Revision to Spec 31 62 51.pdf

P691 Aircraft Development and Maintenance Facility-Ph 2 eProject No. 1737036 Naval Air Station Patuxent River, MD

SECTION 31 62 51

SOIL IMPROVEMENTS USING DENSIFIED AGGREGATE PIERS OR RIGID INCLUSIONS

THIS SECTION HAS BEEN DEVELOPED IN RESPONSE TO PPI-387

PART 1 GENERAL

1.1 DESCRIPTION

Densified aggregate piers or rigid inclusions must be used to improve the soil bearing conditions and provide tension capacities at individual attachment points to achieve the specified criteria indicated herein and on the drawings. The contractor has the option of using densified aggregate piers or rigid inclusions, or a combination of both.

Performance criteria includes allowable uniform bearing pressures, tension capacities for single attachment points to foundations, and long-term settlement limits. Individual column loads will not be provided to the contractor.

The project will require surcharging to densify the underlying soils, as indicated on the civil drawings and specifications. The general contractor and specialty designer of the soil improvements must coordinate the surcharging work with the design and installation of the soil improvements. The specialty designer must review the settlement monitoring data of the surcharging and provide approval when the site is ready for the installation of soil improvements.

Work consists of designing, furnishing, installing, monitoring, and testing of the densified aggregate pier foundations to the lines and grades designated on the project foundation plan or rigid inclusions and as specified herein. Work will include all equipment, material, labor, and supervision to design and install aggregate pier elements, load transfer platforms and to perform soil and aggregate pier testing.

Drawings and general provisions of the Contract, including General and Supplementary Conditions and other Division 00 and Division 01 Specification Sections, apply to this Section.

The aggregate pier (number, diameter, and depth) and/or rigid inclusions (number, diameter, and depth) to be determined by the specialty designer.

Design must rely on subsurface information presented in the project geotechnical report. The information on ground conditions must be assessed to determine its suitability for the specified ground improvement system. Prepare site and predrill as necessary for aggregate pier installation.

The aggregate piers will be columns of compacted aggregate constructed in a columnar-type configuration to produce an intermediate foundation system for support of foundation loads to achieve the degree of improvement (allowable bearing capacity for maximum allowable settlements) as indicated in paragraph PERFORMANCE CRITERIA. The piers can be constructed with a down-hole vibratory probe, displacement mandrel system, or a down-hole tamper. It is the aggregate pier contractor's responsibility to determine and implement the systems and criteria to ensure that the specified performance is achieved.

Rigid inclusions will be columns of concrete or grout filled, slender

SECTION 31 62 51 Page 1

CUI

columns constructed in a configuration to produce an intermediate foundation system for support of foundation loads to the degree of improvement (allowable bearing capacity for maximum allowable settlements) as indicated in the paragraph PERFORMANCE Criteria.

The information on ground conditions must be assessed to determine its suitability for the specified ground improvement system after the soil surcharge is removed from areas requiring soil improvements . Prepare site for aggregate pier installation. For soils and groundwater conditions in which the predrilled hole remains open and stable, the aggregate can be placed by a loader into the open hole and compacted in lifts using a down-hole tamper. In unstable conditions, the hole stability must be maintained either with a down-hole vibratory probe, displacement mandrel system, or casing if the tamper method is used.

Removal of spoils from the site (which result from aggregate pier construction), removal of spoils off the working pad, footing excavation, and subgrade preparation following aggregate pier installation are not included. For removal of spoils from site due to aggregate pier installation, footing excavation and subgrade preparation, conform to Section 31 00 00 EARTHWORK, paragraph DISPOSITION OF SURPLUS MATERIAL.

1.1.1 Definitions

a. Aggregate piers are columns of compacted aggregate used to reinforce the ground to increase bearing capacity and reduce settlement of embankments or structures or to increase the density of soil. They can be constructed with a down-hole vibratory probe, a down-hole tamper, or a displacement mandrel system.

b. Designer is the firm employed by the Installer to design aggregate piers.

c. Installer: The firm that installs aggregate piers, who can be the general contractor or his subcontractor.

d. Load Transfer Platform: A crushed stone load transfer platform for rigid inclusions below the spread footings. The load transfer platform must be a minimum of 3 feet thick and comprised completely of No. 57 crushed stone and contain a minimum of one layer of geogrid.

The system must be designed to limit penetration (punching shear) of the Rigid Inclusions into the load transfer platform. The load transfer platform is not required for aggregate piers unless determined to be required by the specialty design engineer to meet the prescribed performance criteria .

e. Soil reinforcement refers to the aggregate piers being installed in the ground to increase the overall strength and stiffness of the soil mass, with little or no increase in the density of the soils in between the aggregate piers. A soil modulus test is typically performed to verify settlement and bearing capacity of the aggregate piers in both cohesive and cohesionless soils.

f. Soil densification refers to the aggregate piers being installed in the ground to increase the density of the soil in between the aggregate piers as well as the density of the overall soil matrix.

