{"data":{"id":"us-nyc/n.y.c.-admin.-code-bc-1812","jurisdiction":"us-nyc","citation":"N.Y.C. Admin. Code § BC 1812","heading":"Section BC 1812: Cast-in-Place Concrete Piles","body":"1812.1 General.\n\nThe materials, reinforcement and installation of cast-in-place concrete piles shall conform to Sections 1812.1.1 through 1812.1.3.\n\n1812.1.1 Materials.\n\nConcrete or grout shall have a 28-day specified compressive strength (f '\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\tc\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t) of not less than 2,500 psi (17.24 MPa), except in micropiles and caisson piles where the minimum compressive strength shall be 4,000 psi (27.58 MPa). Where concrete is placed through a funnel hopper at the top of the cast-in-place concrete pile, the concrete mix shall be designed and proportioned so as to produce a cohesive workable mix having a slump of not less than 4 inches (101.6 mm) and not more than 6 inches (152.4 mm). Where concrete is to be pumped, the mix design shall be such that material produced is suitable for pumping.\n\nGrout shall consist of a pumpable mixture of portland cement, water, and any required fine aggregate, supplemental cementitious materials, or admixtures as permitted by Chapter 19 of this code. Grout proportioning shall be determined from trial mixes or on the basis of field experience using documented test results provided that such test results are not older than 24 months. The water to cement ratio of grout shall not exceed 0.45. The required average compressive strength of grout shall be determined in a manner consistent with the procedures outlined in ACI 301 as utilized for concrete. The evaluation of grout compressive strength shall be in accordance with procedures established for concrete in Chapter 19 of this code. All grout mix design shall be submitted for review and approval of the registered design professional of record. Copies of the grout mix design shall be submitted to the department.\n\n1812.1.1.1 Concrete sampling and testing.\n\nSampling and testing of concrete shall be in accordance with Chapter 19.\n\n1812.1.1.2 Grout sampling and testing.\n\nSampling and testing of grout shall be in accordance with Sections 1812.1.1.2.1 through 1812.1.1.2.3.\n\n1812.1.1.2.1 Interval.\n\nGrout samples shall be collected and testing shall be performed for the lesser of the following conditions:\n\n1. each element installed;\n\n2. each batch of site-mixed grout; or\n\n3. each load of ready-mixed grout used.\n\n1812.1.1.2.2 Compressive strength.\n\nCompressive strength tests shall be performed using cylinders having a maximum diameter of 3 inches (72.3 mm). Grout shall be tested in accordance with ASTM C 39. A minimum of six (6) samples shall be prepared for each test group.\n\n1812.1.1.2.3 Specific gravity.\n\nSpecific gravity testing shall be performed using the American Petroleum Institute (API) Recommended Practice 13B-1 or in accordance with ASTM C 138.\n\n1812.1.2 Placement of reinforcement.\n\nReinforcement, where required, shall be placed in accordance with Section 1812.3.4 and shall be assembled, tied together, and placed in the cast-in-place concrete pile as a unit before concrete or grout is placed.\n\nExceptions: Where approved by the engineer, reinforcement may be placed after the cast-in-place concrete piles are filled with concrete or grout under the following situations:\n\n1. Tied reinforcement in augered uncased cast-in-place concrete piles, while the concrete or grout is still in a semifluid state.\n\n2. Tied reinforcement in cast-in-place concrete piles filled with grout, while the grout is in a semifluid state.\n\n3. Steel dowels embedded 5 feet (1524 mm) or less in the cast-in-place concrete pile while the concrete or grout is still in a semifluid state.\n\n1812.1.2.1 Design cracking moment.\n\nThe design cracking moment (ØM\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\tn\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t) for a cast-in-place deep foundation element not enclosed by a structural steel pipe or tube shall be determined using the following equation:\n\n(Equation 18-6)\n\nwhere:\n\nf '\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\tc\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t = Specified compressive strength of concrete or grout, psi\n\nS\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\tm\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t = Elastic section modulus, neglecting reinforcement and casing, cubic inches\n\n1812.1.2.2 Required reinforcement.