A Framework for Assessing Liquefaction Hazard for Urban Areas Based on Soil Dynamics

Abstract

Soil liquefaction induced by earthquakes poses a great threat to urban areas, not only by causing direct damages to infrastructures but also by delaying rescue and relief actions. Established engineering assessment methods using indices such as factor of safety against liquefaction (FL) tend to overestimate liquefaction hazards. While the standard usage of soil dynamic analysis for liquefaction assessment is limited to a single site with detailed site information. In this paper, we propose a framework based on soil dynamics for assessing liquefaction hazard for urban areas which contain numerous sites with borehole logs only. The framework is featured by generating analysis models and by estimating material parameters automatically from available borehole information. The governing equations for soil dynamics are solved by a finite element code. Liquefaction hazard is assessed according to the solutions of excess pore water pressure for given seismic waves. As demonstrations, we show simulation results of simple shear tests and of seismic response for a target site under loadings of artificial and of actual seismic waves. The automatic model construction and parameter estimation enable this framework being applied effectively for urban-area-wide liquefaction assessment, as an alternative for the current practices based on engineering indices.

Possible Failure Mechanism of Buildings Overturned during the 2011 Great East Japan Tsunami in the Town of Onagawa

“…For each of 18 soil boring data, skin friction capacity (Qs) is shown in Table 3 for pile lengths of 4.0, 6.0, and 8.0 m and including the effect of soil liquefaction ( ) ′ Q s . However, the conventional method to evaluate the effect of soil liquefaction tends to overestimate liquefaction hazards (Chen et al, 2016). These 18 boring data were used to evaluate the potential of overturning for Buildings B and E based on the ORs, which can be classified as no possibility, low possibility, medium possibility, or high possibility.…”

Proposal of Method of Numerically Manufactured Solutions for Code Verification of Elasto-Plastic Problems

“…To demonstrate the proposed MNMS, we first try with a branch of DACSAR-I 15) , which is a general purpose soil dynamics analysis code. The branch for testing is IES-DACSAR-I, featured by an automatic modeling from borehole logs and seismic records 21) . For demonstration purpose, We consider a coupled analysis for a quasi-2D setup as shown in Fig.…”

“…Nevertheless, for a thorough verification, other kinds of boundary conditions should also be checked. Though the geometry considered here is simple, the same as those used for automatic liquefaction assessment 21) , the constitutive model is nonlinear, even for the elastic region:…”