1007MICROPILES

1007.1DESCRIPTION —This work is the furnishing of materials, tools, equipment, and labor for the

installation of micropiles. This includes test micropiles, production micropiles, and load testing. A micropile is a small-diameter, bored, cast-in-place composite pile, in which the applied load is resisted by steel reinforcement, cement grout and frictional grout-ground bond. The following definitions apply:

micropile during testing to keep the testing equipment correctly positioned.

a minimum grout cover is provided.

reinforcement to another.

applies a sustained loading over a relatively long period of time.

total movement at each load increment.

micropile after the primary grout has set.

installation of the reinforcement to transfer the load to the surrounding ground along the pile.

micropile capacity with depth, and establish contractor micropile order lengths.

1007.2MATERIAL—

strength of 2,000 pounds per square inch and a minimum 28- day compressive strength of 5,000 pounds per square inch according to AASHTO T 106. Determine material proportions with adequate flowability without causing segregation at the end of the grout tube.

Section 701.

to the manufacturer’s recommendations to control bleed, reduce shrinkage, improve flowability, reduce water content, or retard setting time. Accelerators and admixtures containing chlorides are not allowed.

to AASHTO M 31, Grade 75. Bars with full -length thread meeting the same material requirements are allowed. Provide bars clean of deleterious substances. When mechanical splice systems are required, they must develop the ultimate tensile strength of the bars and maintain the required grout cover over the splices.

of ASTM A252 Grade 3 with an elongation of 15% and have a minimum yield strength of 50 ksi to 80 ksi as used in the design submittal. Pipe casing diameter and minimum wall thickness as indicated. Pipe casings from 5 inches to 12 inches in diameter will be considered micropiles. Material with visual defects such as dents, cracks or tears will be rejected. Use of material classified as mill secondary is acceptable when tests are performed verifying tensile strength and steel chemical composition. Provide flush-joint type pipe casing splices, threads, and joints. Threaded casing joints and welded joints must develop at least the required compressive, tensile, and bending strength used in the design of the micropile. For permanent pipe casing seams and splices that will be shop or field welded the following fabrication and material conditions apply:

• Maximum carbon equivalency (CE) of 0.45, according to AWS D1.1 as specified in Section 1005, and according to mill certification.

• Maximum sulfur content 0.05%, according to mill certification.

• Use only complete penetration welds.

• Do not use welded lap splicing.

material that is non-detrimental to the reinforcing steel or grout. Do not use wood or aluminum.

1007.3CONSTRUCTION—

of micropiles, and meeting the following qualifications:

• Micropile contractor has c ompleted at least five projects that demonstrate experience in the construction of micropiles.

• Employ a Professional Engineer registered in the State, with at least 3 years of experience in the design and construction of micropiles and pile load test systems, who is to design the system, verify the proper construction of the testing system and the piles, and certify the test results.

• Employ drill operators and on- site supervisors each having at least 3 projects within the last 5 years of experience in micropile construction in similar site and soil conditions.

least 21 calendar days before planned micropile construction. Begin micropile work only after all construction submittals have been received, reviewed, and accepted in writing by the Representative.

company names of consultants or manufacturers , and provide the names of the applicable personnel as follows:

• List at least five completed projects that, together, demonstrate the required experience in the construction of micropiles. Experience must include all phases of micropile construction, from start to finish. Include a brief description of each project, and the name and telephone number of owner’s representative knowledgeable in each project listed.

• The Professional Engineer who is to design the system, verify the proper construction of the testing system and the piles, and certify the test results.

• List of drill operators and on-site supervisors that will be under the direction of the Professional Engineer.

ultimate strength, yield strength, elongation, and material properties composition. For mill secondary pipe casing, coupon test results may be submitted instead of mill certification. Provide testing results for two coupons per 500 linear feet of casing for each lot of mill secondary casing delivered to project site.

Record along with Welding Procedure Specifications according to AWS D1.1, Structural Welding Code, to the Structure Control Engineer for acceptance.

calibration tests by an independent testing laboratory within 6 months before use.

