SECTION_31_56_13_-_Deep_Mix_Method_(DMM)_Walls_R2_0004.pdf

BUREAU OF INDIAN AFFAIRS OGLALA DAM SPILLWAY AND OUTLET WORKS

OGLALA DAM SPILLWAY AND OUTLET WORKS SECTION 31 56 13

JUNE 2023 DEEP MIX METHOD (DMM) SHEAR WALLS

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SECTION 31 56 13

DEEP MIX METHOD (DMM) SHEAR WALLS

PART 1 GENERAL

1.01 SCOPE OF WORK

A. This Section specifies the requirements for all deep mix method shear walls installed to reinforce foundation soils below the downstream toe of the existing embankment between Stations EM 8+90 and EM 17+00, including a working platform bench at the downstream toe of the embankment and the following items:

Submittals and quality control and assurance.

Bench-scale testing report. Report the results of laboratory soil-cement mix testing, physical properties, and proposed mix design.

DMM Shear Wall Test Section used to evaluate CONTRACTOR’s proposed mix design and installation equipment and procedures.

Coring to sample the soil-cement mix and assess the DMM/bedrock interface condition of the constructed elements.

Wet grab sampling to assess in-situ DMM mix of constructed elements.

All labor, equipment, and materials necessary to plan, design, and construct the DMM Shear Walls and associated testing, monitoring, sampling, and recording to meet the performance requirements outlined in these plans and specifications.

B. The layout and spacing of the DMM Shear Walls shown on the Drawings are for bidding purposes only. The COR may adjust the minimum shear wall width and center to center wall spacings oriented transverse to the embankment alignment based on final design revisions.

1.02 REFERENCES

A. ASTM International (ASTM)

ASTM C94 Standard Specifications for Ready-Mixed Concrete

ASTM C150 Standard Specification for Portland Cement

ASTM C192 Standard Practice for Making and Curing Concrete Test Specimens in the Laboratory

ASTM C618 Standard Specification for Coal Fly Ash and Raw or Calcined Natural Pozzolan for Use in Concrete

ASTM C821 Standard Specification for Lime for Use with Pozzolans

ASTM C939 Standard Test Method for Flow of Grout for Preplaced-Aggregate Concrete (Flow Cone Method)

BUREAU OF INDIAN AFFAIRS SECTION 31 56 13

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ASTM C989 Standard Specification for Slag Cement for Use in Concrete and Mortars

ASTM D1633 Test Method for Compressive Strength of Molded Soil-Cement Cylinders

ASTM D2113 Practice for Diamond Core Drilling and Sampling for Site Investigation

ASTM D2166 Standard Specification for Unconfined Compressive Strength of Cohesive Soil

ASTM D4380 Standard Test Method for Density of Bentonitic Slurries

ASTM D5084 Standard Test Method for Measurement of Hydraulic Conductivity of Saturated Porous Materials Using a Flexible Wall Permeameter

B. Federal Highway Administration (FHA)

Deep Mixing Manual for Embankment and Foundation Support

1.03 DEFINITIONS

A. Admixtures: Ingredients in the grout other than binder, bentonite, and water. Admixtures can be fluidifiers, dispersants, or retarding, plugging, or bridging agents that permit efficient use of materials and proper workability of the grout.

B. Bentonite: Ultra-fine natural clay principally comprising sodium cation montmorillonite.

C. Binder: Chemically reactive material (i.e., lime, Portland cement, gypsum, blast furnace slag, pozzolan), or other hardening reagents) that can be used for mixing with in-situ soils to strengthen the soils and form soil mix columns.

D. Binder Content: Ratio of weight of dry binder to dry weight of soil to be treated.

E. Binder Factor: Ratio of weight of dry binder to volume of soil to be treated.

F. Binder Factor In-place: Ratio of weight of dry binder to volume of mixture, which is the volume of the soil to be treated plus the volume of the slurry for the wet method or the volume of the dry binder for the dry method.

G. Binder Slurry: Stable colloidal mixture of water, binder, and admixtures that assists in loosening the soils for effective mixing and strengthening the in situ soil upon setting.

H. BRN: Total number of mixing blade rotations per 3 feet (1 meter) of shaft movement.

I. Column: Pillar of treated soil produced in situ by a single installation process using a mixing tool, to make a round column. A rectangular barrette produced by “element” and “wall,” which are related geometric terms.

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J. Continuous: A continuous wall has no open joints, open seams or open cracks.

K. Deep Mixing Equipment: Deep mixing equipment with various mixing tools including single vertical shaft mixing tools, multiple vertical shaft mixing tools, horizontal rotating circular cutters, chainsaw-type cutters, etc.

