ENVIRONMENT PETP PE PP PVC Acid Sulfate Soils ? NE ? ? Organic Soils NE NE NE X Salt Affected Soils ? NE NE NE Ferruginous NE NE X X Calcareous X NE NE ? Modified Soils X NE NE ?
NE = No Effect ? = Questionable Use X = Not Recommended
RFdu shall not be less than the recommended minimum values discussed in FHWA/RD - 89-186 and listed below:
MINIMUM VALUES FOR RF du Products Aging Reduction factor, RF du – 100 years pH 3 3 pH 5 5 pH 8 8 pH 9 pH 9 PET Uncoated Mn 20,000 40CEG50 * 2.0 1.6 2.0 * PET Coated Mn 25,000 CEG30 * 1.3 1.15 1.3 * HDPE 1.1 1.1 1.1 1.1 1.1 Polypropylene 1.25 1.25 1.25 1.25 1.25 Geotextiles Mn 20,000 40CEG50 * 2.0 1.6 2.0 *
* Use of materials in this pH range is not recommended but can be used if product specific testing is done Mn = Number of Molecular Weight CEG = Carboxyl End Group
645.2.2 -Backfill Material: All backfill material used in the structure volume shall be reasonably free from organic or otherwise deleterious materials and shall conform to the following gradation limits as determined by AASHTO T -27:
Sieve Size Percent Passing 100 mm (4 in ch) 100 No. 4 100-30 No. 20 0-60 No. 200 0-50 Plasticity Index (PI) 20 (AASHTO T -90)
571 A. Backfill pH Testing The contractor prior to incorporating the soil into the RSS shall perform one pH test in each soil type each day of operation and the pH of the soil shall be within the allowable limits of the design for the geosynthetic material used.
Payment for the backfill will be incidental to the various excavation items.
CONSTRUCTION METHODS
645.3 -FOUNDATION PREPARATION : All areas immediately beneath the installation area for the geosynthetic reinforcement shall be properly prepared for a width equal to the length of reinforcement elements plus one three (3) feet or as detailed on the plans or as directed by the Engineer. The surface shall be level, free from deleterious materials, loose, or otherwise unsuitable soils. Prior to placement of Geosynthetic reinforcement, foundation shall be proof -rolled to provide a uniform and firm surface. Any soft areas, as determined by the Engineer, shall be removed and replaced with backfill as per Section 207 of these specifications. Foundation surface shall be inspected and approved by the Engineer prior to fill placement. Benching the backcut into competent soil is recommended to improve stability. The backslope shall not be steeper than 1.5:1.
645.4 -GEOSYNTHETIC INSTALLATION : A representative of the geosynthetic supplier shall be present a minimum of three (3) days and as required thereafter during construction of the reinforced slope to assist the Contractor and Engineer. The cost of the representative shall be considered incidental to the unit cost of the geosynthetic reinforcement. Geosynthetic reinforcement sha ll be placed horizontally unless otherwise shown in the plans. Prior to placement of the geosynthetic reinforcements, backfill shall be compacted in accordance with these specifications.
645.5 -BACKFILL PLACEMENT : Backfill placement shall closely follow the installation of each geosynthetic reinforcement layer. Backfill shall be placed in such a manner as to minimize the development of wrinkles in and/or movement of the geosynthetic material. A mi nimum fill thickness of six ( 6) inches is required prior to the operation of tracked vehicles over the geosynthetic reinforcement. Turning of vehicles should be kept to a minimum to prevent tracks from displacing the fill and damaging the geosynthetic. R ubber tired equipment may pass over the geosynthetic reinforcement at low speeds provided that no sharp turns are made. Geosynthetic material damaged during installation shall be replaced by the Contractor at no additional cost. The maximum lift thickness after compaction shall not exceed six ( 6) inches, The Contractor shall decrease this lift thickness, if necessary to obtain the specified density. Acceptance for compaction shall be in accordance with Section 626.5.3.4. The moisture content of the backf ill material prior to and during compaction shall be uniformly distributed throughout each layer. Backfill materials shall have placement moisture content as per Section 716.3. At the end of each day’s operation, the Contractor shall slope the last level of the backfill away from the slope to rapidly direct runoff away from the slope face and construction area. In addition, the Contractor shall not allow surface runoff from adjacent areas to enter the reinforced soil slope construction site.
