303 SECTION 509 DESCRIPTION
509.01.01 General. This work consists of constructing drilled shaft foundations.
509.01.02 Qualifications of Drilled Shaft Contractors. No later than 30 days prior to constructing drilled
shafts, submit in writing, qualifications to perform the drilled shaft construction as specified and provide a list of 3 projects successfully completed within the previous five years using drilled shaft construction. The list of projects shall contain names and current phone numbers of owner’s representatives who can verify participation on those projects. On-site supervisors shall have a minimum of 3 years experience in supervising construction of dril led shafts of both diameter and length, and similar geotechnical conditions, to those shown on the plans. Drill rig operators shall have a minimum of 1 year drilling experience in construction of drilled shafts of both diameter and length, and similar geotechnical conditions, to those shown on the plans.
509.01.03 Submittals. Submit an installation plan for review a minimum of 15 days prior to constructing drilled
shafts. This plan shall provide information on the following:
1.Name and experience record of drilled shaft superintendent who will be in charge of drilled shaft operations.
2.List of proposed equipment to be used, including cranes, drills, soil augers, rock augers, coring buckets, bailing buckets, chipping and grooving tools, final cleanout e quipment, de -sanding equipment, slurry pumps, slurry tanks, slurry sampling and testing equipment, core sampling equipment, tremies, concrete pumps, and casing .
3.Details of overall construction operation sequence and sequence of shaft construction in be nts or groups.
4.Details of shaft excavation methods , procedures , and sequence . Describe proposed drilling methods, cleanout methods, methods ensuring shaft stability, disposal plan for excavated material, and treatment of hazardous waste material encoun tered.
5.Details of the slurry mix design, including suitability for the subsurface conditions at the site, mixing and storage methods, maintenance methods, slurry disposal procedures, provisions for controlling slurry quality including test types, sampling techniques, test methods, frequency of tests, specified property requirements to ensure the slurry meets its intended functions.
6.Details of reinforcement placement, including support and centralization methods.
7.Details of concrete placement, including concrete delivery schedule , proposed operational procedures for tremie and pumping methods , and methods for removal and disposal of contaminated concrete.
8.Details of casing, including methods of installation, advancement, and remov al.
9.Provide a signed statement from the drilling contractor that inspection has been made of both the project site and all the subsurface information made available, including any soil or rock samples referenced in the contract documents. The drilled shaft installation plan will be evaluated for conformance with the contract requirements. Notification will be given within 14 days after receipt of the installation plan of any additional information required and/or changes necessary. Approval of the plan shall not operate to relieve the responsibility under the contract for the successful completion of the work, nor shall approval of the plan operate as a warranty that the plan will succeed or will be the most economical or efficient method of completing the work. Adhere to the approved plan for the remainder of the contract. Subject to acceptable field performance, or if changes in equipment or construction methods occur, submit a revised plan for review and approval.
509.01.04 Pre -Activity Meeting. A pre-activity meeting will be scheduled prior to commencement of drilled
shaft construction. As a minimum, the Contractor, the drilling sub -contractor, and the Engineer shall attend the meeting. 509 DRILLED SHAFT FOUNDATIONS 304 MATERIALS
509.02.01 General. Material shall conform to the foll owing Sections:
Portland Cement Concrete ................................ ................................ ................................ ................................ ..................... Section 501 Reinforcing Steel ................................ ................................ ................................ ................................ ................................ .... Section 505 Concrete Curing Materials and Admixtures ................................ ................................ ................................ ............................ Section 702 Concrete for drilled shafts for bridge structures shall be Class S where shown on the plans. Concrete for all other drilled shafts shall be Class S or Class D. Concrete shall conform to Section 501 with the following modifications: Minimum Compressive Strength for Class D ................................ ................................ ................................ ............... 28 MPa (4,000 psi) Grading Limits of Combined Aggregates * ................................ ................................ ................................ ......................... 13 mm (1/2 in.) Slump Range ** ................................ ................................ ................................ ................................ ................ 175 to 225 mm (7 to 9 in.) * See Section 706 for Grading Limits of Combined Aggregates. If approved, 10 mm (3/8 in.) may be used in lieu of 13 mm (1/2 in.). For drilled shafts required as specified in Section 623, the grading requirements shall be a s specified in Table I of Subsection 501.0 2.05. ** See Section 501 for Slump Range requirements for Class S concrete. All classes of concrete shall have a minimum slump of 175 mm (7 in.) at 3 hours. For 3 hour, or extended time slump tests, store a suffic ient quantity of concrete in sealed five gallon buckets at room temperature. CONSTRUCTION
509.03.01 Construction Sequence. Complete excavation to top of shaft elevation without pauses or stops ,
except for casing splicing or removal of obstructions, before s haft construction begins, unless otherwise noted or approved. Recompact and regrade any disturbance to the footing or pile cap area prior to the footing or pile cap concrete placement. If the shaft excavation is not completed at the end of the sh ift or series of continuous shifts, the shaft excavation operation may be stopped, provided the shaft is protected against sidewall instability. Do not leave shaft excavations unprotected overnight. Protect shaft excavations against sidewall instability by casing full depth. If approved in writing, slurry may be used to protect a shaft during a drilling stoppage or overnight shutdown. Casing will not be required in stable rock formations during shaft excavation stoppages. When drilled shafts are to be installed in conjunction with embankment placement, construct drilled shafts after the placement of embankment, unless otherwise noted or approved. In the case of drilled shafts constructed prior to the completion of the embankment, place pile caps or foot ings after the embankment has been placed as near to final grade as possible. Leave only the necessary work room for construction of the caps or footings.