L. Element: This is an inclusive term that refers to a soil mix element produced by a single stroke of the mixing tools at a single equipment location. A column produced by a single-axis machine, a set of overlapping columns produced by a single stroke of a multiple shaft mixing tool, and a rectangular barrette produced by a mixing tool with horizontal axis rotating cutter blades are each considered an element. An element consisting of overlapping columns produced by a single stroke of a multiple-shaft mixing tool is sometimes referred to as a “panel.” A chainsaw-type mixing tool that travels as it mixes produces a continuous wall, which is not an element.

M. Filler: Non-reacting materials (i.e., sand, limestone powder, etc.).

N. Homogeneous: Homogeneous material is mixed uniformly throughout, exhibits consistent quality, and minimizes voids and inclusions.

O. Mix Design: Ratios of soil, binder, water, and additive quantities required to meet the design requirements of the project.

P. Mixing Process: Mechanical disaggregation of the soil structure and dispersion of binders and fillers in the soil.

Q. Mixing Tool: Equipment used to disaggregate the soil and distribute and mix the binder with the soil. Consists of one or several rotating units equipped with several blades, arms, and cutters with or without continuous or discontinuous flight augers, horizontal rotating cutter blades, or chainsaw-type cutters. All of the cutters shall have rock cutting tools.

R. Penetration (downstroke): Stage/phase of mixing process cycle in which the mixing tool is delivered to the appropriate depth (disaggregation phase) for withdrawal injection and disaggregation and mixing for penetration injection.

S. Penetration/Retrieval Speed: Vertical movement per unit time of the mixing tool during penetration or withdrawal.

T. Restroke: Additional penetration and withdrawal cycle of the mixing tool to increase the binder content and/or the mixing energy.

U. Retrieval: Withdrawal of mixing tool from bottom depth to the ground surface. Binder may be injected during retrieval, which also imparts additional mixing energy.

V. Rotation Speed: Number of revolutions of the mixing tool per unit time.

W. Soil-cement: Product of soil mix consisting of a mixture of the in situ soil and binder.

Also referred to as treated soil or deep mixed material.

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X. Soil Mix: In situ ground treatment in which fill and soil is thoroughly blended with cementitious and/or other binder materials homogeneously to improve strength, and compressibility characteristics.

Y. Stroke: One complete cycle (penetration and withdrawal) of the mixing process.

Z. Volume Ratio: Ratio of the volume of slurry injected (in wet mixing) to the volume of soil to be treated.

AA. Wall: Group of overlapping elements arranged to form a continuous wall.

BB. Water: Fresh water that is free of deleterious substances that adversely affect the strength and mixing properties of the grout and is used to manufacture grout.

CC. Water-to-Binder Ratio: Weight of water added to the dry binder divided by the weight of the dry binder. In wet mixing, the water-to-binder ratio of the slurry is determined from the weights of water and dry binder used to manufacture the slurry in a plant at the ground surface. In either wet or dry mixing, the total water-to-binder ratio is the weight of water in the mixture divided by the weight of dry binder. For wet mixing, the total water-to-binder ratio is the weight of slurry water plus the weight of soil water divided by the weight of dry binder. For dry mixing, the total water-to-slurry ratio is the weight of soil water divided by the weight of dry binder.

DD. Wet Mixing: Process of mechanical disaggregation of the soil in situ and its mixing with slurry consisting of water and binders with or without fillers and admixtures. Binder is delivered on mixing tool penetration for vertical and horizontal axis mixing tools.

EE. Withdrawal (upstroke): Stage or phase of retrieval of the mixing tool in which the final mixing occurs for penetration injection and initial mixing for withdrawal injection.

Disaggregation occurs during the penetration for both penetration injection and withdrawal injection.

FF. Withdrawal Rate: The average up-hole retrieval rate of the mixing tool.

1.04 PERFORMANCE REQUIREMENTS

A. CONTRACTOR shall be fully responsible for the means and methodology for the construction of the required DMM Shear Walls using wet mix technologies. In addition, CONTRACTOR is fully responsible for the DMM Shear Wall mix design.

CONTRACTOR shall perform all survey, layout, and utility clearance required for the DMM Shear Walls. The completed DMM Shear Walls shall meet the performance criteria described within this Specification.

B. The completed DMM Shear Walls shall be continuous, overlapping, homogeneous and cemented.

C. Allowable parameters for DMM Shear Walls construction are outlined in Table 31 56 13-1.4.

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Table 31 56 13-1.4

Parameter Minimum, Maximum, or Typical

Value

Top elevation of DMM Shear Wall elements

Typical Varies from approximately

Elevation 2975 to 3000

Bottom elevation of DMM Shear Wall elements

Typical Seated at least 3 feet into intimate contact with claystone bedrock

Shear Wall length (perpendicular to embankment)

Typical 21 feet

Overlap between individual elements Minimum 9 inches

Unconfined compressive strength of DMM Shear Wall material (fsc’) at 28 days

Specified 275 psi

D. Layouts and sizes of DMM elements that adhere to the minimum and maximum values of the parameters listed in Table 31 56 13-1.4 and included in the Drawings and/or Specifications will be deemed acceptable to meet the requirements of the design.

