5-53 Sectio N 503 – Drille D Shafts
503.0 1 DESCRIPTION . This work shall consist of mobilizing and furnishing all materials, equipment, labor, and services necessary to construct drilled shafts in accordance with these provisions, the Plans, Section 506 , Section 507 , Section 541 , and as directed by the Enginee r. 503.0 2 MATERIALS . Materials shall meet the requirements of the following subsections: Mortar, Type IV ................................ ................................ ................................ ......... 707.0 1(e) Bar Reinforcement ................................ ................................ ................................ .....713.01 Steel Casing for Drilled Shafts ................................ ................................ .................. 730.03 Water ................................ ................................ ................................ .......................... 745.01 Concrete shall conform to the requirements of Section 541 for Concrete, Class SCC, with the exceptions that the maximum aggregate size shall be 1/2 inch , the 56 day surface resistivity test is not required , and an anti -washout admixture shall not be used f or underwater concrete . Additionally, concrete shall have a blocking assessment of “ No Visible Blocking” during a period equal to the anticipated pour period plus 2 hours, as determined in accordance with ASTM C1621 . Temporary steel pipe piles shall be smooth walled structural steel. Centralizers for bar reinforcement shall be constructed of a non -corrosive material that is compatible with and as durable as the shaft concrete. Water shall have a pH conforming to the slurry requirements listed herein.
a.Mineral Slurry . Mineral (bentonite) slurry shall remain in suspension with sufficient viscosity and gel characteristics to transport excavated material to a suitable screening system. The slurry percentage and specific gravity used to make the suspension shall be sufficient to maintain the stability of the excavation and allow proper concrete placement. The acceptable ranges of values for mineral slurry are specified in Table 503.02A .
5-54 Table 503.02a – Range of Values for Mineral Slurry At 68ºF
Property Test Requirement Density (lb s/ft3) Mud weight (density) ( API RP 13B -1, Section 1 ) 64.3 – 72.0 1 Viscosity (sec ./quart) Marsh funnel and cup ( API RP 13B -1, Section 2.2 ) 28 – 50 pH Glass electrode, pH meter, or pH paper 8.0 – 11.0 Sand content immediately prior to placing concrete Sand content test ( API RP 13B-1, Section 5 ) 4.0% max. 1 Unit weights stated are exclusive of weighting agents that may be proposed by the Contractor with the agreement of the slurry manufacturer’s representative and the Agency. Mineral slurry shall be de -sanded so that the sand content does not exceed 4% (by volume) measured 1 foot from bottom of shaft prior to concrete placement. All referenced tests shall be conducted by the Contrac tor with results presented to the Engineer. All necessary equipment and materials shall be provided by the Contractor.
b.Polymer Slurry . Polymer slurry shall have sufficient viscosity and gel characteristics to stabilize the excavation and to transport e xcavated material to a suitable screening system. Polymer slurry (vinyl (dry) or natural polymers) shall be made from partially hydrolyzed polyacrylamide polymer (PHPA) (emulsified). The polymer slurry product shall be approved for use by the Agency. Slurry properties at the time of mixing and at the time of concreting shall be in conformance with the written recommendations of the manufacturer. The use of a blended mineral -polymer slurry is not permitted. The acceptable range s of values for polymer sl urry are specified in Table 503.02B .
5-55 Table 503.02b – Range of Values for Polymer Slurry At 68 ºF
Property Test Requirement Density (lb s/ft3) Mud weight (density) ( API RP 13B -1, Section 1 ) 64 max. 1 Viscosity (sec ./quart) Marsh funnel and cup ( API RP 13B -1, Section 2.2 ) 32 – 135 pH Glass electrode, pH meter or pH paper 8.0 – 11.5 Sand content immediately prior to placing concrete Sand content test (API RP 13B-1, Section 5 ) 1.0% max. 1 Unit weights stated are exclusive of weighting agents that may be proposed by the Contractor with the agreement of the slurry manufacturer’s representative and the Agency. Polymer slurry shall be de -sanded so that the sand content is less than 1% (by volume) prior to concrete placement. All referenced tests shall be conducted by the Contractor with results presented to the Engineer. All necessary equipment and materials shall be provided by the Contractor. 503.0 3 PREQUALIFICATION .
a.Drilled Shaft Contractor . The Contractor shall submit proof and det ails of the following:
1.Three projects in the past five years where the Contractor or subcontractor performing the work has successfully installed drilled shafts of similar diameter, length, and difficulty as shown on the Plans, and a minimum of one project requiring similar on -site topographical and geotechnical conditions to those described in the Plans.
2.The on -site superintendent shall have a minimum of two years of experience in supervising construction of drilled shaft foundations of similar size (diameter and depth) and difficulty to those shown on the Plans, and in similar geotechnical conditions to those described in the Contract. The work experience shall be direct supervisory responsibility for the on -site drilled shaft construction opera tions. Project management level positions indirectly supervising on -site drilled shaft construction operations will not be considered acceptable for this experience requirement.
3.The drill rig operators shall have had a minimum of one year of experience installing drilled shafts with similar diameters and lengths, and in similar conditions.
