Assessment and Evaluation of Post-Liquefaction Lateral Spread Impact on Bridge Deep Foundations
Mohamed Ashour, PI, Alabama A&M University
Sudip Bhattacharjee, Co-PI, Alabama A&M University
Durability and serviceability of bridges and their deep foundations could be at high risk due to the vulnerability to unexpected and underestimated post-liquefaction lateral soil spread destructive forces. The proposed work quantifies the mobilized damaging forces acting on the bridge foundation pile groups with caps as a result of the post-liquefaction triggered lateral soil spreading. The interaction mechanism between the pile group foundation and surrounding soil layers is determined based on soil/pile properties and the variation of the excess porewater pressure ratio (ru) in the near-field. The proposed technique allows the evaluation of the lateral loads acting on the individual piles in the group and pile cap during and after the phase of lateral spreading where the strength of the liquefied soil around the pile group varies with the variation of the near-field porewater pressure, as the lateral spread forces continue to grow with soil spreading.
The Strain Wedge (SW) model technique cited in AASHTO (2016) for the analysis of piles and pile groups is utilized in the proposed research work. The SW model has the capability of analyzing laterally loaded pile groups with caps ( Ashour et al. 2004a; Ashour and Ardalan 2011a; Ashour et al. 2019), piles in partially and fully liquefied soils (Ashour and Norris 2003; and Ashour and Ardalan 2012), isolated piles under lateral spread (Ashour and Ardalan 2011b).
The proposed work will be integrated into a software package that employs soils and pile properties along with earthquake parameters, as input data. The software detects the development of soil liquefaction, subsequent lateral spreading and variation of porewater pressure (i.e. varying soil strength) and calculates the response of the pile group under the growing lateral spreading force (i.e. pile’s deflection, moment and shear force).
Sudip Bhattacharjee, Ph.D., P.E.