509.03.02 Construction Methods. Perform excavations required for shafts, through whatever materials are
encountered to the dimensions and elevations shown in the plans or as required. Use construction methods suitable for the intended purpose and materials encountered. Blasting will not be permitted unless noted on the plans or authorized in writing.
a.Dry Construction Method. The dry construction method consists of drilling the shaft excavation, removing accumulated water and loose material from the excavation, placement of the reinforcing cage, and placement of concrete in a relatively dry excavation . Use the dry construction method when :
1.There is less than 75 mm (3 in.) of standing water in the bottom of the shaft excavation, and less than 0.3 m (1 ft) of ground water accumulates above the base of the excavation over a one hour period when no pumping is permitted.
2.The sides and bottom of the excavation remain stable, with no detrimental caving, sloughing, or swelling occurring prior to placement of reinforcement.
3.The sides and bottom of the shaft can be visually inspected prior to place ment of reinforcing steel and/or concrete. If conditions are such that the above requirements are not satisfied, use wet construction and/or casing construction methods. DRILLED SHAFT FOUNDATIONS 509 305 (b) Wet Construction Method. The wet construction method consists of using drilling slurry to maintain the stability of the borehole perimeter while advancing the excavation to the specified bottom elevation, placement of the reinforcing cage, and concreting the shaft. Where drilled shafts are located in open water areas, extend exterior casings from above the water elevation into the ground to protect the shaft concrete from water action during placement and curing. Install exterior casings in a manner that will produce a positive seal at the bottom of the casing so that no piping of wate r or other materials occurs into or from the shaft excavation. Use the wet construction method at sites where a dry excavation cannot be maintained for placement of the shaft concrete.
c.Casing Construction Method. The casing construction method consist s of placing a casing into a predrilled hole or advancing a casing through the ground by twisting, driving , or vibration before being cleaned out. Use the casing method 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. Use permanent casing only at locations shown on the plans or when a pproved .
509.03.03 Equipment. Use excavation and drilling equipment having adequate capacity, including power,
torque , and down thrust to exc avate a shaft of the required diameter and to a depth 20% greater than required. Excavation and overreaming tools shall be of adequate design, size , and strength to perform the work. When the material encountered cannot be drilled using conventional earth augers with soil or rock teeth, drill buckets, grooving tools, and/or overreaming tools, provide special excavation equipment such as rock core barrels, rock tools, air tools, blasting materials, and other equipment as necessary to construct the shaft excavation to the size and depth required.
509.03.04 Excavations. Excavate shafts at locations and to the top of shaft elevations, estimated bottom of
shaft elevations, shaft geometry and dimensions shown in the contract documents. Extend drilled shaft tip (base) elevations as directed, when the material encountered during excavation is d etermined to be unsuitable. Overream sidewalls of shafts when the sidewalls have either softened due to excavation methods, swelled due to delays in concreting, or degraded due to slurry cake buildup. Overream to a minimum thickness of 13 mm (1/2 in.) and a maximum thickness of 75 mm (3 in.). Accomplish overreaming with a grooving tool, overreaming bucket or other approved equipment. The thickness and limits of sidewall overreaming will be determined. Utilize suitable excavated material for backfilling or in embankments. Dispose of unsuitable or surplus material according to Subsection 107.14.