• Grout mix design. Include type of materials used, certified test data, trial batch reports, and density of the wet mix. In addition to a planned standard mix design, include data for modified mix design(s) containing fine aggregate or admixtures that may be needed to control excessive grout loss.

• Methods and equipment for accurately monitoring and recording the grout depth and volume as the grout is being placed.

• Procedure and equipment for monitoring grout quality. At a minimum, immediately before grout placement, measure the density of mixed grout from each batch or truckload using a mud balance, according to API RP-13B-1.

• Estimate curing time for installed grout to achieve the specified minimum 3-day 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. Any previous test results must have used the same materials and proportions as the proposed mix design.

• Method to control and dispose of surface water, groundwater, and excess waste grout generated by the work.

micropile load testing method. Include 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 according to this specification. The Professional Engineer must verify that the load test system is constructed correctly, and the testing is done according to the approved plan.

105.02(c), showing proposed sequence of pile installation, including pile number and location. Define the

personnel, equipment, and materials to ensure quality control. Provide step by step description of the proposed procedures to be used to install the micropiles. Provide sufficient detail to allow the Representative

to monitor the construction and quality of the m icropiles. Include i nformation on headroom and space requirements for installation equipment, which verify that the proposed equipment can perform at the site.

micropile construction and related excavation as indicated, and according to the approved submittals.

adjacent or overlying facilities, structures, or newly installed piles. Provide an open borehole free of loose material and of minimum diameter and length as indicated, before placing reinforcement and grout. Do not use bentonite-based muds or other drilling slurries that adversely affect the grout to rock bond.

adjacent ground to avoid water and other drill material from entering and contaminating the drillhole. Lengths of casing and reinforcing bars to be spliced must be secured in proper alignment and in a manner to avoid eccentricity or angle between the axis of the two lengths to be spliced. Splices and threaded joints must meet the requirements of the reinforcement. Threaded pipe casing joints must be located at least two casing diameters (OD) from a splice in any reinforcing bar. When multiple bars are used, stagger bar splices at least 12 inches. Bar reinforcement groups, if used, must be sufficiently strong to withstand the installation and grouting process without damage or displacement . Use only threaded couplers for bar reinforcement splices. Bars must be threaded sufficiently into the couplers to develop the full tensile strength of the bar. Do not weld bar reinforcement. Bar reinforcement may be placed before or after the drillhole grout is placed. If placing bar reinforcement before grouting, first perform sufficient visual inspection or water retention testing of the borehole, or both to ensure the pile can be fully grouted. Lower the bar reinforcement steel with centralizers into the stabilized drillholes to the desired depth. Do not drive or force partially inserted reinforcing bars into the drillhole. Provide centralizers at 10-foot maximum spacing on bar reinforcement. Locate the upper-most and lower- most centralizers 3 feet maximum from the top and bottom of the central reinforcement. Use no less than 3 centralizers per micropile. If steel is placed first, c entralizers must allow insertion of grout tremie pipe to the bottom of the drillhole. Securely attach and position centralizers and spacers to the reinforcement; sized and positioned to allow grout to flow freely and entirely within the length of the drillhole and casing, and between adjacent reinforcing bars without causing misalignment of the reinforcement.