\n\nWhere subject to uplift, or where the required moment strength determined using the load combinations of Section 1605.2 exceeds the design cracking moment determined in accordance with Section 1812.1.2.1, cast-in-place concrete piles not enclosed by a structural steel pipe or tube shall be reinforced.\n\n1812.1.2.3 Reinforcement in Seismic Design Categories C \u0026 D.\n\nWhere a structure is assigned to Seismic Design Category C in accordance with Section 1613, reinforcement shall be provided in accordance with Section 1812.1.2.4. Where a structure is assigned to Seismic Design Category D, reinforcement shall be provided in accordance with Section 1812.1.2.5.\n\n1812.1.2.4 Seismic reinforcement in Seismic Design Category C.\n\nFor structures assigned to Seismic Design Category C in accordance with Section 1613, cast-in-place concrete pile elements shall be reinforced as specified in this section. Reinforcement shall be provided where required by analysis. A minimum of four longitudinal bars, with a minimum longitudinal reinforcement ratio of 0.0025, shall be provided throughout the minimum reinforced length of the element as defined below starting at the top of the element. The minimum reinforced length of the element shall be the greatest of the following:\n\n1. One-third of the element length;\n\n2. A distance of 10 feet (3048 mm);\n\n3. Three times the least element dimension; or\n\n4. The distance from the top of the element to the point where the design cracking moment determined in accordance with Section 1812.1.2.1 exceeds the required moment strength determined using the load combinations of Section 1605.2.\n\nTransverse reinforcement shall consist of closed ties or spirals with a minimum diameter of 3/8 inch (9.5 mm). Spacing of transverse reinforcement shall not exceed the smaller of 6 inches (152.4 mm) or 8-longitudinal-bar diameters, within a distance of three times the least element dimension from the bottom of the pile cap. Spacing of transverse reinforcement shall not exceed 16 longitudinal bar diameters throughout the remainder of the reinforced length.\n\nExceptions:\n\n1. The requirements of this section shall not apply to concrete cast in structural steel pipes or tubes.\n\n2. A spiral-welded metal casing of a thickness not less than manufacturer's standard No. 14 gage (0.068 inch) (1.73 mm) is permitted to provide concrete confinement in lieu of the closed ties or spirals. Where used as such, the metal casing shall be protected against possible deleterious action due to soil constituents, changing water levels or other factors indicated by boring records of site conditions.\n\n1812.1.2.5 Seismic reinforcement in Seismic Design Category D.\n\nFor structures assigned to Seismic Design Category D in accordance with Section 1613, cast-in-place concrete pile elements shall be reinforced as specified in this section. Reinforcement shall be provided where required by analysis. A minimum of four longitudinal bars, with a minimum longitudinal reinforcement ratio of 0.005, shall be provided throughout the minimum reinforced length of the element as defined below starting at the top of the element.\n\nThe minimum reinforced length of the element shall be the greatest of the following:\n\n1. One-half of the element length;\n\n2. A distance of 10 feet (3048 mm);\n\n3. Three times the least element dimension; or\n\n4. The distance from the top of the element to the point where the design cracking moment determined in accordance with Section 1812.1.2.1 exceeds the required moment strength determined using the load combinations of Section 1605.2.\n\nTransverse reinforcement shall consist of closed ties or spirals no smaller than No. 3 bars for elements with a least dimension of up to 20 inches (508 mm), and No. 4 bars for larger elements. Throughout the remainder of the reinforced length outside the regions with transverse confinement reinforcement, as specified in Section 1812.1.2.5.1 or 1812.1.2.5.2, the spacing of transverse reinforcement shall not exceed the least of the following:\n\n1. 12 longitudinal bar diameters;\n\n2. One-half the least dimension of the element; or\n\n3. 12 inches (304.8 mm).