516.02 Drilled Shaft Founda Tions
464 SECTION 516
516.01 Description
This work consists of constructing drilled shafts and providing and placing reinforcing steel, concrete, and procedures for integrity testing of drilled shafts including remedial actions.
516.02 Materials
A.General Use materials in accordance with the following sections: Material: Section: Structural Concrete 509 Reinforcing Steel for Structures 511
B.Concrete Provide and modify Class AA concrete as follows: Limit the maximum aggregate size to ¾ in [19 mm], Ensure that water/cement ratio is 0.44 or lower, Use a High Range Water Reducing admixture to achieve 6 in to 8 in [150 mm to 200 mm] of slump at the placement start. Ensure at least 4 in [100 mm] of slump exists at the completion of placement and casing or reinforcement alignment, Maintain the concret e temperature below 85 °F [30 °C] during placement. For concrete placed under water or slurry, use cementitious material such as slag or fly ash (not cement) to increase the minimum cementitious content 10%, and Submit optional anti -washout additives to th e Engineer for approval
C.Casings Provide smooth, clean, watertight, steel casings for exterior casings that can withstand handling, driving, driving stresses, and pressures from the concrete and surrounding earth. Provide permanent casing with the dimen sions specified by the American Pipe Institute tolerances for regular steel pipe. If only a single casing is used in a shaft, the casing is considered an exterior casing. Use steel in accordance with AASHTO M 270 Grade 36 (ASTM A 709M Grade 250), unless o therwise specified by the Contract for permanent exterior casings. Weld permanent exterior casings in accordance with Section 506, “Structural Steel.” The Department defines permanent exterior casing diameters shown on the Plan s as outside diameters. Ensure that a Registered Professional Engineer in the State of Oklahoma stamps, designs, the design and submits calculations for when the Contract require s permanent exterior casings, or if electing to provide a permanent exterior c asing. Submit permanent casings and design calculations to the Engineer. Provide casing thicknesses not less than shown in Table 516:1. DRILLED SHAFT FOUNDATIONS 516.04 465 Table 516:1 Minimum Permanent Exterior Casing Wall Thickness Diameter Minimum Wall Thickness <48" [<1220 mm] 0.375" [10 mm] 48" - 78" [1220 --1980 mm] 0.500" [13 mm] > 78" [1980 mm] 0.625" [16 mm] Use round corrugated galvanized steel pipe for permanent interior casings with 2 -2/3 in x ½ in [68 mm x 13 mm], 3 in × 1 in [75 mm × 25 mm] or 5 in x 1 in [125 x 25 mm] corrugations except for drilled shaft diameters 30” [76.2 cm] and less use 2 -2/3 in x ½ in [68 mm x 13 mm] corrugations. Use permanent interior casings in in accordance with ASTM A760 in accordance with AASHTO M 36, for permanent interior casings. Ensure the pipe gauge stays round and can withstand the required concrete pressure. Reject p ermanent casings that do not maintain a round shape as determined by the Engineer.
516.03 Equipment — Vacant
516.04 Construction Methods
A.Plan for Drilled Shaft Installation Use personnel experienced in constructing drilled shafts. Submit an installation plan or work plan that includes the following details before constructing drilled shafts: List of personnel experienced in constructing drilled shafts including resumes of project experiences and documentation that verifies the information; Concrete mix design including results of concrete trial mix and tests for slump loss over time. Include procedures for introducing admixtures during mixing operations including set retarders; List of proposed equipment to be used, including cranes, drills , augers, bailing buckets, final cleaning equipment, slurry pumps, core sampling equipment, tremies, and concrete pumps; List types of casings to be used by the Contractor in accordance with Subsection 516.02.C, “Casings.” Include diameters and thicknesses for all permanent, temporary, and surface casings; Details of shaft excavation methods and procedures for maintaining horizontal and vertical alignment of the excavation; When the slurry method is used, include de tails of the methods to mix, circulate, desand, and dispose of the slurry; Details of methods to clean the shaft excavation, and use or disposal of the excavated materials; Placement of reinforcing steel including support and centering methods required to minimize lateral movement of the steel cage including bolsters and the type of spacers: plastic rollers, concrete rollers, or sleds (when permitted). Provide any required material documentation for bolsters and spacers;
516.04 Drilled Shaft Foundations
466 Concrete placement, including pro posed operational procedures for tremie and pumping methods. Include procedure that will be used to verify the outlet end is at least 10 ft (3 m) into the fluid concrete ; and Type and/or method of shaft inspection device including camera specifications, f ormat of video for device (mov/avi), and method of delivery (DVD/flash drive). Revise and resubmit the installation plan if it does not produce Contract required results. Submit requests for changing the top of shaft elevations with the installation plan.
B.Trial Drilled Shafts Construct trial drilled shafts if required by Contract adjacent to the permanent shafts before constructing the permanent drilled shafts u nless otherwise approved. Show that the methods and equipment can construct the Contract req uired drilled shafts. Include reinforcemen t and CSL tubes consistent with for the most heavily reinforced drilled shafts as noted on the Plans. Construct the trial shaft to the size and tip elevation of the deepest shaft shown on the Plans. To monitor ex cavation stability and groundwater seepage, leave completed excavation open for at least 4 hr before concreting. Clean the excavation and fill the hole completely with mix design concrete. Remove the concrete 2 ft [0.6 m] below the finished grade. If the Engineer determines that trial drilled shaft is unsatisfactory, modify and resubmit the installation plan and drill a new trial shaft. The Engineer will not allow changes to the installation plan without resubmission.