pressure during the grouting operations. Determine and schedule adequate installation methods such that there will be no grout communication between boreholes or damages to micropiles in which grout has not achieved final set. Keep and provide records for inspection by the Representative that show the quantities, test data, and grout pressures as indicated. After drilling is complete and immediately before grouting, assure the drillhole is free of drill cuttings and loose debris. Clean the final drillhole by f lushing with air or water if necessary. When in a karst geology, protect groundwater and surface water quality during drilling and grouting. When significant voids are encountered within the bonded zone, stop installation activity and notify the Representative. When voids greater than 12 inches are encountered, or grout takes begin to exceed 200% of the neat theoretical borehole volume, be prepared to take immediate measures to control grout take by modifying the grout mix or placement, or both, as detailed in the approved Grouting Plan. Provide neat-cement or sand- cement grout meeting the specified minimum unconfined compressive strengths that is colloidally-mixed, completely and thoroughly disbursed, free of clumped cement or sand. Use a mixer capable of continuous agitation of the grout. Use a progressing cavity pump capable of developing sufficient pressures and flow rates. Monitor grout consistency and delivery pressures with a pressure gauge equipped pump. The pressure gauge must be capable of measuring pressure twice the actual grout pressures used. Size the grouting equipment to enable the grout to be pumped in one continuous operation. Estimate the required grout take volume needed based on borehole dimensions and geologic conditions. In the presence of the Representative, test grout cube samples for compressive strength according to AASHTO T 106 at a frequency of no less than one set of three 2- inch grout cubes from each grout plant each day of operation or every 10 micropiles, whichever occurs more frequently. The compressive strength for acceptance is considered the average of the cubes tested. Provide compressive strength and density

test results to the Representative within 24 hours of testing. Place primary grout in one continuous operation within 24 hours after the load-transfer (rock bond zone) length is drilled. Place the grout by tremie tube method only, to deliver grout from the lowest point of the drill hole. Use pumping pressure only as required to aid grout delivery through the tremie tube, countering the flow resistance within the tube. Grout take should mimic gravity-head placement. Control grout delivery pressures to prevent fracturing of the adjacent rock and soil formations and ground heave. If the tremie is withdrawn as the grouting progresses, extract it incrementally that the tube remains extended a minimum of 3 feet below the wet grout level in the micropile. If the tremie tube remains permanently within the pile, it must be filled with grout. Fill the entire rock socket and the annulus between the rock and casing with grout without voids from the pile bottom to the top of the rock plunge depth. Continue grout placement until uncontaminated grout flows from the top of the micropile. If excessive grout loss into subsurface voids prevents a fully grouted pile, allow the first stage of primary grout to set a minimum of 18 hours before redrilling the grouted zone to the bottom of the pile. Take measures to minimize quantities of both grout loss and redrilling. Redrill to a diameter equal to the nominal inside diameter of the micropile casing. Grout the entire micropile with a second stage of primary grout until grout flows from the top of the micropile. If the grout level drops below the designed cut -off level because of seepage or shrinkage, top off with additional grout. High-pressure p ost-grouting methods employed after the primary grouting/regrouting are not allowed unless approved by the Chief Bridge Engineer. Check the micropile top elevations and cut off installed piles to plan elevations.

into the micropile drill holes is prohibited. Dispose of these fluids as indicated and according to local, state, and federal regulations and standards.

• Center of top of pile within 2 inches of the indicated planned pile center location.

• The pile alignment within 2% of the specified alignment (vertical or specified batter) for the entire length of the pile.

• Pile top vertical elevation within plus 1 inch to minus 1 inch of the design top of pile elevation including required pile embedment in footing.

• Center of the entire length of reinforcement bar or bar group within 0.5 inches from the center of the micropile.

because of improper or inadequate construction or due to damage caused by the Contractor. Before making a modification which requires changes to the design or construction of the structure, the Representative must review the modification and accept in writing.

installation and testing of any micropile scheduled for load testing. The grout within a micropile must attain the minimum required 3-day compressive strength of 2,000 pounds per square inch before performing the load testing. Design and construct the test reaction frame to be sufficiently rigid and of adequate dimensions such that excessive deformation of the testing equipment does not occur, and settlement of the apparatus does not occur for the duration of the test. Reaction testing that utilizes weighted-frames or crib-type frames must not cause instabilities in supporting ground or adjacent embankment slopes, and must not cause settlement during the load test. An analysis may be required to verify ground and slope stability during loading imposed by the weighted or cribbed test platforms. During test set -up, align the testing jack, bearing plates, and stressing anchorage such that unloading and repositioning will not be required during the test. An AL may be applied to the micropile before setting the movement recording devices. Zero the dial gauges at the first setting of AL.

Perform the required V erification Load Testing by l oading piles in compression at the loads and increments in Table A.