\n\nExceptions:\n\n1. The requirements of this section shall not apply to concrete cast in structural steel pipes or tubes.\n\n2. A spiral-welded metal casing of a thickness not less than manufacturer's standard No. 14 gage (0.068 inch) (1.73 mm) is permitted to provide concrete confinement in lieu of the closed ties or spirals. Where used as such, the metal casing shall be protected against possible deleterious action due to soil constituents, changing water levels or other factors indicated by boring records of site conditions.\n\n1812.1.2.5.1 Site Classes A through D.\n\nFor Site Class A, B, C and D, transverse confinement reinforcement shall be provided in the element in accordance with Sections 18.7.5.2, through 18.7.5.4 of ACI 318 within three times the least element dimension of the bottom of the pile cap. A transverse spiral reinforcement ratio of not less than one-half of that required in Section 18.7.5.4(a) of ACI 318 shall be permitted.\n\n1812.1.2.5.2 Site Classes E and F.\n\nFor Site Class E or F, transverse confinement reinforcement shall be provided in the element in accordance with Sections 18.7.5.2 through 18.7.5.4 of ACI 318 within seven times the least element dimension of the pile cap and within seven times the least element dimension of the interfaces of strata of Class 4b or better and strata that are liquefiable or are composed of material meeting Class 4c or 6.\n\n1812.1.3 Concrete or grout placement.\n\nConcrete or grout shall be placed in such a manner as to ensure the exclusion of any foreign matter and to secure a full-sized shaft. Concrete or grout shall not be placed through water except where a tremie or other approved method is used. When depositing concrete from the top of the cast-in-place concrete pile, the concrete shall not be chuted directly into the cast-in-place concrete pile but shall be poured in a rapid and continuous operation through a funnel hopper centered at the top of the cast-in-place concrete pile. Grout for auger cast piles shall be pumped through a hollow stem auger and shall be maintained as fluid throughout placement.\n\n1812.2 Enlarged base piles.\n\nEnlarged base piles shall conform to the requirements of Sections 1812.2.1 through 1812.2.5.\n\n1812.2.1 Materials.\n\nThe maximum size of coarse aggregate for concrete shall be 3/4 inch (19.1 mm). Concrete to be compacted shall have a zero slump.\n\n1812.2.2 Allowable stresses.\n\nFor allowable stresses, see Table 1810.8.\n\n1812.2.3 Installation.\n\nEnlarged bases formed either by compacting concrete or driving a precast base shall be formed in or driven into granular soils. Enlarged base piles shall be constructed in the same manner as successful enlarged base test piles installed for the project. Enlarged base pile shafts extending through peat or other organic soil shall be encased in a permanent steel casing. Where a cased shaft is used, the shaft shall be adequately reinforced to resist column action or the annular space around the enlarged base pile shaft shall be filled sufficiently to re-establish lateral support by the soil. Where heave of an enlarged base pile or other deep foundation occurs, the enlarged base pile or other deep foundation, shall be replaced unless it is demonstrated that the enlarged base pile or other deep foundation is undamaged and capable of carrying twice its design load.\n\n1812.2.4 Load-bearing capacity.\n\nThe load-bearing capacity of enlarged base piles shall be verified by load tests in accordance with Section 1810.4.\n\n1812.2.5 Concrete and grout cover.\n\nFor minimum concrete and grout cover requirements, see Table 1803.13.*\n\n1812.3 Drilled, drilled displacement, or augered uncased piles.\n\nDrilled, drilled displacement, or augered uncased piles shall conform to Sections 1812.3.1 through 1812.3.5.\n\n1812.3.1 Allowable stresses.\n\nFor allowable stresses, see Table 1810.8.\n\n1812.3.2 Dimensions.\n\nThe minimum diameter of drilled or drilled displacement piles shall be 8 inches (203.2 mm). The minimum diameter of augered uncased piles shall be 12 inches (304.8 mm).\n\n1812.3.3 Installation.\n\nWhere shafts for drilled piles are formed through unstable soils and concrete is placed in an open-drilled hole, a steel liner shall be inserted in the hole prior to placing the concrete. Where the steel liner is withdrawn during concreting, the level of concrete shall be maintained above the bottom of the liner at a sufficient height to offset any hydrostatic or lateral soil pressure.