C.Drilled Shafts
1.Hole Excavat ion Excavate holes in accordance with the installation plan. Before drilling, excavate for structure footings supported on drilled shafts and construct embankments and fills. Place the drilled shaft horizontally at the top of the shaft elevation within 3 in [75 mm] of the position shown on the Plans. Ensure the vertical shaft alignment does not vary by more than 1 percent of shaft depth. Use excavation equipment and methods that provide a shaft bottom normal to the axis of the shaft within 5 percent of the shaft diameter. Measurement of the shaft bottom tolerance will be left to the discretion of the Engineer. Use excavation equipment that provides a drilled shaft diameter larger than or equal to the plan diameter minus 1 in [25 mm]. Excavate below the elevation shown on the Plans if the load bearing material does not satisfy Plan requirements. Notify the Engineer immediately of deviations in subsurface conditions that may change the shaft depth or result in a reduced capacity for the bearing area. When excavated material is substantially different than soundings show on the plans as determined by the Engineer, take soil samples or rock cores consistent with soundings shown in the Plans to determine the character of the material directly below the sha ft excavation. Extend rock core samples at least two shaft diameters, or as specified by the Engineer, below the drilled shaft plan elevation logging the type of DRILLED SHAFT FOUNDATIONS 516.04 467 material and rock quality. Use a geotechnical engineer approved by the Bridge Division to mo nitor and document observations. Check dimensions and alignment of shaft excavations in the presence of the Engineer. The Engineer will measure final shaft depth after final cleaning. If the sidewall of the hole softens due to excavation methods, swells due to delays in concreting, or degrades due to slurry cake buildup, over -ream the sidewall from ½ in to 3 in [12 mm to 75 mm] to sound material. When a shaft constructed using the mineral slurry technique sets more than 4 hours without agitation, ream th e shaft to remove the cake build up. Clean the hole immediately before placing concrete so 50 percent of each hole bottom has less than ½ in [12 mm] of sediment. Ensure the remaining 50 percent of the hole has no greater than 1½ in [38 mm] of sediment or debris. For dry holes, reduce the water depth to 6 in [150 mm] or less before placing concrete. Verify that the hole bottom of every drilled shaft wet or dry has been adequately cleaned. When the bottom of the hole is under water, use an inspection devi ce with a watertight chamber. Fit chamber with depth gages to determine the thickness of the debris on the shaft bottom. Fill chamber with air, nitrogen gas, or other means to pump out water of the interior of the chamber such that the bottom of the shaft is visible. Do a minimum of five (5) drops with the inspection device as follows: north, south, east, west, and center as directed by the Engineer. The number of drops may be increased for diameters larger than 8 ft [2.4 m], and the number of drops may be decreased for diameters less than 4 ft [1.2 m] as directed by the Engineer. Operate the camera and supporting equipment under t he direction of the Engineer to obtain best, largest clarity from the equipment. Use television cameras and lighting equipmen t capable of operating in dry or submerged conditions encountered during the inspection. Record the observations for the shaft bottom on a DVD or flash drive in .mov, .avi or other acceptable electronic format specified by the Engineer to become the prope rty of the Department upon completion of the project. Store DVD’s or flash drives in proper containers with dust tight closures. Label DVD’s or flash drives as to shaft number, project number, job piece, contract number, and contractor name. Furnish DVD ’s or flash drives to the Engineer upon completion of the inspection. Continue cleaning until the Engineer is satisfied that the hole bottom is adequately cleaned and the excavation is approved. Use at least one of the following methods for excavation:
a.Dry Method Use the dry construction method at sites where the Engineer can visually inspect the shaft before concrete placement. For the dry method: Drill the shaft, Remove accumulated water, Remove loose material from the excavation, Place the reinfo rcing cage, and Concrete the shaft in dry conditions.
516.04 Drilled Shaft Foundations
468 If caving, sloughing, or swelling conditions exist or if depth of groundwater seepage exceeds 6 in [150 mm], discontinue the dry construction method and use and alternative method approved by the engine er.
b.Wet Method Use the wet construction method or a casing construction method for shafts that do not meet the requirements for dry construction. For the wet method, use water or slurry to maintain the stability of the hole while advancing the excav ation to final depth, placing the reinforcing cage, and concreting the shaft. The wet method involves the following work: De-sanding and cleaning the slurry, Final cleaning of the excavation, Placing the shaft concrete with a tremie or concrete pump begin ning at the shaft bottom, Providing temporary surface casings to aid shaft alignment and positioning, and Providing temporary surface casings to prevent sloughing of the top of the shaft excavation. Refer to Subsection 516.04.C.2, “Slurry,” for slurry requirements.
c.Casing Methods
1.General The Department will not allow casing to the bottom of the shaft. Discontinue the casing at the top of the founding stratum as shown on the Plans. Excavate below the c asing using the dry or wet method. To provide design frictional load capacity, excavate into the founding stratum to the deepest length or depth shown on the Plans. Install casing in accordance with Subsection 516.04.C.3, “Exterior Casings.” Do not use the double casing method when a rock socket is not present or if stated in the plans. With the approval of the Bridge Engineer, temporary sectional casing with a cutting shoe on the bottom acting as a core barrel ma y be used and drilled into rock.