E. CONTRACTOR may propose different shear wall thicknesses, geometry or strengths to match their equipment provided the alternative configuration is equivalent in area replacement, geometric section, sliding and overturning factors of safety and bearing pressures.

F. The BIA Representative will work with CONTRACTOR to evaluate the proposed alternative to confirm it meets the design intent and meets the applicable design criteria.

The COR and BIA Representative will make the determination as to whether the proposed alternative configuration will satisfy the design intent.

1.05 QUALIFICATIONS

A. CONTRACTOR performing DMM shall have at least 5 years of experience in DMM comparable in scope to the work of this project. Experience shall include projects with that involve keying into the bedrock surface and DMM installations to depths of at-least 50 feet or greater using overlapping elements to create continuous wall structures similar to those shown on the drawings.

B. The DMM CONTRACTOR must assign a project manager who has had significant project experience on at least five DMM projects of similar size and complexity.

C. The DMM CONTRACTOR must assign a project technician to supervise the construction of the DMM work. The project technician must have had significant relevant project experience on at least five DMM projects.

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D. The DMM CONTRACTOR must assign a full-time field superintendent. The superintendent shall have at least 3 years of experience in DMM construction, including projects with installations to depths of 50 feet or greater using overlapping soil mixed elements to create continuous wall structures similar to those shown on the drawings.

E. The DMM CONTRACTOR must provide at least one equipment operator with at least 3 years of experience with the specific specialized equipment that is to be used to create the DMM elements.

F. The DMM CONTRACTOR must provide at least one field representative to collect samples for testing by a third party Testing Laboratory. Field representatives shall each have at least 3 years of experience in taking concrete samples in the field and have demonstrated a knowledge and ability to perform the necessary test procedures.

G. The independent (third party) Quality Control Testing Laboratory shall have at least 5 years of experience as a materials-testing laboratory with direct experience testing soil-mixed materials on projects comparable to that required for this project. The person in charge of the Work for the Quality Control Testing Laboratory shall be a Professional Engineer.

1.06 SUBMITTALS

A. Statement of Qualifications:

Submit documentation evidencing the experience requirements outlined in Paragraph

1.05 QUALIFICATIONS, including the names and telephone numbers of references that can verify the experience.

B. Bench-scale Testing Report: The CONTRACTOR must submit results from bench-scale tests conducted. The report should provide all data collected, including, at a minimum, descriptions of sampling techniques used, boring logs, classifications of all major soil strata to be mixed, site groundwater conditions, binder materials used, mixed design proportions, laboratory mixing techniques used, and curing curves for unconfined compressive strength versus time for each major soil type. Discussion of tests results should be provided, including proposed mix designs for use in the field.

C. Prior to construction of the DMM Shear Wall Test Section, submit a DMM Shear Wall Construction Plan that includes the following elements:

Description of the general layout of operations, including scale drawings which depict material preparation (batch plant) and storage areas.

Description of the work sequence and schedule.

Soil treatment mix design(s) that will be testing during the DMM Shear Wall Test Section including the binder types, additives, fillers, reagents, and their relative proportions, and the required mixing time, water-to-binder ratio of the slurry, binder factor, and volume ratio for a deep mixed element.

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If the source of water is not a source of potable water, submit water quality test data to demonstrate that the water will not have an adverse effect on the compressive strength of the soil-cement and grout.

A list and description of all equipment to be used for the DMM Shear Wall Test Section installations.

Procedure CONTRACTOR will utilize to verify the key in depth into the bedrock surface.

Plans, sketches, and a narrative that describes the procedures used to collect, contain, and dispose of mixing spoils. The plans and sketches shall show the proposed locations of holding tanks, holding basins, or other temporary facilities required to manage the mixing spoils.

D. Submit a revised DMM Shear Wall Construction Plan after completing the DMM Shear Wall Test Section that incorporates the results of the Test Section. Prior to submission of the DMM Shear Wall Construction plan, submit a DMM Shear Wall Test Section summary report that includes, but not limited to:

Dates of the test trial program, Summary of the Test Section work plan and any changes/deviations made from that plan, A summary table of the mix designs tested with the QC tests performed and results, and

A narrative section that provides an evaluation of results with recommendation of a mix design and DMM parameters that are to be used for production of the DMM Shear Walls.

E. Submit a Project Quality Control (QC) Plan that includes at a minimum the following:

Names and qualifications of any subcontractors used for QC activities.

Names and qualification of independent laboratory for QC testing.