\n\nWhere drilled displacement piles are used, the auger segments shall be installed into the ground with both a vertical force and a torque such that the soil is displaced laterally within the ground. The void created after installation shall be filled with grout or concrete.\n\nWhere grout is placed by pumping through a hollow-stem auger, the auger shall be permitted to rotate in a clockwise direction during withdrawal. An initial head of grout shall be established and maintained on the auger flights before withdrawal. The auger shall be withdrawn in a continuous manner in increments of about 12 inches (304.8 mm) each. Grout pumping pressures shall be measured and maintained high enough at all times to offset hydrostatic and lateral earth pressures. Grout volumes shall be measured to ensure that the volume of grout placed in each drilled pile is equal to or greater than the theoretical volume of the hole created by the auger. Where the installation process of any drilled pile is interrupted or a loss of grout pressure occurs, the drilled pile shall be re-drilled to 5 feet (1524 mm) below the elevation of the tip of the auger when the installation was interrupted or grout pressure was lost and reformed.\n\nAugered cast-in-place piles shall not be installed within a distance equivalent to the center-to-center spacing equivalent to six times the diameter of a drilled pile filled with concrete or grout less than 12 hours old, unless approved by the engineer. The level at which return of the grout occurs during withdrawal shall be recorded. If the grout level in any completed drilled pile drops during installation of an adjacent drilled pile, the drilled pile shall be replaced. The installation shall be performed under the direct supervision of the engineer. The engineer shall certify to the commissioner that the drilled piles were installed in compliance with the approved construction documents.\n\n1812.3.4 Reinforcement.\n\nFor drilled piles installed with a hollow-stem auger, where full-length longitudinal steel reinforcement is placed without lateral ties, the reinforcement shall be placed through ducts in the auger prior to filling the drilled pile with concrete. Concrete cover for reinforcement of the drilled pile shall be in accordance with Table 1810.2.13.\n\nException: Where physical constraints do not allow the placement of the longitudinal reinforcement prior to filling the drilled pile with concrete or where partial-length longitudinal reinforcement is placed without lateral ties, the reinforcement is allowed to be placed after the drilled piles are completely concreted but while concrete is still in a semifluid state.\n\n1812.3.5 Reinforcement in Seismic Design Category C or D.\n\nWhere a structure is assigned to Seismic Design Category C or D in accordance with Section 1613, the corresponding requirements of Sections 1812.1.2.3 through 1812.1.2.5 shall be met.\n\n1812.4 Driven uncased piles.\n\nDriven uncased piles shall not be permitted.\n\n1812.5 Steel-cased piles.\n\nSteel-cased piles shall comply with the requirements of Sections 1812.5.1 through 1812.5.4.\n\n1812.5.1 Materials.\n\nShells or casings for steel cased piles shall be of steel and be sufficiently strong to resist collapse and sufficiently water tight to exclude any foreign materials during the placing of concrete. Steel shells shall have a sealed tip with a diameter of not less than 8 inches (203.2 mm).\n\n1812.5.2 Allowable stresses.\n\nFor allowable stresses, see Table 1810.8.\n\n1812.5.2.1 Shell thickness.\n\nThe thickness of the steel shell shall not be less than manufacturer's standard No. 14 gage (0.068 inch) (1.75 mm) minimum.\n\n1812.5.2.2 Shell type.\n\nThe shell shall be seamless or provided with seams of strength equal to the basic material and be of a configuration that will provide confinement to the cast-in-place concrete.\n\n1812.5.2.3 Strength.\n\nThe ratio of steel yield strength (f\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\ty\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t) to 28-day specified compressive strength (f '\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\tc\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t) shall not be less than six.\n\n1812.5.2.4 Diameter.