Effects of non-liquefiable crust layer and superstructure mass on the response of 2 × 2 pile groups to liquefaction-induced lateral spreading

Abstract

In this research, two shake table experiments were conducted to study the effects of non-liquefiable crust layer and superstructure mass on the responses of two sets of 2 × 2 pile groups to liquefaction-induced lateral spreading. In this regard, an inclined base layer overlain by a very loose liquefiable layer was constructed in both models; while only in one model, a non-liquefiable crust layer was built. A lumped mass, being representative of a superstructure, was attached to the cap of one pile group in both models. The models were fully instrumented with various sensors, including acceleration, displacement, and pore water pressure transducers. Also, the piles were instrumented with pair strain gauges to measure pure bending moments induced by cyclic and monotonic loadings associated with ground shaking and lateral spreading, respectively. The results showed that the existence of the non-liquefiable crust layer increases both the maximum and residual soil displacements at the free field and also the maximum bending moments in the piles. The results of the experiments indicated that the crust layer induces a high kinematic lateral soil pressure and force on the piles which are not present in the crustless case. The crust layer increases the pile cap displacement before liquefaction, albeit decreases it after liquefaction, due to the elastic rebound of the piles in the liquefiable layer. The crust layer postpones both liquefaction triggering and dissipation of excess pore water pressure. The existence of the superstructure mass on the pile caps decreases the acceleration amplitude of the pile caps, while increases their maximum displacement.

Keywords

• Soil liquefaction
• Lateral spreading
• 1g shake table test
• Pile group
• Crust layer
• Superstructure