509.03.05 Excavation Inspection. Provide all equipment for checking the dimensions and alignment of each
shaft excavation. Provide lights, mirrors, weighted tape, w eighted probe, personnel, and all assistance required to perform inspection of the drilled shaft construction. Use the equipment to obtain all measurements as directed. Measure final shaft depth with a suitable weighted tape or other approved methods afte r final cleaning. The maximum depth of sediment or any debris at any place on the base of the shaft shall not exceed 25 mm (1 in.) . For dry shafts, remove all cuttings that may have been smeared on the sidewalls during the insertion and removal of drilling tools. In addition, for dry excavations, the maximum depth of water shall not exceed 75 mm (3 in.) prior to concrete placement. Shaft inspection will be made after final cleaning by visual inspection for dry shafts or other methods deemed appropriate for wet shafts, such as sounding with a weighted tape or probe. Do not proceed with shaft construction until the shaft has been inspected and accepted.
509.03.06 Obstructions. Give notification immediately when obstructions are encountered. Remove surface
and subsurface obstructions at drilled shaft locations. Such obstructions may include, but are not limited to, man-made materials such as old foundations or construction debris and natural materials such as cobbles, boulders, or cemented soils. Employ special procedures and tools when the shaft cannot be advanced using augers, drilling buckets, or overreaming tools. Such special procedures and tools may include, but are not limited to , chisels, boulder breakers, core barrels, air tools, hand excavation, tempor ary casing, and increasing the shaft diameter. Do not blast to remove obstructions unless approved in writing. Retrieve and dispose of all excavating equipment and tools lost during shaft excavation.
509.03.07 Exploration (Shaft Excavation). Obtain soil samples or rock cores to determine the character of the
material directly below the completed shaft excavation where shown on the plans or as directed. Extract soil samples with a split spoon sampler or undisturbed sample tube, using the designated so il sampling technique. 509 DRILLED SHAFT FOUNDATIONS 306 Cut rock cores with an approved double or triple tube core barrel to a minimum of 3 m (10 ft) below the shaft excavation either before the excavation is made or at the time the shaft excavation is approximately complete. Extend the depth of coring to 6 m (20 ft) below the bottom of the shaft when directed. Measure, visually identify, and record rock core samples in an appropriate field log. Also, describe and record standard penetration test blow counts and samples in the log. Place samp les in suitable containers, identified by shaft location, elevation, and contract number and deliver with the field log to the Engineer. When samples are obtained after completion of the shaft excavation, deliver the field log and samples immediate ly upon completion of sampling. The material will be inspected and a decision will be made on the suitability of the bearing stratum within 2 days. When samples are obtained prior to excavating the shaft, deliver the samples and field log within 24 hours of sampl ing. Inspection of the samples/cores will be made and the final depth of required excavation will be determined within 3 days. Furnish 2 typed copies of the final log at the time the shaft excavation is completed and accepted.
509.03.08 Casings. Use steel casings which are smooth, clean, watertight, and of sufficient strength to
withstand both handling and driving stresses and the pressure of both concrete and the surrounding earth materials. The outside diameter of the casing and the diameter of any excav ation made below the casing shall not be less than the specified diameter of the shaft, or more than 150 mm (6 in.) greater than the specified diameter of the shaft at no cost to the Department. Remove all casings, except permanent casings, from shaft exca vations. Any length of permanent casing installed below the shaft cutoff elevation shall remain in place. Extract casing prior to initial set to allow the concrete cast against the surrounding soil to develop the designed skin friction. Leave casing not extracted within the allotted time in the excavation. If casing is not extracted from the excavation, the shaft will be reevaluated to determine if any loss of capacity has occurred. Any loss of capacity may be grounds for the shaft to be considered defect ive. If any shaft is determined to be defective, submit a plan for remedial action for approval.
a.Temporary Casing. Provide temporary casing in sufficient quantities to meet the needs of the anticipated shaft condition. All subsurface casing shall be considered temporary unless specifically shown as permanent casing in the contract d ocuments. Remove temporary casing before completion of concreting the shaft. Telescoping, predrilling with slurry, or overreaming to beyond the outside diameter of the casi ng may be required during installation. If electing to remove a 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 me thods may be used to control the stability of the excavation and protect the integrity of the foundation materials when approved. Extract casing at a uniform rate with the pull in line with the shaft axis. As the casing is withdrawn, 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. Temporary casings which become bound or fouled during shaft constr uction and cannot be practically removed shall constitute a defect in the shaft. Submit a plan for approval to correct such defective shafts. Such improvement 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. Any foundation redesign must be performed by a Registered Professional Engineer, licensed to prac tice in the State of Nevada.
b.Permanent Casing. Use permanent casing when shown in the contract documents. Provide continuous full length casing between the top and bottom elevations of the shaft. Splice permanent casing according to
Article 6 — 13.3 of the AASHTO LRFD Bridge Design Specifications . Cut off permanent casing, after installation is
complete, at the prescribed elevation, and complete the shaft construction by installing necessary reinforcing steel and concrete in the casing.
