. - An ultrasonic voltage pulser to excite the source with a synchronized triggering system to start the recording system. - A depth measurement device to determine and record depths. - Appropriate filter/amplification and cable systems for CSL testing.

Before the placement of concrete, a minimum of one tube per shaft shall be plumbed and the tube length recorded, including a notation of the stickup of the tubes above the shaft tops. Information on the shaft bottom and top elevations and/or length, along with construction dates shall be provided to the Engineer and the approved testing organization before the CSL tests are performed. The CSL tests shall be carried out with the source and receiver probes in the same horizontal plane unless test results indicate potential defects in which case the questionable zone may be further evaluated with angled tests (source and receiver vertically offset in the tubes). CSL measurements shall be made at depth intervals of 2 inches {50 mm} or less, and shall be done from the bottom of the tubes to the top of each shaft. The probes shall be pulled simultaneously, starting from the bottoms of the tubes, over a depth measuring device. Any slack shall be removed from the cables prior to pulling to provide for accurate depth measurements of the CSL records. DRILLED SHAFT CONSTRUCTION 345

Prior to leaving the job site, the approved testing organization shall notify the Engineer that all data was collected satisfactorily or if there were discrepancies in the supplied CSL tube lengths, difficulties in obtaining the data or if tube access was obstructed anywhere in the supplied lengths. CSL tests shall be conducted between pairs of tubes. The approved testing organization shall test at least two diagonals through the center and between each tube pair around the perimeter of all tested shafts. Two diagonal tests shall be as close as possible to being at right angles to each other. Additional logs shall be conducted at no additional cost in the event anomalies are detected. The Contractor shall attempt to clear all tube obstructions reported to the Engineer so that tubes can be retested to full depth while the approved testing organization is on site. If obstructions cannot be cleared in a tube the approved testing organization shall conduct the CSL test in the adjacent pair of unobstructed tubes so that the measurements are made as close as possible to the obstructed tubes. Any anomalies indicated by longer pulse arrival times and significantly lower amplitude/energy signals shall be reported to the Engineer and further tests such as fan shaped tests, tests with probes raised at a fixed offset distance, or other topographical techniques shall be conducted as required to evaluate the extent of such anomalies. Additional NDT methods which may be used to evaluate possible defects include Singlehole Sonic Logging, Gamma-Gamma Nuclear Density Logging, and/or Surface Sonic Echo and Impulse Response tests.

The CSL results shall be presented to the Engineer in a report. This report shall include recommendations as to the acceptability, unacceptability, soundness, etc., of the drilled shaft. The report shall be checked, stamped approved, and signed by a Professional Engineer licensed by the Alabama Board of Licensure for Professional Engineers. This Professional Engineer shall not be an employee of the ALDOT. The report shall be submitted directly to the Materials and Tests Engineer with a copy to the Project Manager. The test results shall include CSL logs with analyses of:

- Pulse energy/amplitude versus depth A CSL log shall be presented for each tube pair tested with any defect zones indicated on the logs and discussed in the test report as appropriate.

The Engineer will evaluate the CSL test results and determine whether or not the drilled shaft construction is acceptable. This evaluation will be completed within 14 calendar days of the date of receipt of the report by the Materials & Tests Engineer. If the Engineer determines that the drilled shaft is acceptable, the CSL tubes shall be dewatered and grouted. The grout shall be of the same strength or higher than the strength of the concrete used in the original drilled shaft. The contractor may use any of the grout mixes listed in Table 1 of Item 453.03(b)2. with the exception that calcium chloride will not be allowed. The contractor may submit another design mix for approval. If the Engineer determines that the drilled shaft is unacceptable, the shaft shall be cored in accordance with the requirements given in Subarticle 506.10(b) to allow further evaluation of the shaft. Cores shall be taken without additional compensation unless the testing of the cores indicates that the concrete in the shaft meets all specification requirements. If the testing of the cores indicates that the concrete meets specification requirements, the cost of the coring will be paid for as Extra Work.