Details of QC testing plan specific to the DMM trial test program. The QC plan shall include, but not limited to:

a. Number of test columns to be installed as part of the test trial program,

b. Mix design(s) that will be tested,

c. Description of the sampling methodology that will be used and the frequency and depth intervals that treated samples will be collected and tested, and

d. Description of the QC field verification tests that will be performed during the test program and schedule of expected results.

Details of all means and methods proposed for QC activities, including surveying, process monitoring, sampling, testing, documenting, and meeting schedule milestones.

Wet grab sampling and coring procedures, equipment, driller(s)’ resume, location, and frequencies.

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Wet grab soil-cement sampling procedures, equipment, locations and frequencies.

Reporting procedures, forms and frequencies.

F. Submit the following reports daily during construction of the DMM Shear Walls:

Daily Production Report, completed within one workday after any DMM Shear Wall construction activities. The Daily Production Report shall include:

a. Date and times of shifts, names of key personnel on site, and summary of equipment used.

b. The locations, installation sequence, and as-installed top and bottom elevations of the soil mix elements installed during the work shift(s), and any deviations from the planned locations and vertical alignment.

c. Time of start and completion of each DMM element installed during the work shift and a summary of any downtime during the shift including time of work stoppage, duration, reason, and if work stoppage occurred while mixing an element.

d. Mix design used, mixing equipment rotational speeds, penetration, and withdrawal rates, grout injection quantity per vertical foot (injection rate), and mixing time at the bottom of each element. Include printouts of all automatic batch plant data coinciding with the DMM element installation.

e. Other pertinent observations including, but not limited to, description of spoil returns, grout escapes, ground settlement and/or heave, collapses of the element, remixing of elements, obstructions, and any unusual behavior of the equipment during the soil mixing process.

f. Records of soil mix samples taken during the work shift(s).

G. Submit weekly during construction of the DMM Shear Walls:

Results of quality control testing.

Results of laboratory testing.

H. Submit after completion of DMM Shear Walls:

As-built plans showing the actual locations of each element, including the element dimension, the element verticality, the top and bottom elevations of each element and a tabular and graphical summary of all laboratory test data collected by the independent Quality Control Testing Laboratory during the course of the work, as well as copies of all test reports prepared by the independent Quality Control Testing Laboratory.

1.07 CONTRACTOR QUALITY CONTROL

A. CONTRACTOR shall be responsible for quality control and shall establish and maintain an effective quality control system. The CONTRACTOR’s minimum quality control for DMM Shear Walls is described in Paragraph 3.05 CONTRACTOR QUALITY

CONTROL.

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B. Provide all quality control data to the COR and BIA Representative within 24 hours of obtaining results in the format agreed to in the submittals. Required quality control data is described in Paragraph 3.05 CONTRACTOR QUALITY CONTROL.

1.08 QUALITY ASSURANCE TESTING BY THE COR

A. Provide safe access to the COR and BIA Representative at all times to all parts of the construction site for checking adequacy of equipment in-use, excavation, backfill placement and mixing procedures, and verification of material properties.

B. COR may perform field and laboratory quality assurance tests to confirm that DMM Shear Walls meets the requirements of this Section. CONTRACTOR shall obtain samples for testing by the COR at locations as directed by the COR.

C. Final acceptance of all materials and placement methods will be based on a review of quality control tests performed by CONTRACTOR, quality assurance tests performed by COR, and visual observations made by the COR and BIA Representative during construction.

D. If a test fails to meet the specified criteria, another test shall be performed after CONTRACTOR has completed the necessary corrective work. CONTRACTOR shall bear the expense of all the necessary corrective action and re-tests performed.

1.09 GEOTECHNICAL SITE CONDITIONS

A. Subsurface exploratory borings have been performed. Locations of the borings are shown on the Drawings.

B. The following geotechnical data report is available to the CONTRACTOR for review upon request from the COR:

GEI Consultants (2021), Geotechnical Data Report, Oglala Dam Subsurface Investigation, December.

1.10 DMM SHEAR WALL TEST SECTION

A. Schedule: Complete construction, testing, and evaluation of the Test Section no less than 14 calendar days prior to the start of construction of the production walls.

B. The purpose of the Test Section is to evaluate:

Equipment and construction methods.

Soil mix design performance.

Soil-mix condition at the bedrock interface by coring of the elements.

C. The DMM Shear Wall Test Section should be constructed as shown in the drawings over a three-day period and shall include cold joints between specified elements.

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MATERIALS AND EQUIPMENT

2.01 MATERIALS

A. Rock:

Parameters for site rock at the bottom of weathered are outlined in Table 31 56 13-2.1.

Table 31 56 13-2.1

Parameter Value

Bottom elevation of weathered rock Approximately Elevation 2938

Unconfined compressive strength at bottom of assumed weathered rock

65 to 250 psi

Unconfined compressive strength at 10 feet below assumed bottom of weathered rock

65 to 250 psi

Rock Quality Designation at assumed bottom of weathered rock

Varies from 75 to 90%

B. Grout:

Grout for the DMM Shear Walls shall be a homogeneous mixture of cement, water, and other additives.