5-56 Details describing the equipment and methods used, difficulties encountered and how they were
overcome, and the results of any testing performed, shall be included. For each project cited, the name and telephone number of someone who can be contacted as a reference shall be included.
b.Drilled Shaft Integrity Testing Firm . The Contractor sh all submit the name of the drilled shaft integrity testing firm, and the names of the personnel who will conduct nondestructive QA testing and analysis of the drilled shafts. The testing firm and the testing personnel shall meet the following minimum quali fications:
1.The testing firm shall have performed nondestructive tests on a minimum of two drilled shaft projects in the last two years.
2.Personnel conducting the tests, performing the analysis, and preparing the report shall have a minimum of two ye ars of experience in drilled shaft nondestructive testing and interpretation.
3.The experience requirements for the firm and personnel shall be consistent with the testing methods the Contractor has selected for nondestructive testing of drilled shafts.
4.Personnel supervising collection of the data and preparing test reports shall be a professional engineer . The Contractor shall submit this information to the Engineer for review, evaluation, and approval prior to submitting detailed information as req uired under Subsection 503.04 . The Engineer will render a decision within 7 calendar days after receipt of the submission. The Contractor or subcontractor will not be permitted to install drilled shafts without this approval. The Engineer may suspend the d rilled shaft construction if the Contractor substitutes unapproved field personnel without prior approval by the Engineer. The Contractor shall be fully liable for the additional costs resulting from the suspension of work and no adjustments in Contract time resulting from such suspension of work will be allowed. 503.0 4 SUBMITTALS . All approvals are subject to satisfactory field performance. Approval of a submittal does not relieve the Contractor or its subcontractor of their responsibilities to satisfactorily complete the work detailed in the Contract. If the approved submittal procedures do not produce satisfactory field performance, the Contractor will be responsible for submitting revised procedures. No further drilled shaf t work will be allowed until the revised procedures have been approved.
5-57 (a) Drilled Shaft Installation Plan . The Contractor shall s ubmit a drilled shaft installation plan that
documents the proposed procedures and equipment for installing drilled shafts. The submittal shall include, but not be limited to, the following information:
1.Proposed equipment for drilled shaft installation. This shall include a narrative describing equipment suitability to the anticipated site and subsurface conditions, including a project history of the drilling equipment demonstrating the successful use of the equipment on shafts of equal or greater size in similar subsurface conditions. A list describing the type of equipment to be used, including drill rigs, cranes, drilling tools, casing installation equipment, final cleaning equipment, de -sanding equipment, slurry pumps, bailing buckets, tanks, sampling equipment, tremies or concrete pumps, and any other equipment necessary for drilled shaft installation shall also be included.
2.Drawings and details showing the proposed sequence of drilled shaft installation. The drawings shall include the sequence for each shaft, the overall construction sequence, areas that are planned to be used for staging, and detailed drawin gs of all over -water equipment for drilled shaft installation including containment measures to prevent drilling spoils from entering the water.
3.Where a casing is proposed or required, detailed procedures for permanent casing installation and temporary casing installation and removal shall be provided. This shall include casing dimensions, material, and splice details. Welding procedures shall be submitted in accordance with Subsection 506.10 for permanent casing splices.
4.Details of shaft excavation methods, including proposed drilling methods, methods for removal of sediment from the shaft bottom, and procedures for control, removal, and disposal of spoils. This shall include details of proposed methods to clean the shaft after initial excavation an d details of proposed methods to check shaft bottom cleanliness.
5.Details of the methods to be used to ensure drilled shaft hole stability (e.g. prevention of caving, bottom heave, etc., using temporary casing, slurry, or other means) during excavation and concrete placement. The details shall include a review of method suitability to the anticipated site and subsurface geotechnical conditions.
6.Details of equipment and procedures for obstruction removal, including the types of chisels and grabs.
5-58 (7) Verification methods of final shaft dimensions and verticality. Include details of proposed
corrective measures to be implemented as necessary.
8.Description of equipment and methods to be used for drilled shaft inspection. The inspection program shall be thorough enough to assure the Engineer that each drilled shaft meets the requirements of these provisions.
9.Description of equipment and method s to be used for drilled shaft integrity testing.
10.Fabrication drawings in accordance with the requirements of Subsection 105.06 for the steel reinforcement cage including bar count, bend schedule, dimensions, splices, and bracing.
11.Description of the type of feet and centralizers to be used to support the reinforcing steel cage in the drilled shaft.
12.Construction drawings in accordance with the requirements of Subsection 105.06 for the methods and sequence of steel reinforcement cage erection, the temporary support, and the equipment to be used for erection. The erection plan shall identify specific lifting points on the cage and demonstrate that all of the erection equipment has adequate capacity for the work to be performed.
13.Approved concrete mix design and the results of the blocking assessment test performed in accordance with Subsection 503.02 .
14.Details, methods, and procedures for concrete placement. This shall include concrete batching, delivery to the site, how concrete acceptance samples will be collected, quality control testing, proposed location for concrete acceptance testing, proposed operational procedures for concrete pump, initial tremie pipe insertion, raising tremie pipe during concrete placement, rein sertion of a tremie pipe if required, method to accurately monitor the volume of concrete being placed at all times during the placement, removal of waste concrete, and provisions to prepare the completed shaft top at its final shaft top elevation.
