Numerical prediction of settlement due to the Pohang earthquake

Abstract

On 15 November 2017, an earthquake with a magnitude of 5.4 caused geotechnical damage over a wide area of Pohang, South Korea. In this study, the UBCSAND constitutive effective stress model is calibrated by cyclic direct simple shear (CDSS) tests conducted on a type of sand from liquefied paddy fields at Pohang under confining stresses of 100 and 200 kPa. The calibrated UBCSAND model is then used to assess the liquefaction and calculate the ground settlement based on standard penetration test (SPT) data near the epicenter of the Pohang earthquake. The liquefaction characteristics from the UBCSAND model matched those from laboratory tests. According to the numerical results, liquefaction mostly occurred within the uppermost 10 m, and ground surface settlement from excess pore water pressure dissipation varied from 3.86 to 10.95 cm. These settlements were higher than the surface displacement estimated by satellite image analysis with interferometric synthetic aperture radar (InSAR) and lower than the ground subsidence observed solely by visiting the sites.

Liquefaction assessment using alternative approaches: a case study of Ho Chi Minh City stratigraphy

“…The key input parameter of this model is the corrected SPT data (N1)60 of the site's ground. Many researchers have applied the UBCSAND model to laboratory tests and practical seismic designs (Doan, 2021;Doan et al, 2020aDoan et al, , 2020bNguyen et al, 2021bNguyen et al, , 2021aS.-S. Park et al, 2021;S. S. Park et al, 2020;S.-S. Park et al, 2020).…”

“…Many researchers have applied the UBCSAND model to laboratory tests and practical seismic designs (Doan, 2021;Doan et al, 2020aDoan et al, , 2020bNguyen et al, 2021bNguyen et al, , 2021aS.-S. Park et al, 2021;S. S. Park et al, 2020;S.-S. Park et al, 2020). A detailed explanation and verification of this model were described by Puebla et al (1997), Byrne et al (2004) and Beaty and Byrne (2011).…”

Constitutive modeling of principal stress rotation associated with sand under simple shear loading

“…For example, Beaty and Byrne, 15 and Chowdhury 50 suggested protocols of UBCSAND for modeling the postliquefaction residual shear strengths inferred from field case histories of earthquake-induced liquefaction. 42,[51][52][53][54][55] Additionally, Park et al, 17 and Ferdosi 56 performed the effective stress analysis using the UBCSAND model adopt the analytical function of Sento et al 57,58 for postliquefaction reconsolidation volumetric strains.…”

“…There are many versions of the UBCSAND model over two decades of the development, and the UBCSAND v.904aR model is the most widely used version that includes some important modifications made by Beaty and Byrne 15 . However, some limitations has still been existing, such as: (i) elastic unloading until shear stress reversal, (ii) effects of principal stress rotation, (iii) single assessment of stress reversals on horizontal (or 45˚) planes, and (iv) simplification of postliquefaction volumetric strains due to the reconsolidation process, as pointed out by Beaty, 16 Park et al., 17 and Doan et al 18 . In this study, the model has been continuously developed to better model observed sand behavior and account for the effects of PSR or K 0 states, and plastic unloading.…”