\n\nThe nominal diameter of steel cased piles shall not be greater than 16 inches (406.4 mm).\n\n1812.5.3 Installation.\n\nSteel shells shall be mandrel driven for their full length in contact with the surrounding soil. The steel shells shall be driven in such order and with such pacing as to ensure against distortion of or injury to steel cased piles already in place. A steel cased pile shall not be driven within four and one-half average diameters of a steel cased pile filled with concrete less than 24 hours old unless approved by the commissioner. Concrete shall not be placed in steel shells within heave range of driving.\n\n1812.5.4 Reinforcement.\n\nReinforcing shall be required for unsupported lengths of steel cased piles or where the steel cased pile is designed to resist uplift or unbalanced lateral loads. For minimum concrete cover requirements, see Table 1810.2.13.\n\n1812.5.4.1 Seismic reinforcement.\n\nWhere a structure is assigned to Seismic Design Category C or D in accordance with Section 1613, the reinforcement requirements of Sections 1812.1.2.3 through 1812.1.2.5 shall be met.\n\n1812.6 Concrete-filled steel pipe and tube piles.\n\nConcrete-filled steel pipe and tube piles shall conform to the requirements of Sections 1812.6.1 through 1812.6.5.\n\n1812.6.1 Materials.\n\nSteel pipe and tube sections used for concrete-filled steel pipe and tube piles shall conform to ASTM A 252 or ASTM A 283. Concrete shall conform to Section 1812.1.1. The maximum coarse aggregate size shall be 3/4 inch (19.1 mm).\n\n1812.6.2 Allowable stresses.\n\nFor allowable stresses, see Table 1810.8.\n\n1812.6.3 Minimum dimensions.\n\nConcrete-filled steel pipe and tube piles shall have a nominal outside diameter of not less than 8 inches (203.2 mm) and a minimum wall thickness in accordance with Section 1811.7.4. For concrete-filled steel pipe and tube piles driven with a mandrel, the minimum wall thickness shall be 1/10 inch (2.5 mm).\n\n1812.6.4 Reinforcement.\n\nReinforcement steel shall conform to Section 1812.1.2. For minimum concrete cover requirements see Table 1810.2.13.\n\n1812.6.4.1 Seismic reinforcement.\n\nWhere a structure is assigned to Seismic Design Category C or D in accordance with Section 1613, minimum reinforcement no less than 0.01 times the cross-sectional area of the concrete within the concrete-filled steel pipe and tube piles shall be provided in the top of the concrete-filled steel pipe and tube piles with an embedment length equal to two times the required cap embedment anchorage into the pile cap, but not less than the tension development length of the reinforcement. The wall thickness of the steel pipe shall not be less than 3/16 inch (4.8 mm).\n\n1812.6.5 Placing concrete.\n\nThe placement of concrete shall conform to Section 1812.1.3.\n\n1812.7 Caisson piles.\n\nCaisson piles shall conform to the requirements of Sections 1812.7.1 through 1812.7.7.\n\n1812.7.1 Construction.\n\nCaisson piles shall consist of a shaft section of concrete or grout-filled pipe, extending to bedrock, with an uncased socket drilled into bedrock of Class 1c or better and filled with concrete or grout. The caisson pile shall have a full-length structural steel core, full length steel reinforcing, or a stub core or steel reinforcing installed in the rock socket and extending into the pipe portion a distance equal to the socket depth. The minimum outside diameter of the caisson pile shall be 7 inches (177.8 mm), and the diameter of the rock socket shall be approximately equal to the inside diameter of the caisson pile.\n\n1812.7.1.1 Drilling with air.\n\nWhere existing structures may be affected by subsurface disturbances, air drilling shall be prohibited.\n\n1812.7.2 Materials.\n\nPipe and steel cores for caisson piles shall conform to the material requirements in Section 1811.7. Pipes shall have a minimum wall thickness of 3/8 inch (9.5 mm) and shall be fitted with a suitable steel-driving shoe or cutting teeth welded to the bottom of the pipe. Concrete or grout shall have a 28-day specified compressive strength (f '\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\tc\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t) of not less than 4,000 psi (27.58 MPa).\n\n1812.7.2.1 Reinforcing bars.\n\nFor the purposes of Section 1812.7, threaded bars conforming to ASTM A 615 and ASTM A 722 shall be considered the same as deformed reinforcing bars.