Report - Oregon State Library: State Employee Information Center ...

Figure 2.17: Observed Pile Deformation and Soil Conditions at NFCH Building
The experience of the Niigata earthquake developed an awareness of the following types of
damage and behavior due to liquefaction.
1. Distinct failure modes can be recognized in piles subjected to liquefaction-induced lateral
spreading. These failure modes include (a) lateral pile deflections induced by horizontal
soil displacements, which may result in the pile reaching its bending capacity and
developing a plastic hinge, and (b) a lack of sufficient lateral support due to the reduced
stiffness of the liquefied soil and the lateral deflection imposed on the pile, which may
result in buckling.
2. Other pile failure modes may include (a) excessive rigid body rotation of the pile, which
would be characteristic of large diameter piles and piers, and (b) flow of liquefied soil
around the pile, which would usually be associated with stiff foundations, such as large
diameter piles, piers, and closely spaced groups.
3. Settlement, tilting, and toppling of bridge foundation elements due to a reduction in
ground bearing capacity.
4. Tilting, rotation or collapse of retaining walls, abutments and quay walls as a result of
increased earth pressure and reduction in soil shear strength.
5. Failure of earth structures, such as embankments, due to decreases in the strengths of
sandy soil materials.
2.3.3 1989 Loma Prieta Earthquake
The 1989 Loma Prieta Earthquake provided valuable data on the role of site response and soil
liquefaction on the seismic performance of bridges. This M w 6.9 earthquake was centered 97 km
southeast of San Francisco and had approximately 8 to 10 seconds of strong shaking. Peak
23