15.Method used to fill or eliminate all voids between the plan shaft diameter and excavated shaft diameter, or between the shaft casing and surrounding soil, where permanent casing is specified.
16.If slurry is used to construct the shafts, the submittal shal l include the following:
a.The name and contact information of the slurry manufacturer’s technical representative assigned to the project.
5-59 b. The names of the Contractor’s personnel assigned to the project and trained by the
slurry manufacturer’s techni cal representative in the proper use of the slurry. The submittal shall include a signed training certification letter from the slurry manufacturer for each individual, including the date of the training.
c.Detailed procedures for mixing, using, maintaini ng, and disposing of the slurry. A detailed mix design (including all additives and their specific purpose in the slurry mix), and a narrative describing its suitability to the anticipated subsurface geotechnical conditions, shall also be provided for the proposed slurry.
d.Detailed plan for quality control of the proposed slurry, including tests to be performed, test methods to be used, and minimum or maximum property requirements which must be met to ensure that the slurry functions as intended, consider ing the anticipated subsurface conditions and shaft construction methods, in accordance with the slurry manufacturer ’s recommendations and these specifications.
e.Description and details of the slurry sampling tool to be used. Tool shall be capable of tak ing a slurry sample at a specific depth, without being contaminated by slurry from another depth.
f.An alternate procedure to be used which will secure the shaft in the event of slurry loss or loss of slurry stabilization properties. The Agency will revie w the submittal for compliance with the requirements of the Contract. If the drawings or procedures have misinterpreted the Plans or specifications, the submittal will be returned as rejected. The submittal shall not be marked as approved or approved as no ted until all of the required information has been received and reviewed. Once a complete submittal has been received, the Agency shall be allowed 21 calendar days for the initial review period and 14 calendar days for the review of each subsequent resubmi ttal. The Contractor will not be permitted to install drilled shafts until the drilled shaft installation plan has been marked as approved or approved as noted by the Agency. The Contractor or fabricator shall assume all risk for materials ordered or work performed prior to written notification by the Agency. After the drilled shaft installation plan has been marke d approved or approved as noted, no changes shall be made without the written approval of the Agency.
5-60 (b) Drilled Shaft As -Built Location Data . Actual drilled shaft location data shall be submitted to the
Engineer within 1 working day after a drilled shaft is installed. The submittal shall include the following information:
1.Drilled shaft location.
2.Elevation of top of drilled shaft measured to the nearest 1/2 inch.
3.Deviation from design plan location measured to the nearest 1/4 inch.
4.Plumbness (deviation from vertical) as determined along the entire length of the shaft where required.
c.Drilled Shaft As -Built Plan . Within 10 calendar days after the completion of installation of all drilled shafts, and before removing the drilled shaft installation equipment from the site, the Contractor shall provide the Engineer with a plan showing the as -installed location of all drilled shafts installed to the tolerances specified in the Contract. 503.0 5 CONSTRUCTIO N TOLERANCES . In-place tolerances for drilled shafts shall be as follows:
a.The top of the shaft shall not vary horizontally from the location shown on the Plans by more than 3 inches for shafts supporting a single column less than 5 feet in diameter and otherwise by no more than 6 inches.
b.The allowable tolerance from the required verticality is 2% for shafts socketed in rock and 1.5% for shafts that are not socketed in rock. This tolerance applies for the total length of shaft.
c.The top of shaft elevation sha ll be within 1 inch above or 3 inches below the elevation shown in the Plans.
d.Reinforcing steel projection elevation tolerance, after all shaft concrete has been placed, is ± 2 inches from the projection elevation shown in the Plans. Drilled shaft exca vations and completed shafts not constructed within the required tolerances are unacceptable. The Contractor shall submit written correction procedures to the Engineer for approval prior to correcting the deficiencies. The Contractor is responsible for cor recting all unacceptable shaft excavations and completed shafts to the satisfaction of the Engineer at no cost to the Agency and without extension of the Contract completion date .
5-61 503.0 6 DRILLE D SHAF T PRE-CONSTRUCTIO N MEETING . A drilled shaft pre-construction
meeting shall be held after the approval of the drilled shaft installation plan , but prior to commencing construction of the drilled shafts. The purpose of the meeting will be to review all aspects of the drilled shaft construction and tes ting and to facilitate coordination between all parties involved. Individuals attending the meeting representing the Agency shall include the Engineer, the Project Manager , the design engineer, the Structural Concrete Engineer, and the Geo technical Engineering Manager . Individuals attending the meeting representing the Contractor and subcontractor shall include the project superintendent and all foremen in charge of excavating the shaft, placing casing and slurry, placing reinforcing steel, and placing the concrete. A representative from the concrete producer shall also attend the meeting. If slurry is to be used, the slurry manufacturer shall be available by phone for technical assistance during this meeting. All parties shall be notified a minimum of 7 calendar days in advance of the meeting date. If the Contractor proposes a significant revision of the approved shaft installation narrative, as determined by the Engineer, an additional conference shall be held before any additional shaft co nstruction operations are performed. 503.0 7 CONSTRUCTIO N REQUIREMENTS .