\n\n1812.7.3 Rock socket design.\n\nThe depth of the rock socket in Class 1c rock or better shall be sufficient to develop the full load-bearing capacity of the caisson pile based upon the sum of the allowable bearing pressure on the bottom of the socket in accordance with Table 1806.1 plus an allowable bond stress of 200 psi (1379 kPa) on the sides of the socket. The depth of the socket in Class 1c rock or better below the bottom of the pipe shall not be less than 3 feet (914.4 mm) or the outside diameter of the pipe.\n\n1812.7.3.1 Increased allowable bond stress.\n\nLoad tests, with instrumentation in the rock socket to demonstrate the transfer of force to the rock, shall be performed to justify the use of bond stresses above 200 psi (1379 kPa). A minimum factor of safety of 2 shall be applied to the ultimate test load where an increase in allowable bond stress is sought. A report summarizing the methods and results of the load test shall be submitted to the commissioner for approval.\n\n1812.7.3.1.1 Minimum number of load tests.\n\nIn each area of the foundation site within which the subsurface soil and rock conditions are \"substantially similar\" in character, as determined by the engineer, at least one load test shall be performed for the largest caisson pile diameter used on a site occupying a total area of 80,000 square feet (7432.2 m\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t2\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t) or less. For sites greater than 80,000 square feet (7432.2 m\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t2\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t), an additional load test shall be performed for every 80,000 square feet (7432.2 m\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t2\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t) of added footprint area.\n\n1812.7.4 Structural core and steel reinforcing.\n\nThe gross cross-sectional area of the structural steel core or bundled center reinforcing shall not exceed 30 percent of the gross area of the caisson pile. For reinforcing placed at the perimeter of the caisson pile, the area of the reinforcing shall not exceed 8 percent of the area inside the casing. Minimum concrete cover shall be in accordance with Table 1810.2.13.\n\n1812.7.4.1 Splicing of steel reinforcing.\n\nSteel reinforcing shall be spliced in accordance with the requirements of ACI 318.\n\n1812.7.4.2 Seismic reinforcement.\n\nWhere a structure is assigned to Seismic Design Category C or D in accordance with Section 1613, the reinforcement requirements of Section 1812.6.4.1 shall be met.\n\n1812.7.5 Allowable stresses.\n\nFor allowable stresses, see Table 1810.8.\n\n1812.7.6 Installation.\n\nThe rock socket and steel pipe shall be thoroughly cleaned of foreign materials before filling with concrete or grout. Steel cores shall be set within 6 inches (152.4 mm) above the base of the rock socket. Concrete shall not be placed through water except where a tremie or other method approved by the commissioner is used.\n\n1812.7.6.1 Drilling with air.\n\nWhere existing structures may be affected by subsurface disturbances, air drilling shall be prohibited.\n\n1812.7.7 Rock socket inspection.\n\nCaisson pile rock sockets shall be subject to special inspection in accordance with Section 1705.19. All caisson pile rock sockets shall be inspected to verify rock quality. Inspection may be accomplished by direct observation, by video methods or by a core boring performed prior to the drilling of the socket.\n\n1812.8 Micropiles.\n\nMicropiles shall conform to Sections 1812.8.1 through 1812.8.6.\n\n1812.8.1 Materials.\n\nReinforcement shall consist of deformed reinforcing bars in accordance with ASTM A 615 Grade 60 or 75 or ASTM A 722 Grade 150. The steel pipe or casing shall have a minimum yield strength of 45,000 psi (310.3 MPa) and a minimum elongation of 15 percent as shown by mill certifications or two coupon test samples per 40,000 pounds (18 143.7 kg) of pipe or casing.\n\n1812.8.2 Dimensions.\n\nMicropiles shall have an outside diameter of between 5 and 14 inches (127 and 355.6 mm). The steel pipe shall have a minimum wall thickness of 3/16 inch (4.8 mm).\n\n1812.8.3 Design.