2.Temporary Casing Method Use the temporary casing construction method if unable to use the dry or wet methods: Use the wet method to advance the excavation through caving material into an impervious formation and set the temporary casing or use a vibratory hammer to drive the casing into the impervious formation before the excavation sets up, Set the casing, and seat into rock by twisting or vibrating the casing, then complete the excavation , Place the reinforcing cage, and Concrete the shaft while removing the casing. DRILLED SHAFT FOUNDATIONS 516.04 469 If approved to use a temporary sectional casing with cutting shoes on the bottom acting as a core barrel, use the following construction method: Use a rotational method to advance the sectional casing thr ough the overburden. Equip the first sectional casing with a cutting shoe for penetration into firm soils and rock, Excavate material inside sectional casing by earth auger, Verify top of rock or foundation material with earth auger, Once top of rock is e ncountered, advance casing to shaft tip, Excavate inside casing with a rock auger and/or digging buckets, Place the reinforcing cage, and Concrete the shaft while removing the casing.
3.Permanent Casing Method Use the permanent casing construction method if shown on the Plans or where drilled shafts are in open water. For the permanent casing method, advance the excavation through caving material by driving or drilling a permanent casing to the Contract required depth or into a nearly impervious formation , whichever is deepest. Excavate to the final depth, place the reinforcing cage, and concrete the shaft. If full penetration cannot be attained during casing installation, excavate within the embedded portion of the casing. Drill a pilot hole if necessa ry. Ensure continuous casing from the top of the shaft to the elevation shown on the Plans. If the drilled shafts are in open water, extend casings from above the water elevation into the ground to protect the shaft concrete from the water during concret e placement and curing.
4.Double Casing Method Use the double casing construction method if the Contract requires or, as an alternative for the temporary casing method, in the presence of severe groundwater or unstable soil conditions. Make the temporary exterior casing larger than the Contract required shaft diameter and set a permanent interior casing into the top of the founding stratum after excavation completion. Supply the interior casing with a permanent inner diameter equal to the shaft diameter shown on the Plans. Use a temporary exterior casing with an inner diameter at least 6 in [150 mm] larger than the interior casing, but not more than 12 in [300 mm] larger. After placing the exterior casing, complete the excavation as shown on the Plans. Set the interior casing into the top of the founding stratum and brace it at the top. Remove the temporary casing after filling interior casing with concrete. Add concrete to maintain top of shaft elevation during removal. After the concrete initially s ets, do not adjust the interior casing position.
516.04 Drilled Shaft Foundations
470 (d) Obstructions The Department defines an obstruction as unexpected manmade materials through which excavation cannot advance. The Department does not consider removal of tools, lost in the excavation, o bstructions. Removal of naturally -occurring material, regardless of difficulty or removal method, is not considered an obstruction. Remove obstructions encountered during excavation. Notify the Engineer, in advance, of the proposed obstruction removal me thod. Include a cost estimate for excess costs in accordance with Subsection 104.03, “Differing Site Conditions, ” for obstruction removal compensation. Use blasting methods if approved by the Engineer.
2.Slurry Hydrate the slurry by premixing the material with fresh water in accordance with the slurry manufacturer’s instructions before introducing it into the shaft. Provide slurry tanks with the capacity for slurry circulation, storage, and treatment. The Depar tment will not allow the use of excavated slurry pits. Use either mineral (bentonite or attapulgite) or polymer slurry. Provide de -sanding equipment to limit slurry sand content at any point in the bore hole. Ensure slurry sand content is less than 4 percent by volume for mineral slurry, and less than 1 percent for polymer slurry. The Engineer does not require de -sanding to set temporary casings. Maintain a slurry surface in the shaft during drilling at least 5 ft [1.5 m] above the highest expected water table elevation or piezometric head and at a level that prevents the hole from caving. Stop drilling when there is a sudden loss of slurry from the hole and take corrective action to prevent slurry loss. Prevent the slurry from “setting up” in the shaft. If the slurry construction method does not produce the Contract required results, stop and use an alternative method approved by the Engineer. Allow at least 30 min for polymer slurry to stand undisturbed when the excavation reaches the elevation shown o n the Plans and clean. Clean the excavation base with a submersible pump or air lift. Maintain the density, viscosity, and pH of the slurry during shaft excavation in accordance with Table 516:2 for mineral slurry and Table 516:3 for polymer slurry. DRILLED SHAFT FOUNDATIONS 516.04 471 Table 516:2 Acceptable Range of Mineral Slurry Property, Method At the Time of Slurry Introduction In Hole at Time of Concreting Density, a Density Balance 64.3 – 69.1 64.3 – 75.0 (lb/ft³ [kg/m³]) [1,030 – 1,107] [1,030 – 1,200] Viscosity, Marsh Cone 28 – 45 [30 – 48] 28 – 45 [30 – 48] |(s/qt [s/L]) pH, pH paper or meter 8 – 11 8 – 11 Note: Perform tests when slurry temperatures are above 40 °F [4 °C]. a Density values are for fresh water. Increase density values 2.0 lb/ft³ [32 kg/m³] for salt water. Table 516:3 Acceptable Range of Polymer Slurry Property, Method At the Time of Slurry Introduction In Hole at Time of Concreting Density, a Density Balance 62.4 – 63.0 62.4 – 63.5 (lb/ft³ [kg/m³]) [1,000 – 1,010] [1,000 – 1,017] Viscosity, Marsh Cone 30 – 40 [32 – 42] 30 – 40 [32 – 42] (s/qt [s/L]) pH, pH paper or meter 9 – 11 9 – 11 Note: Perform tests when slurry temperatures are above 40 °F [4 °C]. a Density values are for fresh water. Increase density values 2.0 lb/ft³ [32 kg/m³] for salt water. Take slurry samples using an Engineer approved sampling tool. Extract slurry samples from the base of the shaft and from 10 ft [3 m] above the shaft base. Perform four sets of tests during the first 8 hr of slurry use. When the results are acceptable and consistent, perform one test set for every 4 hr of slurry use. Make corrections if the test results reveal unacceptable slurry samples. Place concrete when the re sampling and retesting shows acceptable values. Provide test reports to the Engineer, signed by an authorized representative, after completion of each drilled shaft. Dispose of slurry at approved locations.
