844Micropiles

844.01 Description.

This work includes constructing, inspecting, and testing of micropiles and pile top attachments that meet the design load. This work includes drilling, furnishing, and placing the reinforcing steel and casing, grouting, pile top attachments, site drainage control, layout, elevation and location control, measurement, and marking, all asphalt removal, excavation, backfilling, and asphalt patching associated with the pile installation. When the Contract designates Contractor Designed, the Contractor is responsible for the design and shall select the micropile type, size, and pile top attachment; estimate the ground-grout bond value; determine the required bond length and final micropile diameter; and verify the micropile load resistance by proof load testing as required.

844.02 Materials.

Provide the following materials for micropiles. Centralizers and Spacers. Fabricate centralizers and spacers from schedule 40 PVC pipe or tube, steel, or material non- detrimental to the reinforcing steel. Do not use wood. Galvanization. Use galvanization that complies with ASTM A-153. Grout. Ensure that all grout mixture components conform to SECTION 601. Use a RIDOT -approved neat cement or sand/cement mixture with a minimum three- day compressive strength of 2000 psi and a minimum 28- day compressive strength of 4000 psi per AASHTO T106/ASTM C109. Permanent Casing Pipe. Use permanent steel casing/pipe that has the diameter and at least the minimum wall thickness shown on the approved working drawings. Use permanent steel casing/pipe that complies with the following requirements: • The tensile requirements of ASTM A252, Grade 3, except ensure that the yield strength is a minimum of 50,000 psi or as used in the design submittal. • May be new structural grade (a.k.a., mill secondary) steel pipe with Engineer approval. Ensure that the steel pipe meet s the above requirements but without a Mill Certification and must be free from defects (dents, cracks, tears) and with two coupon tests per truckload delivered to the fabricator.

Part 800 — Bridge Structures August 2025

SECTION 844 — MICROPILES 800-207 For permanent casing/pipe that will be welded for structural purposes: • Ensure that the carbon equivalency (CE), as defined in AWS D1.1, Section XI5.1, does not exceed 0.45, as demonstrated by mill certifications. • Ensure that the sulfur content does not exceed 0.05 percent, as demonstrated by mill certifications. P lates and Shapes. Use structural steel plates and shapes for pile top attachments that conform to ASTM A709/AASHTO M270, Grade 50. R einforcing Bars . Use reinforcing steel that are galvanized deformed bars according to Subsection M05.06 . For ungalvanized bars use those that conform to Subsection M05.02 . If threads are cut into a reinforcing bar, provide the next larger bar number designation from that shown on the Plans. Do not use galvanization on high strength bars. Use Grade 150 reinforcing bar couplers of the same material and coating as the bars being connected. W ater . Use water in the grout mix that conforms to AASHTO T 26 and is potable, clean, and free from substances that may damage cement and steel. M icropile Diameter. Ensure that the cased length of the micropile has a nominal pile diameter as shown on the Plans or larger. Casing Steel. Ensure that the casing steel has a minimum thickness of 0.5 in. Compressive Strength. Ensure that the minimum 28-day compressive strength of concrete or cement grout is 4000 psi. 844. 03 CONSTRUCTION METHODS. Pre-Construction Meeting. The Engineer will schedule a preconstruction meeting before the start of micropile construction. The Engineer, prime Contractor, micropile specialty Contractor, micropile design engineer, RIDOT designer (EOR), excavation Contractor and geotechnical instrumentation specialist (if applicable) shall attend the meeting. Attendance is mandatory. The preconstruction meeting objectives are to clarify the construction requirements for the work, to coordinate the construction schedule and activities, and to identify contractual relationships and the delineation of

Part 800 — Bridge Structures August 2025

800-208 SECTION 844 — MICROPILES responsibilities among the P rime Contractor and the various Subcontractors , specifically those pertaining to excavation for micropile structures, anticipated subsurface conditions, micropile installation and testing, micropile structure survey control, and site drainage control. Before the start of any micropile construction activity, the Contractor and Engineer shall jointly inspect the site as stipulated in SECTION 841. S ite Drainage Control . Control and properly dispose of drill flush and construction related waste, including excess grout. Provide positive control and discharge of all surface water that will impact construction, and maintain all pipes or conduits used to control surface water during construction. Repair damage caused by surface water at no additional cost. Upon substantial completion of the work, remove surface water control pipes or conduits from the site. C ontractor Designed Micropiles.