This is only applicable to cohesionless soils and is typically verified by in situ testing of the soil between the aggregate piers, such as standard penetration, cone penetrometer, or flat dilatometer

SECTION 31 62 51 Page 2 tests.

g. Down-Hole Vibrators: Down-Hole Vibrators are specially-designed, high-energy depth vibrators. The horizontal vibrations are created by a motor and eccentric weight located near the tip of the vibrator.

Extension tubes are bolted to the vibrator to allow it to be lowered to the necessary treatment depth.

h. Displacement Mandrel System: Displacement mandrel systems are constructed by advancing a specially designed mandrel augmented by dynamic vertical ramming energy to the full design depth. The hollow-shaft mandrel, filled with aggregate, is incrementally raised, permitting the aggregate to be released into the shaft, and then lowered by vertically advancing and ramming to densify the aggregate and force it laterally into the adjacent soil. The cycle of raising and lowering the mandrel is repeated to the top of pier elevation.

This equipment is most often used in soil conditions with high water tables or for soils where a pre-drilled hole will not remain open.

i. Down-Hole Tampers: Down-Hole Tampers are proprietary high-energy impact apparatus. The vertical tamping energy is provided by a hammer which is connected to a round, beveled tamper. The apparatus is lowered into a pre-drilled hole to the required treatment depth. Down hole tampers may also include minimum 11,000 pound circular steel tampers dropped from minimum heights of 25 feet to create high compactive energies.

j. Rigid inclusions are defined as controlled modulus column to mitigate excessive consolidation settlement of the entire magazine footprint and designated plan area surrounding the magazine. The Rigid Inclusions must be constructed by either auguring, or vibrating a hollow mandrel to the design depth and by backfilling with a controlled modulus cementitious mix (grout)to create the Rigid Inclusion. The Rigid Inclusions must be installed in either a triangular or rectangular spacing and extend a minimum of 50 feet below the bottom of the load transfer platform. The top of the Rigid Inclusions must extend one foot into the load transfer platform. A granular load transfer platform must be constructed at the top of the Rigid Inclusions as indicated on the plans. Rigid inclusion locations must be predrilled, if necessary, to permit installation to the design depth.

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 211.1 (1991; R 2009) Standard Practice for Selecting Proportions for Normal, Heavyweight and Mass Concrete

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)

SECTION 31 62 51 Page 3

ASTM INTERNATIONAL (ASTM)

ASTM C33/C33M (2018) Standard Specification for Concrete Aggregates

ASTM C1077 (2017) Standard Practice for Agencies Testing Concrete and Concrete Aggregates for Use in Construction and Criteria for Testing Agency Evaluation

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

ASTM D1196/D1196M (2012; R 2016) Standard Test Method for Nonrepetitive Static Plate Load Tests of Soils and Flexible Pavement Components, for Use in Evaluation and Design of Airport and Highway Pavements

ASTM D1557 (2012; E 2015) Standard Test Methods for Laboratory Compaction Characteristics of Soil Using Modified Effort (56,000 ft-lbf/ft3) (2700 kN-m/m3)

ASTM D6913/D6913M (2017) Standard Test Methods for Particle-Size Distribution (Gradation) of Soils Using Sieve Analysis

ASTM E329 (2021) Standard Specification for Agencies Engaged in Construction Inspection, Testing, or Special Inspection

ASTM STP 399 (1966) Vane Shear and Cone Penetration Resistance Testing of In-Situ Soils

1.3 SUBSURFACE DATA

Subsurface soil data such as provided on the project drawings. This data represents subsurface information available; however, variations may exist in the subsurface between boring locations .

1.4 BASIS OF DESIGN

1.4.1 Ground Improvement Design Acceptance Criteria

a. The ground improvement Installer is responsible for design of an Aggregate Pier or Rigid Inclusion ground improvement system that meets the global stability, allowable bearing capacity, densification, and settlement requirements stated on the contract plans. Industry recognized standards of design methods specific to the installer's equipment and construction methods must be used. The design must demonstrate by calculation that the spacing and layout fulfills the requirements.

b. The Aggregate Pier or Rigid Inclusion design stiffness modulus value must be verified by the results of the modulus test. The Contractor's Geotechnical Consultant must verify the modulus test based on the modulus test results.

SECTION 31 62 51 Page 4

c. Design Aggregate Piers in accordance with generally-accepted engineering practice and the methods described in Section 1 of these Specifications. The design must meet the following criteria.

