31 63 33_2022-09-13.pdf

CBP IDC-DLC SPECIFICATIONS

HARPERS FERRY, WV 9/13/2022

SECTION 31 63 33

MICROPILES

PART 1 GENERAL

1.1 SUMMARY

Work shall consist of designing, furnishing, installing, monitoring, and testing of the Micropiles, as detailed on the contract drawings, per the specifications described herein. The Contractor shall assume responsibility for the design and performance of the micropile foundation system.

Contractor shall install Micropiles which meet the requirements indicated in paragraph PERFORMANCE CRITERIA. Each micropile shall be constructed by drilling through the overburden soil into rock and installing permanent steel casing to the required depth and achieving the required length of bond zone in competent bedrock. This design bond zone length is commonly referred to as the "rock socket". The casing shall not extend deeper than the top of bond zone. The entire bond zone will rely on the bond capacity between the grout and the rock, and must be drilled into competent bedrock, meeting criteria described herein. The open borehole is injected with grout at the bottom of the pile, filling entire volume of bond zone and casing.

The specified reinforcement shall then be installed with centralizers before the grout begins to set. The locations of, unfactored loads, and conceptual micropile geometry will be provided on the drawings, but the size and spacing of each micropile within the pile cap is the responsibility of the contractor, subject to any constraints or minimum requirements indicated on the drawings or described herein.

1.2 REFERENCES

The publications listed below form a part of this specification to the extent referenced. The publications are referred to within the text by the basic designation only.

AMERICAN CONCRETE INSTITUTE (ACI)

ACI 318 (2014; Errata 1-2 2014; Errata 3-5 2015;

Errata 6 2016; Errata 7-9 2017) Building Code Requirements for Structural Concrete (ACI 318-14) and Commentary (ACI 318R-14)

AMERICAN WELDING SOCIETY (AWS)

AWS D1.1/D1.1M (2020; Errata 1 2021) Structural Welding Code - Steel

ASTM INTERNATIONAL (ASTM)

ASTM A36/A36M (2019) Standard Specification for Carbon Structural Steel

ASTM A252 (2010) Standard Specification for Welded and Seamless Steel Pipe Piles

ASTM A572/A572M (2021; E 2021) Standard Specification for High-Strength Low-Alloy Columbium-Vanadium

SECTION 31 63 33 Page 1

Structural Steel

ASTM A615/A615M (2020) Standard Specification for Deformed and Plain Carbon-Steel Bars for Concrete Reinforcement

ASTM A722/A722M (2015) Standard Specification for Uncoated High-Strength Steel Bar for Prestressing Concrete

ASTM C109/C109M (2021) Standard Test Method for Compressive Strength of Hydraulic Cement Mortars (Using 2-in. or (50-mm) Cube Specimens)

ASTM C150/C150M (2021) Standard Specification for Portland Cement

ASTM C188 (2017) Standard Test Method for Density of Hydraulic Cement

ASTM C494/C494M (2019) Standard Specification for Chemical Admixtures for Concrete

ASTM D1143/D1143M (2007; R 2013) Piles Under Static Axial Compressive Load

ASTM D3689 (2007; E 2013; R 2013) Standard Test Methods for Deep Foundations Under Static Axial Tensile Load

ASTM D3966/D3966M (2007; R 2013; E 2013) Standard Test Methods for Deep Foundations Under Lateral Load

U.S. FEDERAL HIGHWAY ADMINISTRATION (FHWA)

FHWA NHI-05-039 (2005); Micropile Design and Construction

1.3 APPLICABLE PUBLICATION

Unless otherwise specified herein, all micropile construction and testing shall be in accordance with the Federal Highway Administration Manual:

FHWA NHI-05-039 "Micropile Design and Construction".

1.4 MEASUREMENT AND PAYMENT

1.4.1 General

All costs in connection with furnishing all materials, equipment, and performing all labor for the construction of the micropiles for the building foundation system, including disposal of spoil materials from excavation, inspection, testing, mobilization and demobilization, rock probe holes, and load testing, complete as shown on the contract drawings and specifications, shall be paid for as part of the lump sum.

1.4.1.1 Protection and Records

Payment will not be made for any work for which satisfactory records, as

SECTION 31 63 33 Page 2 determined by the Contracting Officer, are not furnished. Drilling logs shall be maintained in accordance with paragraph 1.11.4 "Drilling Logs".

1.4.1.2 Criteria for Bidding

For bidding purposes, the contractor shall assume that a minimum of 4 micropiles will be installed at each individual column pile cap and piles will be installed along strip foundations at the maximum micropile spacing and geometries indicated on the drawings, with each micropile drilled completely through soil and weathered rock overburden, and a minimum of 10 feet into rock below top of bedrock level. Each micropile shall have a minimum diameter of 5 inches through the bond zone. Permanent micropile casing for exterior strip foundation piling and any other piles required to carry design lateral loading and/or bending moment shall have a minimum outside diameter of 7 inches.