TABLE A Verification Test Loading Schedule Cycle Step Applied Load Hold Time (minutes) ApplyAL 1 AL 2.5 Load Cycle 1 2 0.15 DL 2.5 3 0.30 DL 2.5 4 0.45 DL 2.5 5 AL 1 Load Cycle 2 6 0.15 DL 1 7 0.30 DL 1 8 0.45 DL 2.5 9 0.60 DL 2.5 10 0.75 DL 2.5 11 0.90 DL 2.5 12 1.00 DL 2.5 13 AL 1 Load Cycle 3 14 0.15 DL 1 15 1.00 DL 1 16 1.15 DL 2.5 17 1.30 DL 10 to 60* 18 1.45 DL 2.5 19 AL 1 Load Cycle 4 20 0.15 DL 1 21 1.45 DL 1 22 1.60 DL 1 23 1.75 DL 2.5 24 1.90 DL 2.5 25 2.00 DL 10 26 1.50 DL 5 27 1.00 DL 5 29 0.50 DL 5 30 AL 5 Notes: *The verification test pile must be monitored for creep at the

1.30DL. Pile movement during the creep test must be

measured and recorded at 1, 2, 3, 4, 5, 6, 10, 20, 30, 50, and 60 minutes.

Tension load testing for verification according to the loading shown in Table A is allowed in place of compression load testing if indicated on the contract drawings . The tension load test method, if used, requires the reinforcing bar to be sized to handle the test loads, and the bar length must extend adequately above the micropile to allow proper coupling with the load cell. If upsizing the reinforcement bar is needed to complete the tension testing, the larger bar size is not required to be used in the production piles. Within 24 hours of completing a load test, submit a summary report to the Structure Control Engineer that includes time-load settlement data. Indicate in the report if micropile has passed or failed the load test.

Perform Verification Load Test on a test micropile as indicated, or as directed by the Structure Control Engineer. Verification Load test the first production pile installed at each designated substructure unit before the installation of the remaining piles in that unit. Two additional production piles may be installed to serve as reaction piles for the test. The acceptance criteria for the Verification Load Test are:

1.a The pile must sustain the DL with no more than 0.75 inches of total vertical movement at the top of the pile as measured relative to the top of the pile before the start of testing. If an alignment load is used, then the allowable movement will be reduced by multiplying by a factor of (DL- AL)/DL.

1.b Test piles must have a creep rate at the end of the 1.3 DL increment which is not greater than:

• 1/32 inch/log cycle time (1 to 10 minutes), or

• 1/16 inch/log cycle time (6 to 60 minutes) and has a linear or decreasing creep rate.

1.c Failure does not occur by 2.0 DL. Failure is defined as a slope of the load versus deflection curve (at end of increment) exceeding 0.025 inch/kip.

Submit the Verification Load T est time-load settlement data and graph ical representations of the data which show the acceptance criteria and the actual test data of the pile being load tested to the Structure Control Engineer and District Geotechnical Engineer. For test piles, the test results must be reviewed and accepted by the Structure Control Engineer before beginning the construction of any production piles represented by the test pile. The drilling and grouting methods, pipe casing, grout, and minimum depth of embedment of the production micropiles must be identical to those of the accepted verification test micropile. If a verification -tested micropile fails to meet the acceptance criteria, modify the construction procedure. Modifications may include, but are not limited to, modifying the installation method, installation equipment, or installed material as required to achieve acceptable verification tests. Submit proposed modifications of the accepted Work Plan to the Structure Control Engineer and the Designer for review and acceptance. Costs resulting from any micropile construction procedures that deviate from the accepted Work Plan, and the associated costs of additional verification testing, will be at the Contractor's expense. Any modifications of the micropile design that are due to changes or limitations in equipment or material will be at the Contractor's expense. These modifications include, but are not limited to, changes to maximum load, bond length, or micropile type, siz e or spacing. The Structure Control Engineer' s and the Designer's prior review and acceptance is required for any modification that necessitates changes to the structure. If a verification load tested pile fails to meet the acceptance criteria, immediately verification- test another micropile within the footprint of that substructure unit using the accepted modified criteria. At the completion of verification testing, remove the failed micropile down to a minimum of 2 feet below the bottom of the pile cap elevation.