\n\nMicropiles shall develop their load-carrying capacity by means of a bond zone in soil. The design of micropiles shall not consider end bearing. Micropiles shall be grouted and have either a steel pipe or steel reinforcement at every section along the length. It shall be permitted to transition compression loads from the steel pipe to the deformed reinforcing bars by extending the bars into the pipe section by at least their development length in tension, in accordance with ACI 318.\n\n1812.8.3.1 Reinforcement.\n\nFor micropiles or portions thereof grouted inside a temporary or permanent casing or a hole drilled with grout, the steel pipe or steel reinforcement shall be designed to carry at least 40 percent of the design compression load. Micropiles or portions thereof grouted in an open hole in soil without temporary or permanent casing and without suitable means of verifying the hole diameter during grouting shall be designed to carry the entire compression load in the reinforcing steel. Where a steel pipe is used for reinforcement, the portion of the grout enclosed within the pipe is permitted to be included in the determination of the allowable stress in the grout.\n\n1812.8.3.2 Seismic reinforcement.\n\nFor structures assigned to Seismic Design Category C, a permanent steel casing shall be provided from the top of the micropile down to the point of zero curvature. For structures assigned to Seismic Design Category D, the micropile shall be approved by the commissioner in accordance with Section 28-113.2 of the Administrative Code. The alternative system design, supporting documentation and test data shall be submitted to the commissioner for review and approval.\n\n1812.8.4 Splices.\n\nSplices in reinforcing bars shall be made in accordance with ACI 318. Splices in the steel pipe or casing shall be made by use of flush threaded joints, or by welded joints. Reductions for the structural capacity of the threaded joint casing at splice locations shall be accounted for in the design.\n\n1812.8.5 Installation.\n\nMicropile elements shall be permitted to be formed in holes advanced by rotary or percussive drilling methods, with or without casing. The elements shall be grouted with a fluid cement grout. The grout shall be pumped through a tremie pipe extending to the bottom of the element until grout of suitable quality returns at the top of the element. The following requirements apply to specific installation methods:\n\n1. For micropiles grouted inside a temporary casing, the reinforcing bars shall be inserted prior to withdrawal of the casing. The casing shall be withdrawn in a controlled manner with the grout level maintained at the top of the element to ensure that the grout completely fills the drill hole.\n\n2. Subsequent micropiles shall not be drilled near elements that have been grouted until the grout has had sufficient time to harden.\n\n3. Micropiles shall be grouted as soon as possible after drilling is completed.\n\n4. For micropiles designed with a full-length casing, the casing shall be pulled back to the top of the bond zone and reinserted or some other suitable means employed to assure grout coverage outside the casing.\n\n1812.8.5.1 Drilling with air.\n\nWhere existing structures may be affected by subsurface disturbances, air drilling shall be prohibited.\n\n1812.8.6 Pressure grouted bond zone.\n\nMicropiles shall be installed with a pressure grouted bond zone. The bond zone shall be formed entirely in soil of Class 4 or better and the grout shall be placed under pressure exceeding 1.5 times the existing total stress at the midpoint of the bond zone. The bond zone shall be formed by extending the casing to the bottom of the bond zone and withdrawing the casing while the grout is being pumped under pressure. The casing above the bond zone shall remain in place permanently. Reinforcing to the bond zone shall be placed in the casing to the depth of the bond zone prior to placing grout.","path":["New York City Administrative Code","Title 28","Chapter 7: New York City Building Code"],"source_url":"https://files.amlegal.com/pdffiles/NewYorkCity/Admin/XML.zip","current_through":"Local Law 2026/135 (enacted August 31, 2026)","vintage":"","retrieved_at":"2026-09-06T02:48:57Z","sha256":"6ca69d8e28493c9e741062ed341dc45258e442b8e622021c42038aeb862c2a79","source_id":"us-nyc","stale":false,"prev":"us-nyc/n.y.c.-admin.-code-bc-1811","next":"us-nyc/n.y.c.-admin.-code-bc-1813"},"notice":"GroundRules: Original legal text. Not legal advice."}