1.4.2 Rock Probe Holes for Micropile Pile Caps

Verification of competent bedrock at all micropile locations (for bond zone capacity of each micropile and for global stability within micropile groups supporting individual column pile caps) is the part of the Contractor's micropile design. Therefore, payment for rock probing will be part of the lump sum. If the micropile installation ensures global stability without additional (deeper) testing, then rock probe holes are not necessary. The contract lump sum price shall constitute full compensation for furnishing all plant, labor, equipment, materials, and supplies, grouting of rock probe holes and performing all operations required for the completion of all work specified in paragraph 3.4.4 "Rock Probe Holes". Where further inspection of rock quality is deemed necessary beneath bond zone depths, the Contracting Officer will direct that a probe hole be performed. Refer to Paragraphs 1.13.4 and 3.4.4 for additional information.

1.5 SUBMITTALS

Government approval is required for submittals with a "G" classification.

Submittals not having a "G" classification are for information only. When used, a code following the "G" classification identifies the office that will review the submittal for the Government. Submit the following in accordance with Section 01 33 00 SUBMITTAL PROCEDURES:

SD-02 Shop Drawings

Micropile Drawings; G, RO

SD-03 Product Data

Steel Reinforcement; G, RO

SD-05 Design Data

Grout Mix Design; G, RO

Submit grout mix design for approval at least 30 days prior to the production of micropiles. Include test results for the proposed grout mix.

Grouting Plan; G, RO

Micropile Design Analysis; G, RO

SECTION 31 63 33 Page 3

Submit design analysis with calculations for the micropile deep foundation system to the Contracting Officer's Geotechnical Engineer for review and acceptance. Design Analysis shall meet requirements in paragraph 1.13 DESIGN CRITERIA and address all necessary installation methods, pile diameter, length, spacing, and geometry, steel reinforcement, etc., and shall discuss the required bond length in rock, and top and bottom of bond zone, with consideration for voids and weathered rock encountered during drilling. The Design Analysis shall explicitly state how design capacities will be achieved, to handle the service loads provided at each micropile cap location. Design Analysis shall also address global stability. This submittal shall be sealed by a registered professional engineer in the State Of West Virginia.

SD-06 Test Reports

Drilling Logs; G, RO

Detailed records in an approved form, for each micropile, showing shaft diameter, top and bottom elevations, bearing strata description, rock elevations, length and diameter of all permanent casing used in making the excavation, water conditions including the bottom condition at the commencement of grout placement, grout strength, grout volume, dates of excavation and grout placement, and other pertinent information. A record of each micropile shall be delivered to the Contracting Officer within 24 hours of its completion and a final package with all records shall be submitted at the completion of drilled pier activities. Upon completion of micropile construction, the Contractor shall provide a record of centerline locations based on the survey of the registered surveyor or engineer provided by the Contractor. In addition, corrective measures shall be similarly recorded. A complete tabulation of all records pertaining to approved micropiles shall be delivered to the Contracting Officer.

Mill Test Reports G, RO

Grout Strength Tests G, RO

SD-07 Certificates

Survey; G, RO

A certified copy of the survey. Lines and levels shall be established and micropile centerline locations staked and maintained by a registered surveyor or engineer provided by the Contractor.

Qualifications; G, RO

Qualifications of the foundation system Contractor shall show that he has been engaged in the successful installation of micropile deep foundations for at least 5 years. Qualifications of the Geotechnical Engineer shall show that he has a minimum of 5-years' experience in drilled pier construction.

Mill Certifications; G, RO

SECTION 31 63 33 Page 4

Submit mill certifications for steel pipe and bar reinforcement.

1.6 QUALITY CONTROL

1.6.1 Qualifications

The micropile contractor will be experienced in the design, construction, and load testing of micropiles in limestone geology. Submit documentation to exhibit successful completion of no less than five (5) micropile projects in the past ten (10) years in pinnacled limestone geology of similar scope and size. Include a brief project description, including soil and rock descriptions, with owner's name, current phone number, micropile construction details, structural details, and load test reports for each of the previous micropile projects. Submit resumes of superintendent/foreman, driller, and supervising project engineer to be assigned to this project. Submit resumes for each individual assigned to this project that summarize work experience on at least three (3) projects of similar scope and size as this project.

