only contain particles that will pass the 3-inch square mesh si eve. The contractor is required to submit a grain size distribution curve (ASTM D 422) and a mo isture-density relationship curve (AASHTO T-180) for acceptance of the proposed backfill ma terial and determination of the appropriate installation damage reduction factor (RF ID). Walls with reinforced backfill require that the backfill material be subjected to pH testing to determine the appropriate durability reduction facto r (RF D). Backfill materials shall meet the criteria in the following table:
Base Polymer Property Criteria Test Method Polyester (PET) pH 3< pH < 9 AASHTO T-289 Polyolefin (PP & HDPE) pH pH > 3 AASHTO T-289
Material between blocks must be Gravel Borrow, or Crushed Stone, ¾ -Inch .
672.036 Materials Certification Letter The Contractor, or the supplier as his agent,
shall furnish the Resident a Materials Certification Letter for the above materials, including the backfill material, in accordance with Section 700 of the St andard Specifications. A copy of all test results performed by the Contractor or his supplier necessary to assure contract compliance shall also be furnished to the Resident. The Reside nt will base acceptance upon the materials Certificate Letter, accompanying test reports, an d visual inspection.
shall be designed with a s ervice life of not less than 75 years. The Precast Concrete Block Gravity Wall sh all be designed and sealed by a Professional Engineer licensed in the State of Maine. The wall shall be designed in accordance with the following:
LRFD
and FHWA-NHI-10-025, Design and Construction of Mechanically Stabilized Earth Walls and Reinforced Soil Slopes, Volumes I and II, current edition.
Mechanically Stabilized Earth Walls and Reinforced Soil Slopes, current edition.
Where conflicting requirements occur, the more stringent requir ements shall govern. Forty-five days prior to beginni ng construction of the wall, th e design computations shall be submitted to the Resident for review by the Geotechnical Engineer. Any additional
design or costs arising as a result of rejection of a wall desi gn by the Geotechnical Engineer shall be borne by the Contractor. Design calculations that consist of computer program generated output shall be supplemented with at least one hand calculation and graphic dem onstrating the design methodology used. Design calculations shall provide thorough d ocumentation of the sources of equations used and material properties. The design b y the wall system supplier shall consider the stability of the wall as outlined below and in the Contract Documents:
determined in accordance with LRFD Article 11 and be analyzeds o that the soil stabilizing components extend sufficiently beyond the failure plane within the reinforced soil mass to stabilize the material.
those applied through traffic loadings, impact on traffic barrier posts, slope surcharge, hydrostatic, and seismic loads shall be accounted for in the de sign. Traffic surcharge and traffic impact loads shall be calculated and applied in complia nce with LRFD Section 11. C External Stability Loads and load combinations selected for design shall be consistent with LRFD. Application of load factors shall be taken as specified in LRFD Section 11. Sliding resistance factors and bearing resistance factors shall be cons istent with LRFD. Overturning and sliding provisions of LRFD shall apply.
reinforcement/block connection pullout or rupture shall be cons istent with LRFD Section 11, and checked at each level. Loads, load combinations and lo ad factors shall be as specified in LRFD Section 11. Resistance factors for internal design are specified in LRFD approach. Calculations for factored stresses and resistancess hall be based upon assumed conditions at the end of the design life.
reinforcement design strength (T al) shall be determined by reducing T ult by reduction factors (RF) in accordance with the documents referenced above. The designer shall procure and use the manufacturers tested and certified geosynth etic reinforcement reduction factors for creep (RF CR), durability (RF D), and installation damage (RF ID) to determine T al. In absence of manufacturers tested and certified reduction f actors, a combined default reduction factor RF = 7 shall be used in accor dance with the referenced documents. For RF ID, the installation damage reduction factor shall be checked in accordance with LRFD and FHWA-NHI-09-087.
connection strength between the geosynthetic reinforcement and the concrete blocks shall be checked in accordance with LRFD and FHWA-NHI-10-024 an d FHWA-NHI- 10-025.