a.Casing . Welding for casings shall conform to the requirements of Subsection 506.10 . The shaft casing shall be watertight and clean prior to being placed in the excavation and shall be installed or removed without disturbing the surrounding soil. Casings shall have inside diameters not less than the indicated shaft sizes and not more than 6 inches greater than the indicated shaft sizes. Permanent casing shall be of ample strengt h to resist damage and deformation from transportation and handling, installation stresses, and all pressures and forces acting on the casing. It is the Contractor’s responsibility to determine the final wall thickness necessary to meet these requirements. No appurtenances, reinforcement, or holes shall be added to the casings without approval of the Engineer. Temporary casing shall be of ample strength to resist damage and deformation from transportation and handling, installation and extraction stresses, and all pressures and forces acting on the casing. The casing shall be capable of being removed without deforming and causing damage to the completed shaft, and without disturbing the surrounding soil.
5-62 (b) Production Shaft Installation Sequencing and S cheduling .
1.Drilling, installation of reinforcing steel, and concreting shall be scheduled so that each drilled shaft is poured immediately after drilling is complete, the shaft is inspected and accepted by the Engineer, and reinforcing steel placed and accepted.
2.The Contractor will not be permitted to schedule a concrete pour until it is demonstrated that the Contractor can achieve the required bottom of hole cleanliness to the satisfaction of the Engineer.
3.Vibration or excessive wheel loads wil l not be allowed within the immediate vicinity of any drilled shaft. A stable shaft excavation shall be maintained at all times.
c.Drilling and Excavation . The Contractor shall perform the excavations required for the shafts, through whatever materials are encountered, to the dimensions and elevations shown in the Plans or otherwise required by the Contract. The Contractor shall extend the drilled shaft base elevations when the Engineer determines that the material encountered during the excava tion is unsuitable or differs from that anticipated in the design of the drilled shaft. The Contractor’s methods and equipment shall be suitable for the intended purpose and materials encountered. Pre-excavation, using appropriate sediment and turbidity co ntrols when in or near waters of the state, may be needed to advance past shallow obstructions before installing casing.
d.Obstructions . Obstructions may include man -made or man -placed materials and natural materials, including, but not limited to, logs, boulders encountered outside the strata identified on the boring logs, and man -made objects that in the judgment of the Engineer cannot be removed using conventional tools such as conventional augers, drilling buckets, or underreaming tools or revers e circulation drilling (if this is used as the primary drilling method). Reasonable effort shall include operating approved equipment at maximum power, torque, and down thrust for a period of at least 15 minutes with minimal forward movement. Surface and s ubsurface obstructions at drilled shaft locations shall be removed by the Contractor. Drilling tools that are lost in the excavation shall not be considered obstructions and shall be promptly removed by the Contractor without compensation. When suspected o bstructions are encountered, the Contractor shall notify the Engineer and recommend a course of action to advance the drill hole in an expedient manner. The Engineer will determine if an obstruction has been encountered.
5-63 (e) Slurry . The drilled shafts m ay be advanced using a controlled slurry or water to maintain the
excavation. Slurry cannot be made from native materials, or material from the excavation. The level of slurry shall be maintained at a height sufficient to prevent caving of the hole. The sl urry head shall remain above the piezometric head of the groundwater at all times during installation and cleaning out. The slurry shall be pre -mixed, and adequate time for hydration shall be allowed prior to introduction into the shaft excavation. Adequat e slurry tanks shall be provided when specified or when required by the Engineer. Mixing of the slurry shall not occur in the hole for the drilled shaft. Slurry pits will not be allowed without written permission from the Engineer. Adequate de -sanding equi pment shall be provided where required for slurry operations. Appropriate steps shall be taken to prevent slurry from setting up in the shaft excavation, such as agitation, circulation, and adjusting the properties of the slurry. Bentonitic slurry shall no t sit unagitated for more than 4 hours. If the unagitated bentonitic slurry is in the hole for more than 4 hours, or if caking develops, the sides shall be scraped to remove the filter cake before proceeding with the excavation. The properties of the pre -mixed slurry shall be checked as slurry is introduced and periodically thereafter. Control tests shall be performed on the slurry to determine density, viscosity, and pH before and during shaft excavation to establish a consistent working pattern. Immediate ly prior to placing shaft concrete, slurry samples shall be taken from the bottom and 10 feet from the bottom of the drilled shaft excavation using an approved slurry sampling tool. Any heavily contaminated slurry and spoil that has accumulated at the bott om of the shaft shall be removed. The slurry shall be within the specification requirements immediately before concrete placement. If slurry is used, the slurry manufacturer’s technical representative shall:
1.Provide technical assistance for the use of the slurry.
2.Be at the site prior to introduction of the slurry into a drilled hole.
3.Remain at the site during the construction and completion of a minimum of one shaft to adjust the slurry mix to the specific site conditions.