Case 2 Verification and Proof Load Testing is intended for micropiles in highly variable geology, or for verifying consistency of sizeable micropile capacity. If load testing is conducted according to Case 2, micropile details such as bond lengths may be adjusted according to the grout-to-ground bond values from the results of the verification testing and supporting approved design calculations.

2.a Verification Load Testing Perform test in accordance with 1007.3(j)1 Case 1. Submit design calculations, prepared by a Professional Engineer licensed in the State for any proposed modifications to the micropile details, including modifications to the bond length or diameter which may result from the results of the micropile Verification Load Test for approval. If a verification tested micropile fails to meet the acceptance criteria, propose modifications to the design, the construction procedure, or both. Include a copy of the Verification Load Test results with the submittal containing proposed modifications. The

submittal containing modifications to the micropile details is incidental to the micropile item. A subsequent pile redesign requires an additional Verification Load Test to be completed and passed to determine the grout-to-ground bond strength of the redesigned pile. The as-designed pile cannot be modified based on the results of the Verification Load testing without the approval of the District Bridge Engineer.

2.b Proof Load Testing After Verification Load Tests are performed and proposed modifications to the micropile details are approved by the District Bridge Engineer, perform Proof Load tests at the micropile locations indicated on the plans, or as directed by the Structure Control Engineer. Proof Load test the first post-verification load tested production pile installed at each designated substructure unit before the installation of the remaining piles in that unit. Two additional production piles may be installed to serve as reaction piles for the test. Submit the Proof Load Test time-load settlement data and graphical representations of the data which show the acceptance criteria a nd the actual test data of the pile being load tested to the Structure Control Engineer and District Geotechnical Engineer. The Proof Load Test results must be reviewed and accepted by the Structure Control Engineer before beginning the installation of the remaining piles for a given pile group or substructure represented by the proof-tested pile. The drilling and grouting methods, pipe casing, grout, and minimum depth of embedment of the production micropiles must be identical to those of the accepted proof-tested micropile. Perform the required Proof Load Testing by loading piles in compression at the loads and increments in Table B.

TABLE B Proof Test Loading Schedule Cycle Step Applied Load Hold Time (minutes) ApplyAL 1 AL

2.5 Load Cycle 2 0.15 DL 2.5 3 0.30 DL 2.5 4 0.45 DL 2.5 5 0.60 DL 2.5 6 0.75 DL 2.5 7 0.90 DL 2.5 8 1.00 DL 2.5 9 1.15 DL 2.5 10 1.30 DL 10 to 60* 11 1.45 DL 2.5 12 1.60 DL 2.5 Unload Cycle 13 1.30 DL 4 14 1.00 DL 4 15 0.75 DL 4 16 0.50 DL 4 17 0.25 DL 4 18 AL 4 Notes: *Depending on performance, either a 10-minute or 60-minute creep test mustl be performed at the 1.30DL Test Load. Where the pile top movement between 1 and 10 minutes exceeds 0.04 inches, the 1.30DL Test Load must be maintained an additional 50 minutes. Movements must be recorded at 1, 2, 3, 5, 6, l0, 20, 30, 50 and 60 minutes.

The acceptance criteria for the Proof Load test are:

2.b.1 The pile must sustain the DL with no more than 0.75 inches of total vertical movement at the top of the pile as measured relative to the top of the pile before the start of testing. If an alignment load is used, then the allowable movement will be reduced by multiplying by a factor of (DL- AL)/DL.

2.b.2 Test piles must have a creep rate at the end of the 1.3 DL increment which is not greater than: • 1/32 inch/log cycle time (1 to 10 minutes), or

• 1/16 inch/log cycle time (6 to 60 minutes) and has a linear or decreasing creep rate.