509.03.09 Slurry . During construction, maintain the level of the slurry at a height sufficient to prevent caving of
the hole. In the event of a sudden significant loss of slurry in the hole, cease construction of the foundation until either a method to stop slurry loss or an alternate construction procedure has been approved. Provide a manufacturer’s representative, slurry supplier’s representative, or third -party technical representative to oversee slurry operations and perform slurry control tests. DRILLED SHAFT FOUNDATIONS 509 307 Perform tests during the shaft excavation to verify specification requirements and ensure material consistency. Conduct a minimum of 4 sets of tests during the first 8 hours of slurry use. When the results show consist ency , the testing frequency may be decreased to 1 set every 4 hours of slurry use. Sample and test slurry immediately prior to placing concrete. 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 conc rete in any shaft excavation, take slurry samples using an approved sampling tool. Extract 2 slurry samples, 1 from within 0.6 m (2 f t) of the base of the shaft and 1 at mid-height in the shaft, until the samples produce acceptable test results . When slu rry samples are found to be unacceptable, take whatever action is necessary to bring the slurry within specification requirements. Do not place concrete until the slurry in the hole is re -sampled and test results produce acceptable values. Furnish signed test reports of all tests required upon completion of each drilled shaft.
a.Mineral Slurry. Mineral slurry shall have both 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 mineral suspension shall be sufficient to maintain the stability of the excavation and to allow proper concrete placement. Premix mineral slurry thoroughly with clean water and allow adequate time (as prescribed by the mineral slurry manufacturer) for hydration prior to introduction into the shaft excavation. Provide slurry tanks of adequate capacity for slurry circulation, storage, and treatment. Use of slurry pits will not be allowed . Provide desanding equipment to control slurry sand content to within specification any point in the borehole at the time slurry is introduced, including situations in which temporary casing is used. Take steps necess ary to prevent the slurry from “setting up” in the shaft. Such methods may include agitation, circulation , and adjusting the properties of the slurry . Dispose of slurry material according to Subsection 107.14. Mineral slurry shall be at least 4 °C (40 °F) when tested and shall conform to the following requirements: Property Test Method Requirement Density, lb/ft3 ................................ ......................... Mud Weight, API 13B -1, Section 1 ................................ ...... 64 to 72 Viscosity, sec/qt ................................ Marsh Funnel and Cup, API 13B -1, Section 2.2 ................................ ...... 28 to 50 pH ................................ ................................ Glass Electrode, pH Meter, or pH Paper ................................ ....... 8 to 11 Sand Content, % by volume ................................ ............ Sand, API 13B -1, Section 5 ................................ ..... 4.0 Max.
b.Synthetic Slurry. Mix synthetic slurry in accordance with the manufacturer’s recommendations. Follow the manufacturer’s recommendations for disposal of synthetic slurry and d ispose of according to Subsection 107.14. Synthetic slurry shall be at least 4 °C (40 °F) when tested and shall conform to the following requirements: Property Test Method Requirement Density, lb/ft3 ................................ ......................... Mud Weight, API 13B -1, Section 1 ................................ ...... 64 Max. Viscosity, sec/qt ................................ Marsh Funnel and Cup, API 13B -1, Section 2.2 .................. Manufacturer’s Recommendation pH ................................ ................................ Glass Electrode, pH Meter, or pH Paper ................................ ..... 8 to 11.5 Sand Content, % by volume ................................ ............ Sand, API 13B -1, Section 5 ................................ ..... 1.0 Max.
c.Water Slurry. Do not use water only as a drilling fluid, unless approved in writing. Consider naturally occurring water as drilling fluid. When water only is approved for use, the fluid shall conform to the following requirements: Property Test Method Requirement Density, lb /ft3 ................................ ......................... Mud Weight, API 13B -1, Section 1 ................................ ...... 64 Max. Sand Content, % by volume ................................ ............ Sand, API 13B -1, Section 5 ................................ ..... 1.0 Max.