5-64 (f) Rock Socket ing. If shafts are intended to be socketed into rock per the Plans, minimum rock socket
lengths shall be as shown on the Plans. The top of rock socket elevation shown on the Plans has been estimated based on test borings and survey. The actual top of rock socket may vary in the field based on observations made by the Geotechnical Engineering Manager during drilling. The rock socket shall begin beneath any weathered or highly fractured rock encountered.
g.Excavation Inspection . The Contractor shall provide equipment for checking the dimensions and alignment of each shaft excavation (moving drilling equipment against the sidewalls, weighted tapes, or other means approved by the Engineer). Electronic measuring equipment may be used but is not required. The Co ntractor shall determine the dimensions and alignment under the direction of the Engineer. The Contractor shall measure the final shaft depth after cleaning. Unless otherwise stated in the Plans, a minimum of 50 % of the base of each shaft shall have less than 1 inch of sediment. Debris at any place on the base of the shaft shall not exceed 2 inches.
h.Reinforcing Steel . Bar reinforcement shall be installed in accordance with Section 507 . Ties shall be installed at every intersection between vertical and horizontal (or spiral) reinforcing. Centralizers shall be installed at the bottom and along the axial length of the steel reinforcing at sufficient spacing to maintain proper concrete cover. The longitudinal spacing shall not exceed 10 feet. A minimum of four centralizers shall be placed at each longitudinal spacing and shall be spaced no greater than 4 feet and equally spaced around the shaft circumference.
i.Placing Concrete . Concrete placement shall commence as soon as possible after completion of drilled shaft excavation by the Contractor and inspection by the Engineer. Concrete placement shall continue in one operation to the top of the shaft, or as shown in the Plans. Concrete shall be placed underwater by use of a concrete pump or tremie. A tre mie shall have a hopper at the top that empties into a tube at least 10 inches in diameter constructed of heavy -gauge steel pipe with watertight joints . If a pump is used, a watertight tube with a minimum diameter of 4 inches constructed of heavy -gauge steel pipe with watertight joints shall be used . Throughout the underwater concrete placement operation, the discharge end of the tube shall remain submerged in the concrete at least 5 feet until the work is completed, resulting in a seamless, uniform shaft. If at any time during the concrete pour the end of the tube is removed from the fluid concrete and discharges above the rising concrete level, a measurement will be made to determine the elevation and the shaft will be considered defective. The Contractor shall take appropriate and immediate action to correct the deficiency. The Contractor’s construction operations in the vicinity of a drilled shaft excavation with freshly placed concrete and curing concrete are subject to the following restr ictions:
5-65 (1) The Contractor shall not drive piling or advance drilled shaft casing in a 100 foot radius of
a drilled shaft within 72 hours after the conclusion of placing concrete.
2.During the time period between six hours before concrete placement o perations and 7 calendar days after completing concrete placement operations, the Contractor shall not place and advance a casing, or perform drilling, within four shaft diameters of the centerline of the shaft.
j.Shaft Top Preparation .
1.The top-most concrete placed in the shaft shall be considered waste concrete and shall be removed by one of the following methods:
a.Pumped upward to a level a minimum of 24 inches clear distance above the Plan shaft top level and allowed to cure in place for removal later.
b.Placed a minimum of 24 inches above the Plan shaft top level via tremie, the casing dewatered prior to initial concrete set, and waste concrete removed in the dry by methods approved by the Engineer. The Contractor shall submit calculati ons demonstrating that the concrete in the shaft at the time of dewatering provides a minimum factor of safety against uplift of 1.25.
c.Pushed upward and ejected completely out of the top of the casing and wasted as final concrete is placed. Waste concre te shall be allowed to evenly overflow the full top circumference of the casing and may not channel or bleed off by notches or holes cut in the casing top. Any fresh concrete in the casing at a level above the Plan shaft top level after ejecting all waste concrete may be dipped or pumped out to the Plan shaft top elevation while still plastic by methods and equipment approved by the Engineer, or allowed to cure in place for removal later. If fresh concrete will be removed to the Plan shaft top elevation whi le still plastic, the Contractor shall submit calculations demonstrating that the concrete in the shaft at the time of fresh concrete removal provides a minimum factor of safety against uplift of 1.25. Waste concrete shall be considered to be the top 24 in ches of initial concrete placed, plus the height of any additional volume of waste concrete deposited in the shaft where concrete placement was halted and restarted, plus any additional amount necessary to produce full strength, non -segregated concrete at the Plan shaft top level.
5-66 (2) Final shaft top preparation may commence only once the drilled shaft concrete obtains an
average unconfined compressive strength of 2,500 psi or, in lieu of concrete strength testing, beginning 7 calendar days after complet ion of concrete placement. Final top preparation steps shall consist of:
a.Cutting off any extra casing above the top of casing elevation .
b.Removing any cured over pour concrete to the Plan shaft top elevation by approved methods .
c.Dressing the final shaft top surface .
d.Verification by the Engineer that the exposed concrete consists of full-strength concrete without any signs of segregation or contamination .
e.Approved non -destructive strength testing by the Contractor where required by the Engineer to verify that concrete has full design strength .
f.Removal of additional concrete below the Plan shaft top level as necessary to reach full-strength, non -segregated concrete.
k.Temporary Casing Removal . All temporary casing shall be removed unless oth erwise approved by the Engineer. The Contractor may submit a request to the Engineer to leave some or all temporary casing in place. The Agency reserves the right to reject any and all proposals. 503.0 8 RECORDS . The Contractor shall keep a record, independent of that which may be kept by the Engineer, of all pertinent data relative to the installation of the drilled shaft. This record shall be available for the Engineer’s inspection until the completion of the project, and a copy shall be transmitte d to the Engineer within 3 calendar days of the completion of each shaft. For each shaft, this record shall include:
a.Shaft location and dates of installation.
b.Excavation log containing information such as the description and approximate top and bot tom elevation of each soil or rock material encountered during shaft excavation, and any obstruction encountered.
c.Slurry data.
d.Total length of each shaft.
e.Plumbness of shaft.