Part 800 — Bridge Structures August 2025

SECTION 844 — MICROPILES 800-209

Part 800 — Bridge Structures August 2025

800-210 SECTION 844 — MICROPILES ● Design notes including an explanation of any symbols and computer programs used in the design ● Micropile-to-footing connection calculations

Part 800 — Bridge Structures August 2025

SECTION 844 — MICROPILES 800-211 ● Details. Details, dimensions, and schedules for all micropiles, casing, and reinforcing steel, including reinforcing bar bending details. Revise the working drawings when plan dimensions are changed due to field conditions or for other reasons. Within 30 days after completion of the work, submit as-built drawings to the Engineer. Provide revised design calculations signed by the approved S tate of Rhode Island registered Professional Engineer for all approved design changes made during the construction of the micropile structure.

Part 800 — Bridge Structures August 2025

800-212 SECTION 844 — MICROPILES ○ Estimated curing time for grout to achieve specified strength. Previous test results for the proposed grout mix completed within one year of the start of grouting may be submitted for initial verification and acceptance and start of production work. ○ Procedure and equipment for monitoring of grout quality. ● Load Testing. Submit detailed plans for the proposed micropile load testing method. Include all drawings, details, and structural design calculations necessary to clearly describe the proposed test method, reaction load system capacity and equipment setup, types and accuracy of apparatus to be used for applying and measuring the test loads, and pile top movements. ● Calibration. Calibration reports and data for each test jack, pressure gauge, master pressure gauge, and electronic load cell to be used. Ensure that the calibration tests have been performed and certified by an independent testing laboratory within 90 calendar days of the date submitted. Obstructions. When obstructions are encountered during the installation of micropiles, notify the Engineer. Make all reasonable efforts to install the piles at the required location and to the proper depth. Excavate to remove the obstruction or employ all usual methods to install piles. Do not relocate piles until the Contractor submitted Shop Drawings have been approved by the Engineer. Allowable Construction Tolerances and Acceptance Criteria. Ensure that: • The center of gravity of the entire group of micropiles at an individual abutment is not more than 2 in. from the required center of gravity for the group. • The centerline of piling is not more than 3 in. from the required location. • The pile is plumb within 2 percent of the total-length plan alignment. • The top elevation of pile is plus 1 in. or minus 2 in. maximum from the required vertical elevation. • The centerline of reinforcing steel is not more than ¾ in. from the required location. The Engineer will not accept piles that are damaged or defective due to defective materials or an improper installation procedure, or piles that have an installed volume of cement grout not exceeding a volume equal to 110 percent of the theoretical volume of the drill hole. Cut off piles that are damaged or defective 1 ft below bottom of footing elevation, and document on the as -built drawing. Replace these piles by additional pile(s) installed adjacent to the removed/abandoned pile, and ensure that the replacement piles com ply with Subsection 844.03.3. Install the replacement pile(s) where the center of gravity of the group complies with the location criteria above. The Engineer must approve in writing any modification that necessitates changes to the structure.

Part 800 — Bridge Structures August 2025

SECTION 844 — MICROPILES 800-213 Correct piles that are mislocated beyond the specified tolerances by installing an additional pile at no additional cost to the Department. Ensure that the center of gravity of the combination of the two piles is within the location tolerance for the original location and the allowable tolerance for the abutment. Installation. Select the drilling method, the grouting procedure, and the grouting pressure used for the installation of the micropiles. Determine the micropile casing size, final drillhole diameter and bond length, and central reinforcement steel sizing necessary to develop the specified load capacities and load testing requirements. Estimate the grout take. Ensure that t he drillhole is open along its full length to at least the design minimum drillhole diameter before placing grout and reinforcement. Use temporary casing or other method of pile drillhole support in caving or unstable ground to permit the pile shaft to be formed to the minimum design drillhole diameter. The Engineer will review and approve the proposed method(s) to provide drillhole support and to prevent detrimental ground movements. Detrimental ground movement is defined as movement that requires remedial repair measures. Do not use drilling fluid containing bentonite. During construction, observe the conditions in the vicinity of the micropile construction site on a daily basis for signs of ground heave or subsidence, and immediately notify the Engineer if signs of movements are observed. Immediately suspend or modify drilling or grouting operations if: • Ground heave or subsidence is observed • The micropile structure is adversely affected • Adjacent structures are damaged from the drilling or grouting If the Engineer determines that the movements require corrective action, take corrective actions necessary to stop the movement or perform repairs. Immediately before grouting, ensure that the hole is flushed with clean water to remove all contaminated water and cuttings with the grout pipe located at the bottom of the hole. Pump the water at a high velocity until the wash water at the top of the casing is clear. Place reinforcement into the drillhole before grouting and before temporary casing (if used) is withdrawn. Ensure that the reinforcement surface is free of deleterious substances such as soil, mud, grease, or oil. Ensure that pile cages and reinforcement groups, if used, can withstand the installation and grouting process and the withdrawal of the drill casings without damage or disturbance. Check pile top elevations and adjust all installed micropiles to the required elevations. Provide centralizers and spacers at a maximum 10-ft on center spacing to provide a minimum 2 in. of grout cover over all steel reinforcing. Locate the upper and lower most centralizer a maximum of 5 ft from the top and bottom of the micropile. Ensure that centralizers and spacers permit the free flow of grout without misalignment of the reinforcing bar(s) and permanent casing. Lower the central reinforcement bars with centralizers into the stabilized drillhole and set. Insert the reinforcing steel into the drill hole to the desired depth without difficulty. Do not drive or force