3.Exterior Casings Ensure casings produce a po sitive seal that prevents water or other material from piping into or out of the hole. If substituting a casing with a longer or larger diameter casing through caving soils, stabilize the excavation with slurry or backfill before installing the new casing .
516.04 Dril Led Shaft Foundations
472 Consider subsurface exterior casings as temporary unless designated in the Contract as permanent casing. Remove temporary casing before completing placement of concrete in cased drilled shaft. While removing casing from the hole, maintain at least 5 ft [1.5 m] of fresh concrete in the casing above the surrounding level of water or slurry. Ensure the excess concrete within the casing displaces fluid trapped behind the casing upward and discharges it at the ground surface without contaminating or displac ing the shaft concrete. The Department defines defects in the drilled shaft as temporary casings that are bound or fouled during shaft construction and cannot be practically removed, as determined by the Engineer. Extend casings above the surface to keep t he excavation clean through concrete placement. Cut the casing off of permanent casings at the elevation shown on the Plans and leave in place after concrete placement.
4.Reinforcing Steel Cages for Drilled Shafts
a.General Support the reinforcing ste el off the ground when tying the drilled shaft cage. Protect epoxy coated reinforcing steel from exposure to the sun and ensure that the surface of the bars is free of excessive rust, soil, oil, and as specified in subsection 511.04.A.(2) “Epoxy Coated Reinforcing .” Place the reinforcing steel cage as a unit only after the shaft excavation is approved by the Engineer and before concrete placement. Tie reinforcing steel lap splices together using wire. Tie and sup port the reinforcing steel to keep it within the Contract required tolerances. Tie spacing devices at least at fifth points around the cage perimeter or one per 12 in [300 mm] of shaft diameter. Space them at intervals no greater than 10 ft [3 m] along t he length of the cage. Place spacers within 18 in [450 mm] of the top and bottom of the shaft. Use spacers that equal the shaft concrete in quality and durability. Concrete sleds are acceptable instead of the rollers but only when permanent casing is us ed down to the rock line. Alternate reinforced or non -reinforced virgin plastic spacers may be used provided the plastic spacers meet the following requirements: Use spacers of adequate strength to withstand a 300 lb [1,335 N] concentrated load without permanent deformation or breakage, Limit deformation under a 300 lb [1,335 N] load to a maxi mum of 5% of the support height, Use spacers able to meet the concentrated load requirements within a working temperature range of 20 to 150°F [ -7 to 65°C], and have a maximum water absorption rate of 0.5%, as per ASTM D 570 , and Provide reinforced or non -reinforced virgin plastic when tested in accordance with ASTM D695 having a compressive strength greater 4,000 psi [27.6MPa] at 1% deformation based on a 2"x2"x 2" [50x50x50 mm] cubic test specimen. Protect plastic spacers from exposure to sunlight until placed in the reinforcing steel cage. Remove and replace any broken, cracked, or damaged spacers. DRILLED SHAFT FOUNDATIONS 516.04 473 Temporarily strengthen the reinforcing steel cage to resist the lifting forces when the cage is lifted from a horizontal position to a vertical position. Use multiple pick -up points, strongbacks, slings or other means to support the reinforcing cage while it is being lifted. If there is evidence of excessive bending of the steel cage and/or if slippage of the spiral or tie bars occurs, repair or replace the reinforcing steel cage as needed, including CSL tubes. Provide positive support from the top for t he reinforcing steel cage during concrete placement. Support the cage concentrically to prevent racking and distortion. Maintain the top of the reinforcing steel cage no greater than 6 in [150 mm] above and no greater than 3 in [75 mm] below the Contract required position. Make corrections if the reinforcing steel cage is not maintained in that position. Do not construct additional shafts until the method of reinforcing steel cage support has been approved by the Engineer. Support the bottom of the reinforcing steel cage using footing attachments consisting of concrete, mortar, or plastic bolsters as approved by the Engineer. Use bolsters capable of supporting a 1,000 pound [4,450 N] load without breakage. Do not use bolsters which will extend abov e the bottom of the reinforcing steel as it may interfere with the CSL testing. Provide additional reinforcing steel if conditions require shafts longer than shown on the Plans.