Use Type I or II Portland cement conforming to ASTM C150. Measure, handle, transport, and store bulk cement in accordance with the manufacturer’s recommendations.

Supply water of sufficient quantity and quality required for construction. Water must meet the requirements of ASTM C94. Identify water supply locations in the DMM Shear Wall Construction Plan.

Ensure that grout temperature remains between 35° and 90°F.

If grout admixtures are used, provide a written statement from the manufacturer as to the use of the admixture, its effect on the soil mix material, its long-term performance and stability, and its effect on the environment.

The grout shall not have begun its initial set before it is injected into the ground.

C. Soil Mix: Soil mix design is the responsibility of CONTRACTOR. Mix design should allow for a homogeneous and continuous backfill material that meets the requirements outlined in Paragraph 1.04 PERFORMANCE REQUIREMENTS

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2.02 EQUIPMENT

A. The DMM Shear Wall construction equipment shall be described in the DMM Shear Wall Construction Plan, and shall meet the following requirements:

The equipment shall be capable of constructing the DMM Shear Walls as specified and shown on the drawings by mixing in-place, thoroughly blending the in-situ soils and grout to the appropriate depths.

The equipment shall be of sufficient size, capacity, and torque to perform the soil mixing to the desired depths and widths.

The equipment should be capable of advancing through previously installed elements to achieve designed overlapping or remixing as needed and be sufficient to maintain the necessary revolutions per minute and penetration rate at the maximum depth to achieve thorough mixing.

The mixing and injection equipment should be sufficient to adequately blend and evenly distribute the grout with the in-situ soils to provide the required treatment, per the mix design.

Provide electronic sensors on the equipment to record vertical alignment in two directions: Fore-aft and left-right. Output from the sensors shall be routed to a console that is visible to the operator during construction.

Mark the equipment to allow the COR or BIA Representative to visually confirm the penetration depth to within 6 inches during construction.

Pre-mix the grout in a mixing plant, combining dry materials and water in predetermined proportions. Inject the grout directly into the ground via the soil mixing equipment.

The cutting tools shall be strong enough to penetrate weathered rock and roughen factored or solid bedrock.

Provide equipment with devices to permit accurate and continuous monitoring, recording, and control of: cement-grout injection pressures and quantities, injection rates, mixing rotational speeds, advancement and withdrawal rates of the mixing tools, and other operations required to construct the walls.

EXECUTION

3.01 GENERAL

A. Deep mixed elements shall be constructed to the lines, grades, and cross sections indicated in the plans and shall meet the strength and uniformity requirements indicated in these specifications. CONTRACTOR shall establish consistent procedures during construction to ensure that the acceptance criteria are satisfied. The procedures shall be established based on the results of the field validation program.

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3.02 DMM SHEAR WALL TEST SECTION

A. Prior to construction of production DMM Shear Walls, construct a Test Section at the location shown in the drawings for COR and BIA Representative testing and approval.

Construct the DMM Shear Wall Test Section using the same means, methods, materials, and equipment scheduled and approved for construction of the DMM Shear Walls. The Test Section shall be constructed over 3 days and shall include cold joints between elements as indicated.

B. Each test wall element shall be seated at least 3 feet into the bedrock to provide intimate contact between the element and the rock as shown on the drawings with no cuttings or untreated soils left in place.

C. CONTRACTOR shall obtain full-depth core samples, soil-cement wall/bedrock interface core samples, and wet grab soil cement samples from the test elements in accordance with the CONTRACTOR Quality Control requirements with the following increased frequency:

Wet Grab Samples:

a. Sample five DMM elements or columns per DMM Shear Wall.

b. Sample within the top half and bottom half of the element or column height or as directed by the BIA Representative.

c. Prepare 5 full 3” x 6” cylinders, per sample depth.

d. Test cylinders for unconfined compressive strength in accordance with ASTM D1633 at the following:

1) One break at 7 day.

2) One break at 14 days.

3) Two breaks at 28 days.

4) One break at 56 days.

Coring and Sampling:

a. Obtain four full depth cores per DMM Shear Wall. Two cores shall be tested at 14 days. Two cores shall be tested at 28 days.

b. Cores shall retrieve samples that are a minimum diameter of 3 inches.

c. Cores shall extend 2.5 feet into bedrock.

d. Test core samples for unconfined compressive strength in accordance with ASTM D2166 at the following at 28 days. Test a sample of the core every 2.5 feet, or a minimum of eight samples per core run, whichever is greater.

e. Test cores shall be extruded in near vertical manner and all efforts shall be made to prevent the core from bending. All cores shall be placed in wooden boxes and stored under cover.