Part 800 — Bridge Structures August 2025

800-214 SECTION 844 — MICROPILES partially inserted reinforcing bars into the hole. Redrill and reinsert reinforcing steel when necessary to facilitate insertion. Secure the lengths of casing and reinforcing bars to be spliced in proper alignment and to avoid eccentricity or angle between the axes of the two lengths to be spliced. Locate threaded pipe casing joints at least two casing diameters (OD) from a splice i n any reinforcing bar. When multiple bars are used, stagger bar splices at least 12 in. Grout the micropiles the same day that the load transfer bond length is drilled. Use a stable, neat, cement grout or a sand cement grout with a minimum 28 -day unconfined compressive strength of 4000 psi. Mix admixtures, if used, according to the manufacturer’s recommendations. Ensure that the grouting equipment produces a grout free of lumps and undispersed cement. Measure the grout quantity and pumping pressure during the grouting operations. Equip the grout pump with a pressure gauge to monitor grout pressures. Place a second pressure gauge at the point of injection into the pile top. Ensure that the pressure gauges can measure pressures of at least 150 psi or twice the actual grout pressures used, whichever is greater. Ensure that the grout remains in agitation before placing. Place grout within one hour of mixing. Size the grouting equipment to enable each pile to be grouted in one continuous operation. Inject the grout from the lowest point of the drill hole, and continue the injection until uncontaminated grout flows from the top of the pile. The grout may be pumped through grout tubes, casing, hollow -stem augers, or drill rods. Extract temporary casi ng, if used, in stages ensuring that, after each length of casing is removed, the grout level is elevated to the ground level before the next length is removed. Ensure that the tremie pipe or casing always extends below the level of the existing grout in the drillhole. Control the grout pressures and grout takes to prevent excessive heave or fracturing of rock or soil formations. Upon completion of grouting, the grout tube may remain in the hole but must be filled with grout. Allow the grout within the micropiles to attain the required design strength before being loaded. If the Contractor elects to use a post-grouting system, submit the working drawings and details to the Engineer for review and approval. Ensure that the grout within the micropile verification and proof test piles attains the minimum required three-day compressive strength of 2000 psi before load testing. During production, test the micropile grout for compressive strength according to AAS HTO T106/ASTM C109 at a frequency of no less than one set of three 2 -in. grout cubes from each grout plant each day of operation or for every 10 piles, whichever occurs more frequently. Complete unconfined compressive testing at three, seven, and 28 days. Use the average of the three cubes tested for the compressive strength. Take grout samples directly from the onsite grout plant. Provide grout cube compressive strength and grout density test results to the Engineer within 24 hours of testing. Install micropiles under the full -time inspection of the Engineer or authorized representative. Notify the Engineer a minimum of 48 hours before any initiating any micropile operations. The Engineer will not accept any pile installed when the representative of the Engineer is not present to obtain the necessary records. Install additional pile(s) to replace any pile(s) constructed without the presence of the Engineer, as directed, and at no additional cost to the Department.