(1) Minimum Allowable Bearing Pressure for Aggregate Pier or Rigid Inclusion Reinforced Soils: 4,000 psf under spread footings and 3,000 under strip footings, hangar door foundations, and as indicated on the drawings .

(2) Estimated Total Long-Term Settlement for Footings: Less than or equal to 1.0 inches .

(3) Estimated Long-Term Differential Settlement of Adjacent Footings:

Less than or equal to 0.5 inches .

( 4) The modulus of the aggregate material within the aggregate piers must have a minimum modulus of 100 pci . Rigid inclusions must provide a minimum modulus of 100 pci at the top of the load transfer platform where the footings bear.

(5) The Rigid inclusions must have a minimum diameter of 12 inches unless a larger diameter is determined to be required by the Designer to accommodate the specified allowable bearing pressure and settlement tolerances. Larger diameter rigid inclusions must be provided at no additional cost to the Government.

(6) The Rigid inclusions must have a minimum triangular or rectangular spacing of 5 feet center to center, unless a further spacing is determined to be adequate by the Designer to accommodate the specified allowable bearing pressure and settlement tolerances.

Further spaced rigid inclusions must be provided at no additional cost to the government.

d. The design submitted by the Installer must consider the bearing capacity and settlement of all footings and other structures supported by aggregate piers and/or rigid inclusions , and must be in accordance with acceptable engineering practice and these specifications. Total and differential settlement must be considered. The design life of the structure must be 50 years.

e. Aggregate piers must be installed to a depth of at least 25'-0" below finish grade. Rigid inclusions must be installed to depth of at least 50'-0" bellow finish grade.

f. If rigid inclusions are used, a load transfer platform must be used between the bottom of the footings and top of rigid inclusions. No substitutions or omittance of the load transfer platform will be allowed regardless of the contractor's request.

1.4.2 Measurement and Payment

Measurement and payment will be on a lump sum basis. Include the cost of all design, engineering and testing/inspection services, and all necessary plant, equipment, tools, material, labor, and supervision required to meet the contract requirements. Include provisions for pre-drilling. The Contractor and Installer are responsible for clearly defining their respective roles and responsibilities for compliance with this section and related contract drawings and specifications. No additional payment will be made for rejected or misplaced elements; withdrawn and reinstalled

SECTION 31 62 51 Page 5 elements; any portion of element remaining above the planned top elevation; buildups of elements installed below planned top elevation; or other excesses for which the Contractor is responsible.

1.5 SUBMITTALS

Government approval is required for submittals with a "G" or "S" classification. Submittals not having a "G" 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-01 Preconstruction Submittals

Designer and Installer's Qualifications ; G

Contractor's Geotechnical Consultant Documentation ; G

Testing Agency Qualifications ; G

SD-02 Shop Drawings

Uplift Anchor Hardware ; G

Aggregate Pier and/or Rigid Inclusions Installation Work Plans and Construction Drawings ; G

Load Test ; G

Progress and Final Reports ; G

Excavation Adjacent to Soil Improvement ; G

SD-03 Product Data

Uplift Anchor Hardware ; G

Aggregate Material Data ; G

Aggregate Pier and/or Rigid Inclusion Installation Equipment ; G

SD-05 Design Data

Design Submittal ; G

Excavation to Adjacent Piers ; G

SD-06 Test Reports

Modulus Testing Test ; G

Progress and Final Reports ; G

Aggregate ; G

Modulus Testing Test

Installer Qualifications Documentation

SECTION 31 62 51 Page 6

Independent Geotechnical Engineering & Testing Agency Documentation

SD-07 Certificates

Aggregate ; G

Cement; G

Load Test Supporting Data ; G

Warranty ; G

Daily Progress and Final Reports ; G

As- built Survey ; G

1.6 QUALITY CONTROL

1.6.1 Aggregate Pier and/or Rigid Inclusion Installation Equipment

Submit descriptions of proposed aggregate pier installation equipment before commencing work. Include details of the rig type and size, auger type, available torque and crowd. Include work procedures and control criteria.

1.6.2 Modulus Load Test Apparatus

Submit equipment description lists or catalog cuts and a brief description of the modulus load test procedure, including maximum load and modifications in accordance with the procedure required by ASTM D1143/D1143M and ASTM D1196/D1196M before commencing tests.

1.6.3 Contractor's Geotechnical Consultant Documentation

Hire the services of an independent, Registered Professional Geotechnical Engineer, experienced in soil mechanics, to observe test pier installation and production pier installation as specified herein. The Contractor's Geotechnical Consultant must be independent of the Contractor and must have no employee of employer relationship which could constitute a conflict of interest. The consultant must demonstrate that they have been engaged in successful inspection of aggregate piers for at least 5 years and inspected similar projects in similar scope utilizing the methods being performed for the subject project.