509.03.10 Construction Tolerances. Construct shaft foundations to plan dimensions within the tolerances
specified herein. The diameter of the shaft shall not be less than the specified diameter and shall not be more than 150 mm (6 in.) greater than the specified diameter. Construct the center of the drilled shaft within 75 mm (3 in.) of plan position in t he horizontal plane at the plan elevation for the top of the shaft. 509 DRILLED SHAFT FOUNDATIONS 308 The vertical alignment of a vertical shaft excavation shall not vary from the plan alignment by more than 20 mm per m (1/4 in. per ft) of depth. After concrete placement, the top of the r einforcing steel cage shall be no more than 150 mm (6 in.) above and no more than 75 mm (3 in.) below plan position. Provide minimum cover of 150 mm (6 in.) for all reinforcing steel for shafts 1.5 m (5 ft) or larger in diameter, and a minimum cover of 100 mm (4 in.) for all reinforcing steel for shafts less than 1.5 m (5 ft) in diameter. A casing larger in diameter than shown in the plans may be used only when approved. The top elevation of the shaft shall not be less than 75 mm (3 in.) below the plan to p-of-shaft elevation and shall not be more than 25 mm (1 in.) above the plan top -of-shaft elevation. Employ excavation equipment and methods so that the completed shaft excavation will have a level planar bottom. The cutting edges of excavation equipment shall be normal to the vertical axis of the equipment within a tolerance of ± 30 mm per m (0.375 in. per ft) of diameter. Drilled shaft excavations and completed shafts not constructed within the required tolerances are unacceptable. Correct all unacceptable shaft excavations and completed shafts by approved methods. Engineering analysis and/or drilled shaft redesign to correct out -of-tolerance drilled shafts shall be performed by a Registered Professional Engineer, licensed to practice in the Sta te of Nevada. Submit proposed corrective measures for approval.
509.03.11 Reinforcing Steel Cage Construction and Placement. Reinforcing steel shall conform to the
details shown on the plans and the requirements of Section 505. Double tie, with double wir es, every other intersecting vertical and spiral or hoop members of the reinforcing cage in each direction. Assemble and place the reinforcing steel cage, consisting of longitudinal bars, spiral or hoop reinforcement, cage stiffeners, spacers, centralizers , integrity testing tubes , and other necessary appurtenances, as a unit within 30 minutes after the shaft excavation is inspected and accepted. Remove internal stiffeners as the cage is placed in the shaft so as not to interfere with the placement of concr ete. Support the reinforcing steel cage from the top at all times until completion of concrete placement. Tie and support the reinforcing steel in the shaft so that the reinforcing steel will remain within allowable tolerances given in Subsection 509.03.1 0. Use non corrosive rollers of sufficient strength and durability to withstand construction stresses near t he bottom and at intervals not exceeding 3 m (10 ft) up the shaft to ensure concentric spacing for the entire cage length in the excavation. Use rol lers of adequate dimension to ensure a minimum of 150 mm (6 in.) annular space between the outside of the reinforcing cage and the side of the excavation for shafts 1.5 m (5 ft) or larger in diameter. Provide rollers of adequate dimension to ensure a minim um of 100 mm (4 in.) annular space between the outside of the reinforcing cage and side of the excavation for shafts less than 1.5 m (5 ft) in diameter. Provide approved cylindrical feet (bottom supports) to ensure that the bottom of the cage is maintained the proper distance above the base. Verify the elevation of the top of the steel cage before and during the concrete placement. If the upward displacement of the rebar cage exceeds 50 mm (2 in.) or if the downward displacement exceeds 150 mm per 6.1 m (6 in. per 20 ft) of shaft length, the drilled shaft will be considered defective. Submit correction procedure for approval. Cease shaft construction until the method of supporting the reinforcing steel cage is modified to produce acceptable results.
509.03 12 Concrete Placement. Place concrete using a concrete pump by means of extension pipe or a tremie
pipe with a hopper attached to the top. Do not use pipes having aluminum parts that will come into contact with the concrete. The inside and outside surface s of the pipe shall be clean and smooth to permit both flow of concrete and unimpeded withdrawal during concreting. Use watertight pipes consisting of solid steel or jointed tube of sufficient length, weight, and diameter to discharge concrete at the shaft base elevation. The wall thickness of the pipe shall be adequate to prevent crimping or sharp bends, which restrict concrete placement. Concrete pump extension pipes shall have a minimum 125 mm ( 5 in.) inside diameter. Tremie pipes shall have an inside di ameter at least six times the maximum size of aggregate used in the concrete mix but shall not be less than 250 mm (10 in.). A "Concrete Brake ," which allows a head of concrete to be built up in the delivery pipe and reduces the air pumped into shaft , is required at the top of the pipe. The brake shall consist of a bladder valve or French horn. Ensure that concrete completely fills the pipe without air gaps. DRILLED SHAFT FOUNDATIONS 509 309 Place concrete within 1 hour after the shaft excavation is inspected and accepted. If this 1 hour limit is exceeded, remove the reinforcing cage to allow for reinspection as dire cted. Do not exceed 3 hours from the beginning of concrete placement in the shaft to the completion of concrete placement. A longer placement time may be approved, when r equested, provided that the supplied concrete mix maintain a slump of 175 mm ( 7 in.) or greater over the longer placement