a.Access Tubes for Crosshole Sonic Logging Include CSL access tubes in the c onstruction of each drilled shaft when the Contract requires Crosshole Sonic Logging (i.e. CSL testing) to be performed. Use access tubes with 2 in [50 mm] inner diameters that are made of schedule 40 steel pipe. Provide tubes, including pipe joints, wit h a round regular internal diameter that allows a 1.3 in [33 mm] diameter source and receiver probes to pass unobstructed. Make the tubes and joints watertight and corrosion free, with clean surfaces that allow a good bond between the concrete and the tub es. Install access tubes to the full depth of each shaft for CSL testing equipment. Unless otherwise required by the Contract, install the number of access tubes in each drill shaft in accordance with Table 516:4. Table 516:4 Minimum Number of Access T ubes per Drilled Shaft Planned Shaft Diameter, ft [m] Minimum Number of Access Tubes D≤3.0 [D≤0.9] 3 3.0 < D ≤ 4.0 [9.0 < D ≤ 1.2] 4 4.0 < D ≤ 5.0 [1.2 < D ≤ 1.5] 5 5.0 < D ≤ 6.0 [1.5 < D ≤ 1.8] 6 6.0 < D ≤ 8.0 [1.8 < D ≤ 2.4] 7 8.0 < D ≤ 10.0 [2.4 < D ≤ 3.0] 8 10.0 < D ≤ 12.0 [3.0 < D ≤ 3.7] 9 Fit tubes with a watertight shoe on the bottom and a removable cap on the top. Attach the tubes to the interior of the reinforcement cage in a regular, symmetric pattern, equally spaced
516.04 Drilled Shaft Foundations
474 around the perimeter of the cage. Install the tubes parallel to each other and vertical. Start the tubes from the shaft bottom and end at least 3 ft [0.9 m] above the shaft top. If the shaft top is subsurface, extend the tubes at least 3 ft [0.9 m] above the ground, water surface, or both. Ensure tubes remain equally spaced and parallel during installation operations in the drilled shaft hole. Avoid bending the CSL tubes during lifting of steel cage. Before concrete placement, fill the access tubes with clean water and ca p the tube tops. Ensure that the tubes remain full of water until CSL testing is complete. When temperatures below freezing are anticipated, protect the access tubes against freezing by wrapping the exposed tubes with insulating material, adding antifree ze to the water in the tubes, or other methods as approved by the Engineer. Remove insulation before placing column concrete. After concrete placement, avoid breaking the bond between the access tubes and the concrete.
5.Concrete Placement Inspect the hole in the presence of the Engineer and immediately before concrete placement for caving material falling from the sides or a change in the water elevation. Place drilled shaft concrete within two hours after hole excavation for the shaft bott om has been approved. Place reinforcing cage prior to concrete placement. If the concrete placement is delayed or if the hole has become contaminated, remove the cage and verify the integrity of the excavated area, and ensure loose material is removed fr om the bottom of the hole in accordance with 516.04.C(11) “Hole Excavation” before resetting the reinforcing steel cage. Complete concreting in a shaft and remove the temporary casing within 2 hr of beginning concre te placement. The Department will not allow retempering concrete that has developed an initial set. Ensure that the static water or slurry level is properly maintained in the excavation when the wet method is used and before placing concrete. Place concre te in one continuous operation from the bottom to the top of the shaft using a watertight tremie. Place concrete until acceptable quality concrete reaches the top of the shaft. For a dry shaft, overflow the top with at least 1 ft [300 mm] of concrete. F or a wet shaft, overflow the top with at least 5 ft [1.5 m] of concrete. Continue overflow of concrete in shafts until uncontaminated concrete is evident. Before initial concrete sets, consolidate the top 10 ft [3 m] of the shaft using Engineer approved vibratory equipment. Finish the top of the shaft from 3 in [75 mm] lower to 1 in [25 mm] higher than the elevation shown on the Plans. In wet holes, consolidate after removing water above the concrete surface. Place the discharge end of the watertight tr emie at one tremie diameter above the shaft base elevation. Keep the discharge end immersed at least 10 ft [3 m] below the surface of the fluid concrete except when concrete is initially placed. Maintain a positive head of concrete in the tremie during c oncrete placement. If the discharge end is removed from the fluid concrete column during the concrete placement and concrete is discharged above the rising concrete surface into displaced water, remove the reinforcing cage and concrete, complete sidewall removal as directed by the Engineer, and reconstruct the shaft. Form the shaft from the top to at least 2 ft [0.6 m] below finished ground if the top of the shaft is above ground. If the top of the shaft is below ground, use a temporary oversize surface c asing to DRILLED SHAFT FOUNDATIONS 516.04 475 control material caving into the freshly placed concrete. Cure exposed concrete surfaces in accordance with Section 509, “Structural Concrete .” Ensure that the concrete temperature does not exceed 150 °F [65 °C] during concrete placement and curing. When drilled shaft diameter exceeds 6 ft [1,830 mm], use recording thermometers, maturity meters, or other means as directed by the Engineer to monit or temperatures inside the drilled shaft. Ensure that the temperature difference between the core of the shaft and the outer edges does not exceed 36 °F [20 °C]. Reject the shaft when drilled shaft concrete temperatures exceed 150 °F [65 °C] or when the temperature difference between the core and the outer edges exceed 36 °F [20 °C] reject the shaft. Record and document the volume of concrete placed as a function of elevation and provide this information to the Engineer.