1.6.4 Design Submittal

The installer must submit detailed design calculations for aggregate piers and/or rigid inclusion, and load transfer platforms for approval at least four weeks prior to the beginning of construction. A detailed explanation of the design parameters for settlement and bearing calculations must be included in the Design Submittal. Additionally, the quality control test program for aggregate piers and/or rigid inclusions , confirming the design requirements, must be submitted. All calculations and drawings must be prepared and sealed by a Professional Engineer in the State in which the project is constructed.

The design must consider the bearing capacity and settlement of all footings supported by aggregate piers and/or rigid inclusions , and be in accordance with acceptable engineering practice and these specifications.

SECTION 31 62 51 Page 7

Total and differential settlement will be considered. The design life of the structure is 50 years. Detailed calculations, including anticipated loads, design assumptions and relevant subsurface information, must be provided. Drawings prepared for construction use and must include site plans showing Aggregate Pier or Rigid Inclusions locations and depths, and footing details showing layout beneath footings and uplift anchor connection details when applicable. Minimum Modulus at maximum design stress must be as specified in the final design documents provided by the Aggregate Pier Designer.

1.6.5 Aggregate Pier and/or Rigid Inclusions Installation Work Plans and Construction Drawings

The installer must submit construction drawings; installation work plan with aggregate pier installation details and testing details; and shop drawings with the location, spacing, numbering, diameter, and depth of the aggregate piers for approval at least 28 calendar days prior to the beginning of construction sealed by the Designer who must be a Professional Engineer in the State in which the project will be constructed.

1.6.6 Concrete Mix Design

Certify, using a Government-approved independent commercial testing laboratory, that proportioning of mix is in accordance with ACI 211.1 or ACI 318 for specified strength and is based on aggregate data which has been determined by laboratory tests during last twelve months. Submit a complete list of materials including type; brand; source and amount of cement , fly ash, and admixtures; and applicable reference specifications.

Submit additional data regarding concrete aggregate if the source of aggregate changes. Submittal must clearly indicate where each mix design will be used when more than one mix design is submitted.

1.7 QUALIFICATIONS

Installation of aggregate piers must be performed by a specialty Contractor experienced and competent in the installation of aggregate piers and/or Rigid Inclusions as specified herein. Submit evidence that the contractor has worked on similar type of projects. The projects must demonstrate proficiency of the designer as applicable to the intent of the project. The Designer must be a Professional Engineer registered in the state where the project is located.

Designers and Installers of aggregate pier foundation systems must have a minimum of 5 years of experience with the design and installation of aggregate piers and rigid inclusions in similar soil conditions and must have completed at least 20 similar projects of comparable size and type in similar soil conditions. These projects must demonstrate proficiency of the designer and the installer with either reinforcement or densification applications as applicable to the intent of the project. A list of projects, including name and description of the project, relative size, and contact person with phone number must be provided.

1.8 Independent Quality Control

1.8.1 Installer Qualifications Documentation

Documentation must be provided that the Aggregate Piers and/or Rigid Inclusion installer has qualifications that meet or exceed the

SECTION 31 62 51 Page 8 requirements of Park 1.4 of this Specification at least 45 Calendar days prior to the start of the work.

1.8.2 Independent Geotechnical Engineering & Testing Agency Documentation

The General Contractor is responsible for retaining an independent geotechnical engineering and testing agency (IGETA) to provide Independent Quality Control services. The IGETA must meet the accreditation requirements and comply with the testing and reporting requirements of Specifications Section 01 45 00 QUALITY CONTROL, Part 1.13.

1.8.3 Responsibilities of Geotechnical Engineering & Testing Agency

a. The IGETA must monitor the load test Aggregate Piers and/or Rigid Inclusion(s) installations and testing. The installer must provide and install all necessary dial indicators, load cells, and other measuring devices. The Rigid Inclusion Designer is responsible for directing and supervising the load test.

b. The IGETA must monitor the installation of Aggregate Piers and/or Rigid Inclusions to verify that the production installation practices are similar to those used during the installation of the load test Aggregate Piers and/or Rigid Inclusions and meet the deign depth and spacing.

c. The IGETA must report any discrepancies to the Installer. General Contractor and Contracting Officer immediately.

d. The IGETA must maintain a daily report and must include, at a minimum of the following information:

1. Installation equipment used.

2. Installation records including predrill depth (if applicable), Aggregate Piers and/or Rigid Inclusion number, installation start/finish time, length, volume of grout used, and depth of rigid inclusion.

