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DPART SIXAppendix D3H:1V SLOPING SURCHARGE AASHTO METHODOLOGIESInternal Stability - The internal analysis must look at the maximum loads at each grid level,connection strength, pullout resistance, and local stability concerns.UXK1400ZUXK1400H=10'UXK1400UXK1400UXK1400σ ah1.0'B = 8.0'B = 9.0'The internal earth pressure at any level is calculated as follows:σ ah = γ Z k a cos(β)= (120pcf)(Z)(0.328)cos(18.4)= 37.3 (Z) plfThe calculated pressure is applied to the tributary area of each reinforcement level which determinesthe tensile load in the geogrid reinforcement. This AASHTO method calculates the internal activeearth pressure coefficient based on a sloping backfill in accordance with the Rankine earth pressureformula for sloping backfill.D.6