1.6.2 Quality Control

Government and Micropile Contractor shall meet at the jobsite prior to commencing micropile construction. Attendees shall include Construction Manager, Micropile Contractor, Geotechnical Engineers (both the Contractor's and the Government's), Contracting Officer, and QA personnel. The meeting shall discuss the Micropile Design, Construction Methods, Work Plan, Specifications, and resolve any conflicts related to the construction of micropiles.

1.6.3 Field Testing

Field testing shall be performed by the contractor's Geotechnical Engineer, to meet requirements listed in paragraph 3.4 TESTING AND EVALUATION.

1.7 PROJECT/SITE CONDITIONS

1.7.1 Subsurface Data

The Contractor shall pay particular attention to the subsurface exploration logs, the drilling notes, and groundwater levels contained in the contract documents. It is suggested that the bidders examine the actual soil samples and rock core samples to determine what equipment and methods will be necessary to construct the micropiles to achieve required bearing capacity. Subsurface boring logs are shown on the drawings. The Geotechnical Report and soil and rock core samples from the subsurface investigation are available for examination by bidders by notifying the Corps of Engineers. Advance notice must be given so these samples can be made available.

1.7.2 Bedrock Characteristics

1.7.2.1 General

The bearing capacity of the rock used for design purposes is not necessarily indicative of the hardness or the difficulty in removal of the rock which will be encountered in the excavation above the planned micropile design bond zone (rock socket).

SECTION 31 63 33 Page 5

1.7.2.2 Characteristics

Site specific bedrock characteristics are contained in the Geotechnical Report. The rock is typically slightly to moderately weathered, highly to moderately fractured, and medium hard to hard. The bedrock surface is pinnacled. The bedrock has the potential for solution features that are both air filled and filled with clay. These features are common in karst terrain. Open cavities in the bedrock are common.

1.8 SURVEY

Lines and levels shall be established, and micropile locations staked and maintained by a registered surveyor or engineer provided by the Contractor. A certified copy of the Survey shall be submitted to the Contracting Officer.

1.9 SEQUENCE OF WORK

The sequence of micropile construction shall be coordinated with other construction operations in order to minimize interferences. Micropile construction should not begin until after excavation and placement of fill has been completed within the building footprint unless otherwise approved by the Contracting Officer. Excavation for groups of micropiles shall be performed so that reinforcing steel and grout placement is a continuous operation performed the same day that the excavation is completed. For unforeseen reasons when excavations cannot be filled with grout the same day the excavation is completed, the rock socket shall be protected and cleaned just prior to placing concrete. Concrete shall be placed within 3 hours after approval of the completed excavation.

1.10 DIMENSIONS

Micropiles shall be circular in cross section. The Contractor's Micropile Design Analysis shall include all micropile sizing and spacing and shall match the micropile cap locations and details shown on the contract drawings. Rock sockets shall have a minimum length specified in the Design Analysis, and this length must be achieved in competent bedrock.

1.11 SUPERVISION, INSPECTION, AND RECORDS

1.11.1 Contractor Supervision

The Contractor shall provide for the supervision of all phases of micropile construction. Supervision shall be the Contractor's responsibility as outlined in paragraph 1.6 QUALITY CONTROL. Each micropile excavation shall be checked by the Contractor for its depth, workmanship, and for all tolerance requirements before any grout is placed.

1.11.2 Geotechnical Inspection

An independent licensed Professional Engineer with expertise in Geotechnical Engineering, hereinbefore and hereafter referred to as the Geotechnical Engineer, shall be paid for by the Contractor and shall be provided for micropile inspection and to oversee the recording and monitoring of all micropile construction. This includes completing and submitting the Drilling Logs, and preforming the requirements specified in paragraphs 1.6 QUALITY CONTROL and 3.4 TESTING AND EVALUATION. Each

SECTION 31 63 33 Page 6 micropile excavation shall be checked by the Geotechnical Engineer to ensure that it meets the requirements herein and supplementary guidance provided by the Contracting Officer. The Geotechnical Engineer shall have at least 5 years' experience in micropile construction. This Geotechnical engineer shall not be confused with the Contracting Officer's Geotechnical Engineer.

1.11.3 Government Inspection

In addition to the inspection by the Geotechnical Engineer, the Contracting Officer may inspect each micropile excavation and all drilling logs.

After inspection of the drilling logs, any micropile that is determined to be unacceptable shall be replaced by the contractor, at no additional cost to the Government.