3. Load Transfer Platform construction details.

4. Any unusual activity during installation.

e. The IGETA must observe the final excavations of the load transfer platform to the planned subgrade elevation, placement of the geotextiles and geogrid, and construction of the load transfer platform in accordance with the requirements of this specification.

PART 2 PRODUCTS

2.1 MATERIALS

a. Aggregate used by the aggregate pier Installer must be pre-approved by the Contracting Officer and must demonstrate suitable performance during modulus testing. Gradation curves and physical property tests results must be submitted 28 calendar days prior to scheduled start.

Aggregate stone consisting of ASTM C33/C33M No. 57 stone, or other graded aggregate approved by the Contracting Officer. For piers constructed below the water table, particles passing the No. 40 sieve must be eliminated. Where material is deemed appropriate for a dynamic penetration test ( ASTM STP 399 ), aggregate must be compacted to a densification and strength, which provides resistance to the

SECTION 31 62 51 Page 9 dynamic penetration test of a minimum average of 15 blows per 2 inches vertical movement. Test aggregate gradation in accordance with

ASTM D6913/D6913M .

The Installer must provide the soil laboratory test data on the proposed aggregate material including the source, type, and gradation of the aggregate to be used. Submit aggregate material data at least 30 calendar days before installation. Provide letters of certification and material delivery tickets from the aggregate supplier.

b. Materials selected must remain stable during construction and working life in the anticipated soil and ground water conditions.

c. Potable water or other suitable source supply must be used to increase aggregate moisture content where required. Access to water on site must be provided to the Installer by the General Contractor.

d. General Contractor to coordinate adequate and suitable marshalling areas on the project site for the storage of aggregate and equipment.

e. Provide uplift anchor hardware as specified in on the structural drawings . Provide drawings, diagrams, and schedules which detail hardware integration and installation. Letters of certification and material delivery tickets from the hardware suppliers must be submitted 28 calendar days prior to the scheduled start of the uplift test to verify that the materials are of the appropriate size, grade, and strength.

PART 3 EXECUTION

3.1 CONSTRUCTION OF AGGREGATE PIERS

3.1.1 Aggregate Pier Construction

Aggregate piers and rigid inclusions must be constructed in accordance with generally-accepted construction and engineering practices and the methods described in Section 1 of these Specifications. If pre-drill holes do not remain open before or during aggregate pier construction, bottom feed down-hole equipment must be used. Aggregate piers and rigid inclusions must be installed after the soil surcharging program is complete .

The construction of the aggregate piers must not start until the aggregate pier Geotechnical Design Engineer has determined that any ground settlement associated with surcharge program has ceased.

a. Section 03 30 00 CAST-IN-PLACE CONCRETE.

b. Section 31 00 00 EARTHWORK.

c. Geotechnical Report and Recommendations.

3.1.2 Plan Location and Elevation of Aggregate Pier Elements

The location of each pier or rigid inclusion must be determined by the Designer to provide compliance with the design requirements of paragraph AGGREGATE PIER AND RIGID INCLUSIONS DESIGN ACCEPTANCE CRITERIA. The final measurement of the top of piers must be the lowest point on the aggregate in the last compacted lift. Piers or rigid inclusions not properly located and deemed not acceptable must be rebuilt at no additional expense

SECTION 31 62 51 Page 10 to the Owner. The allowable construction tolerance must be within 6 inches both for horizontal and vertical design locations.

3.1.3 Rejected Elements

Aggregate pier or rigid inclusion elements improperly located or installed beyond the allowable tolerance must be abandoned and replaced with new elements , unless the Designer approves other remedial measures. For aggregate piers, aggregate must be replaced with fresh aggregate if cave-ins occur during aggregate placement where the volume of caved-in soil exceeds the volume of the aggregate being compacted by more than 10 percent. All material and labor required to replace rejected elements must be provided at no additional cost to the Owner, unless the cause of the rejection is due to an obstruction that is not pre-identified or mislocated by the Contracting Officer. Obstructions include boulders, timbers, concrete, bricks, abandoned utilities. Aggregate piers must be monitored for heave immediately after installation and after adjacent aggregate piers are installed. If piers heave more than 1/2 inch notify the Contracting Officer.

3.1.4 As-built Survey

After the installation of each aggregate pier group is complete provide the Contracting Officer with an as-built survey showing actual location and top elevation of each aggregate pier. Present a survey in such form that it gives deviation from plan location in two perpendicular directions and elevations of each aggregate pier to nearest half inch . Survey must be prepared and certified by a licensed land surveyor.

3.1.5 Protection of Existing Structures

Mitigate impact on existing facilities due to aggregate pier installation activities.

