645Reinforced Soil Slopes

645.1-DESCRIPTION: The following are specification guidelines for Reinforced Soil Slope (RSS) construction. Work shall consist of constructing the proposed RSS as specified and furnishing all materials for use in construction of reinforced soil slopes. The minimum length of the soil reinforcing as measured from the slope face to the back of the soil stabilized mass, is as shown in the plans. Any staged or temporary construction affecting the RSS stability shall be the responsibility of the Contractor. The Engineer shall approve the geosynthetic material and supplier. 645.2-MATERIALS: 645.2.1-Geosynthetics Soil Reinforcing: Cutting of geosynthetic reinforcing longitudinal to the Slope face or at vertical obstacles shall not be permitted. End to End splicing of geosynthetic material will not be permitted. The geosynthetic used shall meet the minimum requirements shown on the plans. Each roll of geosynthetic material shall be labeled as to its properties. Geosynthetics shall be made of polypropylene, high -density polyethylene or high -tenacity polyester fibers having cross - sections sufficient to permit significant mechanical interlock with the soil /backfill. Geosynthetics shall have a high tensile modulus in relation to the soil/backfill. Geosynthetics shall have a high resistance to deformation under sustained long term design loads while in service and resistant to ultraviolet degradation, to damage under normal construction practices and to all forms of biological or chemical degradation normally encountered in the material being reinforced. Store the geosynthetics in conditions above 20º F and not greater than 140º F. Prevent mud, wet cement, e poxy, and like materials from coming into contact with and affixing to the geosynthetic material. Rolled geosynthetic may be laid flat or stood on end for storage. Cover the geosynthetic and protect from sunlight prior to placement in the wall system. Carefully inspect all reinforcement to ensure they are the proper size and free from defects that may impair their strength and durability. The geosynthetic reinforcement structure shall be dimensionally stable and able to retain its geometry under constru ction stresses and shall have high resistance to damage during construction. The contractor shall submit a manufacturer’s certification that the geosynthetics supplied meets the design criteria shown on the plans, measured in full accordance with all test methods and standards specified. In case of dispute over validity of values, the Engineer can require the contractor to supply test data from an approved laboratory to support the certified values submitted. The Contractor’s submittal's package shall include actual test results for tension/creep, durability/aging, construction damage, pullout, quality control and a copy of the Manufacturers installation procedures. Also included shall be the Long -Term Design Strength (LTDS) of the Geosynthetic material with the assumptions used to calculate it. The Manufacturer shall also provide written certification that all resin used to produce the geosynthetic is virgin and classified as high density polyethylene, polypropylene, or high tenacity polyester and is capable of withstanding 150 hours of testing per ASTM D4355 with no measurable reduction in the ultimate tensile strength or the deterioration of the coating of the geosynthetic material. If the geosynthetic material is to be used to wrap the face of the sl ope then the testing per 567 ASTM D4355 will be 500 hours with no measurable reduction in the ultimate tensile strength or the deterioration of the coating of the geosynthetic material. The allowable tensile strength shall not exceed 25% of the ultimate tens ile strength of the reinforcement used. The LTDS of geosynthetic reinforcement shall be calculated using the following method. Property Method Tensile Strength Ultimate, kN/m Geotextiles ASTM D4595 Geogrids ASTM D6637 Long-Term Design Strength (Ta), kN/m FHWA/SA-93-025 Where: Ta = Tult/{(RFcr)(RFid)(RFdu)} (as described in FHWA/SA-93-025) Tult, Ultimate Tensile Strength shall be the minimum average roll value ultimate tensile strength as tested per ASTM D4595 for geotextiles and for geogrids ASTM D6637 with the minimum tested value of the single-rib and multi-rib test. RFcr, Partial Factor for Creep Rupture, is the ratio of T ult to the creep limited strength determined in accordance with ASTM D5262 and FHWA NHI-00-043. The test results shall be extrapolated for a 100-year design life at 68° F per FHWA NHI-00-043. Creep rupture data of a polymer product at a designed temperature is limited to one order of magnitude in extrapolation. Creep rupture data at an elevated temperature can permit an additional order of magnitude in extrapolation with time temperature superposition principals. Creep Rupture limited strength testing is required on representative samples of the finished product for each product proposed for use and not a single component of the geogrid (i.e. polymer strand and / or yarn). Default values for RF cr are not allowed. If product specific testing is not provided the product shall be rejected for use. However, in no event shall the minimum value for Creep Rupture be less than the following: MINIMUM VALUES FOR RFcr Geosynthetic Min RFcr High Density Polyethylene (HDPE) 2.65 Polypropylene (PP) 4.50 High Tenacity Polyester (PET) 2.00 RFid, Partial Factor for Installation Damage, shall be determined from construction damage tests for each product proposed for use with project specific representative or more severe backfill and construction techniques. Testing shall be consistent with GRI GG4. A Maximum RFid value shall be used if such testing has not been conducted. 568 RECOMMENDED VALUES FOR RFid Geosynthetic Min RFid Max RFid HDPE uniaxial geogrid 1.20 1.45 PP biaxial geogrid 1.20 1.45 PVC-coated PET geogrid 1.30 1.85 Acrylic-coated PET geogrid 1.30 2.05 Woven geotextiles (PP and PET) 1.40 2.20 Nonwoven geotextiles (PP and PET) 1.40 2.50 Silt-film woven PP geotextiles 1.60 3.00 RFdu, Partial Factor for Durability / Aging is the combined partial factor for potential chemical and biological degradation. RF du shall be determined from polymer specific (HDPE and PP as identified by specific gravity and melt flow index and PETP as identified by CEG number and intrinsic viscosity) durability testing covering the range of expected soil environments. Prior to approval by the Engineer, the manufacturer shall submit test results from a minimum of at least four (4) tests conducted in accordance with EPA 9090 at temperatures of 73° and 122°F. EPA 9090 test results shall include the following minimum number of leachate types: Minimum # of pH test results 3≤pH≤7 1 7<pH≤9 1 9<pH<11 1 11≤pH≤14 1 As a minimum, the following tests should be performed for geogrids after immersion in the above-described leachates: TEST TEST PROCEDURE MAX % CHANGE ALLOWED Mass per Unit Area EPA 9090 ±1.0 Dimensions EPA 9090 ±1.0 Thickness ASTM D374C ±5.0 Wide Width Strip Tensile ASTM D4595 -2.0

characteristics of the interior reinforcement polymer. Therefore, any protective coating shall be removed prior to durability testing unless a minimum 40 micron coating thickness is used on flexible geogrids and certified by the manufacturer.

stabilized soil, cement stabilized soil or concrete), only polymers listed as “no effect” shall be used within or adjacent to (3 feet shortest measurable distance) these soil environments (Ref: Table 28, FHWA/RD-89-186). 569 SOIL 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 RFdu Products Aging Reduction factor, RFdu – 100 years pH  3 3 ≤ pH  5 5 ≤ pH ≤ 8 8  pH ≤ 9 pH > 9 PET Uncoated Mn  20,000 40CEG50 * 2.0 1.6 2.0 * PET Coated Mn > 25,000 CEG30 * 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 40CEG50 * 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 inch) 100 No. 4 100-30 No. 20 0-60 No. 200 0-50 Plasticity Index (PI) ≤ 20 (AASHTO T-90) 570

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. 571 645.6-EROSION 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 considered 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, respectively, 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 572