Part 800 — Bridge Structures August 2025

SECTION 844 — MICROPILES 800-215 Installation Records. Submit to the Engineer full-length installation records for each micropile installed within one work shift after that pile installation is completed. Record the data on the micropile installation log. Provide a separate log for each micropile. Submit for approval a pile numbering plan identifying a unique pile designation number for each micropile. The Engineer will keep an independent record of each micropile installation. Ensure that each micropile installation log includes the following information: • Top of pile elevation immediately after installation to the nearest 0.1 ft • Pile cut-off elevation as installed to the nearest 0.1 ft • Bottom of pile casing elevation to the nearest 0.1 ft • Pile tip elevation as installed to the nearest 0.1 ft • Deviation from specified plan location in inches to the nearest ½ in. • Pile length immediately after installation to the nearest 0.1 ft • Pile designation number • Damage (if any) to pile and any required corrective action taken • Grout takes and pressures Verification Testing. Before starting the work, submit to the Engineer for approval a pile load test plan including a written description of the equipment and methods to be used. Ensure that t he methods are an approved type and are revised as necessary to meet the approval of the Engineer. Ensure that the pile load test plan and description are stamped by a Professional Engineer registered in the State of Rhode Island. Design the testing reaction frame to be sufficiently rigid and of adequate dimensions such that excessive deformation of the testing equipment does not occur. Ensure that t his determination, and the possible design of any required bracing, are performed by a Professional Engineer registered in the State of Rhode Island. Submit the c alculations, procedures, and working drawings stamped by the Professional Engineer for approval before the start of any load test work. Construct the test pile consistent with the production piles. Ensure that t he drilling and grouting method, casing length and outside diameter, reinforcing bar lengths, and depth of rock socket for the test micropile are consistent with the specifications for the production piles, increasing steel sizes as needed for test loads . Size the verification test micropile structural steel sections to safely resist the maximum test load. The testing can be performed as a tension or compression test using other piles, earth anchors, or dead load as reaction. Perform compression load testing according to ASTM D1143, and perform tension load testing according to ASTM D3689, except as modified herein. Perform pile load testing to verify the design of the pile system and the construction methods proposed before the installation of any production piles. Construct the test piles in conformance with the approved working drawings at the required locations. Perform load tests to verify that the installed micropiles will meet the required load capacities and load test acceptance criteria and to verify that the length of the micropile bond zone is adequate.

Part 800 — Bridge Structures August 2025

800-216 SECTION 844 — MICROPILES The micropile load test results must verify the Contractor ’s design and installation methods and be reviewed and accepted by the Engineer before the installation of production micropiles. Ensure that the maximum test loads applied to the micropile do not exceed 80 percent of the structural capacity of the micropile structural elements, including steel yield in tension, steel yield or buckling in compression, or grout crushing in compression. If there is any required increase in strength of the verification test pile elements above the strength required for the production piles, provide this at no additional cost to the Department. Position the jack at the beginning of the test so that unloading and repositioning during the test will not be required. Use testing equipment that includes dial gauges, dial gauge support, jack and pressure gauge, electronic load cell, and a reaction frame. Provide a description of the test setup and jack, pressure gauge, and load cell calibration curves. Design the testing reaction frame to be sufficiently rigid and of adequate dimensions so that excessive deformation of the testing equipment does not occur. Align the jack, bearing plates, and stressing anchorage so that unloading and repositioning of the equipment will not be required during the test. Apply the test load and measure using a hydraulic jack and pressure gauge. Use a pressure gauge that is graduated in 100 psi increments or less. Use a jack and pressure gauge that have a pressure range not exceeding twice the anticipated maximum test pressure. Ensure that the jack ram travel allows the test to be performed without resetting the equipment. Monitor the creep test load hold during testing with both the pressure gauge and the electronic load cell. Use the load cell to accurately maintain a constant load hold during the creep test load hold increment of the test. Provide an independently supported reference beam with supports firmly embedded in the ground at a distance of between 8 ft to 10 ft from the test pile. Ensure that one end of the reference beam is free to move as the length of the beam changes due to temperature variations. Measure pile top movement using three dial gauges mounted equidistant from the center of the test pile at 120° intervals around the pile. Rigidly attach the dial gauges to the reference beam. Vertically align the gauge stems on a smooth glass horizontal bearing surface. Ensure that the dial gauges can measure to 0.001 in. and have a travel sufficient to allow the test to be performed without having to reset the gauge. Establish reference points on the test pile at each end or at the center of the reference beam and on critical points of the reaction frame. Ensure that the reference points include graduated scales machine divided into 0.02 in. and attached securely to t he pile, reference beam, and other locations. Monitor the reference points during the pile load test. Protect the pile movement measuring system against rain, wind, frost, and any other disturbances that could affect the reliability of the movement measurements. Provide sun shading for the measuring system for the duration of the test and for a minimum of one hour before the start of the test.