3.1.6 Excavation Adjacent to Soil Improvement

Impacts to installed aggregate pier must be minimized. Submit a complete design and evaluation by the Soil Improvement Designer in the event that utility excavations are required at horizontal distances of less than five feet from installed pier locations.

3.2 CONSTRUCTION OF RIGID INCLUSIONS

The following sections provide general criteria for the construction of Rigid Inclusion elements. Unless otherwise approved by the Designer, the installation method used for Rigid Inclusion construction must be that as used in the construction of the successful load test.

3.2.1 Vibratory Installation Method

a. Vibratory Rigid Inclusion systems must be constructed by advancing a bottom-feed mandrel with a top-mounted vibrator through the week strata to the full design depth. The hollow-shaft mandrel, is than raised, at a uniform rate while grout is injected under pressure through the shaft.

b. Grout must be supplies at a sufficient rate during tool withdrawal to ensure continuous Rigid Inclusion of the full designed cross-section is formed, free of debris. Depth of tool and volume of grout must be

SECTION 31 62 51 Page 11 recorded for each Rigid Inclusion. If the grout placement in any rigid inclusion cannot be completed as described, then the Rigid Inclusion must be reaugured before the grout has hardened and the grout placed in the final cutoff elevation or the Rigid Inclusion completely replaced.

c. Pre-auguring must be performed as necessary to allow the mandrel to penetrate through the known soil conditions to archive the specified Rigid Inclusion design depth.

d. For Rigid Inclusions, three sets of samples of the grout must be taken daily per ASTM C31/C31M to confirm the 28-day grout compressive strength.

e. The volume of grout must be periodically checked throughout installation to verify volume of grout is consistent with the load test volume.

3.2.2 Augured Installation Method

a. Augured Rigid Inclusion system must be constructed with the rotation of a displacement hollow-shaft auger through the weak strata to the full design depth. The auger is than raised, at a uniform rate while grout is injected under pressure through the shaft.

b. The volume of anticipated auger spoils must be estimated by the Installer and provided to the Contractor. All auger spoils will be disposed of the Contractor in the designated Surplus Soil Waste Areas.

c. Grout must be supplies at a sufficient rate during tool withdrawal to ensure continuous Rigid Inclusion of the full designed cross-section is formed and free of debris. Depth of tool and volume of grout must be recorded for each Rigid Inclusion. If the grout placement is any rigid inclusion cannot be completed as described, then the Rigid Inclusion must be reaugured before the grout has hardened and the grout placed to the final cutoff elevation or the Rigid Inclusion completely replaced.

d. For Rigid Inclusions, three sets of samples of the grout must be taken daily per ASTM C31/C31M to confirm the 28-day grout compressive strength.

3.2.3 Plan Location and Elevation of Rigid Inclusions Elements

The as-built center of each Rigid Inclusion must be within six (6) inches of the plan locations indicated. The tops of the Rigid Inclusions shall be installed within six (6) inches of the indicated elevations. Rigid Inclusion installed outside the above tolerances and deemed not acceptable must be rebuilt at no additional expense to the Government.

3.2.4 Rejected Rigid Inclusion Elements

Rigid Inclusions improperly located or installed beyond the maximum allowable tolerances must be abandoned and replaced with new piers, unless the Designer approves other remedial measures. All material and labor required to replace rejected Rigid Inclusions must be provided at no additional cost to the Government, unless the cause of the rejection is due to an obstruction.

SECTION 31 62 51 Page 12

3.3 FIELD QUALITY CONTROL

3.3.1 Quality Control Representative

The Contractor's Geotechnical Consultant must verify and report all aggregate pier and/or rigid inclusions installation procedures.

Immediately report any unusual conditions encountered during installation to the Contracting Officer. The QC procedures must include the preparation of Aggregate Pier and/or Rigid Inclusions Progress Reports completed during each day of installation and containing the following minimum information:

a. Aggregate Piers i . Footing and Aggregate Pier location.

ii . Aggregate Pier length and installed diameter.

iii .Planned and actual Aggregate Pier elevations at the top and bottom of the element.

iv . Average lift thickness for each Aggregate Pier.

v. Soil types encountered at the bottom of the Aggregate Pier and along the length of the element, if the holes were pre-drilled.

vi . Depth to groundwater, if encountered.

vii .Documentation of any unusual conditions encountered.

ix . Type and size of densification equipment used.

x. Quality of aggregate in each individual pier xi . Any additional quality control testing performed, such as modulus tests, dynamic penetrometer tests, and standard penetration tests, as deemed appropriate by the Contracting Officer.

b. Rigid Inclusions

i. Footing and rigid inclusion locations.

ii. Rigid inclusion length and installation diameter.

iii.Planning and actual rigid inclusion elevations at top and bottom of element.

iv. Soil type encountered at the bottom of the rigid inclusion and along the length of the element.

v. Depth to groundwater, if encountered.

vi. Documentation of any unusual conditions encountered.

vii.Any additional quality control testing performed, such as modulus tests, as deemed appropriate by the Contracting Officer.