2.b.3 Failure does not occur by 1.6 DL. Failure is defined as a slope of the load versus deflection curve (at end of increment) exceeding 0.025 inch/kip. For failed micropiles and further installation of other micropiles, modify the construction procedure. Modifications may include, but are not limited to, revising the installation method, the installation equipment, the installed material, installing replacement micropiles, or incorporating micropiles at not more than 50% of the maximum load attained. Costs for modifications due to non- performance of the accepted Work Plan will be at the Contractor's expense, including modifications to installation procedures, additional production micropiles, additional verification tests and verification and/or proof load testing. Submit variations from the approved Work Plan to the Structure Control Engineer and the Designer for review and acceptance. Any modifications of the micropile design that are due to changes or limitations in equipment or material will be at the Contractor's expense. These modifications include, but are not limited to, changes to maximum load, bond length, or micropile type, siz e or spacing. The Structure Control Engineer's and the Designer's prior review and acceptance is required for any modification that necessitates changes to the structure design. If a proof -tested micropile fails to meet the acceptance criteria, immediately proof test another micropile within the footprint of that substructure unit using the modified criteria. Re-submit the Proof Load Test time-load settlement data and graphical representations of the data which show the acceptance criteria and the actual test data of the pile being load tested to the Structure Control Engineer. At the completion of proof testing, remove any failed micropiles down to a minimum of 2 feet below the bottom of the pile cap elevation, at no additional cost to the Department.

a pile installation report to the Structure Control Engineer for acceptance. The report must be sealed by a Professional Engineer licensed in the State. Include written confirmation that the test load system was properly constructed, the tests were completed correctly, and the test piles have met the required acceptance criteria. Provide a separate log for each micropile that includes the following:

• Pile identification.

• Pile materials and dimensions.

• Pile drilling start and finish times along with drilling observations.

• Description of soil, rock and water encountered.

• Actual pile location.

• Actual top of rock elevation.

• Final tip elevation.

• Cut-off elevation for top and bottom of casing.

• Grout pressure measurements.

• Grout quantities pumped, including start and finish times.

• Grout cube compression test results.

• Description of unusual installation behavior or conditions.

• Deviation from plans or planned parameters.

• Load testing time-load settlement data and graphs, including items required by ASTM D1143.

• Comparison of load testing results and acceptance criteria.

1007.4MEASUREMENT AND PAYMENT—

Measured from the micro pile tip elevation (bottom of the bonded zone) to the final cutoff elevation (top of the casing) for accepted test micropiles and production micro piles. Includes compensation for labor, materials, equipment and incidentals necessary to perform the intended work to complete micro pile installation. Includes temporary casing if required and drilling through, soil, rock, concrete and obstructions. No payment will be made for r eaction piles installed solely to provide reaction loads for the verification testing of a test pile. The Representative will reject micropile(s) because of mis -location, misalignment, damage, or failure to meet other installation criteria. No payment will be made for rejected piles. Replace rejected piles as directed.

Payment will be lump sum per each including all testing apparatus design and analysis, furnishing and placing materials, furnishing, erecting, maintaining, and replacing equipment, and for labor and incidentals necessary to complete the verification testing and installation report as specified. No payment will be made for a Verification Load Test when the contractor has not performed the Verification Load Test in accordance with this specification, or when a load test fails due to improper pile construction.

Payment will be lump sum per each including all testing apparatus design and analysis (if it differs from Verification Load Test apparatus design and analysis) , furnishing and placing materials, furnishing, erecting, maintaining, and replacing equipment, and for labor and incidentals necessary to complete the proof testing and installation report as specified. No payment will be made for Proof Load Test when the contractor has not performed the Proof Load Test in accordance with this specification, or when a load test fails due to improper pile construction.

Grout in excess of two (2) times the neat theoretical volume of the drill hole. Grout volume includes primary first-stage, primary second- stage, and top-off grout, if required. Any grout required to fill the pile that is less than two times the neat volume is incidental to the micropile.

Measured from the top of the first stage of primary grouting to the bottom of the redrilling.