6.Tremies Use watertight tremie s to place concrete in wet or dry holes. The Department defines tremies as tubes that discharge concrete at the shaft base. Ensure the bottom of the tremie can be sealed and charged with concrete in the dry, and then opened in place at the bottom of the s haft. The Department will not allow the use of tremies containing aluminum parts that will come in contact with concrete. Ensure that the tremie can be lowered rapidly to retard or stop the flow of concrete. Mark tremie to ensure it is placed to the pro per depth before lowering tremie. Provide a tremie with an inner diameter from 10 in to 14 in [254 mm to 350 mm] with clean and smooth surfaces and a wall that prevents crimping or sharp bends. Fit the top with a hopper. Ensure the tremie joints are wate r tight. Construct the discharge end of the tremie to allow free radial concrete flow during placement. Do not pump concrete directly into the drilled shaft. Pump concrete into the watertight tremie as specified above. Pump concrete in one continuous o peration from the bottom to the top of the shaft. For wet holes, use a device at the end of the discharge tremie to seal out water while the tremie fills with concrete. If a plug is used, remove it from the hole. Use a plug of Engineer approved materia l that will prevent a defect in the shaft.
7.Concrete Acceptance The Engineer will sample concrete for acceptance at the point of discharge into the tremie or concrete pump hopper. The Department may accept drilled shafts with low concrete strengths in accordance with Subsection 105.03, “Conformity with Plans and Specifications.” In such cases the Department will use the strength reduction equation as noted in Subsection 509.06, “ Basis of Payment.”
8.Application of Construction Loads If the Contract requires Nondestructive Testing (NDT), the shaft must pass NDT before application of any loads or proceeding with the construction of the pier. If the Contract does not require NDT or the NDT passes the tests, allow concrete in the shaft to reach strengths in accordance with the requirements of 509.04 .I, "Application of Loads Including Bridge Decks and Approach Slabs."
516.04 Drilled Shaft Foundations
476 (9) Nondestructive Testing of Drilled Shafts Make the determination to conduct non -destructive testing on drilled shafts based on one or more of the following criteria: ADT > 750, ADTT > 100 ; Bridge deck area > 10,000 ft2 ; Span length > 100 ft ; Drilled shaft depth > 50 ft ; Drilled shaft diameter > 60 in ; Emergency Detour length > 20 miles ; Bridge contains three (3) or more piers ; The pier is located in greater than fifteen feet (15 ft) of water (e.g. a lake); Construction of the pr oject involves grade separation; The bridge is on the Interstate, the National Highway System (NHS), or Defense Route; The bridge is categorized as an essential or critical structure by either the owner or designer; The design of the drilled shaft(s) foundat ion is based solely on friction; The Contract re quires the drilled shaft(s) to be constructed using the slurry method, or the Contractor elects to construct the drilled s haft(s) using the slurry method; The geological formation is such that voids are present in the rock formation, water is flowing withi n the soil or rock layers, Artesian water is present, or significant layers of material are suspect to caving and sloughing (e.g. loose sand, loose gravel, etc.) ; No CSL testing will be required when the drilled shaft is used for the support of light poles , overhead sign structures, sound walls, or traffic signals.
a.General Perform CSL when requirement for non -destructive testing is specified in the Contract documents. Perform CSL when required on the first production shaft of each diameter specified in the plans. No additional shafts may be placed until: The Contractor shows that the drilled shafts can be constructed in accordance with the Contractor’s drilled shaft installation plan, and to the satisfaction of the Engineer, and A third party integrity testing consultant, provided by the Contractor and registered in the State of Oklahoma, has provided the analysis of the tests results, including their recommendation to the Engineer. If the Engineer concurs with the consultant’s recommendation for accep tance, then construction may continue on the remaining shafts using the same construction methods which were used to produce the tested shaft. Construct all subsequent shafts with CSL tubes for the purposes of additional testing. If the Engineer elects t o allow the Contractor to continue construction of the remaining drilled shafts before acceptance of the original CSL tested shaft in question, each additional shaft shall be CSL tested until the Engineer provides acceptance of the original shaft. DRILLED SHAFT FOUNDATIONS 516.04 477 Perform additional CSL testing on every sixth drilled shaft provided that all procedures are followed and repeated from the tested sh aft. The Department may require testing, at no additional cost to the Department, on any subsequent shaft not constructed in the s ame manner as the tested shaft, or where a construction incident occurs which could compromise the shaft’s integrity. If defects are discovered, but the Engineer determines that the defects are structurally adequate, the Engineer may accept the shaft in a ccordance with Subsection 105.03 of the Standard Specifications. Otherwise, repair defective shafts in accordance with Subsec tion 516.04.C(10 ), “Defective Shafts .” Except for the initial shaft, CSL testing is not required on any shaft constructed using the dry method.
b.PIT (Pile Integrity Testing - Pulse Echo) Provide Pile Integrity Testing (PIT) only when no other means of testing is readily available and when CSL tubes are not provided. When the Engineer does approve PIT testing, test in accordance with ASTM D5882 . After placing concrete in a drilled shaft, wait at least 7 days or ensure the drilled shaft concrete obtains 75% of its design strength before the start of the test. Limit PIT to drilled shafts having L/D ratio ≤ 30, where L is the length of the drilled shaft and D is the diameter of the drilled shaft. The Engineer will reject the shaft when PIT testing shows voids or discontinuities.
c.Crossho le Sonic Logging (CSL)
1.General Provide Crosshole Sonic Logging (CSL) in accordance with ASTM D6760 and as specified in the contract or as required by the Engineer. Wait at least three (3) days or four (4) days if retarders are used before starting CS L testing. Provide the Engineer notice at least 24 hours before starting the testing.