SECTION 31 62 51 Page 13

3.3.2 Quality Control Verification Program

The Installer must be responsible for design of a verification program to assure the quality of the construction. The program must verify that the installed ground improvement system satisfies the performance requirements noted on the contract plans and the design requirements determined by the ground improvement system designer. The quality control program must include testing and observations by the Contractor's Geotechnical Consultant. As a minimum, the verification program must include the following:

a. Program to monitor performance of the ground improvement system during and after construction of the proposed structure. This program may include installation of settlement plates, monitoring points, inclinometers, piezometers, or other instrumentation.

b. Proposed means and methods for verification that the installed aggregate piers and rigid inclusions meet the strength and stiffness criteria required by the design. This may include, but must not be limited to modulus or load tests on individual elements and groups, soil borings, and other methods such as monitoring by instrumentation or settlement plates as approved by the Designer. Submit load test set-up and procedures utilized to confirm that the installation procedure develops the pier modulus utilized in design. Submit load test supporting data .

c. Quality control program to verify that the ground improvement system is installed in accordance with the designer's specifications and the requirements in this specification. The quality control program must include testing and observations by Contractor's Geotechnical Consultant.

3.3.3 Bottom Stabilization Verification Test for Aggregate Piers

After completion of the bottom pier bulb, or at any time during the process of construction of the pier, the energy source may be turned off, and bottom stabilization verification test may be performed. These tests must be performed when a new soil formation is encountered, or at the beginning of a project to provide quantitative information on pier stabilization. Acceptable performance is indicated if the vertical movement of the shaft is less than 150 percent of the vertical movement measured for the modulus test pier.

3.3.4 Modulus Testing Test

A modulus test must be performed by the Installer to obtain the parameter values used in design. The number of tests and locations must be determined by the Contracting Officer. A minimum of two modulus tests must be performed. Additional test can be performed at the discretion of the design engineer (PPI #387). The Installer must provide and install all dial indicators and other measuring devices, conduct tests, and prepare the test reports. The tests must be performed generally in accordance with ASTM D1143/D1143M and ASTM D1196/D1196M . The aggregate piers and rigid inclusions must be tested to satisfy bearing capacity at 150 percent of the design stress and to satisfy the settlement criteria in paragraph SOIL IMPROVEMENT DESIGN ACCEPTANCE CRITERIA at 100 percent of the design stress. The Installer must submit test reports for each test no later than seven days after the test is completed. Report must include a description of the testing equipment, records, complete test data, SECTION 31 62 51 Page 14 analysis of the test data and recommended design parameter values based on the modulus test results. The report must be prepared under supervision of and sealed by a professional engineer registered in the state of project location.

3.3.5 Testing Agency Qualifications

Engage an independent testing agency qualified according to ASTM C1077 and ASTM E329 for testing indicated. Submit testing agency qualifications to the Contracting Officer for approval.

3.3.6 Responsibilities of Contractor's Geotechnical Consultant

a. Review and verify that design meets the project requirements.

b. Report any discrepancies immediately.

c. Monitor the modulus compressive load tests when performed.

d. Monitor the installation of aggregate pier and/or rigid inclusion elements to verify that the production installation practices are similar to those used during the installation of the modulus compressive load test elements.

3.3.7 Aggregate Pier and Rigid Inclusion Records

Keep a complete and accurate record of each aggregate pier and/or rigid inclusion installed. Indicate the design location, deviations from pier and/or rigid inclusion location, cross section shape and dimensions, original length, ground elevation, tip elevation, cut-off elevations, volume of aggregate used or number of lifts, densification forces during installation, and final elevations or depths of the base and top of piers and/or inclusion . The records must also indicate the type and size of the installation equipment used, and the type of aggregate and/or grout used and testing and material sampling that was performed. Provide a complete and accurate progress drawing of aggregate pier and/or rigid inclusion installation. Provide final drawing upon completion of installation activities.

Submit test aggregate pier records for aggregate piers . Submit load test data and results.

The Installer must furnish a complete and accurate record of Ground Improvement installation to the Government and the General Contractor.