1.11.4 Drilling Logs

An accurate record shall be kept by the Contractor of each micropile as drilled (installed). Records shall identify the micropile as indicated on the drawings. A record of each micropile shall be delivered to the Contracting Officer within 24 hours of its completion and a final package with all records shall be submitted at the completion of micropile activities. The Contractor shall furnish detailed records in an approved form for each micropile, showing diameters, locations and depth of test holes, top and bottom elevations, design bond zone (rock socket) description, rock elevations for top of bedrock, and top and bottom of rock socket, length and diameter of all casing used in making the excavation, water conditions, grout strength, grout volume, date micropile is excavated, date and time of commencement and completion of grout placement, steel reinforcement placement, plumbness and direction of deviation in plumbness, and any other pertinent information. Upon completion of micropile work, the Contractor shall provide a record of as-excavated centerline locations based on the survey of the registered surveyor or engineer provided by the Contractor. In addition, corrective measures shall be similarly recorded. A complete tabulation of all records pertaining to approved micropile shall be delivered to the Contracting Officer. Records shall be signed by the inspector and the Contractor's superintendent.

1.12 ALLOWABLE TOLERANCES

For dimensions referenced below that are not provided on contract drawings, use dimensions provided in the approved Micropile Design Analysis.

1. Centerline of micropiles to be within 2 inches from indicated plan location, except deviation of exterior strip foundation piling in transverse direction (perpendicular to longitudinal axis of wall/footing)from indicated plan location shall be no more than 1 inch.

2. Pile shall be plumb within 2 percent of total length plan alignment.

Plan length shall be determined from both the Design Analysis and Drilling Logs.

3. Top elevation of pile shall be within plus or minus 1 inch from vertical elevation indicated on plans.

4. Centerline of reinforcement pipe shall not be more than 1/2 inch from location indicated in Design Analysis.

SECTION 31 63 33 Page 7

1.13 DESIGN CRITERIA

1.13.1 General

The micropiles shall be designed to meet the axial and lateral capacities (unfactored loads) shown on the contract drawings, for both compression (downward) and tension (uplift). At locations where pile caps are adjacent to shallow foundations, micropiles shall also be designed to support induced stress from adjacent footings. Where necessary, the design analysis for exterior strip foundation piling shall consider the possible increase in pile bending moments due to eccentricity of applied vertical loading resulting from the maximum allowable pile installation tolerances indicated in paragraph 1.12. The calculations and drawings supporting design capacities shall be included with the Micropile Design Analysis submitted to the Government for review and acceptance.

The design analysis for laterally loaded piles shall incorporate the lateral pile design parameters provided in the Triad Engineering Geotechnical Report for the site, dated September 14, 2022, or alternatively justified parameters, subject to review and acceptance.

The overall length of each micropile will be determined such that the required capacity is developed through shear bond capacity between grout and rock over the length of contact with competent bedrock. This length of contact (surface area) with competent bedrock is defined as the rock bond zone, and also referred to as the "rock socket". The design analysis shall address how competent bedrock will be determined during drilling and construction of micropiles, but shall meet the minimum requirement stated herein. Micropiles shall be constructed to extend a minimum length of 10 feet below top of bedrock level for each micropile. This 10 foot minimum length shall include a minimum rock bond contact length of 6 feet with competent bedrock, or shall extend to the length of bond zone determined in the approved Micropile Design Analysis, whichever length is greater. Each micropile shall be a minimum diameter of 5 inches through the bond zone.

Permanent micropile casing for piles that are not part of a multi-pile group within a single cap, including exterior strip foundation piling, as well as any other piles required to carry design lateral loading and/or bending moment, shall have a minimum outside diameter of 7 inches. Voids encountered within the bond zone shall not exceed 4 inches for any individual void and the total sum of voids within the bond zone shall not be more than 12 inches.

Due to potential corrosivity of site soils, the design shall consider a minimum thickness loss of 1/16 inch in the steel outer casing of the micropiles from corrosion.

The proposed micropile connection to pile cap shall be provided in the Micropile Design Analysis and shall be integrated with pile caps as shown on drawings.

1.13.2 Factor of Safety - Axial

Use a factor of safety of 3 to determine the minimum design capacity for each micropile. The provided capacity for both compression (downward) and tension (uplift) shall be at least three times the unfactored load provided on drawings. If load testing is included as part of the approved Micropile Design Analysis, then the factor of safety may be reduced to 2.

SECTION 31 63 33 Page 8

1.13.3 Buckling

Micropiles shall also be designed to resist buckling. These criteria must be satisfied for the scenario of sinkhole formation, in which all lateral support from overburden soil is lost. Use a factor of safety of 2 for buckling failure. The Design Analysis shall also address potential unbraced pile length impacts to pile capacity in the event piles are extended through encountered voids.

1.13.4 Global Stability

Design for micropiles shall address the global stability of a single micropile and micropile group at each pile cap. It is possible that large voids will exist beneath micropiles, even when bond zones are achieved in competent bedrock. It is necessary to ensure that no void exists beneath a micropile group, to a sufficient depth beneath the bottom of the bond zone.