time. The slump test will be performed according to Subsection 509.02.01. Concrete shall be placed for each shaft with the flow of co ncrete directed down the center of the shaft. Install a foam or inflatable 'pig' in the top of the pipe. The 'pig' shall form a tight seal within the pipe. Fill the pipe completely and force the 'pig' to the bottom of the drilled shaft, thus forcing the w ater out of the pipe, providing separation between the concrete and the ground water. Lift the full pipe one pipe diameter to start the flow and seal the discharge end of the pipe in concrete. Do not raise the pipe until it is immersed at least 1.5 m (5 ft ) in concrete. Keep the discharge end of the pipe in a minimum of 1.5 m (5 ft) of concrete at all times after starting the flow of concrete. Maintain a continuous flow of concrete and keep the level of the concrete in the pipe above the level of slurry or water in the shaft at all times to prevent water or slurry intrusion into the shaft concrete. Concrete placement shall be continuous from the bottom elevation to the top of the shaft, and shall continue after the shaft excavation is filled until quality c oncrete is evident at the top of the shaft. Do not begin underwater or under -slurry concrete placement until the pipe is placed to the shaft base elevation. Keep the concrete completely separated from the water or slurry prior to the time it is discharged. Pump debris, mud, water , and contaminated concrete forced up during concrete placement directly into a truck for disposal unless alternate methods are approved. When Class D concrete is specified and casing is utilized, vibrate the concrete d uring withdrawal of the last 4.5 m (15 ft) of the casing. Do not vibrate Class S concrete. Keep the vibrator below the bottom of the casing during removal. Where steel casings have been used to support the excavation walls, withdraw the casing as the concrete is being placed within the limits previously specified in Subsection 509.03.08. Remove the steel liner in a manner so that the lower edge of the steel liner always remains a minimum of 1.5 m (5 ft) bel ow the surface of the concrete being placed to prevent water or soil from entering the shaft excavation from below the bottom of the casing. Submit for approval, appropriate procedures and methods of withdrawal of steel liners to ensure that the concrete i s not being lifted or contaminated as the steel liner is being withdrawn. Before placing any fresh concrete at a cold joint or construction joint , remove all scum, laitance, loose gravel, and sediment from the surface of the concrete . Cure the top surfac e of the shaft as prescribed in Subsection 501.03.0 8. If at any time during the concrete pour the pipe orifice is removed from the fluid concrete column and/or discharges concrete above the rising concrete level, the shaft, as determined by the Engineer, will be considered defective. All costs of testing, mitigation , and/or replacement of defective shafts shall be at no cost to the Department.
509.03.1 3 Inspection Report. Provide any assistance that may be required for the Engineer to prepare and
submit d aily reports for the complete drilled shaft construction program. The reports will include: logging all excavated soils, concrete quantities and rate of delivery, description of tools and drill rigs used and any changes necessitated by changing ground cond itions, recording actual elevations at top and bottom of each drilled shaft, elevation of rock (if any), plumbness of casing and rebar cages, seepage of water, elevation of top and bottom of any casing left in place, any unusual conditions, and any other p ertinent information deemed necessary.
509.03.1 4 Integrity Testing. All completed drilled shafts may be tested with a nondestructive testing (NDT)
method called Crosshole Sonic Logging (CSL) or other approved method. Testing will be performed by an approved independent testing organization under a separate co ntract with the Department. For the purposes of the above tests, install integrity testing tubes to permit access for the test probes. The tubes shall have an inside diameter of 50 mm (2 in.) ± 6 mm (1/4 in.) and shall be Grade B Schedule 40 steel pipe conforming to ASTM A53. The tubes shall have a round , regular inside diameter free of defects or obstructions, including obstructions at any pipe joints, in order to permit the free, unobstructed passage of 35 mm (1.375 in.) diameter test probes. 509 DRILLED SHAFT FOUNDATIONS 310 The tubes shall be watertight, free from corrosion with clean internal and external faces to insure goo d bond between the concrete and the tubes. Fit the tubes with a watertight cap on the bottom and a removable watertight cap on the top. Securely attach the tubes at equal spacings along the interior circumference of the reinforcement cage of each drilled shaft or as shown in the plans. Install tubes at least 0.9 m (3 ft) above the shaft top to within 25 mm (1 in.) of the actual drilled shaft tip elevation. Take care to prevent damaging the tubes during reinforcement cage installation operations in the dril led shaft excavation. Fill the tubes with potable water, verify the tubes are water tight, and cap the tube top s prior to concrete placement. Check within 6 to 12 hours to verify water remains above the level of the poured concrete and top off water as nee ded. Refer to Section 722 for water requirements. Testing will be p erform ed after concrete has cured between 4 days and 8 days. Additional curing time prior to testing may be required if the shaft concrete contains admixtures, such as set retarding admixt ure or water reducing admixture. Results of the testing will be given within 7 days after testing is completed. If the inspection equipment cannot pass through the full length of the inspection tube or a tube is determined to be defective and unable to be used for testing