1.3 DEFINITIONS AND ABBREVIATIONS

ASTM - American Standards f or Testing Materials

Grout - A stable colloidal mixture of water and Type I Portland Cement. (Type of cement may be specified, if other than Type I.) [Additional materials such as, bentonite, clay, attapulgite clay, lime, dilute acids, fly ash retarding agents and quick setting agents may be added.]

Owner - The Owner referenced herein is ___________________

Owners' Representative - A person or firm designated in the contract to act on behalf of the Owner in the execution of these specifications.

Shallow Soil Mixing - A soil improvement technique used to construct in-place walls or to treat soils in-situ to depths near 45 feet. This is accomplished with a series of overlapping stabilized soil columns (typically 6-12 feet in diameter). The stabilized soil columns are formed by a crane mounted drill attachment that turns a single shaft large diameter auger head consisting of two or more cutting edges and mixing blades. As the auger head is advanced into the soil, grout is pumped through a hollow drill shaft and injected into the soil at the pilot bit. The cutting edges and mixing blades blend the soil and grout with a shearing motion. When the design depth is reached, the auger head is raised to expose the mixing blades at the surface and then allowed to readvance to the bottom. Once the shaft is completed, another column is drilled using a specified pattern of overlapping columns, which becomes a series of interlinked columns having the following (property/properties): improved bearing capacity, or shear strength, immobilized contaminants, neutralized soil and when reinforced, able to withstand differential soil and hydrostatic loading.

Work Area - A relatively level and stable surface of compacted fill and/or excavated earth from where the SSM unit can begin work.

1.4 QUALIFICATIONS OF CONTRACTOR

Four soil mixing projects. The name and qualifications of the contractor (or specialty subcontractor) shall be submitted with the bid.

Three soil mixing environmental projects. In particular, a SSM superintendent / specialist shall be submitted and approved by the Owners' Representative to supervise the construction and quality control.

The contractor shall submit evidence and references of similar projects. Project descriptions shall include depth, width, and length of the area as well as a description of the type of reagents used for the construction, soil conditions and any difficulties encountered in construction. (Project descriptions should be submitted with the bid.)

The SSM Superintendent shall be knowledgeable and experienced in soil improvement and waste stabilization construction using SSM techniques. This experience shall include, but not necessarily be limited to: 1) the use and control of SSM advancement and injection of grout in SSM construction; 2) methods required to properly mix the grout (and additives, as required); 3) laying out the proper shaft drilling patterns; 4) knowledge of construction equipment and material; and 5) routine field quality assurance/quality control testing. The Superintendent shall control the mixing of the grout, SSM rate of advancement, and the grout injection rate. The Superintendent shall supervise and ensure that the SSM shafts have been properly mixed and interconnected. The credentials of the SSM Superintendent shall be submitted at least one week prior to the start of the SSM [in-place wall, in-situ stabilization, in-situ treatement, in-situ fixation] construction.

1.5 SSM IN-PLACE

The SSM shall be constructed to the lines and grades and cross sections as indicated on the drawings. The SSM shall have essentially vertical columns having a nominal width of ____ feet and shall extend through the overburden to a minimum specified depth of ___ feet. The completed SSM shall be a homogeneous mixture of grout and the ____ (types of in-situ soils). Mixing is to be accomplished by the number of shaft revolutions, penetration rate and the amount of grout injected. A ______ description of overburden through which the SSM is to be drilled is presented in the boring logs listed in Appendix _____.

1.6 SUBMITTALS

1.6.1 Work Plan

The contractor shall submit a preconstruction work plan for approval by the Owners' Representative at least ___ days prior to the start of work. The work plan shall include the following items:

• Schedule: A schedule in sufficient detail to identify the major segments of the work. Starting and ending dates for all major work items shall be clearly identified.
• SSM Construction Method: A detailed description of the methods of construction, which shall include the column construction methods, grout mixing and monitoring, rate of advancement, percent overlap of shafts and the minimum gallons [based on proposed cement to water ratio] of grout per shaft.
• Equipment: A list of major equipment, by type and capacity, which shall include crane, grout mixer, drilling attachment, auger [diameter] support, and transport equipment.
• Quality Control: The quality control plan shall be submitted along with the work plan. The plan shall include a list of test methods and minimum standards with which to gauge the quality of the work during construction including grout density, depth measurements, densities of mixed materials, penetrometer testing of mixed materials and UCS testing. The plan shall address the physical properties and manufacturers stated properties for all permanent materials including manufacturer's certifications of quality, mill certificates, gradation test data, etc. The plan shall state when all quality control data will be submitted to the Owner and the correction procedures to be employed in the case of substandard results.

1.6.2 Preconstruction Mix Design

Prior to construction, a mix design program shall be conducted to determine the mix design's ingredients, sequence of mixing, grout properties and soil mix properties. The basic guiding principal for the laboratory mix program is to strive to accurately model expected field results. [Appendix ___ presents the results of a mix design study performed for the representative soil types found at the site. Presentation of the data from this study in no way relieves the Contractor of the responsibility to verify to his satisfaction that the results are accurate.]

2.1.1 Grout

The material added to the soil will be water based grout. The purpose of the grout is to 1) assist in loosening the soil for penetration and mixing, 2) (lower permeability, aid in structural support, treat in-situ soils, and fixate in-situ contaminants). The grout will be premixed in batch or continuous-mix plants that combine materials in predetermined proportions.

2.1.2 Equipment

The Contractor shall furnish the necessary plant and equipment for construction of the facilities shown on the contract documents. The equipment shall be of the type and capacity to complete the work in an efficient manner and shall be maintained in operable condition at all times.