D. Test samples should be submitted to the approved independent laboratory for testing.

CONTRACTOR may propose other sampling techniques to obtain continuous samples of the deep mixed material which, if approved by the COR, could be submitted as further evidence of compliance with the acceptance requirements.

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E. The performance of the Test Section will be judged in accordance with the design requirements specified in the Paragraph 1.04 PERFORMANCE REQUIREMENTS above.

F. Construction of the production DMM Shear Walls shall not be allowed to proceed until successful performance of the Test Section has been demonstrated, and a revised submittal of the DMM Shear Wall Construction Plan has been approved by the COR.

G. The Test Section may remain in place when construction is complete.

3.03 DMM SHEAR WALL CONSTRUCTION

A. Mobilize and maintain a sufficient number of soil-cement mixing rigs, materials, cement grout batching plants, and crews to complete the Work in accordance with the project schedule and milestones.

B. Perform all survey, lay out and utility clearance required for the soil-cement mixing.

C. Provide spoil containment facilities and other measures necessary to protect and maintain the site in a workable condition.

D. Perform DMM only in the presence of the COR or BIA Representative.

E. The DMM element shall be seated into the rock to provide intimate contact between the element and the rock as shown on the drawings. The top of rock elevation will be determined based on an observed spike in crowd force and reductions in penetration rate results recorded on the production log or by other methods approved by the COR or BIA Representative.

F. Use guide trenches or templates, and survey control as a minimum to maintain proper horizontal location and alignment of the DMM equipment.

G. Continuously monitor and adjust the vertical alignment of the DMM equipment leads using electronic sensors that provide continuous measurements of vertical alignment displayed directly to the equipment operator.

H. Continuously monitor and control the grout injection rate, rotation speed, penetration rate, and withdrawal rates. The injection rates, rotation speed, penetration rate, crowd force, and withdrawal rate shall be the same as used in the satisfactorily completed Test Section.

I. Once mixing of an element is started, continue the mixing operation until the element is completed. If an interruption of more than 1.0 hours occurs, the entire element shall be remixed using the correct dosage of fresh grout, at no additional cost to the AGENCY.

J. Mixing of elements shall be sequenced such that previously mixed elements are sufficiently soft to allow overlapping of elements producing a continuous wall with the minimum specified width.

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K. Immediately after installation of the element, obtain wet grab samples of in-situ DMM mix in accordance with the locations and frequencies specified in CONTRACTOR Quality Control section of this specification.

L. Do not allow debris to enter the top of the element while it is curing.

M. If observations during installation of an element indicate a potential for discontinuity of the element due to improper installation procedures, equipment problems or collapse of the surrounding soil, the element shall be remixed to full depth, at no additional cost to the

AGENCY.

N. If an obstruction is encountered that prevents drilling advancement, the CONTRACTOR should immediately notify the COR and BIA Representative within 30 minutes.

CONTRACTOR shall begin work to break up, push aside, or remove the obstruction.

CONTRACTOR will be compensated for removal or clearing of obstructions that take more than 30 minutes only with prior approval from the COR. If the element cannot be installed at the design location due to obstructions, the element should be relocated as directed by the COR.

3.04 SPOILED MATERIAL

A. Provide positive means for containing all spoil return, flush water and other waste materials within the immediate work area. Pipe or channel spoils material into holding ponds, tanks, or other retention structures or facilities. Implement measures to prevent any spoil return, other waste materials, or stockpiled materials from entering White Clay Creek or from leaving the site via surface runoff. In the event spoil return, waste materials, or stockpiled materials enter an area or facility outside the approved work area or mixing spoils storage area, CONTRACTOR shall be responsible for immediately and completely cleaning and removing these materials, at no additional cost to the AGENCY.

B. CONTRACTOR to assume removal of all spoils from site.

3.05 CONTRACTOR QUALITY CONTROL

A. CONTRACTOR Quality Control is the means by which the CONTRACTOR ensures that the construction, to include that of subcontractors and suppliers, complies with the requirements of the contract. Minimum requirements for DMM Shear Walls are specified herein.

B. Implement procedures to monitor, control, and document DMM Shear Wall locations (horizontal and vertical), DMM Shear Wall vertical alignments, water-cement ratios, cement factors, cement-grout injection pressures and quantities, mixing rotational speeds, penetration and withdrawal rates of the mixing equipment; horizontal and vertical alignments of the DMM elements and other related aspects of the soil-cement mixing process. Document these procedures in a Daily Production Report as described above in Paragraph 1.06F.1.

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C. Retain an independent Quality Control Testing Laboratory to obtain grout and DMM samples, perform laboratory testing, and report the laboratory test results in accordance with applicable ASTM standards and the requirements specified.

D. Grout:

Implement procedures to ensure that grout is prepared, mixed, and injected in a manner that is consistent with methods used for the successful Test Section installation. Test grout unit weight in accordance with ASTM D4380 at the start of each grout batch, at least once per DMM Shear Wall, and as required by the COR or BIA Representative.