Part 800 — Bridge Structures August 2025

SECTION 844 — MICROPILES 800-217 Install two telltales, one extending to the bottom of the test pile and a second extending to the bottom of the cased section or top of the bond zone. Use the telltales to determine movement at the top of the bond zone and at the pile tip. The Micropile Contractor’s Engineer will record the required load test data, and the Engineer will keep an independent record of the data. Test the piles to a maximum test load of 2.0 times the required micropile design load shown on the Plans or working drawings. Perform the pile load tests by incrementally loading the micropile according to the following cyclic load schedule for both compression and tension loading. Step Loading Applied Load Hold Time (Min.) 1 Apply AL 2.5 2 Cycle 1

Part 800 — Bridge Structures August 2025

800-218 SECTION 844 — MICROPILES The acceptance criteria for micropile verification load tests are: • Ensure that the pile sustains the first compression or tension 1.0 DL test load with no more than 0.50 in. total vertical movement at the top of the pile, relative to the position of the top of the pile before testing. • At the end of the 1.30 DL creep test load increment, ensure that test piles have a creep rate not exceeding 0.04 in./log cycle time (1 to 10 minutes) or 0.08 in./log cycle time (6 to 60 minutes or the last log cycle if held longer). Ensure that t he creep rate is linear or decreasing throughout the creep load hold period. • Take t he maximum test load as 50 percent of the applied test load that results in a movement under load of 0.5 in. at the pile tip. Measure the movement at the pile tip directly by the telltale. • Failure does not occur at the 2.0 DL maximum test load. Failure is defined as the load where the slope of the load vs. head settlement curve first exceeds 0.025 in./kip. The Engineer will provide written confirmation of the micropile design and construction methods for production piles within three working days of the submission of the micropile load test results report. Do not install production piles until approved by the Engineer. If a tested micropile fails to meet the acceptance criteria, modify the design, the construction procedure, or both , which may include modifying the installation methods, increasing the bond length, or changing the micropile type. The Engineer must provide a prior review and approval for any modification that necessitates changes to the structure. Any modifications of design or construction procedures or cost of additional piles and load testing shall be at the Contractor ’s expense. Test piles may be used as production piles provided that no failure has occurred. Cut off piles that are not used as production piles as indicated in the Contract and at least 1 ft below the bottom of the footing elevation and document on the as-built drawing. Proof Testing. Protect the pile movement measuring system against rain, wind, frost, and any other disturbances that could affect the reliability of the movement measurements. Provide sun shading for the measuring system for the duration of the test and for a minimum of one hour before the start of the test. The required load test data shall be recorded by the Micropile Contractor ’s Engineer. The Micropile Contractor’s Engineer shall submit a report of the results indicating the performance and acceptability of the test pile for the required factored axial load and displacement criteria specified below. Do not install production piles until approved by the Engineer. Test designated piles to a maximum test load of 1.60 times the Factored Axial Load (FAL). Conduct the tests by incrementally loading the micropile according to the following schedule, to be used for both compression and tension loadings. Design and use equipment as detailed under Subsection 844.03.8.

Part 800 — Bridge Structures August 2025

SECTION 844 — MICROPILES 800-219 Step Loading Applied Load Hold Time (min.) 1 Apply AL AL 4 2 Cycle 1

Part 800 — Bridge Structures August 2025

800-220 SECTION 844 — MICROPILES • Failure. Failure does not occur at the 1.60 FAL maximum test load. Failure is defined as the load where the slope of the load versus head settlement curve first exceeds 0.025 in/kips. If a micropile fails to meet the acceptance criteria, test another micropile at a location determined by the Engineer. For failed piles and further construction of other piles, modify the construction procedures. The Engineer must review and accept any modification that necessitates changes to the structure design. Any modifications of construction procedures, or cost of additional test piles and load testing, or replacement production micropiles will be at no additional cost to the Department.

Part 800 — Bridge Structures August 2025

SECTION 844 — MICROPILES 800-221 Micropile. The price constitutes full compensation for all design, labor, materials, tools, equipment, and other incidental items of work necessary to finish the work, complete and accepted, including drilling, furnishing, and placing the reinforcing steel and casing, grouting, and pile top attachments. The micropile Contractor is also responsible for estimating the grout take. No extra payment will be made for grout overruns. Verification Load Test. The price constitutes full compensation for all labor, materials, and equipment, including instrumentation and report, and all other incidentals required to finish the work, complete and accepted by the Engineer. Proof Load Test. The price constitutes full compensation for all labor, materials, tools, equipment, including instrumentation and report, and other incidentals required to complete the work, complete and accepted by the Engineer.

Micropiles in other states

• Alabama 546 · MICROPILES
• Connecticut 7.06 · Micropiles
• Maryland 413 · Micropiles
• Pennsylvania 1007 · MICROPILES