Extensible Reinforcements - Active Earth Pressure
Active earth pressure is considered in the calculation of internal stability for extensible reinforcements (Standard - straight slip surface, AASHTO - Extensible, FHWA NHI-10-024).
The program allows us to multiply the calculated earth pressure by coefficient kr/ka (according to the AASHTO standards). Recommended values are shown in the following picture.
Variation of the coefficient of horizontal stress ratio kr/ka with depth for extensible reinforcements
Literature:
AASHTO LRFD Bridge Design Specifications 2004 (SI).