E. Wet Grab on In-Place DMM Mix Samples:

Obtain wet grab soil-cement samples from each DMM Shear Wall, but not less than one set per work shift per rig, at locations selected by the COR or BIA Representative.

Wet grab samples at the depths outlined below shall be from the same DMM element.

Obtain wet grab soil-cement samples at a minimum at the following depths.

a. Within the top half of the element or column height.

b. Within the bottom half of the element or column height.

c. Alternative depths shall be sampled at the direction of the COR or BIA Representative.

Sample locations will be selected that are representative of the lowest cement factors, for example, the middle auger location where a multiple auger rig has been used.

Retrieve the soil-cement samples and prepare all test cylinders within 60 minutes of the withdrawal of the mixing equipment from the soil-cement element. The device used to retrieve the wet grab soil-cement samples shall be capable of obtaining a discrete fluid sample of soil-cement at a pre-determined depth and shall be capable of accepting lumps of soils not thoroughly mixed that are up to 6 inches in dimension.

Once filled with the soil-cement the sampler shall be closed to exclude entry or loss of soil-cement and be expeditiously raised to ground surface.

Each retrieved soil-cement sample shall be of sufficient volume to produce five full cylinders (3-inch diameter by 6-inch height). The entire sample shall be passed through a 1/2-inch sieve, and any particles retained on the sieve shall be cut to a size that will just pass the 1/2-inch sieve and then be returned to the sample.

Form, preserve, and cure all soil-cement samples in accordance with ASTM D1632.

Protect soil-cement samples from freezing and extreme weather conditions at all times.

Test the wet grab samples for unconfined compressive strength in accordance with ASTM D1633. Unless directed otherwise by COR, at a minimum, test:

a. One sample at 7 days.

b. One sample at 14 days.

c. Two samples at 28 days.

d. One samples at 56 days.

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Submit the laboratory test results to the COR in accordance with this section.

F. Core Samples:

CONTRACTOR shall collect cores, for the purpose of testing in-situ samples of the soil-cement mix from 2.0 percent of the production elements. Locations of core holes must be approved by the COR.

Coring must be done in the presence of the COR and BIA Representative.

No coring shall be done until the soil-cement mix has cured in-place for at least 14 days. CONTRACTOR shall determine the time interval between element installation and coring except that the interval should be no longer than required to conduct 28-day strength testing.

Cores should be continuous and extend full depth of the wall and at least 2.5 feet into the underlying bedrock.

Perform coring of soil-cement in accordance with ASTM D2113 and the requirements stated herein. Use a large diameter triple tube, swivel type design core barrel, with a split inner tube. The core barrel shall be sized to provide a core sample diameter of at least 3 inches. Adjust sampling methods or time of sampling to minimize disturbance and breakage of samples. Do not perform coring until the DMM mix strength is suitable for obtaining intact core samples. Grout the borehole with a cement grout to the ground surface using the tremie grouting method after coring. Protect core samples from drying.

The driller shall operate his drill at such speeds and with such down pressures and shall control drill fluid pressures and quantities to ensure maximum core quality and recovery in whatever hardness material is encountered. The driller shall exercise particular care in recording zones of water loss, cavities, rod jerks, rough drilling, and other unusual and non-ordinary coring experiences that, supplementing the core record, could shed light on the nature and the extent of any abnormalities. The core drilling method is up to the driller; however, as information, the following methods and drilling features have been used successfully in the coring of soil mix construction:

a. Experienced core drillers.

b. Wireline tools.

c. Triple tube coring equipment.

d. Diamond coring bit.

e. Side discharge bit.

f. Lubrication of inside surface of sample tube.

Each core boring shall be monitored, logged, and photographed by the BIA Representative. The BIA Representative will prepare a boring log in accordance with ASTM D2113 and ASTM D5434. All recovered cores shall be marked with two parallel lines using permeant markers (pens) of different color to document the orientation of recovered cores.

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Once the full depth core is collected the Driller shall flush the core hole with water to remove sediment and allow the BIA Representative to perform a down-hole camera inspection. Allow the BIA Representative a minimum of 1 hour to perform the inspection.

All core holes should be filled with cement grout that will obtain a 28-day unconfined compressive strength equal to or greater than the 28-day unconfined compressive strength of the mixed material.

Wash the retrieved cores and arrange them neatly in partitioned boxes in the same sequence they were retrieved from the hole. Label boxes clearly to designate date, time, depths, and location of core samples. Take a digital photograph of each core run clearly showing the labeled core box and the washed core, before sample preservation activities. When a box is full, fill the space between the core and the sides of the box with suitable packing materials.

After retrieving the soil-cement core samples from a specific boring, the BIA Representative will select up to seven core samples per boring to be submitted to the Quality Control Testing Laboratory for unconfined compression testing. Test core samples in accordance with ASTM D2166.