5-67 (f) Placement and condition of reinforcing cage.
g.The time, method, and duration of the concrete placement.
h.A log of the ambient and concrete temperatures at the time of placement.
i.A comparison of the computed volume of the excavation (theoretical) with the volume of concrete placed (actual) and a plo t of depth versus volume. 503.0 9 INTEGRIT Y TESTING . Drilled shaft integrity testing and analysis shall be conducted on all completed drilled shafts. The testing and analysis shall be performed by an integrity testing firm retained by the Contractor. The f inal test report shall be stamped and signed by a professional engineer and submitted to the Engineer for approval. When not otherwise specified in the Contract, the Contractor shall perform integrity testing in accordance with one of the following methods :
a.Cross -Hole Sonic Log (CSL) Testing . CSL is a down -hole ultrasonic test method used to evaluate the condition of the concrete within drilled shafts. The test shall meet ASTM D6760 requirements as modified herein. The Contractor shall install access tu bes for CSL testing in the drilled shafts to permit access for the CSL test probes. One tube per 1.0 foot of shaft diameter, rounding up to the nearest whole number of tubes, (e.g. 8 tubes for an 8 foot diameter shaft) shall be installed. Access tubes for CSL testing shall be steel pipe s with a minimum wall thickness of 0.145 inches and an inside diameter of at least 1 -1/2 inches. The access tubes shall have a round, regular inside diameter free of defects and obstructions, including all pipe joints, in ord er to permit the free, unobstructed passage of 1.3 inch maximum diameter source and receiver probes used for the CSL tests. The Contractor shall securely attach the access tubes to the interior of the reinforcement cage for the shaft. The access tubes shal l be equally spaced around the shaft, inside the spiral or hoop reinforcement and midway between adjacent vertical reinforcement. The access tubes shall be placed 2 inches clear of the vertical reinforcement. If these minimums cannot be met due to close spacing of the vertical reinforcement, then the access tubes shall be bundled with the vertical reinforcement. The access tubes shall be installed in straight alignment and as near to parallel to the vertical axis of the reinforcement cage as possible. The t ubes shall be secured, such that the tubes stay in position during reinforcement cage and concrete placement. The tubes shall extend from 6 inches above the shaft bottoms to a minimum of 2 feet above the top of the shaft. The tubes shall not be allowed to rest on the bottom of the drilled shaft excavation.
5-68 The access tubes shall be watertight and free from corrosion with clean internal and external faces
to ensure a good bond between the concrete and the access tubes. The access tubes shall be fitted with watertight caps on the bottom and the top. Splice joints in the access tubes, if required to achieve full -length access tubes, shall be watertight. The Contractor shall clear the access tubes of all debris and extraneous materials prior to installing the access tubes. The access tubes shall be full of clean water prior to concrete placement. The caps shall be sealed to prevent debris from entering the pipes after the wate r is placed. Testing shall be performed after the shaft concrete has cured for a minimum of 72 hours. Additional curing time prior to testing may be required if the shaft concrete contains admixtures, such as set retarding admixture or water reducing admix ture. The additional curing time prior to testing required under these circumstances shall not be grounds for additional compensation or an extension of time. All CSL testing shall be completed within 7 calendar days of concrete placement. After placing th e shaft concrete and before beginning CSL testing of a shaft, the Contractor shall inspect the access tubes. Each access tube that the test probe cannot pass through shall be replaced, at the Contractor’s expense, with a 2 inch diameter hole cored through the concrete for the entire length of the shaft. Unless directed otherwise by the Engineer, cored holes shall be located approximately 6 inches inside the reinforcement and shall not damage the shaft reinforcement. Descriptions of inclusions and voids in c ored holes shall be logged and a copy of the log shall be submitted to the Engineer. Any anomalies indicated by longer pulse arrival times and significantly lower energy signals shall be reported to the Engineer and further tests shall be conducted as required to evaluate the extent of possible defects. A written report shall be submitted within 5 working days of the completion of testing. The CSL testing and analysis results shall be presented to the Engineer in a report according to ASTM D6760 requirements. A CSL log for each tube pair tested shall be presented with any defect zones identified on the logs. When required, 3D tomographic analysis shall be performed using all offset data, and color coded 3D tomographic images shall be included in the report. Findings from cored holes shall be preserved, identified as to location, and made available for inspection by the Engineer. Care shall be exercised in the r emoval of caps or plugs from the pipes after installation so as not to apply excess torque, hammering, or other stresses which could break the bond between the tubes and the concrete.