purposes, core a 50 mm (2 in.) diameter hole through the concrete for the full length of the pile (or as directed for testing ) to replace the defective tube at own expense. Unless otherwise directed, place the inspection core holes approx imately 150 mm (6 in.) inside the reinforcing cage, as near as possible to the impassable access tube, without damaging the reinforcing cage. If any shaft is determined to be unacceptable, submit calculations on the structural condition of the shaft, as w ell as a plan for remedial action for approval. Furnish satisfactory materials and work necessary, including engineering analysis and redesign, to mitigate shaft defects at no cost to the Department. Any modifications to the dimensions of the drilled shaft s shown on the contract plans caused by remedial action will require calculations and working drawings stamped by a Registered Professional Engineer licensed to practice in the State of Nevada. Drill a core hole in any shaft of questionable quality (as det ermined from the test results or by observation to explore the shaft condition. Use a coring method that provides complete core recovery and minimizes abrasion and erosion of the core (i.e., double or triple core barrels). If a defect is confirmed, the Con tractor shall pay for all coring costs, regardless of whether mitigation is performed, or if the shaft is accepted. Provide downhole video upon request, to ascertain the condition of the shaft interior, and any defects present. If no defect is encountered, the State will pay for all coring costs, and compensation for the delay will be granted by an appropriate time extension and payment. All delays between the time a shaft is rejected and shaft remediation resulting in shaft acceptance are at the Contractor ’s expense. After completion of the testing and acceptance of the shaft foundation, cut off the testing tubes flush with the top of the shaft foundation. Fill testing tubes and core holes with grout consisting of 0.45 maximum water/cement ratio. Provide m ixing and pumping equipment that can fill the tubes and core holes from the bottom up.
509.03.1 5 Scheduling and Restrictions. After the first drilled shaft has been successfully constructed, make
no significant change in construction methods, equipment, or materials to be used in the construction of such shafts unless approved. The first drilled shaft in each pile group at pie rs and abutments must be approved before proceeding with concrete placement in remaining shafts. Do not place reinforcing steel or concrete above designated shaft construction joints until the testing of the lower portion of the shaft has been completed, test results obtained, and the lower portion of the shaft has been approved. For a period of at least 24 hours after drilled shaft concrete has been placed, do not excavate adjacent shafts, do not place excessive wheel loads, and do not allow vibration to occur or be felt at any point within 3 m (10 ft) or 3 times the shaft diamete r, whichever is greater, from the periphery of the drilled shaft. Failure to satisfactorily perform the procedures described above may result in shut down of the construction operation and/or rejection of the drilled shaft. If the integrity of the drille d shaft is in question, employ core drilling, CSL, or other approved methods as directed. Backfill core -drilled holes with grout. Submit a remediation plan and perform remedial measures as approved or as directed. No compensation will be made for costs, lo sses or damages due to remedial work or any testing required on drilled shafts due to not meeting the requirements. Do not cast pile caps or the footings of pier columns on the drilled shafts until at least 7 days have elapsed, or 80% of the compressive s trength is obtained. DRILLED SHAFT FOUNDATIONS 509 311 509.03.1 6 Load Testing. When the contract documents include load testing of shafts, complete all load tests before construction of any production drilled shafts. Allow 5 working days after the last load test for the analysis of the loa d test data and final determination of base elevations, by the Engineer, before receiving authorization to proceed with the construction of production shafts. The number and locations of load tests will be as shown on the plans or as designated. Provide n otification 10 days before conducting load tests.
a.Static Load Testing. Do not begin static load testing until the concrete has attained a compressive strength of 23.4 MPa (3,400 psi) as determined from cylinder breaks. Drilled shafts shall be load tes ted in the order as directed. Perform static load tests in compliance with ASTM D1143 for axial load testing, and ASTM D3966 for lateral load testing. Supply all equipment necessary to conduct the static test, including equipment to measure loads and defle ctions as shown on the plans. Design the loading frame apparatus to safely accommodate the maximum load to be applied. Unless specified otherwise, load the test shafts to a maximum test load corresponding to failure. Failure is defined as a deflection of t he shaft head equal to 5% of the shaft diameter. Load cells will be required to measure applied load during the drilled shaft load tests. Provide load cells of adequate size to measure the maximum load applied to the shaft and equip with an adequate reado ut device. Before load testing begins, furnish a certificate of calibration for the load cell from an NDOT approved testing laboratory . The calibration shall have been completed for all ranges of proposed loading within the 6 months preceding the load test s. The certified accuracy of the load cell shall be within one percent of the true load. After testing is completed, cut off the non production test shafts (and any reaction shafts) at an elevation 0.6 m (2 ft) below the finished ground surface. Remove an d dispose the portion of the shafts that were cut off.