Wrap the core samples designated by the BIA Representative for possible testing in aluminum foil, thin plastic wrap, or cheese cloth and then seal it by applying wax to prevent moisture loss. Store core samples in a constant temperature, damp environment until tested. Handle and store samples in accordance with ASTM D4832 to prevent drying or freezing.

Place marked spacer blocks in the core box to show where samples have been removed.

Retain core boxes containing untested samples until completion of DMM Shear Wall construction. Upon final acceptance of DMM Shear Wall construction by the COR, dispose of the cores.

Protect all core samples from direct sunlight, freezing and extreme weather conditions at all times.

Records of each completed bore hole shall include:

a. Hole identification, top of wall elevation, station reference.

b. Driller’s name and core hole logger’s name.

c. Make, size, and manufacturer’s model designation of drilling equipment.

d. Type of drilling operation.

e. Hole diameter.

f. Hole angle.

g. Date and time.

h. Time required for drilling each core run.

i. Drill action, rotation speed, hydraulic pressure, water pressure, water volume, tool drops, and any other unusual experience which could indicate the subsurface conditions encountered.

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j. Depths at which cores were recovered or were attempted to be recovered, including top and bottom depth of each run.

k. Classification and description by depths of materials cored including composition, texture, presence and orientation of bedding, foliation or fractures, presence of inclusions, and the recovery for each cored interval.

l. Percentage of core recovered per run.

m. Depth at which groundwater is encountered initially and when stabilized.

n. Depths at which drill water is lost.

o. Depths at which the color of the drill water return changes.

p. Type and weight of drill fluid.

q. Depth of bottom of hole.

The CONTRACTOR shall perform additional core borings, as directed by the COR, to evaluate the homogeneity and continuity of soil mix elements and to ensure the specified strength requirements are being met.

3.06 DMM SHEAR WALLS ACCEPTANCE

A. The COR and BIA Representative shall make the determination as to whether the DMM Shear Walls satisfy the geometric, strength and uniformity acceptance criteria.

B. The DMM element shall be installed within the following general geometric tolerances:

The horizontal alignment of the DMM element should be within 2.0 inches of the planned location at the top of the DMM layout.

Overlap between individual elements at the tip (soil/rock interface) shall be a minimum of 5-inches at the maximum deviation.

The vertical alignment shall be maintained to within 0.5 percent of plumb during the DMM element installation.

The top of the DMM element should extend upward to the designated elevation or higher.

The bottom of the DMM element must be in intimate contact with bedrock.

C. The DMM element shall be installed within the following strength tolerances:

A minimum of 90 percent of all of the test results across the site should equal or exceed the specified unconfined compressive strength as determined by ASTM D2166 at 28 days. No individual test shall be less than 80% of the specified strength.

A minimum of 80 percent of test results from each tested deep mixed element should equal or exceed the specified minimum strength.

Strengths below the specified strength are not permitted within 10 feet of the same elevation in more than two nearby cored elements. Nearby cored elements refer to cored elements without an intervening cored element that has a passing test result in the suspect elevation zone.

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If a strength specimen falls below the specified strength due to an obviously unrepresentative lump of unmixed soil in the specimen, the COR has the option to select and test another core specimen from the same core run. Only one such retest will be allowed per core run.

D. The DMM Shear Walls will meet the following uniformity tolerances:

Evaluated based on full-depth continuous core samples retrieved by CONTRACTOR from the DMM columns used to evaluate uniformity.

The COR and BIA Representative will review the recovered cores. Core recovery (expressed as a percentage) shall be reported and is equal to the total length of recovered core divided by the total core run length. Length of recovered core includes lengths of treated and untreated soil.

The COR or BIA Representative will calculate the percent treatment as the total length of recovered core minus the sum of the lengths of unmixed or poorly mixed soil regions or lumps that extend across the entire diameter of the core divided by the total core run length expressed as a percentage. Percent treatment must be at least 90 percent for every 5-foot (1.5-meter) core run.

3.07 REMEDIAL MEASURE FOR NON-COMPLIANCE

A. CONTRACTOR is responsible for correcting weak DMM mix and correcting the location or alignment of misplaced elements. CONTRACTOR should correct misaligned elements that interfere with the project in a manner acceptable to the COR.

B. If the strength is not achieved for production elements, CONTRACTOR should submit a proposed plan for investigating, remixing, or repairing failed sections for review and approval by the COR.

C. Any and all corrective actions taken by CONTRACTOR shall be at no additional cost to the AGENCY.

3.08 CLEAN-UP

A. Continually clean up waste, debris, and leftover materials resulting from the DMM Shear Wall construction process to maintain the site in a workable condition. Dispose of waste materials off-site in accordance with all Federal, State, and local regulations and codes.

END OF SECTION

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