5-69 Upon completion of CSL testing and acceptance of the shaft by the Eng ineer, all water shall be
removed from the access tubes and any cored holes. The access tubes and cored holes shall be filled using grout tubes that extend to the bottom of the access tube or cored hole or into the grout already placed. The grout used to f ill access tubes and cored holes shall have strength properties equivalent to or better than those of the drilled shaft concrete and be approved by the Engineer. The access tubes and cored holes in a particular shaft shall not be filled with grout until al l testing is completed and the shaft has been accepted by the Engineer.
b.Thermal Integrity Profiling (TIP) Testing . TIP testing records the heat generated by the curing cement to assess the quality of the drilled shaft. The test shall meet ASTM D7949, M ethod B requirements as modified herein. TIP equipment shall include a computer -based TIP data acquisition system that automatically collects data at user defined time intervals to monitor and download temperature versus time after casting. Wires shall be furnished with built -in sensors as recommended by the drilled shaft integrity testing firm. Drilled shafts with TIP testing shall have the number of wires equal to the greater of 4 or the nearest whole integer value, rounded up, of the diameter of the dril led shaft measured in feet. Thermal wire cables shall be installed evenly in each drilled shaft by the integrity testing firm. The thermal wire cables shall be aligned with the longitudinal reinforcement of the drilled shaft and wire slack shall be minimiz ed. The thermal wire cables shall be tied to the longitudinal reinforcement at maximum 3 -foot intervals. Thermal wire cables shall be connected to a thermal access port (TAP) prior to concrete placement. The position and serial number of each thermal wire cable in the drilled shaft shall be recorded. TIP data collection shall begin immediately prior to the start of concrete placement and extend a minimum duration of 30 hours, or as recommended by the integrity testing firm and accepted by the Engineer The t iming interval and duration may be revised by the integrity testing firm or the Engineer as the project conditions require. Potential local anomalies shall be reported immediately to the Engineer, as indicated by locally low temperatures relative to the av erage temperature at that depth, or by average temperatures significantly lower than the average temperatures at other depths. A written report shall be submitted within 5 working days of the completion of testing. The TIP testing and analysis results shal l be presented to the Engineer in a report according to ASTM D7949 requirements. The following information shall also be provided:
5-70 (1) Graphical displays of all temperature measurements versus depth with top and bottom of
shaft adjustments made per the manufacturer’s recommendations, so that temperature plots are adjusted for end effects.
2.Indication of unusual temperatures, particularly significantly cooler local deviations of the average at any depth from the overall average over the entire length .
3.The overall average radius computed from the actual total concrete volume installed and the estimated radius and shape of each shaft along its depth, as calculated comparing the temperature at each depth to the overall average temperature.
4.All possible anomalies indicated in graphical displays and a summary of all possible anomalies, including a characterization and evaluation of the anomaly. The Contractor shall not commence concrete operations in subsequent shaft excavations until the integrity test report has been submitted for the previously completed shaft and the Engineer has given approval. This requirement may be waived at the discretion of the Engineer. 503.1 0 ACCEPTANC E OF DRILLE D SHAFTS . The Engineer will determine final acceptance of each shaft and will provide a response to the Contractor within 7 calendar days after receipt of the final integrity test report. Unacceptable drilled shafts are drilled shafts that are rejected by the Engineer due to damage, failure to advan ce through obstructions, mis -location, misalignment, failure to install the drilled shaft to the proper bearing stratum, or the results of the shaft integrity testing indicate defects. Rejection of a shaft based on the shaft integrity testing shall require conclusive evidence that a defect exists in the shaft. If the shaft integrity test results are complex or inconclusive, the Engineer may require additional testing to confirm the location of the defect. For all shafts determined to be unacceptable, the Co ntractor shall submit a remedial action plan to the Engineer for approval. If the remedial action plan requires any modifications to the dimensions of the shafts detailed in the Plans, they shall be supported by calculations and working drawings. All remed ial correction procedures and designs shall be stamped and signed by a professional engineer and submitted to the Engineer for approval. The Contractor shall not begin repair operations until receiving the Engineer’s approval of the remedial action plan. If the Engineer determines that the concrete placed is structurally inadequate, that shaft will be rejected. The placement of concrete shall be suspended until the Contractor submits to the Engineer written changes to the methods of shaft construction neede d to prevent future structurally inadequate shafts and receives the Engineer’s written approval of the submittal.
