Cyclic shear stress reduction ratio evaluation for liquefiable ground treated by in-ground structural walls

Abstract

Soil liquefaction during seismic events may pose significant risks to the stability of buildings and infrastructure. This study assesses the effectiveness of reducing cyclic shear stress for liquefiable ground treated with in-ground structural walls, simulating an existing foundation surrounded by these walls. The enclosed, in-ground structural walls mitigate liquefaction hazards by reducing shear stress and limiting excess pore pressure generation within enclosed soils. A simplified method was developed to estimate the cyclic shear stress reduction ratio for treated grounds to improve seismic resilience. Numerical simulations were conducted using a series of three-dimensional, fully coupled, nonlinear, dynamic finite element analyses. The investigation focused on assessing the impact of wall spacing, penetration depth (i.e., the thickness of the critical liquefiable layer), and flexural stiffness on shear stress reduction. The results indicated that closer wall spacing and greater wall stiffness enhanced stress reduction, while the thickness of the liquefiable layer also played a critical role in system performance. Importantly, the impact of the in-ground walls on cyclic shear stress reduction across the critical layer depth became minor when the wall spacing exceeded 16 m. A simplified procedure based on the numerical database was proposed for estimating the cyclic shear stress reduction ratio, incorporating factors such as wall spacing and rigidity. Uncertainty estimation was quantified through a probabilistic model factor derived from Bayesian inference. This gave the engineers tools to assess the risks of liquefaction based on safety factors for treated ground. The insight from the numerical database and the simplified procedure aims to guide the design of liquefaction mitigation strategies.