Pseudo-dynamic Analysis For Seismic Active Earth Pressure Behind Retaining Walls

With the propulsion of develop-the-west strategy, the pace of infrastructure is also accelerating, the construction of highway,railway and other transport facilities are carrying on in an unprecedented scale in the west. Because most of the western region is mountainous, it will inevitably encounter a lot of problems on supporting the slope, retaining structures must be used to guarantee the stability of the embankment. Retaining wall which as a cost-effective supporting structure have a common application. Moat parts of the western is in the high-intensity area in the earthquake, so the seismic design of retaining wall is particularly important and the evaluation of dynamic earth pressure behind retaining wall under seismic condition have a great practical signification.Currently, it is commonly used to be pseudo-static method for the calculation of earth pressure behind retaining wall, and it only considers the role of horizontal seismic force. The resultant force which calculated by pseudo-static method is closer to the reality, but this method cann't calculate the distribution of earth pressure and the location of resultant force. It assumes that the soil behind the retaining wall is rigid which has a big gap with the actual. The pseudo-dynamic approach just overcomes the drawbacks. Based on the basic assumptions of the pseudo-dynamic approach, considering the vertical seismic force, this article carried out research in the following areas:(1) Respectively, for cohesionless soil and cohesive soil, consideing the amplifying effect of seismic accelation and wall angle, the model which considers the time and phase difference was obtained to calculate seismic active earth pressure coefficient, the resultant force of seismic active pressure, the distribution of seismic active pressure and the application point of the resultant.(2) The effects of wall angle, amplification factor of seismic accelerations, soil friction angle, wall friction angle and seismic acceleration coefficients on the inclination of the slip surface, active earth pressure coefficient, application point of the resultant and distribution of active earth pressure were investigated. The main fators were identified.(3) The change laws of the inclination of the most dangerous slip surface, seismic earth pressure coefficient and the application point of the resultant varying with the time were analyzed. The orientation of vertical seismic force under the most unfavorable condition was diccussed. This approach was compared with the pseudo-static method.(4) Based on the previous analysis, with the pseudo-dynamic method and level-layer anlysis, the analysis model to calculate seismic active earth pressure was obtained. It overcame the drawbacks of pseudo-dynamic method and the characteristics of dynamic earth pressure distribution was analyzed. The inclination of the most dangerous slip surface and the application point of resultant force were compared with the traditional Mononobe-Okabe method and the pseudo-dynamic approach.