Production or trial drilled shafts that are determined to be unacceptable by the CSL tests may be cored to determine the quality of the shaft. The required number and depth of cores will be determined by the Engineer. Because it is necessary to obtain a high percentage of core recovery for visual inspection and compressive strength testing, the core bit used for core drilling shall be warranted by the manufacturer as being capable of coring the concrete as strong as could possibly be present in the shaft. A new bit or new core barrel will be required at any time the Engineer determines that the equipment may not be capable of obtaining good quality cores. The minimum diameter of the cores shall be 3.0 inches {76 mm}. An accurate log of cores shall be kept and the cores shall be placed in a crate and properly marked showing the shaft depth at each interval of core recovery. The cores along with three copies of the DRILLED SHAFT CONSTRUCTION 346

coring log shall be transported to the ALDOT Bureau of Materials and Tests, Montgomery, Alabama, for inspection. Construction shall not proceed above a drilled shaft until the quality of the shaft, as represented by the core samples, is determined to be acceptable and notification to continue construction is given by the Construction Engineer. If the Engineer determines that the drilled shaft is acceptable, the core holes and the CSL tubes shall be dewatered and grouted. The grout shall be of the same strength or higher than the strength of the concrete used in the original drilled shaft. The contractor may use any of the grout mixes listed in Table 1 of Item 453.03(b)2. with the exception that calcium chloride will not be allowed. The contractor may submit another grout design mix for approval. If the quality of thedrilled shaft is determined to be unacceptable then the Contractor shall construct another foundation to carry the load that will be placed on the shaft or perform corrective work as required by the Department. This foundation or the corrective work shall be constructed without compensation from the Department. The details of the replacement foundation shall be submitted in accordance with the requirements given in Article 105.02 for Working Drawings.

506.11Drilled Shaft Construction Tolerances

The following construction tolerances apply to drilled shafts unless otherwise stated in the contract documents. Drilled shaft excavations and completed shafts not constructed within the required tolerances are unacceptable. The Contractor shall correct all unacceptable shaft excavations and completed shafts to the satisfaction of the Engineer. Materials and work necessary to complete corrections for out of tolerance drilled shaft excavations and/or completed shafts, including engineering analysis and redesign, shall be furnished without either cost to the State or an extension of the contract time of the project.

The drilled shaft shall be within 3 inches {75 mm} of plan position in the horizontal plane at the elevation of the top of the shaft.

The vertical alignment of a shaft excavation shall not vary from the plan alignment by more than 1/4 inch per foot {20 mm/m} of depth. The alignment of a battered shaft excavation shall not vary by more than 1/2 inch per foot {40 mm/m} of depth from the prescribed batter.

The spacers for the reinforcing cage shall have a tolerance of minus 1 inch {25 mm} from the required spacing shown on the plans. The reinforcing steel cage shall be within 1 inch {25 mm} of plan position in the horizontal plane at the elevation of the top of the shaft. After all the concrete is placed, the top of the reinforcing steel cage shall be no more than 6 inches {150 mm} above and no more than 3 inches {75 mm} below plan position.

All casing diameters shown on the plans refer to OD (outside diameter) dimensions. Casing shall be clean, round, straight and free of weld breaks and/or holes that would permit passage of water or wet concrete. When approved by the Engineer, the Contractor may elect to provide a casing larger in diameter than shown in the plans. No payment will be made for additional construction materials used in accommodating the Contractor's request for a larger casing diameter.

The diameter of an excavated socket shall have a tolerance of minus 2 inches {50 mm} from the plan diameter.

The top elevation of the shaft shall have a tolerance of plus 1 inch {25 mm} or minus 3 inches {75 mm} from the plan top of shaft elevation.

Excavation equipment and methods shall be designed so that the completed shaft excavation will have a planar bottom. The cutting edges of excavation equipment shall be normal to the vertical axis of the equipment within a tolerance of +/- 3 % of the diameter.