With sufficient competent rock below the bond zone of each micropile, any load on a group would be sufficiently distributed into surrounding rock below the pile tip, in the event of a void collapse. To verify global stability, probe hole testing shall be completed in accordance with paragraph 3.4.4. In lieu of probe holes, Contractor and/or Engineer may elect to lengthen the bond zone of a single micropile within each multi-pile supported pile cap an additional 5 feet minimum, to ensure competent bedrock beneath each pile. This lengthened micropile is to be the first pile installed within that pile group.

1.14 MICROPILE DRAWINGS

1.14.1 Micropile Detail(s)

The micropile detail(s) shall include design load, pile type, pile diameter & length, casing and reinforcement dimensions, elevations for top of competent rock, bond zone length, and foundation connection (top of pile).

If multiple micropile types are to be used, include details for each type.

1.14.2 Connection Detail(s)

Connection detail(s) shall show how micropile will be structurally connected to pile cap(s), to effectively transfer all loads shown on drawings to micropile foundation. If multiple connection types are to be used, include details for each type. If the pile caps shown on drawings are not sufficient for micropile connections, then an alternative pile cap design shall be provided with the design analysis to included drawings and calculations. Connections shall be designed in accordance with FHWA NHI-05-038 "Micropile Design and Construction". Structural Design of any individual element not covered by the FHWA Manual shall be in accordance with ACI 318 Building Code.

1.14.3 Construction (Work) Plan

Submit layout drawings indicating proposed installation sequence of micropiles. On this sequential layout, indicate locations of piles with dimensioning, pile type, elevation, installation sequence number, etc.

Submit detailed written description of the proposed micropile construction procedure, list of equipment to be used, and plan describing the control/disposal of surface water, drill flush and excess waste grout.

Include a step by step description of the proposed micropile construction procedure, including personnel testing, and equipment to assure quality control. This step by step procedure shall be shown on the shop drawings in

SECTION 31 63 33 Page 9 sufficient detail to allow the engineer to monitor construction and quality of the micropiles.

1.15 LOAD TEST

If Contractor and/or Micropile Designer elects to incorporate a Load Test for design, the Load Test(s) shall be performed in accordance with ASTM D1143/D1143M (compressive), ASTM D3689 (tensile), and/or ASTM D3966/D3966M (lateral), as appropriate.

PART 2 PRODUCTS

2.1 STEEL REINFORCEMENT

Steel pipe conforming to ASTM A252 Grade 3 with minimum yield strength of 80 ksi. May be new "Structural Grade" ("mill secondary") steel pipe meeting requirements herein but without mill certification, free from defects (dents, cracks, tears) and with two coupon tests per truckload delivered to the fabricator. Welded seams and splices shall be complete penetration welds. When welded for structural purposes the following material conditions apply: The carbon equivalency (CE) as defined in AWS D1.1/D1.1M, Section XI5.1, shall not exceed 0.45, as demonstrated by mill certifications.

Threaded couplers are not permitted for splicing the reinforcement pipe.

Threaded casing joints shall develop at least the required compressive and tensile capacities achieved by each micropile.

2.1.1 Mill Test Reports

Submit mill test reports for steel pipe and bar reinforcement showing the results of tests conducted in accordance with ASTM Specifications.

2.2 GROUT

Neat Cement Grout with a minimum 28-day Compressive strength of 4,000 psi per ASTM C109/C109M.

Cement shall be a type I, II, or III cement manufactured in accordance with

ASTM C150/C150M.

Water to Cement ratio shall be 0.45.

All admixtures, if used, shall conform to ASTM C494/C494M. Accelerators will NOT be permitted.

2.2.1 Grouting Plan

Submit grouting pan with complete description and details for the following: Methods and equipment for accurately monitoring and recording the grout depth, volume and pressure as grout is placed, and Procedure and equipment for Contractor monitoring of grout quality.

2.3 STEEL PLATES AND SHAPES

ASTM A36/A36M or ASTM A572/A572M, Grade 50.

SECTION 31 63 33 Page 10

2.4 CENTRALIZERS

Centralizers used for installation of reinforcing steel shall be fabricated from Schedule 40 PVC pipe or tube, steel, or material that is non-detrimental to the reinforcing steel.

2.5 BAR REINFORCEMENT

ASTM A615/A615M Grade 60 or 75, or ASTM A722/A722M Grade 150. Bar couplers, if required, shall develop the ultimate compressive and/or tensile strength of the steel reinforcement.

PART 3 EXECUTION

3.1 SITE PREPARATION

Site grading, to include excavation for cuts and placement of fills shall be completed prior to beginning micropile construction. Excavation for pile caps shall also be completed prior to beginning micropile construction.