5-71 At the Engineer’s direction, a core hole (standard NX size rock core) shall be drilled in any questionable
quality shaft (as determined from shaft integrity testing and analysis or by observation of the Engineer) to explore the shaft condition. Prior to beginning coring, the Contractor shall submit to the Engineer the method and equipment used to drill and remove cores from shaft concrete. The Engineer shall issue written approval before the coring work can be started. The coring method and equipment shall provide for complete core recovery and shall minimize abrasion and erosion of the core. If a defect is confirmed, the Contractor shall pay fo r all coring costs. If no defect is encountered, the Agency will pay for all coring costs as extra work and, if the shaft construction is on the critical path of the Contractor’s schedule, compensation for the delay will be granted by an appropriate time e xtension. Materials and work necessary, including engineering analysis and redesign, to effect corrections for shaft defects shall be furnished to the Engineer’s satisfaction at no additional cost to the Agency. 503.1 1 METHO D OF MEASUREMENT . The quantitie s of Drilled Shaft in Earth and Drilled Shaft in Rock of the size specified to be measured for payment will be the number of linear feet of drilled shaft placed in the complete and accepted work (except where measurement is made for Drilled Shaft Obstructi on Drilling and Removal as specified below) measured to the nearest 0.1 foot from the Plan top of concrete shaft elevation to the bottom of shaft. Measurement will be taken at the cross -sectional center of the shaft. The quantity of Drilled Shaft Obstructi on Drilling and Removal to be measured for payment will be the number of linear feet performed in the complete and accepted work, over the depth range in which obstructions are encountered, measured to the nearest 0.1 feet as determined by the Engineer. No measurement for Drilled Shaft in Earth or Drilled Shaft in Rock will be made within the limits of Drilled Shaft Obstruction Drilling and Removal. The quantity of Mobilization of Drilled Shaft Equipment to be measured for payment will be on a lump sum basi s in the complete and accepted work. 503.1 2 BASIS OF PAYMENT . The accepted quantities of Drilled Shaft in Earth and Drilled Shaft in Rock will be paid for at the Contract unit per price linear foot. Payment will be full compensation for excavation, dewate ring, temporary or permanent casing, slurry, concrete, reinforcing steel, integrity testing , and grouting CSL tubes, and for furnishing all labor, tools, equipment, and incidentals necessary to complete the work.
5-72 The accepted quantity of Drilled Shaft Obstruction Drilling and Removal will be paid for at the Contract
unit price per linear foot. Payment will be full compensation for performing the work of overcoming encountered obstructions and for furnishing all materials, labor, tools, equipment, and incidentals necessary to complete the work. The accepted quantity of Mobilization of Drilled Shaft Equipment will be paid for at the Contract lump sum price. Payment will be full compensation for mobilization, remobilization, and demobilization of drilled shaft equipment from the project including the erecting, dismantling, and all incidental tasks necessary to complete the work, and the furnishing of all supervision, equipment, labor, tools, and incidentals necessary to complete the work. Partial paym ents for Mobilization of Drilled Shaft Equipment will be made as follows:
a.When drilling equipment has been set up and drilling operations start, 75% of the Contract lump sum price will be paid.
b.The remaining 25% of the Contract lump sum price will be paid when the drilling operations are complete and the equipment has been removed from the site. Costs associated with providing all submittals required as part of the work, and any necessary modifications thereto, will be considered incidental to the Contract items in this section. Payment will be made under: Pay Item Pay Unit 503.1000 Drilled Shaft in Earth ................................ ................................ ................ Linear Foot 503.1500 Drilled Shaft in Rock ................................ ................................ ................ Linear Foot 503.2000 Drilled Shaft Obstruction Drilling and Removal ................................ ......Linear Foot 503.2500 Mobilization of Drilled Shaft Equipment ................................ ................. Lump Sum
5-73 Sectio N 504 – Furnishin G Equipmen T for Drivin G Piling
504.0 1 DESCRIPTION . This work shall consist of furnishing the equipment required to drive piles. 504.0 2 EQUIPMENT .
a.General Requirements . The Contractor shall obtain a copy of the Pile and Driving Equipment Data Form from the Engineer. The Contractor shall complete this form in its entirety and shall submit copies to the geotechnical consultant employed by the Contractor when load tests ar e required, and to the Engineer so that a wave equation analysis may be performed. At least 14 calendar day s prior to the beginning of any pile driving, the Contractor shall furnish , for the Engineer’s acceptance, specifications and applicable information to verify the capacity and capability of the proposed pile driving hammer. No test piles or production piles shall be driven prior to this acceptance. During the pile driving operations, no changes to the accepted equipment will be permitted wi thout the Engineer’s permission.
b.Hammers . The type of hammer or driver shall be adequate in size to develop sufficient energy to drive the type and length of pile specified to the maximum ultimate pile capacity or nominal axial pile resistance shown on the Plan s. Each hammer shall be equipped with an anvil or clamp suitable for transmitting the driving force to the pile. The valve mechanism and the other parts of the air or diesel hammer shall be mainta ined in first class condition to ensure that the length of stroke for a single -acting hammer and the design number of blows per minute for a double -acting hammer will be obtained. The drive head shall be axially aligned with the hammer and pile and shall be guided by leads and not be free -swinging. It shall fit around the pile head in such a manner as to prevent transfer of torsional forces during driving while maintaining proper alignment of the hammer and pile. The pile driving equipment shall not induce a compressive stress greater than 90% of the yield stress of the pile material. In addition, the pile driving equipment shall be capable of driving the pile to the required ultimate capacity at a blow count of between 3 blows and 15 blows per inch a s indicated by the wave equation analysis program (WEAP).
c.Leads and Bracing . The Contractor shall locate and brace each pile so that upon driving, its final position and alignment will be as specified and as shown on the Plan s. The selection of leads or form of bracing shall be adequate to align and restrain the piling during placement. If the leads or bracing are not adequate to place the piling to within the specified tolerance, the Contractor shall modify the leads or system of bracing until it obtains results acceptable t o the Engineer.
Source: Vermont Standard Specifications for Construction, 2024 Edition. Pages 467–486 of 1,380.