572 645.6 -EROSIO N CONTROL MATERIAL PLACEMENT : The erosion control material shall be placed and anchored on a smooth graded, firm surface approved by the Engineer. Anchoring terminal ends of the erosion control material shall be accomplished through use of key trenches. The material in the trenches shall be anchored to the soil maximum two ( 2) feet centers. The erosion control material shall meet the specifications of
645.7 -ACCEPTANCE : The Contractor shall furnish the Engineer a Certificate of Compliance certifying the above materials, excluding backfill, comply with the applicable contract specifications. A copy of all test results performed by the Contractor necessary to assure contract compliance shall also be furnished to the Engineer. The backfill shall be in accordance with subsection 626.5.3.4.
645.8 -METHOD OF MEASUREMENT : The pay items shall be measured in square yards geosynthetic reinforcement as determined by the dimensions in the plans. No adjustment of pay quantity shall be allowed for changes in Reinforced Soil Slope design to facilitate the Contractor’s methods of construction or geosynthetic type used. Any adjustments to the required amount of embankment backfill due to the particular geosynthetic reinforcement proposed by the contractor shall be conside red incidental to the project. No separate payment shall be made for increased embankment backfill requirements. The contractor shall be responsible for any of the cost of changes in waste, borrow, or earthwork quantities from those shown in the plans ca used by the requirements of the geosynthetic reinforcement.
645.9 -BASIS OF PAYMENT : The quantities, determined as provided above, will be paid for at the contract price per unit of measurement, respec tively, for each pay item listed below and shown in the bid schedule, which prices and payment will be full compensation for the work prescribed in this section.
645.10PAY ITEM :
ITEM DESCRIPTION UNIT 645001 -* “type” Reinforcement, “long-term design strength” lb/ft Square Yard
*Sequence number “type” Primary or Secondary
SECTION 646 THROUGH SECTION 650-BLANK
573 SECTION 651 FURNISHING AND PLACING TOPSOIL
651.1 -DESCRIPTION : This work shall consist of acquiring sites outside the right -of-way from which topsoil can be obtained and the hauling and placing of such material, or hauling and placing of tops oil from stockpiles within the right -of-way, all in accordance with these Specifications and at locations indicated on the Plans or designated by the Engineer.
651.2 -MATERIALS : Topsoil shall consist of the uppermost layers of fertile and friable soil that contains humus material. This material varies in thickness in accordance with soil groups and usually possesses a darker color than the subsoil. The texture of the topsoil may vary within the range o f natural loam, silty clay loam, and sandy loam. Acceptable topsoil shall contain organic matter in the range of 2% to 20% and be sampled at least once per project using AASHTO T 267 method; multiple sources or change of sources shall also be sampled.
CON STRUCTION METHODS
651.3 -STRIPPING TOPSOIL : Prior to removal from the site, the soil will be tested by the Division to determine the humus and nutrient value. Care shall be exercised as to th e depth of stripping, and any loads with an excess of subsoil shall be discarded. The Contractor shall mow or otherwise remove all heavy grass, weeds, or other vegetation over the areas before stripping. Approval by the Engineer must be obtained prior to transporting any material from the stripping site.
651.4 -TRANSPORTING : Topsoil material shall not be placed until the entire roadway (including surfacing) has been completed, unless otherwise provided for on the Plans or approved in writing. During hauling operations, the surface of the highway shall be kept reasonably clean to avoid creating a traffic hazard.
651.5 -PLACING AND MANIPULATING : Areas to be topsoiled shall be brought reasonably close to the lines and grades shown on the Plans or established by the Engineer. The Contractor shall scarify the surface of the subsoil before the topsoil is placed, unless otherwise permitted, for bonding the topsoil layer with the subsoil. Scarification shall be accomplished by disking, harrowing, raking, or other approved methods. Depressions and ridges formed by construction equipment, during final grading or scarifyin g, shall be parallel to the contours. Topsoil shall not be spread to a greater depth than that required to make the work conform to the natural terrain after shrinkage and settlement have taken place. After spreading the soil, all deleterious materials ( large lumps or clods, brush, litter, or other foreign material, and stones exceeding two ( 2) inches approximately in any dimension) shall be raked up and removed from the site. The Contractor shall take all reasonable precautions to avoid injury to existing plant growth, structures, and roadway surface.