The record must indicate the pier and/or rigid inclusion location, length, average lift thickness and final elevations of the bases and tops. The installation reports must also indicate the type and size of the densification equipment used. The installer must immediately report any unusual conditions encountered during installation to the General Contractor, to the Designer and to the Government. Submit Daily Progress and Final Reports and Progress and Final Reports . Provide a Final Report documenting the results of all observations and tests conducted during the complete installation process. Report will certify that the bearing pressure has been achieved within settlement tolerances.

Provide warranty document good for 1 year.

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3.4 RESPONSIBILITIES OF GENERAL CONTRACTOR

3.4.1 Preparation

a. Locate the underground utilities. The Installer must protect underground and aboveground utilities and other structures from damage during installation of the Aggregate Pier elements.

b. Provide the site to the Installer after earthwork in the area has been completed, if applicable.

c. Site subgrade must be established by the General Contractor within 6 inches of final design subgrade, as approved by the Contracting Officer.

d. Perform layout of the aggregate piers and/or rigid inclusion and provide a work platform if necessary.

3.4.2 Utility Excavations and Excavation to Adjacent Piers

The General Contractor must coordinate all excavations made subsequent to aggregate pier and/or rigid inclusion installations so that at least 5 feet of horizontal distance remains between the edge of any installed Aggregate Pier and/or Rigid Inclusion and the excavation. In the event that utility excavations are required at horizontal distances of less than 5 feet from installed aggregate piers and/or rigid inclusion , the General Contractor must notify the Soil Improvement Designer to develop construction solutions to minimize impacts on the installed aggregate piers.

3.4.3 Footing Bottoms

a. Excavation and surface compaction of all footings is the responsibility of the General Contractor.

b. Foundation excavations to expose the tops of Soil Improvement elements must be made in a workman like manner, and must be protected until concrete placement, with procedures and equipment best suited to (1) prevent softening of the matrix soil between and around Soil Improvement elements before pouring structural concrete, (2) achieve direct and firm contact between the dense, undisturbed Aggregate Pier elements and the concrete footing. Disturbed soil and aggregate must be recompacted per paragraph FOOTING BOTTOMS, list item c.(3) (below).

c. The following criteria must apply, and a written inspection report sealed by the Contractor's Geotechnical Consultant Agency must be furnished to the installer to confirm:

(1) That water (which may soften the unconfined matrix soil between and around the Aggregate Pier elements, and may have detrimental effects on the supporting capability of the aggregate pier reinforced subgrade) has not been allowed to pond in the footing excavation at any time.

(2) That all aggregate pier elements designed for each footing have been exposed in the footing excavation.

(3) That immediately before footing construction, the tops of all aggregate pier elements exposed in each footing excavation have

SECTION 31 62 51 Page 16 been inspected and recompacted as necessary with mechanical compaction equipment, and that the tops of any aggregate pier elements which may have been disturbed by footing excavation and related activity have been recompacted to a dry density equivalent to at least 95 percent of the maximum dry density obtainable by the Modified Proctor method ASTM D1557 unless approved otherwise by the Contracting Officer.

(4) No excavations or drilled shafts must be made after installation of aggregate pier elements within a horizontal distance of five feet from the edge of any pier, without the written approval of the Contracting Officer.

3.5 PRECONSTRUCTION CONDITION SURVEY

Perform preconstruction condition survey of structures and utilities within 200 feet of the aggregate pier and/or rigid inclusions installation specified in the plans. Perform outreach to the owner of the structures 28 days before performing the preconstruction condition survey. The Contractor must obtain written permission from the owner of the structure prior to accessing the structure. The preconstruction condition survey must include video and photographic documentation of the exterior and interior of above ground structures and of the interior of underground structures. Video documentation must be in high definition, and show existing conditions and highlight, where possible, existing cracks, deteriorated concrete, exposed and corroded reinforcement, cracked or broken brick or mortar, and other signs of distress. For utilities, perform the survey when the greatest extent of the interior is exposed.

Provide supplementary artificial lighting as needed. The video must include annotation with location and structure nomenclature which describes any areas of distress over the video and time code superimposed on the video. Photographs must be accompanied by sketches or descriptions that indicate the location and direction of each photograph. For each structure surveyed, provide a Pre-Construction Condition Survey Report following completion of the survey. The report must contain all documentation associated with the survey including DVD copies. In the report, include notes, sketches, photographs, and videos. Provide general information, such as location details and structure type, as well as particular information on materials, condition, existing damage, aperture and persistence of cracks, and disrepair observed during visual survey.

Provide a graphical depiction of locations of damage or other features of concern. Submit the Preconstruction Condition Survey Reports no later than 28 days before the commencement of aggregate pier installation.

Accept responsibility for damages to existing adjacent or adjoining structures created by aggregate pier installation, and repair any damages to these structures without cost to the Government.

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3.5 PRECONSTRUCTION CONDITION SURVEY