3.2 EXCAVATION

3.2.1 General

Excavation for micropiles shall be whatever method necessary to excavate to the required dimensions and elevations. When the excavation has been started by one method and it is found impractical to complete it by such method, the work shall be continued by other methods, but without additional cost to the Government, nor shall completion of the contract be delayed thereby.

3.2.2 Classification of Excavation

Excavation shall be classified as described in Specification Section

31 00 00 EARTHWORK.

3.2.3 Casing

3.2.3.1 General

During excavation of micropiles, the surrounding materials above the rock socket shall be adequately and securely protected against cave-ins, displacement, and from seepage of groundwater or storm water by means of steel casings and/or by other approved methods.

3.2.3.2 Size

Protective steel casing shall have outside diameters greater than the indicated rock socket diameter to allow excavation of the rock socket with the protective casing in place. Casing shall be a minimum of 0.25 inches thick, but shall be of sufficient thickness to resist lateral earth pressures and water pressures for the size and depth of drilled pier required. All casing shall be clean and free of dents.

3.2.3.3 Extent of Casing

The casing shall be provided for the full depth of the overburden soil in each drilled micropile.

SECTION 31 63 33 Page 11

The limestone is pinnacled and therefore the elevations of competent rock will vary throughout the site. The possibility of voids also exists. This creates unpredictability in the elevations of suitable bearing rock. Due to the variability of the top of rock and depth to sound competent rock and potential presence of voids, the Contractor shall anticipate considerable variations in protective casing lengths.

3.2.3.4 Effects of Groundwater

All casings shall be sufficiently watertight to prohibit the entrance of water in order that the excavation, inspection, and cleanup operations can take place.

3.2.4 Spoil Materials

Spoil materials from excavation of micropiles shall be disposed of in spoil areas in accordance with Specification Section 31 00 00 EARTHWORK.

3.2.5 Blasting

Blasting is not permitted in micropile excavation. Excavation of the micropiles shall be limited to appropriate drilling equipment and/or air hammers with suitable attachments.

3.2.6 Dust Control

The use of air for the removal of cuttings from the micropile excavation is permissible provided dust control measures are employed. The measures to be employed are to be clearly stated, in writing, and approved by the Contracting Officer prior to commencement of any operations utilizing air.

3.2.7 Protection

3.2.7.1 Fresh Grout

Micropile drilling and installation shall not take place within 20 feet of grout less than 3 days old.

3.2.7.2 Top of Hole

Provide protection around the top of the excavation to prevent debris and earth from being dislodged into the excavation and grout, and to prevent the inflow of surface water into the excavation and grout.

3.2.8 Spoils, Surface Water, and Excess Grout

The contractor is responsible for control and disposal of surface water, drill flush, and excess grout. Drill flush and drill spoils will be handled as excavated spoils and stockpiled or removed off site in accordance with Specification Section 31 00 00 EARTHWORK. The site shall be graded to direct water to appropriate stormwater management features and/or erosion controls. Any waste grout shall be segregated from other spoils and placed with washed grout.

3.3 MICROPILE INSTALLATION

3.3.1 General

Micropile Contractor shall select the drilling method, grouting procedure, SECTION 31 63 33 Page 12 grouting pressure, and the load test requirement (if necessary) to construct the micropiles. Drilling equipment and methods shall be suitable for drilling through the conditions shown on the boring logs included with the contract drawings. Expect to penetrate intermittent hard rock layers, weathered and broken rock layers, voids, soil seams and to encounter steeply dipping rock pinnacles above the top of competent rock. Drill hole must be unobstructed along its full length and width prior to placing grout and reinforcement. Casing or other approved methods of drill hole support will be required. Use of drilling fluid containing bentonite is not allowed. Proposed methods for drill hole support and for prevention of detrimental ground movement shall be included the Micropile Design Analysis.

Predrilling the borehole and allowing hole to stand open is not acceptable.

Control surface water by gravity flow or pumping to remove from site.

Collection of water within or near the building footprint is not allowed.

Prevent any flow of surface water into previously drilled micropile locations. Dispose on site water in accordance with approved Erosion and Sediment plans, and local, state, and federal regulations. Do not allow water to accumulate at pile locations. Sumps within or near the building footprint must be lined with impermeable materials. Expect variability in finished micropile lengths.

3.3.2 Casing

The contractor is responsible for maintaining an open hole. As drilling advances to the required depth into competent bedrock, contact between the drill casing and the borehole shall be maintained. After drilling to tip elevation and extending casing to top of bond zone, internal rods shall be withdrawn. If steel casing is to be used as the designed reinforcement, then this should be described in the Micropile Design Analysis. Spliced casings shall also be described in the analysis, and shall be installed in a manner to avoid eccentric loading.

