Soil Liquefaction–Induced Uplift of Underground Structures: Physical and Numerical Modeling

Abstract

Underground structures located in liquefiable soil deposits are susceptible to floatation following a major earthquake event. Such failure phenomenon generally occurs when the soil liquefies and loses its shear resistance against the uplift force from the buoyancy of the underground structure. Numerical modeling accompanied with centrifuge experiments with shallow circular structures has been carried out to investigate the floatation failure at different buried depths of the structure. The influence of the magnitude of input sinusoidal earthquake shaking was also studied. Both numerical and experimental results showed matching uplift response of the structures and acceleration and pore-pressure measurements in the liquefied soil deposit. A higher uplift displacement of the structure was observed for shallower buried depth, thereby indicating the influence of overlying soil weight against floatation. Results also showed that the structures commenced floatation in the presence of high excess pore pressure, but they ceased when the earthquake shaking stopped. The higher rate of uplift in stronger earthquake shaking further substantiates the dependency of the uplift to the shaking amplitude. A constant rate of uplift of the structure was attained after the soil liquefied, hence postulating a possible limit to shear modulus degradation of the surrounding soil caused by soil-structure interaction. This is inferred by the lower excess pore-pressure generation near the structure. The displacement of liquefied soil around the displaced structure was also confirmed to resemble a global circular flow mechanism from the crown of the structure to its invert as observed in displacement vector plots obtained from numerical analysis and particle image velocimetry (PIV) in centrifuge tests. Further numerical analysis on the performance of buried sewer pipelines in Urayasu City, Chiba Prefecture following the 2011 Great East Japan Earthquake indicated high damage susceptibility of rigid pipelines in the liquefiable soil deposit. These consistencies with field observations clearly demonstrate and pave the prospects of applying numerical and/or experimental analyses for geotechnical problems associated with the floatation of underground structures in liquefiable soils.

Critical State–Based Interpretation of the Monotonic Behavior of Hostun Sand

“…Furthermore, the recent use of Hostun sand on centrifuge modelling (e.g. Marques et al 2014;Li and Bolton 2014;Chian et al 2014) highlighted the need for high quality testing to be performed on this material. (Table 1), with the small differences between them resulting from the application of different standards.…”

Liquefaction induced displacement and rotation of structures with wide basements

“…Soil was forced sideways to allow the structure to settle downwards into the soil layer, which caused an upward flow of soil adjacent to the basement. The movement of soil beneath the basement is comparable to that beneath light structures on shallow foundations [9] and the movement of the soil adjacent to the basement has similarities to the flow of liquefied soil around buried pipes [35].…”

Seismic Behavior of Triple Tunnel Complex in Soft Soil Subjected to Transverse Shaking

“…Tsinidis [17] conducted FEM to study response characteristics of rectangular tunnels under seismic shaking varying the tunnel-soil interface properties and input motion characteristics embedment depths and concluded in the development of racking-flexibility (RF) relations for rectangular tunnels in soft soils. Apart from this, the response of underground tunnels subjected to seismic ground shaking have been studied experimentally (Chian and Madabhushi [18], Graziani and Boldini [19], Chian and Madabhushi [20], Abuhajar and Naggar et al [21]), analytically (Power et al [1], Chian and Tokimatsu [22], Bobet and Fernandez et al [23]) and numerically (Chou and Yang et al [24], Amorosi and Boldini [25], Baziar and Moghadam et al [26], Huo and Bobet et al [27], Nguyen and Lee et al [28]). However, all literature considers the conventional circular, rectangular or horseshoe shapes.…”