567 SECTION 645 REINFORCED 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 longit udinal 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 dama ge 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 in clude 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
568 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 = T ult/{(RF cr)(RF id)(RF du)} (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.
RF cr, 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 valu e for Creep Rupture be less than the following:
MINIMUM VALUES FOR RF cr Geosynthetic Min RF cr High Density Polyethylene (HDPE) 2.65 Polypropylene (PP) 4.50 High Tenacity Polyester (PET) 2.00
RF id, 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 RF id value shall be used if such testing has not been conducted.
569 RECOMMENDED VALUES FOR RF id Geosynthetic Min RF id Max RF id 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 identifie d 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 w ith EPA 9090 at temperatures of 73° and 122°F. EPA 9090 test results shall include the following minimum number of leachate types:
pH Minimum # of test results 3pH7 1 7<pH9 1 9<pH<11 1 11pH14 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 thickn ess 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 use d within or adjacent to (3 feet shortest measurable distance) these soil environments (Ref: Table 28, FHWA/RD -89-186).