3.3.3 Steel Reinforcement

If central reinforcement is required for design, then it shall be installed prior to grouting the micropile, or immediately after placement before grout begins to set. Centralizers shall be used to ensure the reinforcement is installed with the correct alignment. Centralizers shall be spaced at a maximum 10 feet on center, with the upper and lower centralizer within 3 feet of the end of reinforcement. Centralizers shall permit free flow of grout without misplacement of reinforcement. If placing into wet grout, driving or forcing of the bar is not permitted.

3.3.4 Grouting

Grout shall be consistent with Grout Mix Design submitted to the government for approval. Grout micropiles the same day the bond zone is drilled. Grout shall be free of lumps and undispersed cement. Place grout within one hour of mixing in one continuous operation. Inject grout from the lowest point of the drillhole and continue until uncontaminated grout flows from the top of the pile. Extract temporary casing (if used) in stages, such that level of grout is maintained at ground surface. Control grout pressures and grout takes to prevent excessive heave or fracturing of rock or soil formations.

The contractor shall have a method of measuring grout quantity and pumping pressure during grouting operations. The grout pump shall be equipped with a pressure gauge to monitor pressures of at least 150 psi or twice the actual grout pressure used, whichever is greater. The contractor is responsible for limiting grout flow by either staging the grouting operation or thickening the grout. The grout strength shall not be

SECTION 31 63 33 Page 13 compromised. No additional payments for excessive grout volumes will be made.

3.4 TESTING AND EVALUATION

The Contractor shall give his full cooperation in the performance of the testing and evaluation program and shall allow the following reasonable times for evaluation of the test results by the Contracting Officer:

a. Grout Testing: Testing described herein shall be completed for each micropile.

b. Bearing Elevation: The approved top and bottom of bond zone for each micropile will be determined during drilling and verified by the Contracting Officer's Engineer after evaluation of the Drilling Logs.

c. Rock Probe Holes: If required per Micropile Design Analysis.

d. Load Test: If required per Micropile Design Analysis.

3.4.1 Grout Testing

Test compressive strength of grout samples in accordance with ASTM C109/C109M. Test shall consist of 3 grout cubes, with the achieved Compressive Strength to be the average of all 3 cubes. Test grout density in accordance with ASTM C188. Test shall consist of 3 grout cubes, with the achieved Density to be the average of all 3 cubes. Density shall be within 5% of the approved Grout Mix Design. Compressive Strength and Density shall be tested for each micropile.

Submit grout strength test results for compressive strength testing on grout samples taken from grout mixed for micropile construction.

3.4.2 Load Test

If required per Micropile Design Analysis, load test shall be conducted on a test (verification) micropile before beginning installation of production piles. Test verification pile to a maximum test load of 2 times the service load, as shown on the contract drawings. For compressive loads, load test shall be conducted in accordance with ASTM D1143/D1143M, Quick Test Method.

For uplift loads, load test shall be conducted in accordance with ASTM D3689.

Load test(s) is to verify the construction methods are sufficient to construct a micropile achieving the required design capacity within the bond zone determined during drilling. Results must be approved by the Contracting Officer before construction of production piles can begin.

Construction methods for production piles shall be identical to those used for test pile.

The maximum verification test load applied to the micropile shall not exceed 80 percent of the structural capacity of the micropile structural elements, to include steel yield strengths and grout compression. The hydraulic jack shall be positioned at the beginning of the test such that unloading and repositioning during the test will not be required. Furnish a report consisting of a summary sheet, load settlement graph, test micropile drilling logs, and time-load-settlement data in addition to items required by ASTM D1143/D1143M and ASTM D3689, respectively, within seven working days after completion of the load test. Do not exceed a vertical displacement of 1 inch at any time. If micropile fails, the Contractor shall modify the design, construction procedure, or both, as necessary to

SECTION 31 63 33 Page 14 produce a micropile capable of completing a successful load test.

Modification shall be submitted to the Contracting Officer's Geotechnical Engineer for review and approval. All modifications shall be at the expense of the contractor.

The verification pile load tests shall be made by incrementally loading the micropile in accordance with 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 0.15 DL

0.30 DL

0.45 DL

AL

2.5 2.5 2.5

3 Cycle 2 0.15 DL

0.30 DL

0.45 DL

0.60 DL

0.75 DL

0.90 DL

1.00 DL

AL

2.5 2.5 2.5 2.5 2.5

4 Cycle 3 0.15 DL

1.00 DL

1.15 DL

1.30 DL

1.45 DL

AL

2.5 10 to 60 min.