b.Dynamic Load Testing. Testing requirements will be specified in the Special Provisions.
c.Load Cell Testing. Testing requirements will be specified in the Special Provisions. METHOD OF MEASURE MENT
509.04.01 Measurement. Drilled shafts will be measured by the linear meter (linear foot), measured from the
top of shaft elevation to the bottom of shaft elevation. Exploration (Shaft Excavation) will be measured by the linear meter (linear foot), measured for the length explored. Static, dynamic, and load cell t ests will be measured by the each. If Portland cement concrete is placed and is shown by tests to be below the specified 28 day compressive strength, liquidated damages will be assessed as specified in Subsection 502.04.01. If allowed to remain in place, the entire quantity of concrete in each substandard shaft will be assessed liquidated damages. The unit bid price used to calculate liquidated damages will be $600.00/m3 ($460.00/yd3). BASIS OF PAYMENT
509.05.01 Payment. The accepted quantities, measured as provided above, will be paid for at the contract
price per unit of measurement for the pay items listed below that are shown in the proposal. Payment will be full compensation for the w ork prescribed in this Section. Payment will be made under: Pay Item Pay Unit Drilled Shaft Foundation (size) ................................ ................................ ................................ ......................... Linear Meter (Linear Foot) Exploration (Shaft Excavation) ................................ ................................ ................................ ......................... Linear Meter (Linear Foot) Static Load Test ................................ ................................ ................................ ................................ ................................ ................ Each Dynamic Load Test ................................ ................................ ................................ ................................ ................................ ........... Each Load Cell Test ................................ ................................ ................................ ................................ ................................ ................... Each SECTION 600 T RENCH DRAINS DE SCRIPTION 600.
01.01 General. This work consists of constructing trench drains .
M ATERIALS 600.
02.01 General. Material shall conform to the following Sections:
Portland Cement Concrete ...................................................................................................................................................... Section 501 Reinforcing Steel ..................................................................................................................................................................... Section 505 T rench drains consist of prefabricated drain sections along with concrete backfill. Use prefabricated portions of trench drains listed in the QPL and that meet the minimum requirements specified in the contract documents. B ackfill shall be Class A or Class AA concrete. T rench drains shall be rated for installation in a highway environment where snowplows and high- speed highway traffic will be present. T rench drain channels shall have minimum slope of 0. 5%, unless specified otherwise. Dimensions and depths specified are the minimum acceptable. I ncreased depths shall maintain or increase trench slope and provide positive drainage to the connecting inlet. The trench width (W) specified shall be the minimum internal width of the trench and not the grate width. Changes to the specified dimensions, or minor differences between nominal and actual dimensions will only be allowed with written approv al. F rames and grates shall be capable of withstanding H-20 load ing in accordance with AASHTO M30 6. G rates shall be bicycle safe and removable. Grates shall have a minimum open area of 50%. Removable grates shall be held in place by locking devices that are tamper resistant and provide a minimum repetitive pullout resistance of 223 kg per linear meter (150 pounds per linear foot ) of inlet grate after completion of 1000 hours of salt spray testing in accordance with ASTM B117. G rates shall fit into frames without rocking. Frames shall be secured to the surrounding concrete backfill with steel anchoring rods a minimum of 6 mm ( 1/4 in.) in diameter and a minimum of 125 mm ( 5 in.) in length. Alternatively, other methods of securing the frame to the concrete backfill or trench drain will be acceptable provided that a minimum pullout resistance of 446 kg per linear meter ( 300 pounds per linear foot ) of length of trench drain frame is assured. T rench drain systems selected shall be capable of accommodating any horizontal or vertical curves or deflections of the roadway segment they are to be constructed in. CO NSTRUCTION 600.
03.01 General. Install t rench drains according to the plans, manufacturer’s recommendations , and as
specified. S awcut existing plantmix or concrete surfaces to the required dimensions. Excavate in accordance with Section 206 to the lines and grades as shown on the plans and as directed. G rade and compact the trench bottom to provide a firm and uniform bearing throughout the entire length of the trench drain. Pr ovide the necessary facilities and equipment for lowering and properly p lacing the sections of trench drain in to the trench. La y and join the trench drain in accordance with the manufacturer’s recommendations and connect to the proposed drop inlets .
Source: Nevada Standard Specifications for Road and Bridge Construction, 2014 Edition. Pages 309–318 of 610.