2.CSL Test Equipment Use CSL test equipment that can perform the following functions: Display individual CSL records, Record CSL data, Analyze receiver responses, Print CSL l ogs, Test in 2 in [50 mm] in side diameter (ID) access tubes, Generate an ultrasonic voltage pulse to excite the source with a synchronized triggering syste m to start the recording system, Measure and record the depths of CSL probes at the time signals are recorded, and Filter and amplify signals.
3.CSL Logging Procedures Inspect CSL tubes to ensure that probes will freely pass through the entire tube length. Replace tubes with cored holes that restrict the passage of the probes at no expense to the Department. Should the cored holes encounter any voids, poor quality concrete, or any
516.04 Drilled Shaft Foundations
478 other findings; document the finding and elevations and make this information available to the Engineer. Test all possible combinations of perimeter tube pairs and diagonal tube pairs. Perform CSL tests with the source and receiver probes in the same horizontal plane. Make CSL measurements at depth intervals of 2 in [50 mm]. Pull the probes, starting from the bottom of the tubes, over a depth -measuring device. Remove slack from the cables before pulling to provide accurate depth measurements. Report indicated defects to the Engineer and conduct further tests to evaluate the extent of the defects.
4.CSL Testing Results Include the CSL logs with analyses of the initial pulse arrival time versus depth and pulse energy (or amplitude) versus depth in the final report. Present a CSL log for each tube pair tested with significant anomalies and/or defects indic ated on the logs and discussed in the test report. Unless otherwise specified by the Engineer, accept test results in accordance with Table 516:5 “Acceptance of Drilled Shafts .” Include the following in the report: A summary of the test results, Drilled shaft identification, Test date, Shaft age at time of CSL testing, Drilled shaft diameter, Number of CSL tubes tested, Degree off of North for the CSL tube No. 1, Test length, Average compression velocity for each tube combination and for each shaft, The equation used to compute velocity reductions and a statement that a running average of velocities was used as the baseline velocity, and “Waterfall” diagram plotted as a function of time versus depth Include the followin g items for any significant anomalies and/or defect descriptions in the report: The CSL tube number or tube combinations, Depth below concrete top, Peak concrete wave velocity reduction (%), Depth range corresponding to the velocity reduction, and Desc ription of anomalies and/or defects. The Engineer will evaluate the CSL test results and determine the acceptability of the drilled shaft construction in accordance with Table 516:5, “Acceptance of Drilled Shafts.” DRILLED SHAFT FOUNDATIONS 516.04 479 Table 516:5 Acceptance of Drilled Shafts Concrete Condition Rating Rating Symbol Velocity Reduction Results Good G 0 to 10% Acceptable Concrete Questionable Q 10 to ≤ 20% Minor Concrete Contamination Poor P/D >20% Unacceptable Water W V=4760 to 5005 ft/sec Water or water with gravel, Unacceptable [1,450 to 1,525 m/sec] No Signal NS *Soil intrusion or tube debonding * Additional testing is required to determine cause for no signal, soil intrusion into the drilled shaft is unacceptable, debonding leads to false readings . The percent velocity reduction (VR) based on measured tube spacing is determined using the following equation: VR = (1 - V / Vb) x 100% where, V = theoretical compressional wave velocity in concrete Vb > 12,500 ft/sec [3 ,810 m/sec] baseline velocity (running average of velocity over a 10 ft [3 m] depth, generally 5 ft [1.5 m] above and 5 ft [1.5 m] below excluding anomalous zones in the running average) (Reference: Publication No. FHWA -NHI-10-016, equation 20 -4)
5.Aband oning CSL Access Tubes Dewater the tubes and use portland cement grout to fill the access tubes in the drilled shafts after completing CSL testing and obtaining the Engineer’s approval to continue construction above the shafts. Submit the grout mix design and grouting method for the Engineer’s approval. Saw cut the top of the CSL tubes even with the top of the drilled shaft.
d.Core Drilling of Drilled Shaft Concrete If nondestructive testing reveals voids or discontinuities, or if there are other concerns about a drilled shaft, the Engineer may require full or partial depth coring to determine the soundness of a drilled shaft concrete using continuous coring with a 4" [100 mm] interior diameter core b arrel in accordance with ASTM D2113. The Engineer will specify the number, depth, and location of cores. To ensure that cored holes do not damage the reinforcing steel cage, locate cored holes approximately 6" [150 mm] inside the cage.
516.04 Drilled Shaft Foundations
480 Submit the metho ds and equipment for coring and grouting to the Engineer for approval before coring. Place the cores in a commercially available core box and mark the shaft depth at each core recovery interval. Extend coring to the full shaft length plus 1 ft [0.3 m] in to the foundation material below the bottom of the drilled shaft. Submit the cores and a data log for the recovered cores. Include depth in the coring log documenting actual depth drilled and not just the recovered core sample as void sections may be prese nt. Document the findings and elevations and make this information available to the Engineer. When the Engineer determines that the quality of the concrete in the shaft, represented by the core samples, is acceptable, construction may proceed. Reject the drilled shaft if the quality of the concrete taken from the core is unacceptable.