2.1.2.1 Grout Mixing Plant

The Contractor shall provide a grout mixing plant containing the necessary equipment for preparing the grout including a high-shear/high speed colloidal mixer capable of producing a stable grout mixture. Pumps, valves, volumetric feeders, flow controllers/meter, hoses and other equipment shall be provided as required to adequately supply grout to the SSM equipment.

Dry materials used in the grout mixing shall be stored in silos and fed via a calibrated rotary valve [screw feeder] to the colloidal mixer(s) for agitation and circulation.

The precise arrangements and sequence of mixing shall be based on the results of the mix design program. Other dry ingredient proportions shall be batch or continuously mixed by weight to a predetermined final density. A maximum holding time of three hours will be enforced for the grout. Calibration of mixing components shall be done at the beginning of the project and monthly thereafter. The screw feeders or rotary valve shall be calibrated against time to deliver a predetermined weight. Water shall be controlled by flow meter and/or by the volume level indicators in the colloidal mixer. The specific gravity of the grout shall be determined during the design mix program for double checking grout proportions. Grout volumes from the mixing plant shall be monitored by a flow meter capable of measuring liquids, containing high solids or other acceptable method.

2.1.2.2 SSM Rig

The SSM rig shall consist of a single shaft auger head capable of creating a column with a minimum thickness of ____ feet and achieving a maximum depth of ___. The auger head shall have a bottom discharge capability for grout. The cutting blades and mixing blades shall be configured so that they are capable of blending in-situ soils and grout into a homogeneous mixture. The power source for driving the mixing shafts shall be sufficient to maintain required RPM and penetration rate from a stopped position at the depth specified.

2.1.3 Water

Fresh water, free of excessive amounts of deleterious substances that adversely affect the properties of the grout shall be used to manufacture the grout. Potential water sources shall be tested prior to, or during, the pilot study by the contractor to assure the water is suitable for grout preparation. (If the Owner has an onsite water source, information as to the available gpm of the source, location of source and the chemical characteristics of the water (i.e., pH, chlorides, hardness, total organic carbon (TOC) should be provided to the contractor). The water shall be tested for these parameters prior to construction to confirm that it is suitable for use in the SSM construction.

2.1.4 Cement

Cement used in preparing the grout shall conform to ASTM Designation C-150 "Requirements for Portland Type l-2 Cement". The cement shall be adequately protected from moisture and contamination while in transit. Cement shall be stored in a silo or other appropriate bulk storage container. Storage of cement in bags is not acceptable. Reclaimed cement or cement containing lumps or deleterious matter shall not be used.

The supplier shall provide a certificate which complies with ASTM C 150 for each truckload of material delivered to the site.

2.1.5 Bentonite [Optional]

Bentonite used in preparing slurry shall be a pulverized (powder or granular), premium-grade sodium cation montmorillonite.

2.1.6 Additives [Optional]

Admixtures of softening agents, dispersants, retarders, plugging, or bridging agents may be added to the water or the grout to permit efficient use of materials and proper workability of grout. However, additives shall be approved by the Owners' Representative prior to use.

2.1.7 Proprietary Chemicals [Optional]

Proprietary chemicals based on initial bench scale testing shall be approved by the Owners' Representative.

2.1.8 Environmental Control Equipment [Optional]

Environmental control equipment may consist of any of the following: bag houses, hoods, large diameter casings, activated carbon canisters and/or vapor condensers to regulate and reduce the amount of potentially toxic emissions while drilling.

• The positive displacement grout pumps will be calibrated according to real site conditions to produce a time vs. flow correlation. By adjusting the pump output to the penetration rate, a present grout intake can be achieved.
• The transfer pumps will deliver grout to the SSM rig. A return line must be able to return any overflow back to the plant.
• The application rate can be successfully controlled by experienced operators once the pattern of operation is established. Generally, the injection rate will be 100 percent while the auger is moving downward.

3.10.1 Grout

Based on the mix design program, field testing of the grout properties shall be submitted for approval. Grout control may be performed by one or a combination of the following tests:

• Unit weight by Mud Balance method.
• Viscosity by Marsh Funnel method
• pH by pH meter or paper
• Filtrate by filter press

Frequency and standards for field tests will be determined by the mix design program. Calculations of mix proportions will be by the absolute volume method. Proportions calculations will be based on the weight of the water proportion of the (grout, slurry) i.e., cement/water, bentonite/water, etc.

3.10.2 Mixed Soil [Waste]

Sampling - Samples of the mixed soil [waste] will be taken each day, one set per shift. These samples shall be taken with a special sampling tool at the bottom and middle of the shaft; and a third sample shall be collected at the top, immediately following installation. Sufficient sample shall be collected at each depth to make up three molds. The soil [waste] mix shall be placed in suitable molds, rodded to remove trapped air pockets and then placed in a plastic bag that contains sufficient moisture to keep the mixture damp. [After the initial set, a dead weight load may be imposed on the sample to model the stress from earth pressures.]

Laboratory Testing - Samples shall be transported to an independent geotechnical laboratory for testing once the samples have sufficient strength so as to not adversely affect the properties. At the end of seven days, curing one sample from each shift's daily production shall be tested for UCS, (ASTM C-39). At the end of 28 days a second sample shall be selected for testing using the same tests as above. All test results shall be reported to the Owners' Representative as soon as they become available from the laboratory.

3.10.3 Records

The Contractor shall maintain records for all testing, measurements, observations, and inspections. Quality Control Reports shall be submitted to the Owners' Representative each day [or at the end of each shift] on a form acceptable to the Owner. These reports shall list all test results, measurements, and observations made and/or received by the Contractor for that day.

3.10.4 Owner Quality Control

The Owner reserves the right to perform additional tests, using his own forces, on the SSM area. The Owner's testing will in no way relieve the Contractor of the responsibility to perform the tests as specified in the above sections and to meet this specification.