Seismic Response of Pile Foundations in Clayey Soil Deposits Considering Soil Suction Changes Caused by Soil-Atmospheric Interactions

Extreme variations in weather patterns have become increasingly common across the Southern Great Plains of the United States. The soil layer in the active zone above the groundwater table is often subjected to moisture variations due to seasonal weather changes that will influence the behavior of soils, including their strength and stiffness parameters. Designing a pile foundation in seismic-prone areas without considering the moisture changes in soil interacting with piles may adversely impact the seismic performance of the piles. The main aim of this study is to investigate the role of soil moisture conditions and suction caused by soil-atmospheric interactions on the dynamic behavior of the pile foundations interacting with clayey soils. This study uses a stand-alone finite element computer code called DYPAC (Dynamic Piles Analysis Code) developed using the Beams on Nonlinear Winkler Foundation (BNWF) approach. The influence of soil suction is incorporated into the p-y curves and free-field soil displacements using site response analyses by employing the concept of apparent cohesion. To perform nonlinear site response analyses, DEEPSOIL software V6.1 is utilized. The variation in soil suction with depth along the pile is considered using unsaturated seepage analysis performed by employing the commercial software PLAXIS LE Groundwater for three different clayey soils with plasticity ranging from low to medium to high. The analyses were performed using actual past daily recorded weather data for a testbed that experienced significant back-to-back flash droughts in 2022. This study found that extreme weather events like flash droughts can significantly affect the soil suction and seismic performance of the piles interacting with the unsaturated clayey soils.