Design Recommendations. The resistance factors from the AASHTO LRFD Bridge Design Specifications, latest edition, shall be used to analyze slope stability. Standard Procedure The embankment/excavation slope stability analysis shall consist of (1) modeling the appropriate boring logs to define the critical embankment/excavation geometry (cross-section) with subsurface soils, (2) interpreting the shear strength test data to determine drained and/or un-drained shear strength design parameters, (3) performing the stability analysis utilizing the Bishop, Spencer, and/or sliding block method deemed appropriate by the engineer, (4) determining the maximum resistance factors for both long- and short-term conditions at the critical fill heights at each bridge end, along the approach embankment (intermediate fill height) and in critical cut sections. Maximum resistance factor should also be taken into consideration for rapid drawdown conditions when applicable, (5) analyzing different methods for mitigating possible stability problems and if necessary, make recommendations for geotechnical instrumentation to monitor stability performance, (6) defining areas of highly erodible materials and analyzing erosion control measures, and (7) preparing a report with all the above information and engineering recommendations. Deliverables of Slope Stability Analysis shall include the following: Printout of critical stability circle and/or block for each design case; Geotechnical models (cross-sections) and design input parameters; Summary table with critical fill heights and resistance factors, or critical excavation with resistance factors; Certification that the modeled embankments meet the required long and short-term resistance factors required; Summary of alternatives for mitigating possible stability problems with resistance factors and estimated costs; Specifications for slope stability mitigation measures; Geotechnical Instrumentation Plan (if recommended); Recommended erosion control measures; and Construction Slope Stability notes for the Bridge General Notes Sheet. EMBANKMENT SETTLEMENT The Objective of a Consolidation/Settlement Analysis is to determine the amount of settlement in inches/feet, and the time required for this settlement to take place in days/months/years when the proposed embankment is constructed on the project subsurface soils, and make appropriate Engineering Design Recommendations.
Design Recommendations. The resistance factors from the AASHTO LRFD Bridge Design Specifications, latest edition, shall be used to analyze slope stability. Standard Procedure The embankment/excavation slope stability analysis shall consist of (1) modeling the appropriate boring logs to define the critical embankment/excavation geometry (cross-section) with subsurface soils, (2) interpreting the shear strength test data to determine drained and/or un-drained shear strength design parameters, (3) performing the stability analysis utilizing the Bishop, Spencer, and/or sliding block method deemed appropriate by the engineer, (4) determining the maximum resistance factors for both long- and short-term conditions at the critical fill heights at each bridge end, along the approach embankment (intermediate fill height) and in critical cut sections. Maximum resistance factor should also be taken into consideration for rapid drawdown conditions when applicable, (5) analyzing different methods for mitigating possible stability problems and if necessary, make recommendations for geotechnical instrumentation to monitor stability performance, (6) defining areas of highly erodible materials and analyzing erosion control measures, and (7) preparing a report with all the above information and engineering recommendations. Deliverables of Slope Stability Analysis shall include the following: Printout of critical stability circle and/or block for each design case; Geotechnical models (cross-sections) and design input parameters; Summary table with critical fill heights and resistance factors, or critical excavation with resistance factors; Certification that the modeled embankments meet the required long and short-term resistance factors required; Summary of alternatives for mitigating possible stability problems with resistance factors and estimated costs; Specifications for slope stability mitigation measures; Geotechnical Instrumentation Plan (if recommended); Recommended erosion control measures; and Construction Slope Stability notes for the Bridge General Notes Sheet. EMBANKMENT SETTLEMENT The Objective of a Consolidation/Settlement Analysis is to determine the amount of settlement in inches/feet, and the time required for this settlement to take place in days/months/years when the proposed embankment is constructed on the project subsurface soils, and make appropriate Engineering Design Recommendations.