Seismic response of T-shaped retaining wall in liquefiable sites with interbedded weak clay layers: A large-scale shaking table test

While extensive research has been conducted on the behavior of retaining walls in uniformly saturated sandy soils, actual water-adjacent retaining walls frequently encounter more complex ground soil conditions, including weak impermeable layers. A series of large-scale shaking table tests, employing three distinct ground models: pure sand model (PS model), horizontally interbedded weak clay (HI model), and inclined interbedded weak clay (II model), were performed to investigate the seismic behavior of T-shaped cantilever retaining walls in liquefiable sites containing weak impermeable clay layers. The impermeable weak clay layers within the soil-wall system significantly enhanced liquefaction resistance by reducing both the development rate and the peak level of excess pore water pressure. This effect is especially notable in inclined stratified soil foundations. The presence of impermeable layers notably amplified the acceleration responses and altered its distribution pattern of soil across different depths. Substantial slip displacement was observed at clay-sand interface due to the formation of “water interlayer” beneath the impermeable boundaries. The impermeable clay layer causes an increase in the acceleration responses and a pronounced alteration in the retaining wall's displacement pattern. Specifically, the retaining wall in PS model exhibited combined translation and rotating about the base patterns, while the wall in models incorporating weak impermeable layers (HI and II) displayed combined translation and rotating about the top patterns. The different displacement patterns of the retaining wall are related to the distribution of peak dynamic earth pressure along the wall height. The comparative analysis revealed that Wood's solution was effective in predicting the peak dynamic earth thrust in the PS model, while the M − O method was particularly suitable for the HI and II models with weak impermeable layers. The accumulation of dynamic earth thrust to threshold levels is a necessary precondition for irreversible wall displacement, while the excitation intensity plays a crucial role in determining both the process of displacement development and the magnitude of residual total displacement. The retaining wall in the models with weak clay layers required lower dynamic earth thrust thresholds for initiating irreversible displacement compared to pure sand conditions.