ABSTRACT
Liquefaction
is process by which water-saturated, unconsolidated sediments are transformed into
a substance that acts like a liquid which can undermine the foundations and base
courses of infrastructure like bridges. It can cause serious damage. Liquefaction
can be classified into two. They are Flow Liquefaction and Cyclic Mobility.
Lateral
soil deformations (lateral spreading) have proven to be the most pervasive type
of liquefaction-induced ground failure. Lateral spreading involves the movement
of relatively intact soil blocks on a layer of liquefied soil toward a free face
or incised channel. These blocks are transported down-slope or in the direction
of a channel by both dynamic and gravitational forces. The amount of lateral displacement
typically ranges from a few centimetres to several meters and can cause significant
damage to engineered structures. Different effects on bridge are Ground Failure,
Lateral Displacement, Settlement and Abutments are Vulnerable to Seismic Damage.
Soil liquefaction is caused by the loss of bearing capacity, lateral movement of
substructure and dislodgement of super structure. Lateral ground displacements have
been extremely damaging to bridge foundations and abutments. Movement of foundation
elements may create large shear forces and bending moments at connections and compressional
forces in the superstructure. Subsidence and increased lateral earth pressures can
also lead to deleterious consequences for bridge foundations. Waterfront retaining
structures, especially in areas of reclaimed land, can experience large settlements
and lateral earth pressures adjacent to bridge foundations. These movements lead
to the rotation and translation of bridge abutments and increased lateral forces
on pile foundations. A number of failure modes may occur in pile foundations, depending
on the conditions of fixity, pile reinforcement and ductility. Generally, if concrete
piles were well embedded in the pile caps, shear or flexural cracks occurred at
pile heads, often leading to failure; if steel pipe piles were fixed tightly in
the pile caps, failure was at the connection or pile cap; or if the pile heads were
loosely connected to the pile caps, they either rotated or were detached.
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