2.5

5 Cycle 4 0.15 DL

1.45 DL

1.60 DL

1.75 DL

1.90 DL

2.00 DL

1.50 DL

1.00 DL

0.50 DL

AL

2.5 2.5

Pile top movement shall be measured at each load increment. The load-hold period shall start as soon as each test load increment is applied. The verification test pile shall be monitored for creep at the 1.30 Design Load (DL). Pile movement during the creep test shall be measured and recorded at 1, 2, 3, 4, 5, 6, 10, 20, 30, 50, and 60 minutes. The alignment load shall not exceed 5 percent of the DL load. Dial gauges shall be reset to zero after the initial AL is applied.

The acceptance criteria for micropile verification load tests are:

1. The pile shall sustain the first compression or tension 1.0 DL test

SECTION 31 63 33 Page 15 load with no more than 0.25 inches total vertical movement at the top of the pile, relative to the position of the top of the pile prior to testing.

2. At the end of the 1.30 DL creep test load increment, test piles shall have a creep rate not exceeding 0.04 inches/log cycle time (1 to 10 minutes) or 0.08 inches/log cycle time (6 to 60 minutes or the last log cycle if held longer). The creep rate shall be linear or decreasing throughout the creep load hold period.

3. Failure does not occur at the 2.0 DL maximum test load. Failure is defined as load where the slope of the load versus head settlement curve first exceeds 0.025 inches/kip.

The Engineer will provide the Contractor written confirmation of the micropile design and construction within 3 working days of the completion of the verification load tests. This written confirmation will either confirm the capacities and bond lengths specified in the Working Drawings for micropiles or reject the piles based upon the verification test results.

3.4.3 Verification Test Pile Rejection

If a verification-tested micropile fails to meet the acceptance criteria, the Contractor shall modify the design, the construction procedure, or both. These modifications may include modifying the installation methods, increasing the bond length, or changing the micropile type. Any modification that necessitates changes to the structure shall require the Engineer's prior review and acceptance. Any modifications of design or construction procedures or cost of additional verification test piles and load testing shall be at the Contractor's expense. At the completion of verification testing, test piles shall be removed down to the elevation specified by the Engineer.

3.4.4 Rock Probe Holes

Where inspection of rock quality is necessary beneath bond zone depths, the Contracting Officer will direct that a probe hole be performed. At least one probe hole is required within each multi-pile supported pile cap, prior to the installation of the production micropiles, to a minimum depth of 5 feet below the proposed bottom of the deepest rock socket of all micropiles. If the micropile installation ensures global stability without additional (deeper) testing, then rock probe holes are not necessary. For example, in lieu of probe holes, Contractor and/or Engineer may elect to lengthen the bond zone of a single micropile within each multi-pile supported pile cap an additional 5 feet minimum, to ensure competent bedrock beneath each pile. This lengthened micropile will need to be the first pile installed within that pile group.

If more that 10% of voids are encountered within the 5 foot probe depth, or extension of first micropile, below the proposed pile tip elevation, the rock probing is to be extended and the bottom of rock socket/pile tip lowered for that particular pile group to a level where the bedrock competency and maximum permissible void requirements of this specification are met for the rock both within and below the micropile rock sockets.

When evaluation is complete and approved by the Contracting Officer, the probe hole shall be backfilled as required by the Contracting Officer.

SECTION 31 63 33 Page 16

3.4.4.1 Rock Probe Hole Drilling

The probe hole shall be used to evaluate the rock below the proposed bond zone elevation. The equipment used shall be a percussion drill capable of drilling a vertical hole approximately 2 inches in diameter to required depth. The drilling shall be accomplished under a relatively uniform downward pressure in a manner such as to avoid binding the drill bit. The size of the bit may be reduced as the hole is deepened, if necessary, to avoid binding. The drilled hole will be probed with a "feeler" rod by the Contractor's Geotechnical Engineer to determine whether a suitable bearing surface has been reached or whether the micropile will have to be deepened.

3.4.4.2 "Feeler" Rods

The Contractor shall provide the rock probe (feeler) rod made from a 3/8 or 1/2 inch steel reinforcing bar. The bar shall be longer than the hole depth and shall have a right angled chisel point formed at the end.

3.4.4.3 Record of Rock Probing

The Contractor shall keep accurate records of all rock probing accomplished under this contract and shall deliver complete, legible copies of these records to the Contracting Officer upon completion of each rock probe hole or at such other time or times as directed. All such records shall be preserved in good condition and order by the Contractor until they are delivered and accepted, and the Contracting Officer shall have the right to examine such records at any time prior to their delivery to him.

-- End of Section --

SECTION 31 63 33 Page 17

THIS PAGE INTENTIONALLY LEFT BLANK

SECTION 31 63 33 Page 18