10.Defective Shafts If the Engineer determines a drilled shaft to be potentially defective based on CSL test results, construction inspection records, and/or structural evaluation, the Contractor may do additional testing and/or investigations. Additional testing may include, but is not limited to crosshole tomography imaging using vertically offset crosshole sonic measurements and recordings to evaluate the extent of a nomalous zones, gamma -gamma testing to evaluate differences in relative density surrounding suspected tube debonding, secondary CSL testing 3 days to 10 days after the initial test to investigate for improved concrete condition due to delayed curing, or co ntinuous coring of the drilled shaft. All test procedures must be accepted and approved by the Engineer. Regardless of the test results, all additional integrity testing will be done at the Contractor’s expense and in accordance with the procedure noted a bove. No allowance for an increase in contract time or extension of the contract completion date will be made. Submit a plan for further investigation or remedial action to the Engineer for approval. Provide written procedures or drawings as appropria te to the Engineer for approval showing any modifications to shaft dimensions, plans for remedial actions of the shafts, or proposed testing. When the anomalous zone is near the surface, repair plan may show the mechanical removal and replacement of the c oncrete. Straddle shafts must be designed by a Professional Engineer registered in Oklahoma and reviewed by the Bridge Engineer. Provide qualifications for subcontractors doing mitigation procedures such as pressure grouting, micro piles, perimeter grout ing, or other procedures. At a minimum, provide the following for grouting mitigation: any proposed cutting of high pressure inspection tubes, high pressure washing, water flow testing, flushing (high volume, low pressure washing), down -hole camera observ ations, grouting procedures, conformance testing, and required documentation. Once the plan has been reviewed and approved by the Engineer, proceed with the remedial action or testing as directed by the Engineer. The Engineer will make the determination of final shaft acceptance or rejection based on initial and supplemental integrity testing results or repairs done by the Contractor. The Engineer will provide a determination of acceptance of any remedial action proposed by the Contractor. The Engineer m ay require the complete replacement of the shaft, addition of straddle shafts to compensate for capacity loss, or additional integrity testing including coring. Any remedial action necessary will be done at the Contractor's expense. DRILLED SHAFT FOUNDATIONS 516.06 481 516.05 METHOD OF MEASUR EMENT The Engineer will measure the length of Drilled Shafts and Trial Drilled Shafts from the shaft base to the top of shaft. The Engineer will base measurements on elevations shown on the Plans or approved by the Engineer. The Engineer will not measure corrective work or miscellaneous items, such as, soil samples and rock cores required by the Contract, rebar splices, permanent casings, lost tools and equipment, overreamed excavation, surface excavation and backfill, overflow concrete and concrete place d outside the neat lines of the shaft. If required by the Contract, the Engineer will measure CSL testing per drilled shaft tested. The Engineer will not measure tests for determining the extent of defects. The Engineer will not make reductions in drill ed shaft measurements due to obstructions.
516.06 Basis of Payment
The Department will pay for each pay item at the contract unit price per the specified pay unit as follows: Pay Item: Pay Unit:
A.DRILLED SHAFTS Linear Foot [Meter]
B.TRIAL DRILLED SHAFTS Linear Foot [Meter]
C.CROSSHOLE SONIC LOGGING Each
E.OBSTRUCTIONS Lump Sum
F.CORE DRILLING Linear Foot [Meter] The Department will pay for the following under a Supplemental Agreement: Approved obstruction removal, Additional nondestructive testing or core drilling required by the Engineer that reveals no structural defects, Contractor soil sampling or rock coring directed by the Engineer, that reveals no structural defects, and Additional geotechnical testing when requested by the Department due to encountering material differing from the boring logs in the Plans. The Department will not pay for the following: Nondestructive testing or core drilling directed by the Engineer that reveals structural defects, Additional NDT testing or core drilling requested by the Contractor done after a shaft has been rejected regardless of the results, CSL tubes (all costs for CSL tubes will be included in price bid for drilled shafts), and Shaft inspection devices used to i nspect the shaft bottom.
517.01 Post -Tensioning
482 SECTION 517 POST -TENSIONING
517.01 Description
A.General Post -tensioning work consists of stressing concrete by furnishing, placing, and tensioning of post -tensioning steel in accordance wi th details shown in the contract documents and as specified in these specifications. This work consists of providing and installing any appurtenant items necessary for the particular stressing system to be used, including but not limited to ducts, anchor age assemblies and grout used for pressure grouting ducts.
B.Definitions Anchorage assembly. An assembly of various hardware components that secures the end of a tendon after stressing, transferring the tendon force into the concrete. Anticipated set. The wedge set in the design calculation of post -tensioning forces at the time of load transfer. Bar. Coarsely threaded, high strength steel bars, from ⅝ in to 1¾ in [15 mm to 46 mm] in diameter. Bearing plate. Transfers the tendon force directly into a struct ure or the ground. Bleed. Excess flow of water in or out of new grout. Coupler. Transfers the prestressing force between partial length post -tensioning tendons. Duct. Conduit that accommodates post -tensioning steel and provides a space for the grout that protects the steel. Family of systems. Groups of post -tensioning tendon assemblies that use common anchorage devices and design. Fluidity. Measure of time in seconds for a quantity of grout to pass through a flow cone. Grout. Mixture of cementitious materi als and water (with or without mineral additives or admixtures), proportioned to a consistency that can be pumped without segregation into the duct around the post -tensioning steel. Grout cap. Contains the grout and forms a protective cover sealing the pos t-tensioning steel at the anchorage. Inlet. Tubing or duct used to inject the grout into the duct. Outlet. Tubing or duct that allows air, water, grout, and bleed water to escape from the duct. Permanent stress and permanent force. Stress and force remaini ng in the post -tensioning steel after losses induced by the post -tensioning system.
Source: Oklahoma Standard Specifications for Highway Construction, 2019 Edition. Pages 478–495 of 935.